Reproductive phase depedent circadian variation tn the pineal biochemical constituents of Indian palm squirrel, Funambulus pennanti

In mammals, pineal gland is intimately concerned with the co-ordination of rhythm physiology. Biochemical characteristics of pineal gland in man and o ther mammals may provide strong, yet sometimes elusive support for the beli ef in functional individuality and probable importance of this tiny gland. In seasonal breeding animals, pineal gland function is very much dependent on the reproductive status. Therefore. the aim of this experiment is to not e the circadian rhythmicity of different biochemical constituents of pineal gland during active and inactive phases of reproductive cycle of a seasona lly breeding rodent, F. pennanti. In the present study, pineal biochemical constituents i.e. protein and cholesterol showed higher values during dayti me (1400 h). The plasma melatonin level presented two peaks during active ( April; at 1800 h and 0200 h) and inactive (December; at 1400 h and 0200 h) phases of reproductive cycle. The pineal protein, cholesterol and plasma me latonin values in term of basal and peak levels were higher during the repr oductive inactive/pineal active phase. Therefore, pineal - also known to ha ve antigonadotropic properties and cholesterol which appears conjugated wit h pineal serotonin, presented circadian rhythmicity along with the plasma l evel of melatonin. This rhythmicity noted in present study was dependent on the reproductive and pineal activity status, and might be regulated by the sex steroid receptor present on the pineal gland.