Keith Brain | University of Birmingham (original) (raw)

Papers by Keith Brain

Research paper thumbnail of Simultaneous electrophysiology and Ca 2+ imaging during neurotransmission in rat anococcygeus smooth muscle

Auton Neurosci Basic Clin, 2007

Research paper thumbnail of Electrical and optical study of nerve impulse-evoked ATP-induced, P2X-receptor-mediated sympathetic neurotransmission at single smooth muscle cells in mouse isolated vas deferens

Neuroscience, Aug 10, 2007

Simultaneous electrophysiology and confocal microscopy were used to investigate purinergic neurot... more Simultaneous electrophysiology and confocal microscopy were used to investigate purinergic neurotransmission at single smooth muscle cells (SMCs) in mouse isolated vas deferens, and to explore the relationship between two high-resolution P2X-receptor-mediated measures of per pulse ATP release: transient peaks in the first time derivative of the rising phase of excitatory junction potentials (EJPs) recorded in single SMCs ('discrete events'; DEs) and neuroeffector Ca 2+ transients (NCTs) in the impaled SMCs.

Research paper thumbnail of Autonomic synaptic transmission at single boutons and calyces

Journal of Neurocytology, Oct 1, 1997

Research paper thumbnail of Varicosities of Single Sympathetic Nerve Terminals Possess Syntaxin Zones and Different Synaptotagmin N-Terminus Labelling Following Stimulation

Journal of Neurocytology, Aug 1, 1997

A study has been made of the probability of exocytosis of synaptic vesicles at different varicosi... more A study has been made of the probability of exocytosis of synaptic vesicles at different varicosities in single sympathetic terminal axons in the mouse vas deferens. An antibody (SV2Ab) against SV2, a proteoglycan in synaptic vesicles, labelled an area of individual sympathetic varicosities that was slightly less than that occupied by dextran-rhodamine, previously orthogradely transported into the varicosities. In contrast plasma membrane bound protein syntaxin, found at active zones of motor nerve terminals, occupied an area of the varicosity that was approximately one-third that of SV2. This suggests that sympathetic varicosities possess specialized zones for exocytosis on their plasma membranes. Antibodies against the Nterminal sequence of synaptotagmin 1 (SNAb), a sequence exposed within synaptic vesicles, were used to determine the probability of exocytosis at different varicosities of single terminal branches. The area of SNAb labelling was not significantly different from that of the SV2 labelling, which implies vesicles that have undergone exocytosis may eventually return to the main pool of vesicles. Varicosities belonging to the same terminal axon, and identified with SV2Ab, showed different extents of labelling with SNAb when secretion was evoked with high potassium concentrations (80 mM) for 30 min in the presence of SNAb. There was up to an order of magnitude difference in the average intensity of SNAb labelling between different varicosities of the same terminal axon whereas there was little difference in the average intensity of SV2Ab labelling. These observations suggest that there is considerable variability in the probability of exocytosis at the specialized zones in different varicosities.

Research paper thumbnail of Actions of Two Main Metabolites of Propiverine (M-1 and M-2) on Voltage-Dependent L-Type Ca2+ Currents and Ca2+ Transients in Murine Urinary Bladder Myocytes

J Pharmacol Exp Ther, 2007

The anticholinergic propiverine, used for the treatment of overactive bladder (OAB) syndrome, has... more The anticholinergic propiverine, used for the treatment of overactive bladder (OAB) syndrome, has functionally active metabolites (M-1 and M-2), but the site of actions of these metabolites is uncertain. Propiverine is rapidly absorbed after oral administration and is extensively biotransformed in the liver, giving rise to several active metabolites (M-1, the propiverine Noxide, and M-2, the N-oxide lacking the aliphatic side chain). This study determines the effect of M-1 and M-2 on voltage-dependent nifedipine-sensitive inward Ca 2+ currents (I Ca ) using patchclamp techniques and fluorescent Ca 2+ imaging (following electrical field stimulation (EFS) and acetylcholine (ACh)) in the murine urinary bladder. In conventional whole-cell recording, propiverine and M-1 but not M-2 inhibited the peak amplitude of I Ca in a concentration-dependent manner at a holding potential of −60 mV (propiverine, K i = 10 μM; M-1, K i = 118 μM). M-1 shifted the steady-state inactivation curve of I Ca to the left at −90 mV by 7 mV. Carbachol (CCh) reversibly inhibited I Ca . This inhibition probably occurred through muscarinic type 3 receptors, coupling with G-proteins, since nanomolar concentrations of 4-DAMP greatly reduced this inhibition, while pirenzepine or AF-DX 116 at concentrations up to 1 μM were almost ineffective. In the presence of M-2, the CCh-induced inhibition of I Ca was blocked. In fluorescent Ca 2+ imaging, M-2 inhibited EFS-induced and ACh-induced Ca 2+ transients. These results suggest that M-1 acts, at least in part, as a Ca 2+ channel antagonist (as it inhibited I Ca ), while M-2 has more direct antimuscarinic actions.

