In this study, we investigated the effect of neonatal olfactory bulbectomy (nOBX) on behavioral paradigms related to olfaction such as exploratory behavior, locomotor activity in a novel environment and social interaction. We also studied the effect of nOBX on the activity of the N-methyl-d-aspartate (NMDA) subtype of glutamate receptors during development. The behavioral effects of nOBX (postnatal day 7, PD7) were investigated in pre- (PD30) and post-pubertal (PD60) Wistar rats. NMDA receptor activity was measured with [(125)I]MK-801 in the brain regions associated with the olfactory circuitry. A significant increase in the novelty-induced locomotion was seen in the pre-pubertal nOBX rats. Although the locomotor effect was less marked than in pre-pubertal rats, the nOBX rats tested post-pubertally failed to habituate to the novel situation as quickly as the sham- and normal- controls. Pre-pubertally, the head-dipping behavior was enhanced in nOBX rats compared with sham-operated and normal controls, while normal exploratory behavior was observed between groups in adulthood. In contrast, social interaction was increased in post-pubertal animals that underwent nOBX. Both pre- and post-pubertal nOBX rats recovered olfaction. Interestingly, pre-pubertal rats showed a significant increase in the [(125)I]MK-801 binding in the piriform cortex, dorsal hippocampus, inner and outer layers of the frontal cortex and outer layer of the cingulate cortex. At post-pubertal age, no significant differences in [(125)I]MK-801 binding were observed between groups at any of the brain regions analyzed. These results suggest that nOBX produces pre-pubertal behavioral disturbances and NMDA receptor changes that are transitory with recovery of olfaction early in adulthood.
Keywords: ANOVA; BL; Cg; DG; EDTA; HBT; MK-801; N-methyl-d-aspartate; NAcc; NMDA; NMDA receptor; OBX; OF; OT; PBS; PD; PFC; RMS; SI; SVZ; ablation of the olfactory bulbs; analysis of variance; basolateral; cingulate cortex; dPFC; dentate gyrus; dizocilpine; dorsal part of the prefrontal cortex; ethylenediaminetetraacetic acid; hole board test; limbic system; locomotion; nOBX; neonatal ablation of the olfactory bulbs; neonatal bilateral ablation of the olfactory bulbs; nucleus accumbens; olfactory bulbectomy and depression; olfactory tubercle; open field; phosphate saline solution; postnatal day; prefrontal cortex; rostral migratory stream; social interaction; subventricular zone.
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