5-HYDROXYTRYPTAMINE - A LOCAL REGULATOR OF TESTICULAR BLOOD-FLOW AND VASOMOTION IN RATS

The effects of 5-hydroxytryptamine (5-HT), 5-HT2 receptor antagonists (ritanserin and ketanserin), histamine and substance 48/80 on testicul ar blood flow and microcirculation were studied in adult rats. The sub stances were administered by topical application on the testicular sur face and by intratesticular injections, and blood flow was measured by radioactive microspheres and with a laser Doppler flowmeter. Blood fl ow was decreased by 5-HT in a dose-dependent manner and vasomotion in the testis was inhibited, suggesting that it could be involved in the physiological regulation of the testicular vasculature. The 5-HT antag onists did not significantly influence flow or vasomotion in intact te stes. Histamine did not cause any major effects on testicular blood fl ow. Substance 48/80 caused degranulation of testicular mast cells, and reduced testicular blood flow and vasomotion suggesting that testicul ar mast cells, possibly by releasing 5-HT, could be involved in the lo cal control of the testicular vasculature.