ACTIVITY-DEPENDENT REGULATION OF DOPAMINE CONTENT IN THE OLFACTORY BULBS OF NARIS-OCCLUDED RATS

Several lines of evidence strongly suggest that reduced olfactory nerv e activity results in decreased bulb dopamine content. In the present study, high performance liquid chromatography with electrochemical det ection was used to assess catecholamine levels in bulbs from postnatal day 60 rats that had undergone either unilateral naris cautery or a s ham surgery on day 30. Thirty days of odor deprivation dramatically re duced dopamine and dihydroxyphenylacetic acid levels in functionally-d eprived bulbs (ipsilateral to occluded nares) as compared to contralat eral controls, while norepinephrine and dihydroxyphenylglycol levels w ere unchanged. The loss of dopamine was more severe in medial as compa red to lateral aspects of experimental bulbs, while the loss of dihydr oxyphenylacetic acid was similar on the two sides. To test directly th e hypothesis that afferent activity regulates dopamine and dihydroxyph enylacetic acid content, 1 h of high frequency tetanic nerve stimulati on was provided to the rostral-medial olfactory nerve layer in deprive d olfactory bulbs, and catecholamine levels were assessed from 6 to 19 2 h later. Partial and temporary recovery of dopamine was observed in medial aspects of the bulb when rats were examined 96 h later, while c onsistent recovery of dihydroxyphenylacetic acid content was not appar ent. These data corroborate evidence that olfactory nerve activity is a potent regulator of bulb dopamine and indicate that continued affere nt input is necessary to maintain dopamine levels. (C) 1998 IBRO. Publ ished by Elsevier Science Ltd.