Yanhua Huang - Profile on Academia.edu (original) (raw)

Papers by Yanhua Huang

Proceedings of The National Academy of Sciences, 2009

Author contributions: M.J.M., Y.H.H., and C.J.S. designed research; M.J.M., Y.H.H., and A.D. perf... more Author contributions: M.J.M., Y.H.H., and C.J.S. designed research; M.J.M., Y.H.H., and A.D. performed research; M.J.M. contributed new reagents/analytic tools; M.J.M., Y.H.H., and C.J.S. analyzed data; and M.J.M., Y.H.H., and C.J.S. wrote the paper. The authors declare no conflict of interest. 1 M.J.M. and Y.H.H. contributed equally to this work.

Proceedings of The National Academy of Sciences, 2009

There are more than 50 class I MHC (MHCI) molecules in the mouse genome, some of which are now kn... more There are more than 50 class I MHC (MHCI) molecules in the mouse genome, some of which are now known to be expressed in neurons; however, the role of classical MHCI molecules in synaptic plasticity is unknown. We report that the classical MHCI molecules, H2-Kb and H2-Db, are co-expressed by Purkinje cells (PCs). In the cerebellum of mice deficient for both H2-Kb and H2-Db (KbDb-/-), there is a lower threshold for induction of long-term depression (LTD) at parallel fiber to PC synapses. This change may be a result of additional glutamate release observed at KbDb-/- CF to PC synapses, which are thought to “train” the cerebellar circuit. A behavioral correlate of cerebellar LTD is motor learning; acquisition and retention of a Rotarod behavioral task is significantly better in KbDb-/- mice than in WT cohorts. These physiological and behavioral phenotypes in KbDb-/- mice reveal a surprising role for classical MHCI molecules in synaptic plasticity and motor learning.

Current Opinion in Neurobiology, 2004

Glutamate transporters (GluTs) prevent the accumulation of glutamate and influence the occupancy ... more Glutamate transporters (GluTs) prevent the accumulation of glutamate and influence the occupancy of receptors at synapses. The ability of extrasynaptic NMDA receptors and metabotropic glutamate receptors to participate in signaling is tightly regulated by GluT activity. Astrocytes express the highest density of GluTs and dominate clearance away from these receptors; synapses that are not associated with astrocyte processes experience greater mGluR activation and can be exposed to glutamate released at adjacent synapses. Although less abundant, neuronal transporters residing in the postsynaptic membrane can also shield receptors from the glutamate that is released. The diversity in synaptic morphology suggests a correspondingly rich diversity of GluT function in excitatory transmission.

Nature, 2004

Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of syn... more Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of synaptic glutamate is handled by the glutamate transporter GLT1 (also known as EAAT2; refs 1, 2), the physiologically dominant astroglial protein. In spite of its critical importance in normal and abnormal synaptic activity, no practical pharmaceutical can positively modulate this protein.

Synthesis and Characterization of 4Methoxy7-nitroindolinyl- d -aspartate, a Caged Compound for Selective Activation of Glutamate Transporters and N Methyl d -aspartate Receptors in Brain Tissue

