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Summary Male rats treated with guanethidine 25 mg/kg daily for eight weeks had no demonstrable ejaculatory function immediately after cessation of treatment. Four weeks later, ejaculatory function had returned in two‐thirds of the males, and after eight weeks, all males were able to deposit sperm in the vagina. However, fertility had returned at that time in only two of the nine males. On the basis of these findings it might be expected that fertility would return in the other males after a more prolonged observation period. At autopsy, 66 days after cessation of treatment, the vasa deferentia were congested and filled with viscous material, and along their course dilated regions and pseudocysts containing sperm debris and spermatozoa were found. The isolated ducts of the guanethidine‐treated males showed a markedly increased response to noradrenaline if compared with ducts from control rats. Response to tyramine was similar in both treated and untreated rats. In view of the increased response to noradrenaline it may be concluded that the noradrenaline stores, which are sensitive to tyramine, were still reduced 66 days after guanethidine treatment had been stopped.

In unilaterally nephrectomized rats, 9α-fluorocortisol (9α-FF), in doses of 0.3 and 1.0 mg given daily by intramuscular injection, induced an increase in blood pressure that was independent of additional sodium supply. 9α-FF reduced weight gain and, in the dose of 1.0 mg, increased fluid turnover when 0.9 % saline was given to drink. Haematocrit values were elevated, whether saline or water was given as drinking fluid. The serum sodium concentration was increased when saline was offered, but normal with water as drinking fluid. The serum potassium concentration was diminished in all groups that received 9α-FF. The renin content of the kidney was markedly depressed in all groups that had 9α-FF. The degree of suppression was similar in the groups that had saline and those that had water to drink. Under 9α-FF, plasma concentration of angiotensin II was virtually zero when saline was given to drink, but about ¼ to ½ normal when drinking fluid was water. It is concluded that the type of hypertension developing under high doses of 9α-FF resembles glucocorticoid rather than mineralocorticoid hypertension.

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