Research paper thumbnail of Effects of nicotine on intracellular calcium dynamics in sympathetic nerve terminal varicosities

Research paper thumbnail of Effects of nicotine on calcium dynamics in sympathetic nerve terminals: role of calcium-induced calcium release

Research paper thumbnail of Imaging of neurones and effector cells

Research paper thumbnail of Cellular mechanisms of prostaglandin E2 on mouse urinary bladder

Research paper thumbnail of Changes in calcium dynamics in sympathetic nerve terminal varicosities evoked by nicotinic acetylcholine receptor agonists

Research paper thumbnail of Axonal calcium transients in preterminal sympathetic neurones

Research paper thumbnail of Characterising ATP release from each varicosity on a nerve terminal branch on an impulse-to-impulse basis in the mouse isolated vas deferens

Research paper thumbnail of Nerve-evoked calcium transients in sympathetic axons of mouse vas deferens are modulated by K-A and K-V but not by K-Ca

Research paper thumbnail of A novel, high resolution method to study ATP release from single varicosities on an impulse-to-impulse basis in the mouse isolated vas deferens

Research paper thumbnail of Neuroeffector Ca2+ transients: a method to monitor the packeted release of ATP on an impulse-to-impulse basis in rodent vas deferens

Research paper thumbnail of m-Chlorophenylbiguanide inhibits neurotransmitter release and nerve terminal Ca2+ influx independently of 5-HT3 receptors in the mouse vas deferens

Research paper thumbnail of Syncytial Basis for Diversity in Spike Shapes and their Propagation in Detrusor Smooth Muscle

Procedia Computer Science, 2015

ABSTRACT Syncytial tissues, such as the smooth muscle of the urinary bladder wall, are known to p... more ABSTRACT Syncytial tissues, such as the smooth muscle of the urinary bladder wall, are known to produce action potentials (spikes) with marked differences in their shapes and sizes. The need for this diversity is currently unknown, and neither is their origin understood. The small size of the cells, their syncytial arrangement, and the complex nature of innervation poses significant challenges for the experimental investigation of such tissues. To obtain better insight, we present here a three-dimensional electrical model of smooth muscle syncytium, developed using the compartmental modeling technique, with each cell possessing active channel mechanisms capable of producing an action potential. This enables investigation of the syncytial effect on action potential shapes and their propagation. We show how a single spike shape could undergo modulation, resulting in diverse shapes, owing to the syncytial nature of the tissue. Differences in the action potential features could impact their capacity to propagate through a syncytium. This is illustrated through comparison of two distinct action potential mechanisms. A better understanding of the origin of the various spike shapes would have significant implications in pathology, assisting in evaluating the underlying cause and directing their treatment.

Research paper thumbnail of A computational model of urinary bladder smooth muscle syncytium : validation and investigation of electrical properties

Journal of computational neuroscience, 2015

Certain smooth muscles, such as the detrusor of the urinary bladder, exhibit a variety of spikes ... more Certain smooth muscles, such as the detrusor of the urinary bladder, exhibit a variety of spikes that differ markedly in their amplitudes and time courses. The origin of this diversity is poorly understood but is often attributed to the syncytial nature of smooth muscle and its distributed innervation. In order to help clarify such issues, we present here a three-dimensional electrical model of syncytial smooth muscle developed using the compartmental modeling technique, with special reference to the bladder detrusor. Values of model parameters were sourced or derived from experimental data. The model was validated against various modes of stimulation employed experimentally and the results were found to accord with both theoretical predictions and experimental observations. Model outputs also satisfied criteria characteristic of electrical syncytia such as correlation between the spatial spread and temporal decay of electrotonic potentials as well as positively skewed amplitude fre...

