Changes in orcadian acetylcholinesterase activity in hypothalamus and cerebellum induced by castration or hemicastration in the adult male rat∗

Abstract

Abstract Untouched, sham operated, castrated or hemigonadectomized adult male rats were autopsied at 02.30, 08.00, 11.00, 16.00, 18.00 or 24.00 h. In both the hypothalamus and cerebellum, the acetylcholinesterase (AChE) activity and protein contents were determined. When enzyme activity was expressed as a function of organ weight, sham operation increased hypothalamic AChE activity (10.8 ± 0.4 nmol/min/mg wet tissue vs. control 7.3 ± 0.2, p < 0.01). When results were expressed as a function of protein contents, a decrease in AChE activity was observed both in the hypothalamus (114 ± 4.2 nmol/min/mg protein vs. control 160 ± 5.9) and in the cerebellum (60 ± 1.9 vs. control 71 ±2.1). Both gonadectomy and unilateral gonadectomy decreased the enzymatic activity in both the hypothalamus and cerebellum when compared with the sham operated group. No significant differences were observed between castrated and hemicastrated animals. When the results were expressed as a function of protein contents, circadian changes in AchE activity, both in the hypothalamus and cerebellum, were observed. Sham operation did not abolish the changes, whereas both gonadectomy and hemigonadectomy almost did. Circadian variations were not observed when results were expressed as a function of weight. Our results support those authors who stress the need for expressing results both as a function of protein content and of organ weight. In the male, as in the female, the activity of the hypothalamic cholinergic system seems to present circadian variations. The cerebellum seems to show the same. The fact that both gonadectomy and hemigonadectomy modify the activity suggests the possibility that the rhythm depends, at least in part, on influences other than endocrine, arising from the gonads.