| Abstract: | Superfusion of the isolated sympathetic ganglia of the frog with nicotinic agonists (suberyldicholine, tetramethylamonium, and dimethylphenylpiperazinium), as well as acetylcholine in the presence of atropine led to a brief depolarization of the neurons and blockade of synaptic transmission. The muscarinic agonists methylfurmethide (MFM) and methyldilvasen, cis–, L(+), as well as acetylcholine elicited a stable depolarization which is not accompanied by disturbance in transmission. Oxotremorine at a concentration of 1·10–5 M did not lead to the depolarization of the post-synaptic membrane, but at a concentration of 1·10–6 M decreased the quantal EPSP content twofold, which indicates that the presynaptic receptors belong to the M2 subtype. Inhibition of acetylcholinesterase significantly intensified the postsynaptic effect of MFM: a shift of the concentration-effect curve took place toward the side of lower MFM concentrations. It was shown that the post-synaptic muscarinic receptors of the ganglionic neurons possess varied sensitivity to the enantiomers of methyldilvasen and, consequently, are stereospecific. The identified functional properties of the cholinoreceptors of the ganglionic neurons explain the set of changes in synaptic transmission under conditions of the prolonged presence of a mediator in the synaptic cleft.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 227–234, March–April, 1988. |
