Effects of vasoactive intestinal peptide (VIP) on the testicular vasculature of the rat

Using laser Doppler flowmetry, the effects of unilateral intratesticular injection of vasoactive intestinal peptide (VIP) on testicular blood flow and mean arterial blood pressure were studied in anaesthetized adult rats. At doses of 50 and 500 ng, VIP increased blood flow by 29 ± 8 and by 77 ± 25% ( p < 0.05), respectively (means ±  SEM) at 5 mm, but not at 15 mm, from the injection site. Blood pressure was not significantly affected by 50 ng, but was slightly reduced (by −8 ± 2%) after treatment with 500 ng VIP. The highest dose of VIP (5 μg) reduced blood pressure (by −30 ± 9%), and decreased blood flow at 15 mm, but not at 5 mm, from the injection site. It is concluded that VIP can act as a vasodilator in the rat testis.