Weight and Histology of the Pituitary Gland in Castrated Male Rats With Hypothalamic Lesions

Abstract

The effect of bilateral electrolytic lesions in the ventral hypothalamus at the coronal level of the posterior ventromedial nucleus and anterior premammillary nucleus on the weight and cytology of the pituitary gland of castrated male Lewis rats was investigated. All castrated rats were carrying successful intrasplenic isologous grafts of neonatal testes. The hypothalamic lesions resulted in a significant inhibition of pituitary hypertrophy in the castrated animals, but did not alter appreciably the cytology of the gland as compared with that of castrated rats without hypothalamic damage. The development of castration cells was not impaired by these lesions.It is concluded that hypertrophy of the pituitary gland after castration and the development of castration cells are two manifestations ofthe pituitary response to a low concentration of circulating testicular hormone. The former requires the integrity of the posteroventral hypothalamus while the latter is independent of this hypothalamic region.

Growth and Obesity Following Ventromedial Hypothalamic Lesions Placed in Female Rats at Four Different Ages

“…Previous work (3) in similarly operated rats had suggested interference with growth hormone secretion. M ontem urro (13) has reported that lesions similar to those of the present study resulted in a 50% reduc tion of acidophils in castrated rats. The present findings on reduction of the number of acidophils suggest profound interference with growth hormone synthesis and/or storage and/or secretion, more so in the weanling rats than in those lesioned during early and late ado lescence.…”

“…Thyroids and pituitarics were fixed in 10% for malin; the thyroids were cut at 5 /t and stained with hematoxylin and eosin. Pituitaries were sectioned at 3 fi, stained with Masson's stain and at the largest cross section o f the gland, acidophils were counted in a manner similar to that described by M o n tem u r ro (13) by counting the acidophils in and bordering on the diagonal squares in nine counting zones at a magnification o f 450. The net reticule used had squares o f 1 mm side length.…”

Effect of Lesion Size in the Ventromedial Hypothalamus on Growth Hormone and Insulin Levels in Weanling Rats

“…The size and localization of the lesions were determined according to the atlas of De G root [1959] and inserted in individual lesion charts modified after Montemurro [1964[. In order to obtain adequate numbers of animals in each group for statistical analysis, two separate experiments were performed one month apari.…”

Participation of the dorsomedial hypothalamic nucleus in the “feeding center” and water intake circuitry of the weanling rat

“…Food intake and and dorsomedial (Experiment 1, Group 2) hypothalamic lesions. Lesion charts modified after Montemurro (1964). Localization and extent of the lesions are indicated by stippling.…”