Andreas Bjorefeldt - Academia.edu (original) (raw)
Papers by Andreas Bjorefeldt
Journal of Visualized Experiments, Aug 4, 2021
Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luci... more Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luciferin-has been used in vitro and in vivo to activate light-gated ion channels and pumps in neurons. While this bioluminescent optogenetics (BL-OG) approach confers a chemogenetic component to optogenetic tools, it is not limited to use in neuroscience. Rather, bioluminescence can be harnessed to activate any photosensory protein, thus enabling the manipulation of a multitude of lightmediated functions in cells. A variety of luciferase-luciferin pairs can be matched with photosensory proteins requiring different wavelengths of light and light intensities. Depending on the specific application, efficient light delivery can be achieved by using luciferase-photoreceptor fusion proteins or by simple co-transfection. Photosensory proteins based on light-dependent dimerization or conformational changes can be driven by bioluminescence to effect cellular processes from protein localization, regulation of intracellular signaling pathways to transcription. The protocol below details the experimental execution of bioluminescence activation in cells and organisms and describes the results using bioluminescence-driven recombinases and transcription factors. The protocol provides investigators with the basic procedures for carrying out bioluminescent optogenetics in vitro and in vivo. The described approaches can be further extended and individualized to a multitude of different experimental paradigms.
bioRxiv (Cold Spring Harbor Laboratory), Jun 26, 2023
STAR protocols, Sep 1, 2021
Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as o... more Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as opsins, by either fiberoptics or by administering a luciferin. BL-OG thus confers both optogenetic and chemogenetic access within the same genetically targeted neuron. This bimodality offers a powerful approach for non-invasive chemogenetic manipulation of neural activity during brain development and adult behaviors with standard optogenetic spatiotemporal precision. We detail protocols for bioluminescent stimulation of neurons in postnatally developing brain and its validation through bioluminescence imaging and electrophysiological recording in mice. For complete information on the use and execution of this protocol, please refer to Medendorp et al. (2021).
Hippocampus, Jul 17, 2019
Frontiers in Neural Circuits, Feb 5, 2018
The cerebrospinal fluid (CSF) occupies the brain's ventricles and subarachnoid space and, togethe... more The cerebrospinal fluid (CSF) occupies the brain's ventricles and subarachnoid space and, together with the interstitial fluid (ISF), forms a continuous fluidic network that bathes all cells of the central nervous system (CNS). As such, the CSF is well positioned to actively distribute neuromodulators to neural circuits in vivo via volume transmission. Recent in vitro experimental work in brain slices and neuronal cultures has shown that human CSF indeed contains neuromodulators that strongly influence neuronal activity. Here we briefly summarize these new findings and discuss their potential relevance to neural circuits in health and disease.
Journal of Visualized Experiments
Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luci... more Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luciferin-has been used in vitro and in vivo to activate light-gated ion channels and pumps in neurons. While this bioluminescent optogenetics (BL-OG) approach confers a chemogenetic component to optogenetic tools, it is not limited to use in neuroscience. Rather, bioluminescence can be harnessed to activate any photosensory protein, thus enabling the manipulation of a multitude of lightmediated functions in cells. A variety of luciferase-luciferin pairs can be matched with photosensory proteins requiring different wavelengths of light and light intensities. Depending on the specific application, efficient light delivery can be achieved by using luciferase-photoreceptor fusion proteins or by simple co-transfection. Photosensory proteins based on light-dependent dimerization or conformational changes can be driven by bioluminescence to effect cellular processes from protein localization, regulation of intracellular signaling pathways to transcription. The protocol below details the experimental execution of bioluminescence activation in cells and organisms and describes the results using bioluminescence-driven recombinases and transcription factors. The protocol provides investigators with the basic procedures for carrying out bioluminescent optogenetics in vitro and in vivo. The described approaches can be further extended and individualized to a multitude of different experimental paradigms.
