Resurgent-like currents in mouse vas deferens myocytes are mediated by NaV1.6 voltage-gated sodium channels.

Patch-clamp experiments were performed to investigate the molecular properties of resurgent-like currents in single smooth muscle cells dispersed from mouse vas deferens, utilizing both Na(V)1.6-null mice (Na(V)1.6(-/-)), lacking the expression of the Scn8a Na(+) channel gene, and their wild-type littermates (Na(V)1.

Mechanisms involved in nicotinic acetylcholine receptor-induced neurotransmitter release from sympathetic nerve terminals in the mouse vas deferens.

Prejunctional nicotinic acetylcholine receptors (nAChRs) amplify postganglionic sympathetic neurotransmission, and there are indications that intraterminal Ca(2+) stores might be involved. However, the mechanisms by which nAChR activation stimulates neurotransmitter release at such junctions is unknown. Rapid local delivery (picospritzing) of the nAChR agonist epibatidine was combined with intracellular sharp microelectrode recording to monitor spontaneous and field-stimulation-evoked neurotransmitter release from sympathetic nerve terminals in the mouse isolated vas deferens.

Actions of veratridine on tetrodotoxin-sensitive voltage-gated Na currents, Na1.6, in murine vas deferens myocytes.

Background And Purpose: The effects of veratridine, an alkaloid found in Liliaceae plants, on tetrodotoxin (TTX)-sensitive voltage-gated Na(+) channels were investigated in mouse vas deferens.

Experimental Approach: Effects of veratridine on TTX-sensitive Na(+) currents (I(Na)) in vas deferens myocytes dispersed from BALB/c mice, homozygous mice with a null allele of Na(V)1.6 (Na(V)1.

High spatial resolution studies of muscarinic neuroeffector junctions in mouse isolated vas deferens.

It is acknowledged that neurotransmission in the mouse vas deferens is predominantly mediated by ATP and noradrenaline (NA) released from sympathetic nerves while cholinergic transmission in the rodent vas deferens is often overlooked despite early literature. Recently we have characterized a cholinergic component of neurogenic contraction of mouse isolated vas deferens. In the present paper, by confocal imaging of Ca(2+) dynamics we detected acetylcholine (ACh) action at muscarinic cholinergic neuroeffector junctions at high-resolution.

Actions of kurtoxin on tetrodotoxin-sensitive voltage-gated Na+ currents, NaV1.6, in murine vas deferens myocytes.

Kurtoxin is described as a selective inhibitor of Ca(V)3.1. Using patch-clamp techniques, the modulatory effects of kurtoxin on tetrodotoxin-sensitive voltage-gated Na(+) currents (I(Na)) recorded from mouse vas deferens myocytes were investigated.

Spontaneous purinergic neurotransmission in the mouse urinary bladder.

Spontaneous purinergic neurotransmission was characterized in the mouse urinary bladder, a model for the pathological or ageing human bladder. Intracellular electrophysiological recording from smooth muscle cells of the detrusor muscle revealed spontaneous depolarizations, distinguishable from spontaneous action potentials (sAPs) by their amplitude (< 40 mV) and insensitivity to the L-type Ca(2+) channel blocker nifedipine (1 microm) (100 +/- 29%). Spontaneous depolarizations were abolished by the P2X(1) receptor antagonist NF449 (10 microm) (frequency 8.

Molecular and biophysical properties of voltage-gated Na+ channels in murine vas deferens.

The biological and molecular properties of tetrodotoxin (TTX)-sensitive voltage-gated Na(+) currents (I(Na)) in murine vas deferens myocytes were investigated using patch-clamp techniques and molecular biological analyses. In whole-cell configuration, a fast, transient inward current was evoked in the presence of Cd(2+), and was abolished by TTX (K(d) = 11.2 nM), mibefradil (K(d) = 3.

Bretylium abolishes neurotransmitter release without necessarily abolishing the nerve terminal action potential in sympathetic terminals.