Research paper thumbnail of Ion channel modulators and urinary tract function

Handbook of experimental pharmacology, 2011

The membrane potential fulfils an important role in initiating smooth muscle contraction, through... more The membrane potential fulfils an important role in initiating smooth muscle contraction, through its depolarization and the subsequent influx of Ca(2+) through voltage-gated Ca(2+) channels. Changes in membrane potential can also coordinate contraction across great distances, utilizing the speed of electrical current flow through gap junctions. Hence, regulating membrane potential can greatly influence smooth muscle function. In this chapter, we will consider the influence of ion channels, as dynamic gatekeepers of membrane permeability, on urogenital function. Through their ability to act as key regulators of both the resting membrane potential and its dynamic changes, they provide important pharmacological targets for influencing urogenital function.Urogenital smooth muscle and urothelia contain a diverse range of molecularly and functionally distinct K(+) channels, which are key to regulating the resting membrane and for re-establishing the normal membrane potential following bo...

Research paper thumbnail of Calcium in sympathetic boutons of rat superior cervical ganglion during facilitation, augmentation and potentiation

Journal of the autonomic nervous system, Jan 27, 1998

The sympathetic preganglionic nerve terminals of the rat superior cervical ganglion were loaded w... more The sympathetic preganglionic nerve terminals of the rat superior cervical ganglion were loaded with the calcium indicator oregon green 488 BAPTA-1 to measure the change in calcium concentration in the terminal boutons, (delta[Ca2+]b) following short (1 or 5 impulses) and long (200 impulses) trains at 30 Hz. The delta[Ca2+]b after a single action potential or a short train declined in two phases: a fast phase with a time constant of 530+/-30 ms and a moderate phase with a time constant of 4.0+/-0.2 s. The delta[Ca2+]b following a long train eventually declined with a time constant of 127+/-34 s (slow phase). The addition of either omega-agatoxin TK (100 nM), omega-conotoxin GVIA (100 nM) or nifedipine (20 microM) to block P-type, N-type or L-type calcium channels respectively showed that the rise in delta[Ca2+ ]b in boutons was predominantly mediated by an influx of calcium through P-type (53+/-7%) and N-type (46+/-4%) calcium channels. Experiments with caffeine, ryanodine and thaps...

Research paper thumbnail of Simultaneous electrophysiology and Ca 2+ imaging during neurotransmission in rat anococcygeus smooth muscle

Auton Neurosci Basic Clin, 2007

Research paper thumbnail of Electrical and optical study of nerve impulse-evoked ATP-induced, P2X-receptor-mediated sympathetic neurotransmission at single smooth muscle cells in mouse isolated vas deferens

Neuroscience, Aug 10, 2007

Simultaneous electrophysiology and confocal microscopy were used to investigate purinergic neurot... more Simultaneous electrophysiology and confocal microscopy were used to investigate purinergic neurotransmission at single smooth muscle cells (SMCs) in mouse isolated vas deferens, and to explore the relationship between two high-resolution P2X-receptor-mediated measures of per pulse ATP release: transient peaks in the first time derivative of the rising phase of excitatory junction potentials (EJPs) recorded in single SMCs ('discrete events'; DEs) and neuroeffector Ca 2+ transients (NCTs) in the impaled SMCs.

Research paper thumbnail of Autonomic synaptic transmission at single boutons and calyces

Journal of Neurocytology, Oct 1, 1997

Research paper thumbnail of Varicosities of Single Sympathetic Nerve Terminals Possess Syntaxin Zones and Different Synaptotagmin N-Terminus Labelling Following Stimulation

Journal of Neurocytology, Aug 1, 1997

A study has been made of the probability of exocytosis of synaptic vesicles at different varicosi... more A study has been made of the probability of exocytosis of synaptic vesicles at different varicosities in single sympathetic terminal axons in the mouse vas deferens. An antibody (SV2Ab) against SV2, a proteoglycan in synaptic vesicles, labelled an area of individual sympathetic varicosities that was slightly less than that occupied by dextran-rhodamine, previously orthogradely transported into the varicosities. In contrast plasma membrane bound protein syntaxin, found at active zones of motor nerve terminals, occupied an area of the varicosity that was approximately one-third that of SV2. This suggests that sympathetic varicosities possess specialized zones for exocytosis on their plasma membranes. Antibodies against the Nterminal sequence of synaptotagmin 1 (SNAb), a sequence exposed within synaptic vesicles, were used to determine the probability of exocytosis at different varicosities of single terminal branches. The area of SNAb labelling was not significantly different from that of the SV2 labelling, which implies vesicles that have undergone exocytosis may eventually return to the main pool of vesicles. Varicosities belonging to the same terminal axon, and identified with SV2Ab, showed different extents of labelling with SNAb when secretion was evoked with high potassium concentrations (80 mM) for 30 min in the presence of SNAb. There was up to an order of magnitude difference in the average intensity of SNAb labelling between different varicosities of the same terminal axon whereas there was little difference in the average intensity of SV2Ab labelling. These observations suggest that there is considerable variability in the probability of exocytosis at the specialized zones in different varicosities.