Frontiers in Cellular Neuroscience, 2016
Experimental Neurology, 2014
Previous work implicated the complement system in adult neurogenesis as well as elimination of sy... more Previous work implicated the complement system in adult neurogenesis as well as elimination of synapses in the developing and injured CNS. In the present study, we used mice lacking the third complement component (C3) to elucidate the role the complement system plays in hippocampus-dependent learning and synaptic function. We found that the constitutive absence of C3 is associated with enhanced place and reversal learning in adult mice. Our findings of lower release probability at CA3-CA1 glutamatergic synapses in combination with unaltered overall efficacy of these synapses in C3 deficient mice implicate C3 as a negative regulator of the number of functional glutamatergic synapses in the hippocampus. The C3 deficient mice showed no signs of spontaneous epileptiform activity in the hippocampus. We conclude that C3 plays a role in the regulation of the number and function of glutamatergic synapses in the hippocampus and exerts negative effects on hippocampus-dependent cognitive performance.
Journal of Neurochemistry, 2019
It is well known that the extracellular concentration of calcium affects neuronal excitability an... more It is well known that the extracellular concentration of calcium affects neuronal excitability and synaptic transmission. It is less well known what the physiological concentration of extracellular calcium is in the brain. In electrophysiological brain slice experiments, the artificial cerebrospinal fluid (aCSF) traditionally contains relatively high concentrations (2-4 mM) of calcium to support synaptic transmission and suppress neuronal excitability. Using an ion-selective electrode, we determined the fraction of ionized calcium in healthy human cerebrospinal fluid (hCSF) to about 1.0 mM of a total concentration of 1.2 mM (86%). We then compared the effects of this physiological concentration of calcium with the commonly used 2 mM on neuronal excitability, synaptic transmission and long-term potentiation (LTP) using patch-clamp-and extracellular recordings in the CA1 region in acute slices of rat hippocampus. Increasing the total extracellular calcium concentration from 1.2 to 2 mM decreased spontaneous action potential firing, induced a depolarization of the threshold and increased rate of both depolarization and repolarization of the action potential. Evoked synaptic transmission was approximately doubled with a balanced effect between inhibition and excitation. LTP induced with high-frequency stimulation during blockade of GABAergic inhibition was negligible at 1.2 mM calcium, whereas a prominent LTP was observed at 2 or 4 mM calcium. In conclusion, an increase from the physiological 1.2 mM to 2 mM calcium in the aCSF has striking effects on neuronal excitability, synaptic transmission and the induction of LTP.
Journal of visualized experiments : JoVE, 2021
Bioluminescence - light emitted by a luciferase enzyme oxidizing a small molecule substrate, a lu... more Bioluminescence - light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luciferin - has been used in vitro and in vivo to activate light-gated ion channels and pumps in neurons. While this bioluminescent optogenetics (BL-OG) approach confers a chemogenetic component to optogenetic tools, it is not limited to use in neuroscience. Rather, bioluminescence can be harnessed to activate any photosensory protein, thus enabling the manipulation of a multitude of light-mediated functions in cells. A variety of luciferase-luciferin pairs can be matched with photosensory proteins requiring different wavelengths of light and light intensities. Depending on the specific application, efficient light delivery can be achieved by using luciferase-photoreceptor fusion proteins or by simple co-transfection. Photosensory proteins based on light-dependent dimerization or conformational changes can be driven by bioluminescence to effect cellular processes from protein localization,...
Neuromodulation is a key process determining the function of central neurons. The brain extracell... more Neuromodulation is a key process determining the function of central neurons. The brain extracellular fluid contains numerous neuromodulatory substances (neuromodulators), but how they collective influence neuronal activity in vivo is not known. This thesis work attempts to shed light on this issue by examining the neuromodulatory influence of human cerebrospinal fluid (hCSF) on neurons in rat and mouse hippocampal brain slices, using a matched artificial cerebrospinal fluid (aCSF, devoid of neuromodulators) as control. The methodology comprises intracellular and extracellular recording techniques and, to lesser extent, biochemical and histological procedures. In paper I we examine the effect of hCSF on CA1 pyramidal cells. We find that hCSF induces in vivo-like properties in these neurons, powerfully boosting spontaneous action potential firing, depolarizing the resting membrane potential and lowering the action potential threshold. In paper II we record from GABAergic fast-spiking...