Background And Purpose: The antidysrhythmic bretylium is useful experimentally because it selectively abolishes neurotransmitter release from sympathetic peripheral nerve terminals. Its mechanism of action seemed settled, but recent results from optical monitoring of single terminals now suggests a new interpretation.

Experimental Approach: Orthograde transport of a dextran-conjugated Ca(2+) indicator to monitor Ca(2+) in nerve terminals of mouse isolated vas deferens with a confocal microscope.

Cholinergic innervation of the guinea-pig isolated vas deferens.

Recently, a cholinergic neurogenic component of contraction has been characterised in the aganglionic mouse vas deferens. In this paper, a cholinergic component of contraction in the guinea-pig vas deferens is characterised pharmacologically. A residual, tetrodotoxin-sensitive (TTX, 0.

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.

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. This study shows that discrete events represent neurotransmitter release onto the impaled cell. First, the median amplitude of the first derivative of the EJP was larger when there was a coincident NCT in the impaled cell, compared with instances when no coincident NCT occurred.

The effect of epibatidine on spontaneous and evoked neurotransmitter release in the mouse and guinea pig isolated vas deferens.

Background And Purpose: Nicotinic agonists increase sympathetic field-stimulus-evoked contraction of the rodent vas deferens, presumably by increasing evoked neurotransmitter release. This presumption was tested in two species.

Experimental Approach: The effect of the nicotinic acetylcholine receptor (nAChR) agonist epibatidine on neurotransmitter release in mouse and guinea pig isolated vas deferens was investigated using contraction studies and conventional intracellular recording techniques.

The origin of the skewed amplitude distribution of spontaneous excitatory junction potentials in poorly coupled smooth muscle cells.

The skewed amplitude distribution of spontaneous excitatory junction potentials (sEJPs) in the mouse vas deferens and other electrically-coupled smooth muscle syncytia has been attributed to electrically-attenuated depolarizations resulting from the spontaneous release of quantized packets of ATP acting on remote smooth muscle cells (SMCs). However, in the present investigation surface SMCs of the mouse isolated vas deferens were poorly electrically coupled, with input resistances (176+/-18 MOmega, range: 141-221 MOmega, n=4) similar to those of dissociated cells. Furthermore, the amplitude of evoked EJPs was more variable in surface compared with deeper SMCs (F test, F=17.

Cholinergic innervation of the mouse isolated vas deferens.

Recently, a population of nerves has been described in the aganglionic mouse vas deferens, in which electrically evoked contractions were insensitive to high concentrations of the adrenergic neurone blocker, bretylium. In this paper, the pharmacology of this nerve-evoked contraction has been examined in more detail. Bretylium (20 microM) revealed, after 5 h exposure, a new residual neurogenic contraction (20 stimuli at 10 Hz) that was tetrodotoxin-sensitive.

Correlation of non-uniform protein expression with variation in transmitter release probability.

The strength of synaptic transmission is highly variable between different synapses. The present study examined some factors that may contribute to this variation in the strength of neurotransmission in sympathetic varicosities of the mouse vas deferens. Transmitter release was measured using a focal macropatch electrode placed over pairs of visualised varicosities.

Electrophysiological properties of inhibitory junction potential in murine lower oesophageal sphincter.

The electrophysiological properties of smooth muscle in the murine lower oesophageal sphincter (LOS) were investigated by intracellular microelectrode recording. Inhibitory junction potentials (IJPs) evoked by trains of field stimulation (30 V, 0.2-0.

The sources and sequestration of Ca(2+) contributing to neuroeffector Ca(2+) transients in the mouse vas deferens.

The detection of focal Ca(2+) transients (called neuroeffector Ca(2+) transients, or NCTs) in smooth muscle of the mouse isolated vas deferens has been used to detect the packeted release of ATP from nerve terminal varicosities acting at postjunctional P2X receptors. The present study investigates the sources and sequestration of Ca(2+) in NCTs. Smooth muscle cells in whole mouse deferens were loaded with the Ca(2+) indicator Oregon Green 488 BAPTA-1 AM and viewed with a confocal microscope.

