title: Multiple action of acetylcholine at a muscarinic receptor studied in the rat hippocampal slice.
abstract: Responses of hippocampal pyramidal cells to topical application of acetylcholine (ACh) were measured in the in vitro hippocampal slice preparation. ACh but not cyclic GMP produced a short-latency hyperpolarization associated with a decrease in input resistance. This was followed by a long-latency but long duration depolarization associated in some cells with an increase in input resistance. This change in resistance followed the depolarization and outlasted it by 5--20 min, until complete recovery. During the depolarization there was a reduction in magnitude of EPSPs produced by activation of the Schaffer collateral excitatory afferents. The reversal potential for the hyperpolarization was about -95 mV, and it was blocked by 4-aminopyridine. The depolarization, but not the hyperpolarization was markedly attenuated in slices maintained in low (25 degrees C) temperature. The responses to ACh were blocked by atropine but not by D-tubocurarine. The hyperpolarization as well as the depolarization were present in slices treated with tetrodotoxin (TTX)., but were reduced in slices superfused with a low Ca2+-high Mg2+ medium, and in slices treated with Mn2+ and Co2+ ions. It is suggested that ACh causes a fast increase in gK+, followed by a long-lasting energy-dependent depolarization associated with action potential discharges, a decrease in conductance and a suppression of EPSPs.
mesh_terms: D015761:4-Aminopyridine; D000109:Acetylcholine / Q000494:pharmacology*; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002800:Cholinesterase Inhibitors; D006152:Cyclic GMP / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D009474:Neurons / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D011950:Receptors, Cholinergic / Q000187:drug effects*; D011976:Receptors, Muscarinic / Q000187:drug effects*; D013696:Temperature; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D000631:Aminopyridines; D002800:Cholinesterase Inhibitors; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D001285:Atropine; D015761:4-Aminopyridine; D006152:Cyclic GMP; D000109:Acetylcholine; D014403:Tubocurarine