Pineal complex of rats: effects of superficial pinealectomy on the deep pineal

Previous studies have shown that in rodents the pineal complex may consist of two parts, i.e. the small deep pineal and the large superficial pineal. As commonly used techniques of pinealectomy remove the superficial pineal only, it was decided to examine what effect this operation has on the deep pineal in male Sprague-Dawley rats. 3 and 6 weeks after superficial pinealectomy, the deep pineal exhibited a clear decrease in volume, due to an atrophy of the intrinsic pinealocytes. An atrophy was still noticeable after 6 or 12 months. It is concluded that after superficial pinealectomy the deep pineal is not an important factor with respect to melatonin formation, in particular, as there are extrapineal sites of melatonin formation.