Bulbectomy-induced loss of raphe neurons is counteracted by antidepressant treatment.

1. Bilateral olfactory bulb ablation was performed in C57B1/6j mice (C57). Separate groups of bulbectomized mice were treated with either antidepressants (trazodone, 20 mg/kg i.p., or amitriptyline, 20 mg/kg i.p.) or saline daily for 14 consecutive days starting 14 days after surgery. 2. Celloidine-imbedded 10 microns-thick brain sections containing the nucleus raphe dorsalis (NRD) or locus coeruleus (LC) were stained for Nissl, and the number of functional and pyknotic cells was counted out of 500 total cell count for each animal in every experimental group: sham-operated, bulbectomized treated with saline or one of the two antidepressants. 3. Bulbectomy produced a significant 4 times increase in the proportion of pyknotic cells in NRD as compared to sham-operated control. Both antidepressants reversed the effect bringing the number of pyknotic cells to control level. The proportion of pyknotic cells in LC was also slightly increased (61%) in the bulbectomized mice, but only amitriptyline was able to reverse the effect. 4. Widespread degeneration of the neurons in NRD caused by bulbectomy may be involved in the serotonergic component of the bulbectomy syndrome. The ability of antidepressants to diminish bulbectomy-induced loss of NRD neurons may underlie their restorative effect on the behavior and neurochemical characteristics of bulbectomized animals.