Effect of testosterone on the pressor response to common carotid occlusion in gonadectomized conscious male rats with lesion of the median eminence

The influence of testosterone on the development of the pressor response to common carotid occlusion was investigated in control and median eminence-lesioned male rats. In control rats (N-9), gonadectomy performed 21 days before the experiments reduced by 22% (from 51 ñ 2 to 40 ñ 2 mmHg) and treatment with testosterone (330 µg for 4 days before the measurements) increased the initial peak pressor response (from 51 ñ 2 to 57 ñ 2 mmHg) which depends on carotid innervation. The maintained response which is of central origin (propably ischemic was less affected. In non gonadectomized rats (N=6), lesions of the median eminence (6 days) decreased the initial peak by 19% (from 52 ñ 2 to 42 ñ 3 mmHg) and the maintained response by 56% (from 32 ñ 2 to 14 ñ 1 mmHg). Sham-operated rats served as controls. In gonadectomized animals (N=6) the lesion reduced only the maintained response (from 23 ñ 2 to 11 ñ 1 mmHg). Testosterone supplementation restored the maintained response but did not alter the initial peak. These results indicate that the pressor response to common carotid occlusion in male rats is modulated by testosterone and that the depresiin in the maintained response caused by median eminence lesion can be reversed by steroid supplentation

The efffect of age on the presssor reponse produced by common carotid artery occlusion in conscious rats

The pressor responses to s of common carotid artery occlusion were studied in conscious male rats of different ages. Compared to rats at the age of 2 months, the initial peak and the maintained response in 6-12 and 18 month old rats were well preserved. In 1-onth old rats, both components were significantly depressed but in 24-month old rats only the initial peak of the pressor response was markedly attenuated. These findings demonstrate that age is an important factor in the response to common carotid artery occlusion wich is more marked for the initial than the maintained response

Pressor responses to common carotid occlusion in female rats: effects of gonadectomy and treatment with gonadal steroid hormones

The pressor responses to common carotid occlusion were studied in conscious female rats throughout the estrous cycle, after gonadectomy and after gonadectomy followed by treatment with estrogen and progesterone. The initial peak pressor response was highest during proestrus and fell significantly over the remaining 3 days of the estrous cycle. The maintained pressor response was relatively unchanged throughout the cycle, except during diestrus 1 when it decreased markedly. Gonadectomy reduced and treatment with estradiol alone increased the initial pressor component, respectively. Treatment of gonadectomized rats with estradiol plus progesterone enhanced both components. These findings suggest that gonadal steroid hormones are important modulators of the pressor to common carotid occlusion