Chronic fluvoxamine treatment changes 5-HT2A/2C receptor-mediated behavior in olfactory bulbectomized mice

Aims: Olfactory bulbectomy (OBX) in rodents represents a valuable experimental model of depression. This study was designed to shed further light on the impact of putative serotonergic neuronal degeneration in OBX mice and to assess the effect of a widely used antidepressant on serotonergic related behavioral changes induced by OBX. Main methods: Adult male ddY mice were subject to bilateral OBX or sham surgery. The serotonin (5-HT)(2A/2C) receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI) enhanced a head-twitch response (HTR) in pm mice. Effects of 5-HT2A, 5-HT2C antagonists and fluvoxamine were observed in OBX mice following DOI administration. Key findings: The HTR elicited by the administration of DOI (0.5 mg/kg and 1 mg/kg, i.p.) was increased about twofold in OBX mice when compared with controls on the 14th day after the surgery. The injection of ketanserin (0.025 mg/kg, i.p.), a 5-HT2A receptor antagonist, inhibited the enhancement of the DOI-induced HTR after OBX. Likewise, the administration of SB 242084 (1 mg/kg, s.c.), a 5-HT2C receptor antagonist, also inhibited the DOI-induced HTR in OBX mice. Chronic but not acute treatment with the antidepressant fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), suppressed the enhancement of DOI-induced HTR after OBX. Significance: These findings indicate that OBX, and the subsequent degeneration of neurons projecting from the olfactory bulb, caused a supersensitivity of 5-HT2A/2C receptors which may be involved in symptoms of depression. (C) 2012 Elsevier Inc. All rights reserved.