The effects of prolonged administration of testosterone oenanthate (TE) on sympathetic neurotransmission to the rat isolated seminal vesicle were examined. 2. TE was administered at either 1.2 or 2.4 mg/kg subcutaneously (s.c.) thrice weekly for 8 weeks. A separate group of rats was administered the vehicle, sesame oil, 0.5 mL/kg, s.c. at the same regime and used as controls. TE administration increased plasma testosterone and dihydrotestosterone levels and seminal vesicle weights. TE 2.4 mg/kg suppressed fertility in male rats. 3. The mean -log EC50 values of adrenalin and noradrenaline in seminal vesicles from the control group were 5.30 (95% confidence limits: 5.14, 5.58; d.f. = 14) and 4.92 (95% confidence limits: 4.56, 5.49; d.f. = 14) respectively. Neither of these estimates were modified by TE administration. 4. The mean noradrenaline content (microgram/tissue) in seminal vesicles from control rats was 0.88 +/- 0.09 microgram/tissue. This did not change with TE treatment. Tissue noradrenaline concentration (microgram/g tissue), on the other hand, decreased by more than 50% in preparations from rats treated with TE. This was paralleled by a decrease in the density of catecholamine fluorescence. 5. Mean responses to field stimulation (20 pulses, 60 V dial setting, 2 ms, 1-70 Hz) appeared to decrease in preparations from TE treated groups; this decrease was, however, not statistically significant (P greater than 0.05; d.f. = 15). 6. It is concluded that prolonged administration of testosterone oenanthate to rats, at doses sufficient to suppress fertility, decreases the density of sympathetic innervation to the seminal vesicle by increasing smooth muscle mass. Treatment does not, however, modify the responses of this preparation to exogenously added catecholamines.
