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

Abstract

Abstract:The effects of thermal stimulation, applied to the hindpaw via a hot bath set to either 40°C (non-noxious) or 49°C (noxious), upon ovarian blood flow were examined in nonpregnant anesthetized rats. Ovarian blood flow was measured using a laser Doppler flowmeter. Blood pressure was markedly increased following 49°C stimulation. Ovarian blood flow, however, showed no obvious change during stimulation, although a small increase was observed after stimulation. Ovarian blood flow and blood pressure responses to 49°C stimulation were abolished after hindlimb somatic nerves proximal to the stimuli were cut. Heat stimulation (49°C) resulted in remarkable increases in both ovarian blood flow and blood pressure in rats in which the sympathetic nerves supplying the ovary were cut but the hindlimb somatic nerves remained intact. The efferent activity of the ovarian plexus nerve was increased during stimulation at 49°C. Stimulation at 40°C had no effect upon ovarian blood flow, blood pressure or ovarian plexus nerve activity. Electrical stimulation of the distal part of the severed ovarian plexus nerve resulted in a decrease in both the diameter of ovarian arterioles, observed using a digital video microscope, and ovarian blood flow.The present results demonstrate that noxious heat, but not non-noxious warm, stimulation of the hindpaw skin in anesthetized rats influences ovarian blood flow in a manner that is attributed to reflex responses in ovarian sympathetic nerve activity and blood pressure.Key words: autonomic nervous system, ovarian blood flow, ovarian sympathetic nerve, thermal stimulation, rat.Aside from evoking perception, thermal stimulation of the skin is also known to produce reflex changes in autonomic function. For example, it has been reported that high-or low-temperature stimuli of the skin results in reflex changes in heart rate, urinary vesical contractility and adrenal medullary hormonal secretion in anesthetized animals [1][2][3][4]. Moreover, reflex changes in heart, urinary bladder and adrenal medullary function following cutaneous thermal stimuli were proven to be caused by reflex changes in corresponding autonomic efferent nerve activity.Recent studies have shown that female reproductive organs, such as the ovaries and uterus are controlled not only by hormones but also by autonomic nerves [5][6][7][8][9][10][11][12]. 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. In the present study, we focused upon thermal stimulation using high-temperature. We chose this strategy because thermal stimulation, such as moxibustion, has long been used for the treatment of gynecological disorders [14]. The present study aimed to firstly use laser Doppler flow...

Effects of Electrical Stimulation of the Superior Ovarian Nerve and the Ovarian Plexus Nerve on the Ovarian Estradiol Secretion Rate in Rats

“…The decrease in ovarian blood flow by the electrical stimulation of the splanchnic nerve was completely abolished by the intravenous injection of alpha adrenoceptor antagonist. We also demonstrated that the electrical stimulation of the OPN decreases ovarian blood flow [11]. Our present study showed that an electrical stimulation of either the SON or the OPN produces a decrease in ovarian blood flow (ovarian venous plasma flow rate).…”

“…Autonomic nerves to the rat ovary reach the organ by two routes: the ovarian plexus nerve (OPN) along the ovarian artery and the superior ovarian nerve (SON) in the suspensory ligament [8,9]. We recently demonstrated that electrical stimulation of the splanchnic nerve or the OPN produces a vasoconstriction of ovarian arterioles and a reduction of ovarian blood flow in rats [10,11]. This result suggests a vasoconstrictor role of ovarian autonomic nerves in regulating ovarian blood flow.…”

Types of Skin Afferent Fibers and Spinal Opioid Receptors that Contribute to Touch-Induced Inhibition of Heart Rate Changes Evoked by Noxious Cutaneous Heat Stimulation

“…Noxious stimuli are transmitted to the cerebral cortex and perceived as “pain,” such information is integrated in the spinal cord and brain stem and influences autonomic nerve activity (somatoautonomic reflexes) [1–6]. Sympathetic nerve activity induced by noxious stimulation is thought to contribute to the onset and maintenance of some type of chronic pain [7].…”

Autonomic nervous regulation of ovarian function by noxious somatic afferent stimulation

“…In anesthetized rats, we examined the effects of NA and electrical stimulation of the autonomic nerves to the ovary on the diameter of ovarian arterioles, by use of digital video microscopy, and on ovarian blood flow, by use of laser Doppler flowmetry [ 21 , 22 ]. NA (5 μg/kg), injected intravenously into the jugular vein over 20 s resulted in a decrease in the diameter of ovarian arterioles and in ovarian blood flow, and an increase in mean arterial pressure (MAP) (Fig.…”

“…The thin dashed vertical lines and the thick horizontal bars on the abscissae indicate the time of noradrenaline (NA) injection at 5 μg/kg ( c – e ) or the time of electrical stimulation of the ONP at 10 V and 50 Hz for 20 s ( h – j ). ( a – e , modified from Kanai et al [ 21 ]; f – j , modified from Uchida et al [ 22 ]) …”