Biochemistry, 2005

The D-isomer of aspartate is efficiently transported by high-affinity Na(+)/K(+)-dependent glutam... more The D-isomer of aspartate is efficiently transported by high-affinity Na(+)/K(+)-dependent glutamate transporters and is an effective ligand of N-methyl-d-aspartate (NMDA) receptors. To facilitate analysis of the regulation of these proteins in their native membranes, we synthesized a photolabile analogue of D-aspartate, 4-methoxy-7-nitroindolinyl-D-aspartate (MNI-D-aspartate). This compound was photolyzed with a quantum efficiency of 0.09 at pH 7.4. Photorelease of d-aspartate in acute hippocampal slices through brief (1 ms) UV laser illumination of MNI-d-aspartate triggered rapidly activating currents in astrocytes that were inhibited by the glutamate transporter antagonist DL-threo-beta-benzyloxyaspartic acid (TBOA), indicating that they resulted from electrogenic uptake of D-aspartate. These transporter currents exhibited a distinct tail component that was approximately 2% of the peak current, which may result from the release of K(+) into the extracellular space during counter transport. MNI-D-aspartate was neither an agonist nor an antagonist of glutamate transporters at concentrations up to 500 muM and was stable in aqueous solution for several days. Glutamate transporter currents were also elicited in Bergmann glial cells and Purkinje neurons of the cerebellum in response to photolysis of MNI-D-aspartate, indicating that this compound can be used for monitoring the occupancy and regulation of glutamate transporters in different brain regions. Photorelease of D-aspartate did not activate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors or metabotropic glutamate receptors (mGluRs) in neurons, but resulted in the selective, but transient, activation of NMDA receptors in hippocampal pyramidal neurons; MNI-D-aspartate was not an antagonist of NMDA receptors. These results indicate that MNI-D-aspartate also may be useful for studying the regulation of NMDA receptors at excitatory synapses.

Nature, 2005

Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of syn... more Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of synaptic glutamate is handled by the glutamate transporter GLT1 (also known as EAAT2; refs 1, 2), the physiologically dominant astroglial protein. In spite of its critical importance in normal and abnormal synaptic activity, no practical pharmaceutical can positively modulate this protein. Animal studies show that the protein is important for normal excitatory synaptic transmission, while its dysfunction is implicated in acute and chronic neurological disorders, including amyotrophic lateral sclerosis (ALS), stroke, brain tumours and epilepsy. Using a blinded screen of 1,040 FDA-approved drugs and nutritionals, we discovered that many β-lactam antibiotics are potent stimulators of GLT1 expression. Furthermore, this action appears to be mediated through increased transcription of the GLT1 gene. β-Lactams and various semi-synthetic derivatives are potent antibiotics that act to inhibit bacterial synthetic pathways. When delivered to animals, the β-lactam ceftriaxone increased both brain expression of GLT1 and its biochemical and functional activity. Glutamate transporters are important in preventing glutamate neurotoxicity. Ceftriaxone was neuroprotective in vitro when used in models of ischaemic injury and motor neuron degeneration, both based in part on glutamate toxicity. When used in an animal model of the fatal disease ALS, the drug delayed loss of neurons and muscle strength, and increased mouse survival. Thus these studies provide a class of potential neurotherapeutics that act to modulate the expression of glutamate neurotransmitter transporters via gene activation.

Journal of Neuroscience, 2004

Cerebellar Purkinje cells (PCs) express two glutamate transporters, EAAC1 (EAAT3) and EAAT4; howe... more Cerebellar Purkinje cells (PCs) express two glutamate transporters, EAAC1 (EAAT3) and EAAT4; however, their relative contribution to the uptake of glutamate at synapses is not known. We found that glutamate transporter currents recorded at climbing fiber (CF)-PC synapses are absent in mice lacking EAAT4 but unchanged in mice lacking EAAC1, indicating that EAAT4 is preferentially involved in clearing glutamate from CF synapses. However, comparison of CF synaptic currents between wild-type and transporter knock-out mice revealed that ionotropic glutamate receptors are responsible for Ͼ40% of the current previously attributed to transporters, indicating that PCs remove Ͻ10% of the glutamate released by the CF. The receptors responsible for the nontransporter component accounted for 5% of the CF EPSC, had a slower time course and lower occupancy than AMPA receptors at CF synapses, and exhibited pharmacological properties consistent with kainate receptors. In GluR5 knock-out mice, this current was dramatically reduced, indicating that CF excitation of PCs involves two distinct classes of ionotropic glutamate receptors, AMPA receptors and GluR5-containing kainate receptors.

b-Lactam antibiotics offer neuroprotection by increasing glutamate transporter expression

Nature

Page 1. ..... b-Lactam antibiotics offer neuroprotection by increasing glutamate transporter expr... more Page 1. ..... b-Lactam antibiotics offer neuroprotection by increasing glutamate transporter expression Jeffrey D. Rothstein1,2, Sarjubhai Patel1, Melissa R. Regan1, Christine Haenggeli1, Yanhua ...

