Influence of unilateral olfactory bulbectomy on opiate and other binding sites in the contralateral bulb

The neurochemical consequences of unilateral olfactory bulbectomy (UBX) in mice were determined in the remaining olfactory bulb at various times after surgery. The most significant finding was a progressive decline in opiate ligand (dihydromorphine) and naloxone) binding that appeared within 11 days after surgery and persisted throughout the study. Statistically significant declines in spiroperidol (-67%), clonidine (-48%) and muscimol (-16%) binding were also observed 90 days after surgery. At 180 days postsurgery we observed a 20% increase in diazepam binding. No effect of UBX on dihydroalprenolol, quinucludinylbenzilate or serotonin ligand binding was observed. Bulbectomy resulted in a moderate decrease (-28%) in DOPA decarboxylase activity 14 days after surgery, which returned to normal by 30 days. Glutamic acid decarboxylase activity decreased by 37% 7 days after UBX, returned to normal by 14 days after surgery and then increased by 25% 90 days after UBX. Unilateral bulbectomy had no effect on cholineacetyltransferase activity in the remaining bulb. Thus, following a unilateral procedure, one bulb cannot necessarily serve as a valid control for the other. Possible explanations for the neurochemical changes observed are discussed.