The effect of intranasal zinc sulfate treatment on odor-mediated behavior and on odor-induced metabolic activity in the olfactory bulbs of neonatal rats.

This study describes the effect of lesions of the peripheral olfactory receptor sheet on odor-mediated behavior and on odor-induced metabolic activity in the neonatal olfactory bulb. Nine-day-old rats were treated by intranasal irrigation with a solution of 1% ZnSO4 or 5% ZnSO4 or saline. At 1 and 5 days following treatment they were tested for maternally-directed behaviors which are mediated in large part by olfactory cues. At 1 day following treatment the pups treated with ZnSO4 solutions had significant deficits in their odor-directed behavior. By 5 days however, most pups treated with 1% ZnSO4 had recovered to control levels, while the pups treated with 5% ZnSO4 continued to exhibit profound behavioral deficits. Following the behavioral testing, the pups were tested using the 2-deoxyglucose method for amyl acetate odor-induced metabolic activity in their olfactory bulbs. Control pups had large regions of high focal activity in their anterolateral and caudomedial olfactory bulbs. The 1% ZnSO4 pups had smaller foci which were confined primarily to the medial olfactory bulb. The 5% ZnSO4 pups had very little focal uptake in their olfactory bulbs. There was a clear correlation between intact olfactory nerve and glomerular layers and sites of increased functional activity. The results of this study demonstrate that there is a relationship between the degree of behavioral deficit and the extent of odor-induced functional activity in the olfactory bulb.