Cholinergic disinhibition in area CA1 of the rat hippocampus is not mediated by receptors located on inhibitory neurons.
We studied the effects of carbamylcholine (carbachol; CCh) on monosynaptic inhibitory postsynaptic potentials (IPSPs) evoked in the presence of the excitatory amino acid receptor antagonists 6,7-dinitroquinoxaline-2,3-dione (DNQX) and D,L-2-amino-5-phosphonovalerate (APV). CCh (30 microM) blocked late afterhyperpolarizations but did not depress GABAA receptor-mediated fast monosynaptic IPSPs or GABAB receptor-mediated late monosynaptic IPSPs. In the presence of CCh the GABAB receptor agonist (+/- )-baclofen (2 microM) reversibly hyperpolarized pyramidal neurons and depressed monosynaptic IPSPs as under control conditions. Phorbol-12,13-diacetate (PDAc; 10 microM) increased fast and depressed late monosynaptic IPSPs, and prevented depression of IPSPs by baclofen. These results suggest that cholinergic disinhibition in area CA1 of the hippocampus results from decreased synaptic excitation of inhibitory neurons.
Department of Neurobiology, Northeastern Ohio Universities College of Medicine, Rootstown 44272.
N A
NA
Lambert
T J
TJ
Teyler
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D058787:GABA-A Receptor Antagonists; D006624:Hippocampus / Q000187:drug effects*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects*; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D010703:Phorbol Esters / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D011950:Receptors, Cholinergic / Q000187:drug effects*; D009435:Synaptic Transmission / Q000502:physiology
D058787:GABA-A Receptor Antagonists; D010703:Phorbol Esters; D011810:Quinoxalines; D011950:Receptors, Cholinergic; C008874:phorbol-12,13-diacetate; C056723:FG 9041; D015763:2-Amino-5-phosphonovalerate; D002217:Carbachol; D001418:Baclofen; D000241:Adenosine