| Abstract: | Involvement of the adenylate cyclase system in cholinergic modulation of synaptic transmission was investigated in area CA1 in rat hippocampal slices. Microiontophoretic application of acetylcholine as well as addition of carbachol to the superfusate or of tolbutamide (a cAMP-dependent protein kinase inhibitor) depressed transmission at synapses formed by Schaffer collaterals and commissural fibers with dendrites of pyramidal cells belonging to hippocampal area CA1. Both numbers of free quanta of neurotransmitter and the likelihood of transmitter release decreased following carbachol action. Atropine suppressed the inhibitory action of carbachol on synaptic transmission. Dibutyryl cAMP and forskolin increased the amplitude of synaptic potentials and suppressed, either partially or in full, the inhibitory effects of cholinomimetics on synaptic potentials. It was concluded that cholinomimetics and activators of the adenylate cyclase system exert opposing effects on neurotransmission at synapses formed between Schaffer collaterals/commissural fibers and dendrites of pyramidal neurons belonging to hippocampal area CA1.Institute of Biophysics, Academy of Sciences of the USSR, Pushchino. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 435–442, July–August, 1989. |