Journal of Neuroscience, 2004

Clearance of extracellular glutamate is essential for limiting the activity of metabotropic gluta... more Clearance of extracellular glutamate is essential for limiting the activity of metabotropic glutamate receptors (mGluRs) at excitatory synapses; however, the relative contribution of transporters found in neuronal and glial membranes to this uptake is poorly understood. Hippocampal interneurons located at the oriens-alveus border express mGluR1␣, a metabotropic glutamate receptor that regulates excitability and synaptic plasticity. To determine which glutamate transporters are essential for removing glutamate at these excitatory synapses, we recorded mGluR1-mediated EPSCs from oriens-lacunosum moleculare (O-LM) interneurons in acute hippocampal slices.

Neuropharmacology, 2005

The D-isomer of aspartate is both a substrate for glutamate transporters and an agonist of N-meth... more The D-isomer of aspartate is both a substrate for glutamate transporters and an agonist of N-methyl-D-aspartate (NMDA) receptors. To monitor the behavior of these receptors and transporters in intact tissue we synthesized a new photo-labile analogue of D-aspartate, N-[(6-nitrocoumarin-7-yl)methyl]-D-aspartic acid (Ncm-D-aspartate). This compound was photolyzed rapidly (t 1/2 Z 0.11 ms) by UV light with a quantum efficiency of 0.041 at pH 7.4. In acute hippocampal slices, photolysis of Ncm-D-aspartate by brief (1 ms) exposure to UV light elicited rapidly activating inward currents in astrocytes that were sensitive to inhibition by the glutamate transporter antagonist DL-threo-b-benzyloxyaspartic acid (TBOA). Neither Ncm-D-aspartate nor the photo-released caging group exhibited agonist or antagonist activity at glutamate transporters, and Ncm-D-aspartate did not induce transporter currents prior to photolysis. Glutamate transporter currents were also elicited in cerebellar Purkinje cells in response to photolysis of Ncm-D-aspartate. Photo-release of D-aspartate from Ncm-D-aspartate did not induce a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptor or metabotropic glutamate receptor (mGluR) currents, but triggered robust NMDA receptor currents in neurons; Ncm-D-aspartate and the photolzyed caging group were similarly inert at NMDA receptors. These results indicate that Ncm-D-aspartate can be used to study NMDA receptors at excitatory synapses and interactions between transporters and receptors in brain tissue. transporter; EAAT4, excitatory amino acid transporter 4; GLT-1, glutamate transporter 1; LY 367385, (S )-(C)-a-amino-4-carboxy-2-methylbenzeneacetic acid; TEA, tetraethylammonium. * Corresponding authors. Tel.: C1 410 955 6939; fax: C1 410 955 6942 (D.E. Bergles), Tel.: C1 410 706 4167; fax: C1 410 706 8184 (J.P.Y. Kao).

Neuron, 2009

Studies over the past decade have enunciated silent synapses as prominent cellular substrates for... more Studies over the past decade have enunciated silent synapses as prominent cellular substrates for synaptic plasticity in the developing brain. However, little is known about whether silent synapses can be generated postdevelopmentally. Here, we demonstrate that highly salient in vivo experience, such as exposure to cocaine, generates silent synapses in the nucleus accumbens (NAc) shell, a key brain region mediating addiction-related learning and memory. Furthermore, this cocaine-induced generation of silent synapses is mediated by membrane insertions of new, NR2B-containing N-methyl-D-aspartic acid receptors (NMDARs). These results provide evidence that silent synapses can be generated de novo by in vivo experience and thus may act as highly efficient neural substrates for the subsequent experiencedependent synaptic plasticity underlying extremely long-lasting memory.

