Cutaneous Mechanical Stimulation Regulates Ovarian Blood Flow via Activation of Spinal and Supraspinal Reflex Pathways in Anesthetized Rats

Abstract

Abstract:The reflex effects of noxious mechanical stimulation of a hindpaw or abdominal skin on ovarian blood flow, and the reflex pathways involved in those responses were examined in anesthetized rats. Blood flow in the left ovary was measured using a laser Doppler flowmeter, and the activity of the left ovarian sympathetic nerve and mean arterial pressure (MAP) of the common carotid artery were recorded. Stimulation of the left or right hindpaw for 30 s produced marked increases in ovarian sympathetic nerve activity and MAP. Ovarian blood flow slightly decreased during the stimulation and then slightly increased after the stimulation. After the left ovarian sympathetic nerves were severed, the same stimulus produced a remarkable monophasic increase in ovarian blood flow that was explained by passive vasodilation due to a marked increase in MAP. After spinal transection at the third thoracic (T3) level, the responses of MAP, ovarian sympathetic nerve activity, and ovarian blood flow to hindpaw stimulation were nearly abolished. Stimulation of the abdomen at the right or left side for 30 s produced slight increases in ovarian sympathetic nerve activity and MAP. Ovarian blood flow slightly decreased during the stimulation and then slightly increased after the stimulation. After the ovarian sympathetic nerves were severed, the response of the ovarian blood flow changed to a monophasic increase due to an increase in MAP. After spinal transection, stimulation of the left abdomen produced a moderate increase in MAP, a remarkable increase in ovarian sympathetic nerve activity and a slight decrease in ovarian blood flow during the stimulation. In contrast, stimulation of the right abdomen produced a smaller response in ovarian sympathetic nerve activity during the stimulation while it increased the MAP to a similar degree. Ovarian blood flow slightly increased after the end of stimulation, which was explained as passive vasodilation due to the increase in MAP. In conclusion, stimulation of somatic afferents affects ovarian blood flow by inducing changes in ovarian sympathetic nerve activities and blood pressure. When stimulation was applied to a hindpaw whose segment of afferent input is far from the segment of the ovarian sympathetic nerves, it took a supraspinal reflex pathway. However, when stimulation was applied to the abdomen whose spinal segment of the afferent is close to the segment of the ovarian sympathetic nerve output, there are spinal segmental reflex pathways. The present results demonstrate that spinal reflexes depend on the laterality of the stimulus, while supraspinal reflexes do not depend on the laterality of the stimulus. [The Japanese Journal of Physiology 55: [265][266][267][268][269][270][271][272][273][274][275][276][277] 2005]

Predominance of supraspinal innervation of the left ovary

“…Furthermore, asymmetry in the somato-sympathetic reflex has been demonstrated in studies where noxious mechanical stimulation was applied to the region of the abdomen whose spinal segment of the afferents is close to the segment of the ovarian sympathetic nerve output. Stimulation of the left abdomen induced a much stronger effect on left ovarian sympathetic nerve activity than stimulation of the right abdomen (Uchida et al, 2005).…”

Effects of Thermal Stimulation, Applied to the Hindpaw via a Hot Water Bath, upon Ovarian Blood Flow in Anesthetized Nonpregnant Rats

“…Blood flow in the left ovary was measured in 12 rats using a laser Doppler flowmeter (ALF21D, Advance, Tokyo) as described previously by Uchida et al [13]. In brief, the left ovary was exposed ventrally by opening the abdominal wall.…”

“…In our laboratory, we have recently demonstrated that noxious, but not non-noxious, mechanical stimulation of the hindpaw skin in anesthetized rats exerts influence upon the ovarian blood flow and that this is attributable to reflex responses in ovarian sympathetic nerve activity and blood pressure [12,13]. It is possible that thermal stimulation also exerts reflexive effects upon ovarian blood flow.…”

Anatomical organization and neural pathways of the ovarian plexus nerve in rats

“…The OPN innervates the ovary, bursa, oviduct [3], and cranial uterine horns [1]; the axons enter through the hilum [4–8] and innervate the medullary and cortical region of the ovary. The OPN is mostly composed by sympathetic and sensory fibers, with a small portion of parasympathetic fibers [4, 9, 10].…”