Research paper thumbnail of Actions of Two Main Metabolites of Propiverine (M-1 and M-2) on Voltage-Dependent L-Type Ca2+ Currents and Ca2+ Transients in Murine Urinary Bladder Myocytes

J Pharmacol Exp Ther, 2007

The anticholinergic propiverine, used for the treatment of overactive bladder (OAB) syndrome, has... more The anticholinergic propiverine, used for the treatment of overactive bladder (OAB) syndrome, has functionally active metabolites (M-1 and M-2), but the site of actions of these metabolites is uncertain. Propiverine is rapidly absorbed after oral administration and is extensively biotransformed in the liver, giving rise to several active metabolites (M-1, the propiverine Noxide, and M-2, the N-oxide lacking the aliphatic side chain). This study determines the effect of M-1 and M-2 on voltage-dependent nifedipine-sensitive inward Ca 2+ currents (I Ca ) using patchclamp techniques and fluorescent Ca 2+ imaging (following electrical field stimulation (EFS) and acetylcholine (ACh)) in the murine urinary bladder. In conventional whole-cell recording, propiverine and M-1 but not M-2 inhibited the peak amplitude of I Ca in a concentration-dependent manner at a holding potential of −60 mV (propiverine, K i = 10 μM; M-1, K i = 118 μM). M-1 shifted the steady-state inactivation curve of I Ca to the left at −90 mV by 7 mV. Carbachol (CCh) reversibly inhibited I Ca . This inhibition probably occurred through muscarinic type 3 receptors, coupling with G-proteins, since nanomolar concentrations of 4-DAMP greatly reduced this inhibition, while pirenzepine or AF-DX 116 at concentrations up to 1 μM were almost ineffective. In the presence of M-2, the CCh-induced inhibition of I Ca was blocked. In fluorescent Ca 2+ imaging, M-2 inhibited EFS-induced and ACh-induced Ca 2+ transients. These results suggest that M-1 acts, at least in part, as a Ca 2+ channel antagonist (as it inhibited I Ca ), while M-2 has more direct antimuscarinic actions.

Research paper thumbnail of Effects of nicotine on intracellular calcium dynamics in sympathetic nerve terminal varicosities

Research paper thumbnail of Effects of nicotine on calcium dynamics in sympathetic nerve terminals: role of calcium-induced calcium release

Research paper thumbnail of Imaging of neurones and effector cells

Research paper thumbnail of Cellular mechanisms of prostaglandin E2 on mouse urinary bladder

Research paper thumbnail of Changes in calcium dynamics in sympathetic nerve terminal varicosities evoked by nicotinic acetylcholine receptor agonists

Research paper thumbnail of Axonal calcium transients in preterminal sympathetic neurones

Research paper thumbnail of Characterising ATP release from each varicosity on a nerve terminal branch on an impulse-to-impulse basis in the mouse isolated vas deferens

Research paper thumbnail of Nerve-evoked calcium transients in sympathetic axons of mouse vas deferens are modulated by K-A and K-V but not by K-Ca

Research paper thumbnail of A novel, high resolution method to study ATP release from single varicosities on an impulse-to-impulse basis in the mouse isolated vas deferens

Research paper thumbnail of Neuroeffector Ca2+ transients: a method to monitor the packeted release of ATP on an impulse-to-impulse basis in rodent vas deferens

Research paper thumbnail of m-Chlorophenylbiguanide inhibits neurotransmitter release and nerve terminal Ca2+ influx independently of 5-HT3 receptors in the mouse vas deferens

Research paper thumbnail of Syncytial Basis for Diversity in Spike Shapes and their Propagation in Detrusor Smooth Muscle