Frontiers in Neural Circuits, 2018
The cerebrospinal fluid (CSF) occupies the brain’s ventricles and subarachnoid space and, togethe... more The cerebrospinal fluid (CSF) occupies the brain’s ventricles and subarachnoid space and, together with the interstitial fluid (ISF), forms a continuous fluidic network that bathes all cells of the central nervous system (CNS). As such, the CSF is well positioned to actively distribute neuromodulators to neural circuits in vivo via volume transmission. Recent in vitro experimental work in brain slices and neuronal cultures has shown that human CSF indeed contains neuromodulators that strongly influence neuronal activity. Here we briefly summarize these new findings and discuss their potential relevance to neural circuits in health and disease.
Understanding percepts, engrams and actions requires methods for selectively modulating synaptic ... more Understanding percepts, engrams and actions requires methods for selectively modulating synaptic communication between specific subsets of interconnected cells. Here, we develop an approach to control synaptically connected elements using bioluminescent light: Luciferase-generated light, originating from a presynaptic axon terminal, modulates an opsin in its postsynaptic target. Vesicular-localized luciferase is released into the synaptic cleft in response to presynaptic activity, creating a real-time ‘Optical Synapse’. Light production is under experimenter-control by introduction of the small molecule luciferin. Signal transmission across this optical synapse is temporally defined by the presence of both the luciferin and presynaptic activity. We validate synaptic ‘Interluminescence’ by multi-electrode recording in cultured neurons and in mice in vivo. Interluminescence represents a powerful approach to achieve synapse-specific and activity-dependent circuit control during behavio...
STAR Protocols
Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as o... more Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as opsins, by either fiberoptics or by administering a luciferin. BL-OG thus confers both optogenetic and chemogenetic access within the same genetically targeted neuron. This bimodality offers a powerful approach for non-invasive chemogenetic manipulation of neural activity during brain development and adult behaviors with standard optogenetic spatiotemporal precision. We detail protocols for bioluminescent stimulation of neurons in postnatally developing brain and its validation through bioluminescence imaging and electrophysiological recording in mice. For complete information on the use and execution of this protocol, please refer to Medendorp et al. (2021).
SummaryIn leading models of Autism Spectrum Disorder, and in human data, the efficacy of outgoing... more SummaryIn leading models of Autism Spectrum Disorder, and in human data, the efficacy of outgoing cortical connectivity transitions from overly exuberant to languid from early development to adulthood. This transition begs the question of whether the early enhancement in excitation might be a common driver, across etiologies, of these symptoms. We directly tested this concept by chemogenetically driving neuronal activity in neocortical neurons during postnatal days 4-14. Hyperexcitation of Emx1-, but not dopamine transporter-, parvalbumin-, or Dlx5/6-expressing neurons led to decreased social interaction and increased grooming activity in adult animals. In vivo optogenetic interrogation in adults revealed decreased baseline but increased stimulus-evoked firing rates of pyramidal neurons, impaired recruitment of inhibitory neurons and reduced cortico-striatal communication. These results directly support the prediction that changed firing in developing circuits irreversibly alters ad...
