Ovarian blood flow is reflexively regulated by mechanical afferent stimulation of a hindlimb in nonpregnant anesthetized rats

Abstract

The effects of mechanical afferent stimulation of either a hindpaw or a hind leg on ovarian blood flow and systemic arterial blood pressure were studied in anesthetized nonpregnant adult female rats. Ovarian blood flow at the left side was continuously measured using a laser Doppler flowmeter. A mechanical stimulus (by pinching, brushing or pressing) was delivered for 30 s to either a hindpaw or a hind leg, at the right or left side. Pinching of a hindpaw at the right or left side decreased ovarian blood flow 8±3% accompanied with an increase in blood pressure. Brushing or pressing of a hindpaw produced no effects on these two parameters measured. Pressing stimulation of a hind leg at the right or left side produced a decrease in ovarian blood flow 8±2% accompanied with a decrease in blood pressure. Pinching or brushing of a hind leg produced no effects on both parameters measured. All responses of ovarian blood flow and blood pressure mentioned above were abolished after severing the femoral and sciatic nerves at the same side in which stimulation was unilaterally delivered. The blood pressure response, either increased or decreased depending on the stimulus modality and location stimulated, was not influenced by severing of ovarian sympathetic nerves. However, the decrease response in ovarian blood flow following pinching of a hindpaw reversed to the increase response, while the decrease response in ovarian blood flow following pressing of a hind leg was slightly augmented. The activity of sympathetic nerves innervating the ovary was increased during pinching of a hindpaw of either side, and decreased during pressing of a hind leg of either side. Electrical stimulation of the distal part of the severed splanchnic nerve at the left side decreased the left ovarian blood flow, and this response was abolished by intravenous injection of phentolamine, the α-adrenoceptor antagonist. The present results demonstrate that ovarian blood flow increase or decrease passively to responses of an increase or a decrease in systemic arterial blood pressure following mechanical afferent stimulation of a hindlimb, and these passive responses of ovarian blood flow are modulated by reflexive activity of ovarian sympathetic vasoconstrictor nerves to attenuate blood pressure-dependent passive changes in ovarian blood flow.