Behavioural Brain Research, 2011

Homeostatic response is an endowed self-correcting/maintaining property for living units, ranging... more Homeostatic response is an endowed self-correcting/maintaining property for living units, ranging from subcellular domains, single cells, and organs to the whole organism. Homeostatic responses maintain stable function through the ever-changing internal and external environments. In central neurons, several forms of homeostatic regulation have been identified, all of which tend to stabilize the functional output of neurons toward their prior "set-point." Medium spiny neurons (MSNs) within the forebrain region the nucleus accumbens (NAc) play a central role in gating/regulating emotional and motivational behaviors including craving and seeking drugs of abuse. Exposure to highly salient stimuli such as cocaine administration not only acutely activates a certain population of NAc MSNs, but also induces long-lasting changes in these neurons. It is these long-lasting cellular alterations that are speculated to mediate the increasingly strong cocaine-craving and cocaine-seeking behaviors. Why do the potentially powerful homeostatic mechanisms fail to correct or compensate for these drug-induced maladaptations in neurons? Based on recent experimental results, this review proposes a hypothesis of homeostatic dysregulation induced by exposure to cocaine. Specifically, we hypothesize that exposure to cocaine generates false molecular signals which misleads the homeostatic regulation process, resulting in maladaptive changes in NAc MSNs. Thus, many molecular and cellular alterations observed in the addicted brain may indeed result from homeostatic dysregulation. This review is among the first to introduce the concept of homeostatic neuroplasticity to understanding the molecular and cellular maladaptations following exposure to drugs of abuse.

Brain Research, 2011

Despite sleep-loss-induced cognitive deficits, little is known about the cellular adaptations tha... more Despite sleep-loss-induced cognitive deficits, little is known about the cellular adaptations that occur with sleep loss. We used brain slices obtained from mice that were sleep deprived for 8 h to examine the electrophysiological effects of sleep deprivation (SD). We employed a modified pedestal (flowerpot) over water method for SD that eliminated rapid eye movement sleep and greatly reduced non-rapid eye movement sleep. In layer V/VI pyramidal cells of the medial prefrontal cortex, miniature excitatory post synaptic current amplitude was slightly reduced, miniature inhibitory post synaptic currents were unaffected, and intrinsic membrane excitability was increased after SD.

Proceedings of The National Academy of Sciences, 2009

Author contributions: M.J.M., Y.H.H., and C.J.S. designed research; M.J.M., Y.H.H., and A.D. perf... more Author contributions: M.J.M., Y.H.H., and C.J.S. designed research; M.J.M., Y.H.H., and A.D. performed research; M.J.M. contributed new reagents/analytic tools; M.J.M., Y.H.H., and C.J.S. analyzed data; and M.J.M., Y.H.H., and C.J.S. wrote the paper. The authors declare no conflict of interest. 1 M.J.M. and Y.H.H. contributed equally to this work.

Proceedings of The National Academy of Sciences, 2009

There are more than 50 class I MHC (MHCI) molecules in the mouse genome, some of which are now kn... more There are more than 50 class I MHC (MHCI) molecules in the mouse genome, some of which are now known to be expressed in neurons; however, the role of classical MHCI molecules in synaptic plasticity is unknown. We report that the classical MHCI molecules, H2-Kb and H2-Db, are co-expressed by Purkinje cells (PCs). In the cerebellum of mice deficient for both H2-Kb and H2-Db (KbDb-/-), there is a lower threshold for induction of long-term depression (LTD) at parallel fiber to PC synapses. This change may be a result of additional glutamate release observed at KbDb-/- CF to PC synapses, which are thought to “train” the cerebellar circuit. A behavioral correlate of cerebellar LTD is motor learning; acquisition and retention of a Rotarod behavioral task is significantly better in KbDb-/- mice than in WT cohorts. These physiological and behavioral phenotypes in KbDb-/- mice reveal a surprising role for classical MHCI molecules in synaptic plasticity and motor learning.

