Slow synaptic responses in autonomic ganglia and the pursuit of a peptidergic transmitter.

摘要: This account deals with studies of slow synaptic potentials, a new peptidergic transmitter, and integrative mechanisms at synapses in vertebrate autonomic ganglia. In neurones the cardiac parasympathetic ganglia mudpuppy ( Necturus maculosus ) both rapid excitatory inhibitory potentials interact. The same acetylcholine (ACh), causes individual fast e.p.s.p. lasting up to 50 ms i.p.s.p. about 2 s. sequence processes leading these two differs important respects. Molecules ACh released by terminals vagus combine nicotinic receptors within fraction 1 initiate which, as rule, leads conducted impulse ganglion cells. resembles its ionic events seen most neuromuscular neuronal synapses. also combines muscarinic whose activation is followed an increased flow K+ ions generation There occurs, however, apparent delay over 100 between time reaches detectable conductance. During has declined disappeared from cleft. It suggested that least three distinct are involved conductances. The second part this paper describes sympathetic frog where release initiates different potentials: (i) standard (about 30-50 duration); (ii) (30–60 s); (iii) s). fourth signal, ‘late e.p.s.p.’, lasts 5–10 min not caused ACh. We have evidence peptide, resembling luteinizing hormone releasing (LHRH), secreted specific axons it late e.p.s.p.s. for such transmitter follows: (1) In nerves stimulation e.p.s.p.s one detects radioimmunoassay peptide molecular weight 1000 daltons, LHRH. (2) isotonic KCl if Ca2+ present high solution. (3) Five days after cutting appropriate presynaptic nerves, 95% disappears ganglia. At content central cut increased, suggesting concentrated transported periphery spinal cord. (4) Application synthetic LHRH mimics action nerve-released manner. Both substances cause similar changes postsynaptic membrane conductance excitability neurones, depolarizing effect agents parallel when hyperpolarized. (5) An analogue which mammals blocks gonadotropins applied Similar actions occur application other analogues LHRH, some more potent agonists, others effective. natural act on receptors. The role way they influence effectiveness cholinergic discussed. Since various interact cells, suitable study mechanisms.