Procedia Computer Science, 2015

ABSTRACT Syncytial tissues, such as the smooth muscle of the urinary bladder wall, are known to p... more ABSTRACT Syncytial tissues, such as the smooth muscle of the urinary bladder wall, are known to produce action potentials (spikes) with marked differences in their shapes and sizes. The need for this diversity is currently unknown, and neither is their origin understood. The small size of the cells, their syncytial arrangement, and the complex nature of innervation poses significant challenges for the experimental investigation of such tissues. To obtain better insight, we present here a three-dimensional electrical model of smooth muscle syncytium, developed using the compartmental modeling technique, with each cell possessing active channel mechanisms capable of producing an action potential. This enables investigation of the syncytial effect on action potential shapes and their propagation. We show how a single spike shape could undergo modulation, resulting in diverse shapes, owing to the syncytial nature of the tissue. Differences in the action potential features could impact their capacity to propagate through a syncytium. This is illustrated through comparison of two distinct action potential mechanisms. A better understanding of the origin of the various spike shapes would have significant implications in pathology, assisting in evaluating the underlying cause and directing their treatment.

Research paper thumbnail of A computational model of urinary bladder smooth muscle syncytium : validation and investigation of electrical properties

Journal of computational neuroscience, 2015

Certain smooth muscles, such as the detrusor of the urinary bladder, exhibit a variety of spikes ... more Certain smooth muscles, such as the detrusor of the urinary bladder, exhibit a variety of spikes that differ markedly in their amplitudes and time courses. The origin of this diversity is poorly understood but is often attributed to the syncytial nature of smooth muscle and its distributed innervation. In order to help clarify such issues, we present here a three-dimensional electrical model of syncytial smooth muscle developed using the compartmental modeling technique, with special reference to the bladder detrusor. Values of model parameters were sourced or derived from experimental data. The model was validated against various modes of stimulation employed experimentally and the results were found to accord with both theoretical predictions and experimental observations. Model outputs also satisfied criteria characteristic of electrical syncytia such as correlation between the spatial spread and temporal decay of electrotonic potentials as well as positively skewed amplitude fre...

Research paper thumbnail of Ion channel modulators and urinary tract function

Handbook of experimental pharmacology, 2011

The membrane potential fulfils an important role in initiating smooth muscle contraction, through... more The membrane potential fulfils an important role in initiating smooth muscle contraction, through its depolarization and the subsequent influx of Ca(2+) through voltage-gated Ca(2+) channels. Changes in membrane potential can also coordinate contraction across great distances, utilizing the speed of electrical current flow through gap junctions. Hence, regulating membrane potential can greatly influence smooth muscle function. In this chapter, we will consider the influence of ion channels, as dynamic gatekeepers of membrane permeability, on urogenital function. Through their ability to act as key regulators of both the resting membrane potential and its dynamic changes, they provide important pharmacological targets for influencing urogenital function.Urogenital smooth muscle and urothelia contain a diverse range of molecularly and functionally distinct K(+) channels, which are key to regulating the resting membrane and for re-establishing the normal membrane potential following bo...

Research paper thumbnail of Calcium in sympathetic boutons of rat superior cervical ganglion during facilitation, augmentation and potentiation

Journal of the autonomic nervous system, Jan 27, 1998

The sympathetic preganglionic nerve terminals of the rat superior cervical ganglion were loaded w... more The sympathetic preganglionic nerve terminals of the rat superior cervical ganglion were loaded with the calcium indicator oregon green 488 BAPTA-1 to measure the change in calcium concentration in the terminal boutons, (delta[Ca2+]b) following short (1 or 5 impulses) and long (200 impulses) trains at 30 Hz. The delta[Ca2+]b after a single action potential or a short train declined in two phases: a fast phase with a time constant of 530+/-30 ms and a moderate phase with a time constant of 4.0+/-0.2 s. The delta[Ca2+]b following a long train eventually declined with a time constant of 127+/-34 s (slow phase). The addition of either omega-agatoxin TK (100 nM), omega-conotoxin GVIA (100 nM) or nifedipine (20 microM) to block P-type, N-type or L-type calcium channels respectively showed that the rise in delta[Ca2+ ]b in boutons was predominantly mediated by an influx of calcium through P-type (53+/-7%) and N-type (46+/-4%) calcium channels. Experiments with caffeine, ryanodine and thaps...