Hippocampus
Gamma oscillations (30–80 Hz) are fast network activity patterns frequently linked to cognition. ... more Gamma oscillations (30–80 Hz) are fast network activity patterns frequently linked to cognition. They are commonly studied in hippocampal brain slices in vitro, where they can be evoked via pharmacological activation of various receptor families. One limitation of this approach is that neuronal activity is studied in a highly artificial extracellular fluid environment, as provided by artificial cerebrospinal fluid (aCSF). Here, we examine the influence of human cerebrospinal fluid (hCSF) on kainate‐evoked and spontaneous gamma oscillations in mouse hippocampus. We show that hCSF, as compared to aCSF of matched electrolyte and glucose composition, increases the power of kainate‐evoked gamma oscillations and induces spontaneous gamma activity in areas CA3 and CA1 that is reversed by washout. Bath application of atropine entirely abolished hCSF‐induced gamma oscillations, indicating critical contribution from muscarinic acetylcholine receptor‐mediated signaling. In separate whole‐cell patch clamp recordings from rat hippocampus, hCSF increased theta resonance frequency and strength in pyramidal cells along with enhancement of h‐current (Ih) amplitude. We found no evidence of intrinsic gamma frequency resonance at baseline (aCSF) among fast‐spiking interneurons, and this was not altered by hCSF. However, hCSF increased the excitability of fast‐spiking interneurons, which likely contributed to gamma rhythmogenesis. Our findings show that hCSF promotes network gamma oscillations in the hippocampus in vitro and suggest that neuromodulators distributed in CSF could have significant influence on neuronal network activity in vivo.
Frontiers in Cellular Neuroscience, 2016
For decades it has been hypothesized that molecules within the cerebrospinal fluid (CSF) diffuse ... more For decades it has been hypothesized that molecules within the cerebrospinal fluid (CSF) diffuse into the brain parenchyma and influence the function of neurons. However, the functional consequences of CSF on neuronal circuits are largely unexplored and unknown. A major reason for this is the absence of appropriate neuronal in vitro model systems, and it is uncertain if neurons cultured in pure CSF survive and preserve electrophysiological functionality in vitro. In this article, we present an approach to address how human CSF (hCSF) influences neuronal circuits in vitro. We validate our approach by comparing the morphology, viability, and electrophysiological function of single neurons and at the network level in rat organotypic slice and primary neuronal cultures cultivated either in hCSF or in defined standard culture media. Our results demonstrate that rodent hippocampal slices and primary neurons cultured in hCSF maintain neuronal morphology and preserve synaptic transmission. ...
Frontiers in Cellular Neuroscience, 2016
Experimental Neurology, 2014
Journal of Visualized Experiments, Aug 4, 2021
Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luci... more Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luciferin-has been used in vitro and in vivo to activate light-gated ion channels and pumps in neurons. While this bioluminescent optogenetics (BL-OG) approach confers a chemogenetic component to optogenetic tools, it is not limited to use in neuroscience. Rather, bioluminescence can be harnessed to activate any photosensory protein, thus enabling the manipulation of a multitude of lightmediated functions in cells. A variety of luciferase-luciferin pairs can be matched with photosensory proteins requiring different wavelengths of light and light intensities. Depending on the specific application, efficient light delivery can be achieved by using luciferase-photoreceptor fusion proteins or by simple co-transfection. Photosensory proteins based on light-dependent dimerization or conformational changes can be driven by bioluminescence to effect cellular processes from protein localization, regulation of intracellular signaling pathways to transcription. The protocol below details the experimental execution of bioluminescence activation in cells and organisms and describes the results using bioluminescence-driven recombinases and transcription factors. The protocol provides investigators with the basic procedures for carrying out bioluminescent optogenetics in vitro and in vivo. The described approaches can be further extended and individualized to a multitude of different experimental paradigms.
bioRxiv (Cold Spring Harbor Laboratory), Jun 26, 2023
STAR protocols, Sep 1, 2021
Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as o... more Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as opsins, by either fiberoptics or by administering a luciferin. BL-OG thus confers both optogenetic and chemogenetic access within the same genetically targeted neuron. This bimodality offers a powerful approach for non-invasive chemogenetic manipulation of neural activity during brain development and adult behaviors with standard optogenetic spatiotemporal precision. We detail protocols for bioluminescent stimulation of neurons in postnatally developing brain and its validation through bioluminescence imaging and electrophysiological recording in mice. For complete information on the use and execution of this protocol, please refer to Medendorp et al. (2021).
