Comparison of social interaction and neural activation in the main olfactory bulb and the accessory olfactory bulb between Microtus mandarinus and Microtus fortis.

Abstract

To gain insight into the function of AOB and MOB during different social interaction and in different vole species, the behaviors and neural activation of the olfactory bulbs in social interactions of mandarin voles Microtus mandarinus and reed voles Microtus fortis were compared in the present research. Mandarin voles spent significantly more time attacking and sniffing its opponent and sniffing sawdust than reed voles. During same sex encounters, mandarin voles attacked its opponent for a significantly longer time and sniffed its opponent for shorter time compared with male-female interactions. However, no significant behavioral differences were found during encounters of two individual reed voles, regardless of gender composition of the pair. Using c-Fos as an indicator of neural activation, we observed that neural activation was significantly higher in almost all sub-regions of the main olfactory bulb (MOB) and the accessory olfactory bulb (AOB) of mandarin voles compared with reed voles. Numbers of c-Fos-ir neurons in almost all sub-regions of the AOB and the MOB during male-female interactions were also higher than those in interactions of the same sex. Anterior-posterior ratios of Fos-ir neurons in the AOBM (AOBMR) and the AOBG (AOBGR) in male-female interaction were significantly higher than those in interaction of the same sex. The AOBMR of male mandarin voles and reed voles were larger than those of females in male-female interactions. Behavioral patterns are consistent with cellular activity patterns. Consistent level of neural activation in MOB and AOB suggests important roles of both the main olfactory bulb and the accessory olfactory bulb in social interaction in two species.