Evidence that activation of in vitro hippocampal theta rhythm only involves muscarinic receptors.
The present study was conducted for two purposes: the first was to evaluate whether activation of nicotinic receptors in the hippocampal formation in vitro (slice) preparation was capable of producing type 2 (atropine-sensitive) theta rhythm. The cholinergic nature and involvement of muscarinic receptors in this type of theta has been previously well documented. The second purpose was to determine whether perfusion of a number of (other) putative neurotransmitters shown to be present in the hippocampal formation could elicit type 1 (atropine-resistant) theta in the slice preparation. Further experiments were conducted to determine if these agents interacted in any manner with cholinergically-induced type 2 theta. Electroencephalic (EEG) theta activity was not induced by nicotine, providing evidence for an exclusive muscarinic receptor involvement in this cholinergically-induced type 2 theta. In addition, theta activity was not elicited by the application of gamma-aminobutyric acid (GABA), glutamate, norepinephrine, dopamine or serotonin. The application of any of these agents did not significantly alter the production of cholinergically-induced theta. These results suggest that type 1 theta originates in regions extrinsic to the hippocampus, or is the result of the interaction of several neurotransmitters on different receptors.
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D004569:Electroencephalography; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D009538:Nicotine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D013826:Theta Rhythm; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D005971:Glutamates; D011976:Receptors, Muscarinic; D012701:Serotonin; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D009538:Nicotine; D002217:Carbachol; D004298:Dopamine; D009638:Norepinephrine