Hippocampus, Jul 17, 2019
Frontiers in Neural Circuits, Feb 5, 2018
The cerebrospinal fluid (CSF) occupies the brain's ventricles and subarachnoid space and, togethe... more The cerebrospinal fluid (CSF) occupies the brain's ventricles and subarachnoid space and, together with the interstitial fluid (ISF), forms a continuous fluidic network that bathes all cells of the central nervous system (CNS). As such, the CSF is well positioned to actively distribute neuromodulators to neural circuits in vivo via volume transmission. Recent in vitro experimental work in brain slices and neuronal cultures has shown that human CSF indeed contains neuromodulators that strongly influence neuronal activity. Here we briefly summarize these new findings and discuss their potential relevance to neural circuits in health and disease.
Journal of Visualized Experiments
Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luci... more Bioluminescence-light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luciferin-has been used in vitro and in vivo to activate light-gated ion channels and pumps in neurons. While this bioluminescent optogenetics (BL-OG) approach confers a chemogenetic component to optogenetic tools, it is not limited to use in neuroscience. Rather, bioluminescence can be harnessed to activate any photosensory protein, thus enabling the manipulation of a multitude of lightmediated functions in cells. A variety of luciferase-luciferin pairs can be matched with photosensory proteins requiring different wavelengths of light and light intensities. Depending on the specific application, efficient light delivery can be achieved by using luciferase-photoreceptor fusion proteins or by simple co-transfection. Photosensory proteins based on light-dependent dimerization or conformational changes can be driven by bioluminescence to effect cellular processes from protein localization, regulation of intracellular signaling pathways to transcription. The protocol below details the experimental execution of bioluminescence activation in cells and organisms and describes the results using bioluminescence-driven recombinases and transcription factors. The protocol provides investigators with the basic procedures for carrying out bioluminescent optogenetics in vitro and in vivo. The described approaches can be further extended and individualized to a multitude of different experimental paradigms.
Frontiers in Cellular Neuroscience, 2016
Experimental Neurology, 2014
Previous work implicated the complement system in adult neurogenesis as well as elimination of sy... more Previous work implicated the complement system in adult neurogenesis as well as elimination of synapses in the developing and injured CNS. In the present study, we used mice lacking the third complement component (C3) to elucidate the role the complement system plays in hippocampus-dependent learning and synaptic function. We found that the constitutive absence of C3 is associated with enhanced place and reversal learning in adult mice. Our findings of lower release probability at CA3-CA1 glutamatergic synapses in combination with unaltered overall efficacy of these synapses in C3 deficient mice implicate C3 as a negative regulator of the number of functional glutamatergic synapses in the hippocampus. The C3 deficient mice showed no signs of spontaneous epileptiform activity in the hippocampus. We conclude that C3 plays a role in the regulation of the number and function of glutamatergic synapses in the hippocampus and exerts negative effects on hippocampus-dependent cognitive performance.
Journal of Neurochemistry, 2019
It is well known that the extracellular concentration of calcium affects neuronal excitability an... more It is well known that the extracellular concentration of calcium affects neuronal excitability and synaptic transmission. It is less well known what the physiological concentration of extracellular calcium is in the brain. In electrophysiological brain slice experiments, the artificial cerebrospinal fluid (aCSF) traditionally contains relatively high concentrations (2-4 mM) of calcium to support synaptic transmission and suppress neuronal excitability. Using an ion-selective electrode, we determined the fraction of ionized calcium in healthy human cerebrospinal fluid (hCSF) to about 1.0 mM of a total concentration of 1.2 mM (86%). We then compared the effects of this physiological concentration of calcium with the commonly used 2 mM on neuronal excitability, synaptic transmission and long-term potentiation (LTP) using patch-clamp-and extracellular recordings in the CA1 region in acute slices of rat hippocampus. Increasing the total extracellular calcium concentration from 1.2 to 2 mM decreased spontaneous action potential firing, induced a depolarization of the threshold and increased rate of both depolarization and repolarization of the action potential. Evoked synaptic transmission was approximately doubled with a balanced effect between inhibition and excitation. LTP induced with high-frequency stimulation during blockade of GABAergic inhibition was negligible at 1.2 mM calcium, whereas a prominent LTP was observed at 2 or 4 mM calcium. In conclusion, an increase from the physiological 1.2 mM to 2 mM calcium in the aCSF has striking effects on neuronal excitability, synaptic transmission and the induction of LTP.
