Effects of pinealectomy in the newborn female rat

Abstract

That pinealectomy in the rat is followed by ovarian hypertrophy is an assumption which is rather widely accepted and which is fundamental to much contemporary pineal research. Nevertheless an analysis of the alleged supporting literature shows it to be surprisingly weak and limited to animals operated at three to four weeks of age. In several mammals young pineals have been shown to equal or exceed older pineals in certain metabolic activities, but the effect of pineal ablation in the newborn rat is unknown. This report is based on Holtzman female rats pinealectomized at three days, and sacrificed at 60 days of age. The animals comprise a littermate series of eight normal, eight sham operated and eight pinealectomized; and a non littermate series of 18 normal, 17 sham operated, and ten pinealectomized rats. Pinealectomy was proved complete by microscopy of serial sections. Pinealectomized animals in both series did not differ from normals in the weight of the body, ovary, uterus, adrenal, or hypophysis; nor was there a difference in time of vaginal opening, estrous cycle, or 24 hour urinary sodium and potassium output.Since the turn of the century there has been a sustained controversy whether the pineal body in the mammal inhibits gonadal activity. In the present decade a number of authors have assumed that it does, and interest has been demonstrated in the mechanism by which it acts. (Milcou and Pavel, '60; Meyer et al., '61; Thieblot and Blaise, '63; Chu et al., '64; Moszkowska, '63, '64, '65; Reiter and Hester, '66).This assumption however is based on weak evidence. The weakest, sometimes involving only two or three experimental animals, has only rarely been mentioned since the monograph of Kitay and Altschule appeared in 1954, and since 1954 it is probably this monograph which has been the most frequently used reference on pineal function.2 These authors have summarized the world literature on pineal physiology, but have avoided abstracts and reviews -which they claim are often incomplete, misleading, or inaccurate -and have studied original papers to present a critical analysis of available data, with emphasis on its statistical significance.This valuable reference work has apparently been widely accepted, for I have yet to see it criticised. Nevertheless it is my opinion that the review of Kitay and Altschule is subject to the same criticism these authors have of other reviews -it may be misleading. For example they point out that pineal inhibition of gonadal de-AM. J. ANAT., 120: 391-402. velopment is suggested by several lines of evidence; chiefly, that pinealectomy is followed by gonadal hypertrophy and that pineal extract injection is followed by gonadal atrophy.More specifically, the best evidence available today (including the review of Kitay and Altschule) supports the thesis that pinealectomy induces ovarian hypertrophy in the rat. Indeed, one author (Roth, '65) recently stated that he elected to work on pinealectomy in the male rat because results in females were consistent and adequate...

The mammalian pineal gland, a survey

“…At the author's Institute, no changes in either testicular weight or weight of the seminal vesicles and prostate was observed after pinealectomizing male adult rats (Van Bronswijk et al, to be published). Wragg (1967), criticizing the results obtained after pinealectomy, concludes that. only within a restricted age range, i.e.…”

Endocrine Aspects of the Mammalian Pineal Gland:A Review

“…The morphologists have virtually ignored studies dealing with the consequences of pineal ectomy on the gross and microscopic anatomy of the hypophysis. Of the few existing reports, about half contend that removal of the pineal has little or no effect on pituitary morphology [H olm es, 1956; C a r n ic e l l e et Wragg, 1967], On the other hand, the remainder claim that pinealectomy causes hypophyseal hypertrophy or an increased number of basophils, changes usually associated with hyperactivity [G ir o d et al, 1964; T h ie b l o t , 1965; M oszkow ska, 1965a], One of the most striking findings in this regard is that reported by Q uay [1967b]; he found massive pituitary adenomata in aged pincalectomizcd rats. Whether the incidence of these tumors was in fact related to pineal removal is questionable, however, a point even the investigator readily admits.…”

The pineal gland and the development of salt intake patterns in male rats

“…Bliss and Bates pinealectomized adult animals; in the present work I carried out the surgery on newborns. Pinealectomy carried out in newly born rats has no effect on the weight of accessory sex organs (Kincl & Benagiamo, 1967;Wragg, 1967), whereas the same operation carried out at a later age results in enlargement of these organs (Reiter & Fraschini, 1969). Bliss and Bates offered their animals a free selection between water and saline only when they were adults and only for 2 periods of 7 days; in the present experiment I permitted the animals a free selection between water and saline from the 30th day of life for a period of 2 months.…”