The Activation Of ERK1/2in The Rat Brain Involves In Isosexual Social Interaction

Objective To explore the role of activated extra-cellular signal-regulated kinase (ERK1/2) in adult male rat’s brain during the isosexual social interaction.Methods The study was carried out on male Sprague-Dawley rats. A three-chamber social interaction box was used to test male rats’ isosexual social interaction behavior, the expression of pERKl/2in the brain of male rat was tested by immunohistochemistry. After olfactory deprivation with zinc sulfate treatment, the rats were experimented in the isosexual social interaction test and the expression of pERKl/2was assessed by immunohistochemistry. In order to explore the role of activated ERK1/2in this behaviour, rats were injected with a selective MEK inhibitor SL327(30mg/kg) intraperitoneally30min prior social interaction behaviour test, and the expression of pERKl/2in the brain was determined by immunohistochemistry.Results When faced with social target side and inanimate side, the male rat spent significantly more time and number of contacts in social target side than that in inanimate side (P<0.001). When the two small compartments were empty, there was no difference between the time and number of contacts in the two sides (P>0.05). Significantly more pERK1/2expression were found in most of the brain regions known to be composed of the main olfactory system including the main olfactory bulb (MOB), piriform cortex (PIR), entorhinal cortex (ENT), the central amygdale nucleus (CeA), medial amygdale (MeA), paraventricular nucleus (PVN), orbitofrontal cortex (OFC) and anterior cingulate cortex (ACC) after a brief social interaction with a same sex partner compared with the rat without social interaction or stay in its homecage (P<0.01).However, after olfactory deprivation, the male rats showed no preference between the social target side and inanimate side, indicating by the same amount of time and number of contacts toward each side (P>0.05). Compared with the vehicle group, ZnSO4treatment group showed a significant reduced expression of pERK1/2in the MOB, Pir, Ent, PVN, OFC and ACC (P<0.01), while the expression of pERK1/2in AOB were increased (P<0.01), but in CeA and BLA, there was no difference between the ZnSO4treated group and vehicle group (P>0.05).Surprisingly, the SL327treated rats spent significantly more time and number of contacts in social target side than that in inanimate side (P<0.01). Moreover, compared with the vehicle group, SL327treatment group showed significantly increased time spent in the social target side (P<0.05). But the expression of pERKl/2in the brain was remarked suppressed by SL327treatment compared with the vehicle group (P<0.01).Conclusion Isosexual social interaction induced rapid phosphorylation of ERK1/2in most of the brain regions know to be involved in the main olfactory system, orbitofrontal cortex and anterior cingulate in the brain of male rat. The main olfactory system is related to the male rats’isosexual social interaction. The activation of ERK1/2in the male rat brain is involved in the regulation of isosexual social interaction behaviour.