Ontogeny of olfaction: development of the rats' sensitivity to urine and amyl acetate.

A L B E R T S , J. R. A N D B. MAY. Ontogeny of olfaction: Development of the rats' sensitivity to urine and amyl acetate. PHYSIOL. BEHAV. 24(5)965-970, 1980.--Rat pups, 1 to 17 days of age, were tested for sensitivity to two olfactants, amyl acetate and adult rat urine. Biological and non-biological olfactory stimuli were generated by sparging and delivered to subjects via a dilution olfactometer, Unconditioned respiratory responses, odor-induced polypnea and sniffing, were used to measure detection of an odorant injected into a background stream of filtered air. Amyl acetate was presented in an ascending series of concentrations. Pups of all ages detected amyl acetate; chemosensitivity increased with age to all 3 concentrations of this nonbiological stimulus. Two concentrations of adult rat urine odor were equated to the strength of amyl acetate for 9-day-olds. Each normalized urine stimulus was then tested across the full range of age groups. Again, there was a dramatic age-related increase in chemosensitivity. Moreover, there was no indication of differential sensitivity to these biological and non-biological olfactants. These data were discussed within methodological and conceptual frameworks related to analyses of early olfactory and behavioral ontogenesis.