Effects of pinealectomy on the secretion of luteinizing hormone, testosterone and prolactin in rams exposed to various lighting régimes.

Two experiments were carried out to study the effects of controlled lighting régimes on plasma levels of LH were low in all groups of rams, which made the detection of significant effects of any treatment very unlikely. Pinealectomy reduced the effects of changes in the daily photoperiod on the patterns of secretion of testosterone and prolactin. These findings establish the pineal gland as an organ which influences the endocrine responses of rams to photoperiodic stimuli and it is concluded that the pineal gland is probably important as a mediator of seasonal reproductive changes in these animals.