The effect of posterior hypothalamic injection of cholinergic agents on hippocampal formation theta in freely moving cat.
The effect of intra-hypothalamic micro-injection of muscarinic (atropine sulphate, pirenzepine and gallamine) and nicotinic (hexamethonium) antagonists on spontaneous, sensory and electrically-induced hippocampal formation (HPC) theta EEG activity was investigated in the freely behaving cat. Administration of hexamethonium and gallamine failed to elicit a detectable effect on HPC theta activity. However, the injection of atropine sulphate and pirenzepine abolished the theta rhythm recorded from HPC. This effect was reversible. A substantial difference in the recovery time course between frequency versus amplitude (microV) and power (microV2) of hippocampal theta was observed. While theta frequency exhibited a rapid reappearance with a shallow slope, the power and amplitude showed a gradual recovery with a steeper slope. The injection of carbachol into posterior hypothalamus (PH) produced almost a continuous HPC theta with increased power. These results demonstrate that cholinergic (M1) receptors localised in the posterior area of the hypothalamus are engaged in mechanisms responsible for generating hippocampal theta oscillations in the freely behaving cat. The contribution of posterior hypothalamic region to HPC theta frequency and amplitude is discussed.
Bocian
Renata
R
Department of Neurobiology, University of Łódź, Rewolucji 1905, Street No. 66, Łódź 90-222, Poland.
Konopacki
Jan
J
D000818:Animals; D002415:Cats; D018678:Cholinergic Agents / Q000008:administration & dosage*; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D007034:Hypothalamus, Posterior / Q000187:drug effects* / Q000502:physiology; D007276:Injections, Intraventricular; D009068:Movement; D013826:Theta Rhythm / Q000187:drug effects
D018678:Cholinergic Agents