Long-term effects of pinealectomy on the annual cycle of golden-mantled ground squirrels,Spermophilus lateralis

Summary Pinealectomies and radical sham pinealectomies were performed on adult golden-mantled ground squirrels (Spermophilus lateralis) approximately one month prior to the beginning of the normal winter hibernation season. The cyclic components of the overwintering period and subsequent active season (the rhythms of homeothermy-heterothermy, body mass and testicular function) of the first year were not disrupted in either of the operated groups as compared with the intact animals. In the second year, the initiation of the hibernatory period occurred as usual in all intact, pinealectomized, and sham operated animals, but the pinealectomized group failed to show the progressive increase in the length of heterothermic bouts that was characteristic of the intact and sham-pinealectomized squirrels. The loss of body mass also was accelerated in the pinealectomized squirrels with respect to the intact and sham groups and appeared to be associated with terminal arousal which occurred approximately six weeks earlier in the second year after pinealectomy. Additionally, male squirrels showed a correspondingly early onset of testicular development as compared to the intact and sham operated males.