Regional variation in electrically-evoked contractions of rabbit isolated pulmonary artery.

1. Electrically-evoked contractions in different regions of the rabbit isolated pulmonary artery have been investigated using stimulation parameters generally assumed to stimulate nerves selectively. 2.

Intermittent ATP release from nerve terminals elicits focal smooth muscle Ca2+ transients in mouse vas deferens.

A confocal Ca2+ imaging technique has been used to detect ATP release from individual sympathetic varicosities on the same nerve terminal branch. Varicose nerve terminals and smooth muscle cells in mouse vas deferens were loaded with the Ca2+ indicator Oregon Green 488 BAPTA-1. Field (nerve) stimulation evoked discrete, focal increases in [Ca2+] in smooth muscle cells adjacent to identified varicosities.

Bretylium or 6-OHDA-resistant, action potential-evoked Ca2+ transients in varicosities of the mouse vas deferens.

Action potential-evoked calcium transients in varicosities in mouse vas deferens were monitored using laser scanning confocal microscopy. Their significance was examined by comparison with excitatory junction potentials (EJPs) and neurogenic contractions, both indirect measurements of transmitter release. Bretylium abolished EJPs, as well as the ATP and NA-mediated phases of contraction.

Mechanical and electrophysiological effects of endothelin-1 on guinea-pig isolated lower oesophageal sphincter circular smooth muscle.

1. The effects of endothelin-1 (ET-1) on guinea-pig lower oesophageal sphincter (LOS) circular smooth muscle were investigated by using intracellular microelectrodes and isometric tension recording techniques. 2.

Effect of chronic clonidine treatment on transmitter release from sympathetic varicosities of the guinea-pig vas deferens.

1. Previous studies have demonstrated that chronic pre-synaptic inhibition of transmitter release by morphine evokes a counter-adaptive response in the sympathetic nerve terminals that manifests itself as an increase in transmitter release during acute withdrawal. In the present study we examined the possibility that other pre-synaptically acting drugs such as clonidine also evoke a counter-adaptive response in the sympathetic nerve terminals.

Characterization of action potential-evoked calcium transients in mouse postganglionic sympathetic axon bundles.

1. Action potential-evoked Ca(2+) transients in postganglionic sympathetic axon bundles in mouse vas deferens have been characterized using confocal microscopy and Ca(2+) imaging. 2.

Neurotransmitter release mechanisms in sympathetic neurons: past, present, and future perspectives.

In 1969, Paton and Vizi described the inhibitory actions of noradrenaline on acetylcholine release from the innervation of the guinea-pig ileum longitudinal muscle. They concluded "that acetylcholine output by the nervous networks of the longitudinal strip is under the normal control of the sympathetic by a species of presynaptic inhibition mediated by <==> receptors". This work was carried out in the Pharmacology Department at Oxford University.

Nicotine induces calcium spikes in single nerve terminal varicosities: a role for intracellular calcium stores.

While nicotine is known to act at neuronal nicotinic acetylcholine receptors (nAChRs) to facilitate neurotransmitter release, the mechanisms underlying this action are poorly understood. Some of its effects are known to be mediated by presynaptic receptors. In the mouse vas deferens nicotine (10-30 microM) transiently increased the force of neurogenic contraction by 135+/-25%, increased the amplitude of excitatory junction potentials by 74+/-6% and increased the frequency of spontaneous excitatory junction potentials in four out of six preparations.

Calcium channels controlling acetylcholine release in the guinea-pig isolated anterior pelvic ganglion: an electropharmacological study.

An electropharmacological analysis of the type(s) of calcium channel controlling neurotransmitter release in preganglionic sympathetic nerve terminals in the guinea-pig anterior pelvic ganglion has been carried out. Conventional intracellular recording techniques were used to record excitatory postsynaptic potentials as a measure of neurotransmitter release. Excitatory postsynaptic potentials were abolished by hexamethonium (30-100 microM) and are therefore mediated by acetylcholine acting at nicotinic receptors.