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It is generally accepted that there is a functional antagonism between the sympathetic and parasympathetic (vagal) effects on the heart. In this study guinea-pig right atria loaded either with [3H]noradrenaline or [3H]choline were used and the release of [3H]noradrenaline or [3H]acetylcholine in response to field stimulation was measured under conditions(More)
In order to extend the characterization of muscarinic receptors at presynaptic sites their inhibitory effect on the stimulation-evoked release of [3H]noradrenaline and [3H]acetylcholine from different axon terminals was studied and the dissociation constants and potencies of different antagonists were estimated, in guinea-pig and rat. While oxotremorine(More)
The effects of nicotine and dimethylphenylpiperazinium (DMPP) on resting and stimulation-evoked release of [3H]-acetylcholine ([3H]ACh) from cholinergic interneurons and neuro-effector neurons of the ileal longitudinal muscle and the responses of the smooth muscle to nicotinic agonists were studied. (-)-Nicotine was 15 times more effective than (+)-nicotine(More)
The postsynaptic antimuscarinic properties of different nondepolarizing muscle relaxants were compared with their postsynaptic antinicotinic effect. d-Tubocurarine, pipecuronium and vecuronium were the most selective antagonists on postsynaptic nicotinic receptors. Gallamine, diadonium and Duador (RGH-4201) had relatively greater effect on postsynaptic(More)
The effect of neurotensin (NT) on the release of acetylcholine (ACh) and dopamine (DA) from striatal slices of the rat brain was studied. Neurotensin, 1-150 nM, was able to release ACh from cholinergic interneurons of the striatum. Like the response to electrical stimulation, the ACh-releasing effect of NT was completely inhibited by tetrodotoxin indicating(More)
Stores of transmitter, labelled with [3H]choline, were used to study the negative feedback modulation of the release of acetylcholine by presynaptic M2 muscarinic receptors. The release of acetylcholine was measured by radioassaying the electrical stimulation-evoked release of [3H]acetylcholine from slices of cerebral cortex of the rat and from the Auerbach(More)
The effect of 4-aminopyridine, a potassium channel blocker on the muscarinic and opiate modulation of acetylcholine release, was investigated. Rat frontal cortical slices were loaded with [3H]choline, superfused continuously, and stimulated electrically. 4-Aminopyridine enhanced the stimulation-evoked release of tritium without affecting basal release. The(More)
Three different tissue preparations were used to demonstrate the heterogeneity of presynaptic muscarinic receptors that modulate neurotransmitter release. The presynaptic antimuscarinic potency of several muscarinic antagonists was characterized with the enhancement of the neurotransmitter release evoked by electrical stimulation on the guinea-pig ileum(More)
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