An electrophysiological study on the cholinergic system in the carp retina.
The effects on spike discharges of acetylcholine chloride (ACh), applied electrophoretically at the inner plexiform layer, were examined in air-exposed and superfused preparations of the isolated carp retina. Most of spike-generating units examined (147 of 204 units; 72%) were sensitive to electrophoretically applied ACh. Among the ACh-sensitive ones, 125 units (85%), including all ON-center, most ON-OFF and two-thirds of OFF-center units, were activated, whereas 22 units (15%), including mainly OFF-center units, were suppressed by the agent. In retinas superfused with a medium containing 20 mM M2+ and 0.5 mM Ca2+, units ceased in their spontaneous and light-induced discharges, but they were activated by electrophoretically applied ACh. The ACh-induced activation was reduced in magnitude or abolished during an exposure of the retina to a medium containing hexamethonium chloride (25 micrometer), whereas the ACh-induced suppression was reduced by atropine sulfate (25 micrometer) more effectively than by hexamethonium. Therefore, the results suggest that nicotinic receptors are involved in the ACh-activation, whereas both, but predominantly muscarinic, receptors may participate in the ACh-suppression of spike discharges in the carp retina.
D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002347:Carps; D002799:Cholinergic Fibers / Q000502:physiology*; D004573:Electrolytes / Q000494:pharmacology; D006584:Hexamethonium Compounds / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000187:drug effects / Q000502:physiology; D011950:Receptors, Cholinergic / Q000187:drug effects; D012160:Retina / Q000502:physiology*
D004573:Electrolytes; D006584:Hexamethonium Compounds; D011950:Receptors, Cholinergic; D001285:Atropine; D000109:Acetylcholine