Current Opinion in Neurobiology, 2004

Glutamate transporters (GluTs) prevent the accumulation of glutamate and influence the occupancy ... more Glutamate transporters (GluTs) prevent the accumulation of glutamate and influence the occupancy of receptors at synapses. The ability of extrasynaptic NMDA receptors and metabotropic glutamate receptors to participate in signaling is tightly regulated by GluT activity. Astrocytes express the highest density of GluTs and dominate clearance away from these receptors; synapses that are not associated with astrocyte processes experience greater mGluR activation and can be exposed to glutamate released at adjacent synapses. Although less abundant, neuronal transporters residing in the postsynaptic membrane can also shield receptors from the glutamate that is released. The diversity in synaptic morphology suggests a correspondingly rich diversity of GluT function in excitatory transmission.

Nature, 2004

Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of syn... more Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of synaptic glutamate is handled by the glutamate transporter GLT1 (also known as EAAT2; refs 1, 2), the physiologically dominant astroglial protein. In spite of its critical importance in normal and abnormal synaptic activity, no practical pharmaceutical can positively modulate this protein.

Synthesis and Characterization of 4Methoxy7-nitroindolinyl- d -aspartate, a Caged Compound for Selective Activation of Glutamate Transporters and N Methyl d -aspartate Receptors in Brain Tissue

Biochemistry, 2005

The D-isomer of aspartate is efficiently transported by high-affinity Na(+)/K(+)-dependent glutam... more The D-isomer of aspartate is efficiently transported by high-affinity Na(+)/K(+)-dependent glutamate transporters and is an effective ligand of N-methyl-d-aspartate (NMDA) receptors. To facilitate analysis of the regulation of these proteins in their native membranes, we synthesized a photolabile analogue of D-aspartate, 4-methoxy-7-nitroindolinyl-D-aspartate (MNI-D-aspartate). This compound was photolyzed with a quantum efficiency of 0.09 at pH 7.4. Photorelease of d-aspartate in acute hippocampal slices through brief (1 ms) UV laser illumination of MNI-d-aspartate triggered rapidly activating currents in astrocytes that were inhibited by the glutamate transporter antagonist DL-threo-beta-benzyloxyaspartic acid (TBOA), indicating that they resulted from electrogenic uptake of D-aspartate. These transporter currents exhibited a distinct tail component that was approximately 2% of the peak current, which may result from the release of K(+) into the extracellular space during counter transport. MNI-D-aspartate was neither an agonist nor an antagonist of glutamate transporters at concentrations up to 500 muM and was stable in aqueous solution for several days. Glutamate transporter currents were also elicited in Bergmann glial cells and Purkinje neurons of the cerebellum in response to photolysis of MNI-D-aspartate, indicating that this compound can be used for monitoring the occupancy and regulation of glutamate transporters in different brain regions. Photorelease of D-aspartate did not activate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors or metabotropic glutamate receptors (mGluRs) in neurons, but resulted in the selective, but transient, activation of NMDA receptors in hippocampal pyramidal neurons; MNI-D-aspartate was not an antagonist of NMDA receptors. These results indicate that MNI-D-aspartate also may be useful for studying the regulation of NMDA receptors at excitatory synapses.

Nature, 2005

Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of syn... more Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of synaptic glutamate is handled by the glutamate transporter GLT1 (also known as EAAT2; refs 1, 2), the physiologically dominant astroglial protein. In spite of its critical importance in normal and abnormal synaptic activity, no practical pharmaceutical can positively modulate this protein. Animal studies show that the protein is important for normal excitatory synaptic transmission, while its dysfunction is implicated in acute and chronic neurological disorders, including amyotrophic lateral sclerosis (ALS), stroke, brain tumours and epilepsy. Using a blinded screen of 1,040 FDA-approved drugs and nutritionals, we discovered that many β-lactam antibiotics are potent stimulators of GLT1 expression. Furthermore, this action appears to be mediated through increased transcription of the GLT1 gene. β-Lactams and various semi-synthetic derivatives are potent antibiotics that act to inhibit bacterial synthetic pathways. When delivered to animals, the β-lactam ceftriaxone increased both brain expression of GLT1 and its biochemical and functional activity. Glutamate transporters are important in preventing glutamate neurotoxicity. Ceftriaxone was neuroprotective in vitro when used in models of ischaemic injury and motor neuron degeneration, both based in part on glutamate toxicity. When used in an animal model of the fatal disease ALS, the drug delayed loss of neurons and muscle strength, and increased mouse survival. Thus these studies provide a class of potential neurotherapeutics that act to modulate the expression of glutamate neurotransmitter transporters via gene activation.

