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Results for “Excitatory Postsynaptic Potentials”

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At least 91 records · Page 5Linked to original sources
PubMed1994

A slow excitatory postsynaptic potential mediated by 5-HT2 receptors in nucleus prepositus hypoglossi.

Intracellular recordings were made from neurons of the nucleus prepositus hypoglossi in slices of guinea pig medulla. 5-HT (serotonin) caused a hyperpolarization followed by a late depolarization. The hyperpolarization was mediated by 5-HT1A receptor activation and could be selectively blocked by pindobind-5HT1A (PBD). 5-HT then caused a depolarization only. A selective 5-HT2 agonist, (+)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), also caused a depolarization. Ketanserin and spiperone, 5-HT2 antagonists, blocked the depolarization due to both 5-HT and DOI. Focal electrical stimulation caused an IPSP mediated by 5-HT acting upon 5-HT1A receptors and a slow EPSP (s-EPSP). PBD blocked the IPSP, leaving an isolated s-EPSP. Both spiperone and ketanserin antagonized the s-EPSP, while DOI occluded it. The s-EPSP was from 2 to 10 mV in amplitude and 35-50 sec in duration, and showed voltage dependence consistent with a decrease in potassium conductance. Both the IPSP and the s-EPSP were presynaptically inhibited by the 5-HT1D agonist sumatriptan. These data indicate that the s-EPSP is mediated by 5-HT acting upon 5-HT2 receptors. This represents strong support for the role of 5-HT as an excitatory neurotransmitter in the CNS. Further, it demonstrates that synaptic release of 5-HT can mediate opposing effects on the membrane potential of a single cell.

Amphetamines↗
PubMed1987

Neurokinin A in capsaicin-sensitive neurons of the guinea-pig inferior mesenteric ganglia: an additional putative mediator for the non-cholinergic excitatory postsynaptic potential.

The presence of neurokinin-A-like immunoreactivity in guinea-pig inferior mesenteric ganglia was detected by radioimmunoassay procedures. Pretreating the animals with capsaicin 7 days prior to experimentations reduced the mean content of neurokinin-A-like immunoreactivity by 85% from its control value of 150 +/- 31.3 fmol per ganglion. High-performance liquid chromatography revealed that neurokinin-A-like immunoreactivity was heterogenous as in addition to neurokinin A, peaks corresponding to the amphibian tachykinin eledoisin and to neuropeptide K were detected, and they too were depleted by capsaicin. Electrophysiological studies showed that neurokinin A applied either by superfusion or by pressure ejection evoked a slow depolarization in the majority of inferior mesenteric ganglia neurons in vitro. Neurokinin-A-evoked depolarizations in the majority of cells tested were associated with a small increase in membrane input resistance. However, the responses were increased by membrane hyperpolarization: the extrapolated mean equilibrium potential of neurokinin-A-induced depolarization was -36 mV. Removal of extracellular sodium but not chloride ions suppressed the neurokinin-A-induced depolarization. The slow depolarization elicited either by exogenously applied substance P or by repetitive stimulation of hypogastric nerves was reversibly eliminated in the presence of neurokinin A. Collectively, our studies suggest that neurokinin-A-like immunoreactivity may coexist with substance-P-like immunoreactivity in capsaicin-sensitive fibers in the guinea-pig prevertebral ganglia and that the similarity of the actions of neurokinin A on the one hand and substance P on the other raises the possibility that non-cholinergic excitatory potentials elicited in the inferior mesenteric ganglia may be generated by not one but a number of closely related tachykinins.

Animals↗
PubMed1988

A novel muscarinic receptor antagonist AF-DX 116 differentially blocks slow inhibitory and slow excitatory postsynaptic potentials in the rabbit sympathetic ganglia.

Muscarinic, slow postsynaptic potentials (s-epsp and s-ipsp) in the rabbit superior cervical ganglia were shown to be differentially depressed by a novel cardioselective M2-type antagonist AF-DX 116: it antagonized the s-ipsp with IC50 value of 1.5 X 10(-7) M, which is 16-fold more potent in depressing the s-ipsp than the s-epsp. A hyperpolarizing component in the biphasic potential changes induced by a muscarinic agonist, methacholine, was selectively eliminated by this antagonist. AF-DX 116 was thus shown to be an useful tool for discriminating the M2-type muscarinic responses from those of M1-type in the nervous system.

Action Potentials↗
PubMed1970

Excitatory postsynaptic potential and monosynaptic reflex discharge of spinal motoneurons during anoxic insult.

Almost universally held is the concept that in transmission from one neuron to another the so-called postsynaptic potential is the essential step leading to discharge of the secondary neurons. According to the present experiments this is not so in the monosynaptic reflex system of the cat spinal cord. Its role in facilitation of response and certain other essential data are mentioned.

Animals↗