Effects of Ovariectomy and Ovarian Hormones on Rna Base Ratios in Specific Rabbit Brain Areas

Abstract

The ribonucleic acid (RNA) base percentages were estimated in the hypothalamus, amygdala, hippocampus, frontal cortex, cerebellum and spinal cord of adult intact female rabbits, and after ovariectomy followed by replacement therapy with oestradiol-17\g=b\,progesterone and oestradiol plus progesterone. The results indicate a lack of effect on the spinal cord, but a variable effect on all other brain regions examined. In response to the various treatments, all regions examined produced RNA very rich in guanosine monophosphate indicating synthesis of specific RNA. The hypothalamus showed the most significant overall changes. Progesterone injections resulted in the most persistent effects of the hormonal treatments employed. Hypotheses are proposed to explain the variable hormonal effects on brain RNA base composition. It is suggested that ovarian hormones produce specific molecular changes in nervous tissue related either to 'receptors' for the hormones or to neural functions related to behavioural phenomena which are mediated by these hormones.

Oestrogen‐Insensitive Progestin Receptors in the Central Nervous System: Physicochemical and Immunoreactive Characteristics

“…(10) have demonstrated that progesterone was able to modify pituitary luteinizing hormone secretion in the rat, even in the absence of circulating oestrogens, through its effects exerted upon the cerebellum and the amygdala. This observation is in line with the demonstration of a large in vivo uptake of radio-labelled progesterone (8) and a progesterone-iqduced increase of R N A synthesis (9) in the cerebellum and cerebral cortex. Furthermore, these constitutively expressed PR in the CNS have recently been implicated in progesterone-mediated behaviours other than sexual behaviour, such as aggressiveness ( 1 9).…”

“…In addition, the immunoreactive behaviour of the two PR populations was also studied using a purified preparation of immunoglobulins raised against the oestrogen-dependent PR. The finding that progesterone induces neuroendocrine effects which require hormone-genome interaction in brain areas (8)(9)(10) which exclusively contain oestrogen-insensitive PR, provided additional reasons for conducting this study. 800 pg protein) were incubated with 0.4 nM [3H]-R 5020 in the presence or absence of an excess (100 x ) of radioinert R 5020.…”

Nonmotor functions of the cerebellum.

“…Nevertheless, numerous studies have reported that cerebellar biochemistry was affected by gonadal hormones (Eleftheriou, Desjardins, & Pattison, 1970;Hudson, Vernadakis, & Timiras, 1970;Litteria & Timiras, 1970;McEwen & Pfaff, 1970;Pfaff, 1968;Seiki & Hattori, 1971;Seiki, Miyamoto, Yamashita, & Kotani, 1969). One possible functional importance of these effects might be in the control of hormone secretions.…”