Journal of Neuroscience, 2004

Cerebellar Purkinje cells (PCs) express two glutamate transporters, EAAC1 (EAAT3) and EAAT4; howe... more Cerebellar Purkinje cells (PCs) express two glutamate transporters, EAAC1 (EAAT3) and EAAT4; however, their relative contribution to the uptake of glutamate at synapses is not known. We found that glutamate transporter currents recorded at climbing fiber (CF)-PC synapses are absent in mice lacking EAAT4 but unchanged in mice lacking EAAC1, indicating that EAAT4 is preferentially involved in clearing glutamate from CF synapses. However, comparison of CF synaptic currents between wild-type and transporter knock-out mice revealed that ionotropic glutamate receptors are responsible for Ͼ40% of the current previously attributed to transporters, indicating that PCs remove Ͻ10% of the glutamate released by the CF. The receptors responsible for the nontransporter component accounted for 5% of the CF EPSC, had a slower time course and lower occupancy than AMPA receptors at CF synapses, and exhibited pharmacological properties consistent with kainate receptors. In GluR5 knock-out mice, this current was dramatically reduced, indicating that CF excitation of PCs involves two distinct classes of ionotropic glutamate receptors, AMPA receptors and GluR5-containing kainate receptors.

b-Lactam antibiotics offer neuroprotection by increasing glutamate transporter expression

Nature

Page 1. ..... b-Lactam antibiotics offer neuroprotection by increasing glutamate transporter expr... more Page 1. ..... b-Lactam antibiotics offer neuroprotection by increasing glutamate transporter expression Jeffrey D. Rothstein1,2, Sarjubhai Patel1, Melissa R. Regan1, Christine Haenggeli1, Yanhua ...

Journal of Neuroscience, 2004

Clearance of extracellular glutamate is essential for limiting the activity of metabotropic gluta... more Clearance of extracellular glutamate is essential for limiting the activity of metabotropic glutamate receptors (mGluRs) at excitatory synapses; however, the relative contribution of transporters found in neuronal and glial membranes to this uptake is poorly understood. Hippocampal interneurons located at the oriens-alveus border express mGluR1␣, a metabotropic glutamate receptor that regulates excitability and synaptic plasticity. To determine which glutamate transporters are essential for removing glutamate at these excitatory synapses, we recorded mGluR1-mediated EPSCs from oriens-lacunosum moleculare (O-LM) interneurons in acute hippocampal slices.

Neuropharmacology, 2005

The D-isomer of aspartate is both a substrate for glutamate transporters and an agonist of N-meth... more The D-isomer of aspartate is both a substrate for glutamate transporters and an agonist of N-methyl-D-aspartate (NMDA) receptors. To monitor the behavior of these receptors and transporters in intact tissue we synthesized a new photo-labile analogue of D-aspartate, N-[(6-nitrocoumarin-7-yl)methyl]-D-aspartic acid (Ncm-D-aspartate). This compound was photolyzed rapidly (t 1/2 Z 0.11 ms) by UV light with a quantum efficiency of 0.041 at pH 7.4. In acute hippocampal slices, photolysis of Ncm-D-aspartate by brief (1 ms) exposure to UV light elicited rapidly activating inward currents in astrocytes that were sensitive to inhibition by the glutamate transporter antagonist DL-threo-b-benzyloxyaspartic acid (TBOA). Neither Ncm-D-aspartate nor the photo-released caging group exhibited agonist or antagonist activity at glutamate transporters, and Ncm-D-aspartate did not induce transporter currents prior to photolysis. Glutamate transporter currents were also elicited in cerebellar Purkinje cells in response to photolysis of Ncm-D-aspartate. Photo-release of D-aspartate from Ncm-D-aspartate did not induce a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptor or metabotropic glutamate receptor (mGluR) currents, but triggered robust NMDA receptor currents in neurons; Ncm-D-aspartate and the photolzyed caging group were similarly inert at NMDA receptors. These results indicate that Ncm-D-aspartate can be used to study NMDA receptors at excitatory synapses and interactions between transporters and receptors in brain tissue. transporter; EAAT4, excitatory amino acid transporter 4; GLT-1, glutamate transporter 1; LY 367385, (S )-(C)-a-amino-4-carboxy-2-methylbenzeneacetic acid; TEA, tetraethylammonium. * Corresponding authors. Tel.: C1 410 955 6939; fax: C1 410 955 6942 (D.E. Bergles), Tel.: C1 410 706 4167; fax: C1 410 706 8184 (J.P.Y. Kao).