Journal of visualized experiments : JoVE, 2021
Bioluminescence - light emitted by a luciferase enzyme oxidizing a small molecule substrate, a lu... more Bioluminescence - light emitted by a luciferase enzyme oxidizing a small molecule substrate, a luciferin - has been used in vitro and in vivo to activate light-gated ion channels and pumps in neurons. While this bioluminescent optogenetics (BL-OG) approach confers a chemogenetic component to optogenetic tools, it is not limited to use in neuroscience. Rather, bioluminescence can be harnessed to activate any photosensory protein, thus enabling the manipulation of a multitude of light-mediated functions in cells. A variety of luciferase-luciferin pairs can be matched with photosensory proteins requiring different wavelengths of light and light intensities. Depending on the specific application, efficient light delivery can be achieved by using luciferase-photoreceptor fusion proteins or by simple co-transfection. Photosensory proteins based on light-dependent dimerization or conformational changes can be driven by bioluminescence to effect cellular processes from protein localization,...
Neuromodulation is a key process determining the function of central neurons. The brain extracell... more Neuromodulation is a key process determining the function of central neurons. The brain extracellular fluid contains numerous neuromodulatory substances (neuromodulators), but how they collective influence neuronal activity in vivo is not known. This thesis work attempts to shed light on this issue by examining the neuromodulatory influence of human cerebrospinal fluid (hCSF) on neurons in rat and mouse hippocampal brain slices, using a matched artificial cerebrospinal fluid (aCSF, devoid of neuromodulators) as control. The methodology comprises intracellular and extracellular recording techniques and, to lesser extent, biochemical and histological procedures. In paper I we examine the effect of hCSF on CA1 pyramidal cells. We find that hCSF induces in vivo-like properties in these neurons, powerfully boosting spontaneous action potential firing, depolarizing the resting membrane potential and lowering the action potential threshold. In paper II we record from GABAergic fast-spiking...
Frontiers in Neural Circuits, 2018
The cerebrospinal fluid (CSF) occupies the brain’s ventricles and subarachnoid space and, togethe... more The cerebrospinal fluid (CSF) occupies the brain’s ventricles and subarachnoid space and, together with the interstitial fluid (ISF), forms a continuous fluidic network that bathes all cells of the central nervous system (CNS). As such, the CSF is well positioned to actively distribute neuromodulators to neural circuits in vivo via volume transmission. Recent in vitro experimental work in brain slices and neuronal cultures has shown that human CSF indeed contains neuromodulators that strongly influence neuronal activity. Here we briefly summarize these new findings and discuss their potential relevance to neural circuits in health and disease.
Understanding percepts, engrams and actions requires methods for selectively modulating synaptic ... more Understanding percepts, engrams and actions requires methods for selectively modulating synaptic communication between specific subsets of interconnected cells. Here, we develop an approach to control synaptically connected elements using bioluminescent light: Luciferase-generated light, originating from a presynaptic axon terminal, modulates an opsin in its postsynaptic target. Vesicular-localized luciferase is released into the synaptic cleft in response to presynaptic activity, creating a real-time ‘Optical Synapse’. Light production is under experimenter-control by introduction of the small molecule luciferin. Signal transmission across this optical synapse is temporally defined by the presence of both the luciferin and presynaptic activity. We validate synaptic ‘Interluminescence’ by multi-electrode recording in cultured neurons and in mice in vivo. Interluminescence represents a powerful approach to achieve synapse-specific and activity-dependent circuit control during behavio...
