Objective:To study the effect of short and long term treatment of
venlafaxine on the expression of c fos and c jun protein
at the
hypothalamus of forced swimming rats. Method:The distribution of c fos and c jun neurons within the hypothalamus of forced swimming rats was mapped with the immunohistochemical method during short and long term treatment with
venlafaxine.The change in grey saturation and relative sectional area of FOS and JUN positive neurons at the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus was analysed with computerised imaging technique. Results:The expression of c fos and c jun protein could be induced by forced swimming and long term treatment with venlafaxine could suppress significantly the accumulated immobility time of forced swimming.The relative scctional area of fos and jun positive neurons was significantly decreased ( P <0 05) while grey saturation significantly increased ( P <0 01) during long term treatment with venlafaxine. Conclusion:The PVN and SON might be important structural substrates in the central nervous system mediation the action of antidepressants in despaired subjects like the forced swimming rats.The down regulation of c fos and c jun protein might be related with the delayed onset of action of antidepressants in the clinical setting.