Neuron, 2009

Studies over the past decade have enunciated silent synapses as prominent cellular substrates for... more Studies over the past decade have enunciated silent synapses as prominent cellular substrates for synaptic plasticity in the developing brain. However, little is known about whether silent synapses can be generated postdevelopmentally. Here, we demonstrate that highly salient in vivo experience, such as exposure to cocaine, generates silent synapses in the nucleus accumbens (NAc) shell, a key brain region mediating addiction-related learning and memory. Furthermore, this cocaine-induced generation of silent synapses is mediated by membrane insertions of new, NR2B-containing N-methyl-D-aspartic acid receptors (NMDARs). These results provide evidence that silent synapses can be generated de novo by in vivo experience and thus may act as highly efficient neural substrates for the subsequent experiencedependent synaptic plasticity underlying extremely long-lasting memory.

Behavioural Brain Research, 2011

Homeostatic response is an endowed self-correcting/maintaining property for living units, ranging... more Homeostatic response is an endowed self-correcting/maintaining property for living units, ranging from subcellular domains, single cells, and organs to the whole organism. Homeostatic responses maintain stable function through the ever-changing internal and external environments. In central neurons, several forms of homeostatic regulation have been identified, all of which tend to stabilize the functional output of neurons toward their prior "set-point." Medium spiny neurons (MSNs) within the forebrain region the nucleus accumbens (NAc) play a central role in gating/regulating emotional and motivational behaviors including craving and seeking drugs of abuse. Exposure to highly salient stimuli such as cocaine administration not only acutely activates a certain population of NAc MSNs, but also induces long-lasting changes in these neurons. It is these long-lasting cellular alterations that are speculated to mediate the increasingly strong cocaine-craving and cocaine-seeking behaviors. Why do the potentially powerful homeostatic mechanisms fail to correct or compensate for these drug-induced maladaptations in neurons? Based on recent experimental results, this review proposes a hypothesis of homeostatic dysregulation induced by exposure to cocaine. Specifically, we hypothesize that exposure to cocaine generates false molecular signals which misleads the homeostatic regulation process, resulting in maladaptive changes in NAc MSNs. Thus, many molecular and cellular alterations observed in the addicted brain may indeed result from homeostatic dysregulation. This review is among the first to introduce the concept of homeostatic neuroplasticity to understanding the molecular and cellular maladaptations following exposure to drugs of abuse.

Brain Research, 2011

Despite sleep-loss-induced cognitive deficits, little is known about the cellular adaptations tha... more Despite sleep-loss-induced cognitive deficits, little is known about the cellular adaptations that occur with sleep loss. We used brain slices obtained from mice that were sleep deprived for 8 h to examine the electrophysiological effects of sleep deprivation (SD). We employed a modified pedestal (flowerpot) over water method for SD that eliminated rapid eye movement sleep and greatly reduced non-rapid eye movement sleep. In layer V/VI pyramidal cells of the medial prefrontal cortex, miniature excitatory post synaptic current amplitude was slightly reduced, miniature inhibitory post synaptic currents were unaffected, and intrinsic membrane excitability was increased after SD.