Date of Award
Doctor of Philosophy
Odors were presented under the nose of behaving rats and electrophysiological responses were recorded concurrently from the olfactory bulb and dentate gyrus. The results confirm previous work showing that some organic solvents elicit 15-30 Hz fast wave activity in both the olfactory bulb and dentate gyrus but further show that 2-propylthietane and trimethyl thiazoline (components of weasel and fox odors respectively) also elicit fast waves in the dentate gyrus while other strong odors do not. Noxious tactile stimulation in urethane anesthetized rats was found to produce an activation response in the dentate gyrus and olfactory bulb, similar to that seen in the neocortex, but did not elicit fast wave activity. Gustatory stimuli were also ineffective. Toluene and 2-propylthietane were found to suppress feeding in rats while non-fast wave inducing odors did not. Electrical stimulation of the olfactory bulb elicits long latency evoked potentials in the dentate gyrus with a latency of 16-18 ms and an early component which merges with the stimulus artifact. Results following lesions of the lateral olfactory tract or olfactory bulb suggest that the early component is due to the activation of stimulated olfactory bulb cells which is in turn volume conducted to the dentate gyrus. The late components of the evoked response appear to be generated locally in the dentate gyrus as is shown by the observation that small lesions of the dentate produced by injections of colchicine or kainic acid abolish the late, but not the earliest, components of the evoked response. The fast wave, but not the evoked potential, was shown here to be abolished following scopolamine or atropine in both urethane anesthetized and behaving rats, suggesting that the former is dependent on muscarinic cholinergic synapses. The cellular mechanisms supporting olfactory responses in the dentate gyrus could not be determined in the present thesis. The fast wave response in the dentate gyrus may be part of a cerebral response to the odor of a potential predator such as the weasel and fox.
Heale, Vincent Robert, "An Olfactory Input To The Dentate Gyrus: Electrophysiological, Behavioral, Pharmacological And Anatomical Studies" (1994). Digitized Theses. 2463.