ELECTROPHYSIOLOGICAL ANALYSIS OF THE NASAL CHEMICAL SENSES IN GARTER SNAKES

Electroolfactogram and electrovomeronasogram recordings were made from garter snakes stimulated with vapor of amyl acetate. butanol and of e arthworm wash. The olfactory epithelium was more sensitive than the vo meronasal epithelium to all three stimuli. Volatiles from prey washes were capable of stimulating the olfactory epithelium when delivered as airstreams. The vomeronasal epithelium was sensitive only to the air delivery of vapor of amyl acetate. Single unit recordings from the mit ral cell layer of the accessory olfactory bulb of garter snakes were m ade in response to liquid delivery of a variety of chemical stimuli in cluding classical odorants, amino acids and proteins derived from prey . All three classes of stimuli altered unit firing in the accessory ol factory bulb. Amyl acetate, earthworm wash, goldfish wash and non-vola tile amino acids delivered as liquid stimuli to the vomeronasal epithe lium produced responses in the accessory olfactory bulb that were more distinct and reliable than the electrovomeronasogram responses to air borne odorants recorded at the periphery. Both excitatory and inhibito ry responses were observed in the accessory olfactory bulb of garter s nakes. The direction of the response to a given stimulus differed for different neurons. Responses were frequently biphasic and could last l onger than 50 seconds. Individual neurons responded to different class es of stimuli suggesting that they are broadly tuned.