Reproductive phase dependent sensitivity of pineal-biochemical constituents of Indian palm squirrel, Funambulus pennanti to testosterone propionate treatment

The pineal gland (PG) possesses receptor proteins capable of binding androg en with high affinity and specificity. However, the sensitivity of PG to ex ogenous testosterone (T) in term of biochemical constituents during differe nt reproductive phases is still unknown. Hence, an attempt was made to stud y the effect of testosterone propionate (TP; 20 mu g/animal/day; i.m. injec tion) on the biochemical constituents of PG i.e. protein, cholesterol, sero tonin and plasma melatonin (MEL) level of the subtropical zone rodent, Funa bulus pennanti during reproductive active (RAP) and inactive phases (RIP). During RAP, TP increased the plasma MEL level and prostate gland weight whi le, it had no effect on other biochemical constituents of PG, plasma T leve l and testes weight. It may be suggested that during the RAP, exogenous TP initiates the negative feed back mechanism at leydig cell level. Further, T P is known to affect directly the MEL synthesis by increasing the activity of PG. During RIP, TP decreased the PG weight, plasma MEL level, serotonin and protein content and increased the testes, accessory sex organ's weight and plasma T level. This decrease in PG activity may be due to the decrease in enzyme activity by TP which in turn inhibited the MEL synthesis and ini tiated the gonadal function. Therefore, in this squirrel PG biochemical constituents presented a reprodu ctive phase dependent variation modulated by T. Further, active PG of RIP a ppeared to be more sensitive to exogenous TP treatment in reducing the bioc hemical constituents and increasing MEL synthesis.