Cholinergic theta rhythm in transected hippocampal slices: independent CA1 and dentate generators.
The controversy concerning intrahippocampal theta (theta) generators, arising as a result of in vivo investigations, prompted us to record theta-activity from isolated populations of CA1 pyramidal or dentate granule neurons in vitro. In the present study, transected slices (trans-slices) of the hippocampal formation were used to isolate the CA1 area from the dentate gyrus, providing a method for testing the 'two generator' hypothesis. We demonstrated that neurons in both the CA1 area and dentate gyrus could independently generate carbachol-induced (type 2) electroencephalogram (EEG) theta-activity. This activity could be completely blocked by the muscarinic receptor antagonist atropine sulfate but was unaffected by the nicotinic blocker, (+)-tubocurarine. These in vitro results provide the first direct evidence for the two-generator hypothesis and confirm the cholinergic-muscarinic nature of type 2 slow wave theta.
Department of Pharmacology and Therapeutics, University of Calgary, Alta., Canada.
J
J
Konopacki
B H
BH
Bland
M B
MB
MacIver
S H
SH
Roth
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004569:Electroencephalography; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013826:Theta Rhythm
D002217:Carbachol