STAR Protocols
Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as o... more Summary Bioluminescent optogenetics (BL-OG) allows activation of photosensory proteins, such as opsins, by either fiberoptics or by administering a luciferin. BL-OG thus confers both optogenetic and chemogenetic access within the same genetically targeted neuron. This bimodality offers a powerful approach for non-invasive chemogenetic manipulation of neural activity during brain development and adult behaviors with standard optogenetic spatiotemporal precision. We detail protocols for bioluminescent stimulation of neurons in postnatally developing brain and its validation through bioluminescence imaging and electrophysiological recording in mice. For complete information on the use and execution of this protocol, please refer to Medendorp et al. (2021).
SummaryIn leading models of Autism Spectrum Disorder, and in human data, the efficacy of outgoing... more SummaryIn leading models of Autism Spectrum Disorder, and in human data, the efficacy of outgoing cortical connectivity transitions from overly exuberant to languid from early development to adulthood. This transition begs the question of whether the early enhancement in excitation might be a common driver, across etiologies, of these symptoms. We directly tested this concept by chemogenetically driving neuronal activity in neocortical neurons during postnatal days 4-14. Hyperexcitation of Emx1-, but not dopamine transporter-, parvalbumin-, or Dlx5/6-expressing neurons led to decreased social interaction and increased grooming activity in adult animals. In vivo optogenetic interrogation in adults revealed decreased baseline but increased stimulus-evoked firing rates of pyramidal neurons, impaired recruitment of inhibitory neurons and reduced cortico-striatal communication. These results directly support the prediction that changed firing in developing circuits irreversibly alters ad...
Hippocampus
Gamma oscillations (30–80 Hz) are fast network activity patterns frequently linked to cognition. ... more Gamma oscillations (30–80 Hz) are fast network activity patterns frequently linked to cognition. They are commonly studied in hippocampal brain slices in vitro, where they can be evoked via pharmacological activation of various receptor families. One limitation of this approach is that neuronal activity is studied in a highly artificial extracellular fluid environment, as provided by artificial cerebrospinal fluid (aCSF). Here, we examine the influence of human cerebrospinal fluid (hCSF) on kainate‐evoked and spontaneous gamma oscillations in mouse hippocampus. We show that hCSF, as compared to aCSF of matched electrolyte and glucose composition, increases the power of kainate‐evoked gamma oscillations and induces spontaneous gamma activity in areas CA3 and CA1 that is reversed by washout. Bath application of atropine entirely abolished hCSF‐induced gamma oscillations, indicating critical contribution from muscarinic acetylcholine receptor‐mediated signaling. In separate whole‐cell patch clamp recordings from rat hippocampus, hCSF increased theta resonance frequency and strength in pyramidal cells along with enhancement of h‐current (Ih) amplitude. We found no evidence of intrinsic gamma frequency resonance at baseline (aCSF) among fast‐spiking interneurons, and this was not altered by hCSF. However, hCSF increased the excitability of fast‐spiking interneurons, which likely contributed to gamma rhythmogenesis. Our findings show that hCSF promotes network gamma oscillations in the hippocampus in vitro and suggest that neuromodulators distributed in CSF could have significant influence on neuronal network activity in vivo.
Frontiers in Cellular Neuroscience, 2016
For decades it has been hypothesized that molecules within the cerebrospinal fluid (CSF) diffuse ... more For decades it has been hypothesized that molecules within the cerebrospinal fluid (CSF) diffuse into the brain parenchyma and influence the function of neurons. However, the functional consequences of CSF on neuronal circuits are largely unexplored and unknown. A major reason for this is the absence of appropriate neuronal in vitro model systems, and it is uncertain if neurons cultured in pure CSF survive and preserve electrophysiological functionality in vitro. In this article, we present an approach to address how human CSF (hCSF) influences neuronal circuits in vitro. We validate our approach by comparing the morphology, viability, and electrophysiological function of single neurons and at the network level in rat organotypic slice and primary neuronal cultures cultivated either in hCSF or in defined standard culture media. Our results demonstrate that rodent hippocampal slices and primary neurons cultured in hCSF maintain neuronal morphology and preserve synaptic transmission. ...
Frontiers in Cellular Neuroscience, 2016
Experimental Neurology, 2014