Reflex modulation of ovarian estradiol secretion by noxious mechanical stimulation of a hindpaw in anesthetized rats

Energy expenditure and slow-wave sleep in runners: Focusing on reproductive function, chronic training, and sex

This comparative study focused on chronic exercise training, menstrual cycle, menstruation, and sex related with slow-wave sleep and energy expenditure (EE) during sleep in runners and controls. Participants included 26 highly trained runners (9 males, 8 amenorrheic females, and 9 menstruating females) and 20 controls (10 males and 10 menstruating females) aged 21 ± 2 years. Sleeping metabolic rate and EE during slow-wave sleep were 2.7% and 3.9% higher in the luteal than the follicular phase for female runners. Significant interactions were found between the 8-h time course adjusted EE and menstruation, exercise training, and sex. Sleep stage durations did not differ between groups. Interestingly, amenorrheic runners did not suppress sleeping and overnight metabolic rates, suggesting that EE in sleep may not be a causative factor for amenorrhea in runners. This study highlights the complex relationship between chronic exercise, menstrual cycle, and sex on EE during sleep.

Effects of gentle mechanical skin stimulation on subjective symptoms and joint range of motions in people with chronic neck and shoulder discomfort

This study aimed to examine the efficacy of a 2-week self-administered gentle mechanical skin stimulation on chronic neck and shoulder discomfort. In participants (n = 12) with chronic neck and shoulder discomfort, subjective measures of pain sensation, discomfort, and difficulty in moving using a visual analog scale (VAS, 0-10) and objective measures of 12 different joint range of motions (ROMs) for the cervical and shoulder regions, using a digital goniometer, were collected before and after self-care with contact acupuncture, called microcones. The self-care for 2 weeks significantly (p < 0.001) decreased all VAS scores to 2.2-2.3 from baseline values of 6.0-7.4. Of the 12 ROMs tested, 8 were significantly increased (p < 0.013). This open-label study suggests the use of self-care with microcones in improving subjective symptoms and joint ROMs in people suffering from chronic neck and shoulder discomfort. However, a randomized, double-blind, controlled clinical trial is needed to further investigate the efficacy and safety of microcones.

Thyroxin and calcitonin secretion into thyroid venous blood is regulated by pharyngeal mechanical stimulation in anesthetized rats

The effects of the pharyngeal non-noxious mechanical stimulation on the secretion of immunoreactive thyroxin (iT4), immunoreactive calcitonin (iCT), and immunoreactive parathyroid hormone (iPTH) into thyroid venous blood were examined in anesthetized rats. Secretion rates of iT4, iCT, and iPTH were calculated from their concentration in thyroid venous plasma and the plasma flow rate. A mechanical stimulation was delivered to the pharynx by a rubber balloon placed on the tongue that was intermittently pushed into the pharyngeal cavity. Pharyngeal stimulation increased iT4 and iCT secretion, but iPTH secretion was unchanged. The secretion responses were abolished by transecting the superior laryngeal nerves (SLNs) bilaterally. The activities of the thyroid parasympathetic efferent nerves and the afferent nerves in the SLN increased significantly during pharyngeal stimulation. These results indicate that pharyngeal mechanical stimulation promotes thyroxin and calcitonin secretion from the thyroid gland by a reflex increase in SLN parasympathetic efferent activity, triggered by excitation of SLN mechanoreceptive afferents.

Neural Mechanisms Involved in the Noxious Physical Stress-Induced Inhibition of Ovarian Estradiol Secretion

Stress is known to change the secretion of ovarian steroid hormones via the hypothalamic-pituitary-ovarian (HPO) axis. Noxious physical stress can cause reflex responses in visceral function via autonomic nerves. This article reviews our recent animal studies on neural mechanisms involved in ovarian estradiol secretion induced by noxious physical stress stimulation. In anesthetized rats, noxious physical stress (pinching the hindpaw or electrical stimulation of the tibial nerve) decreased ovarian estradiol secretion. These noxious stress-induced ovarian hormonal responses were observed after decerebration but were abolished after spinal transection. Electrical stimulation of the ovarian sympathetic nerves (superior ovarian nerves: SON) decreased ovarian estradiol secretion. The reduced secretion of ovarian estradiol induced by hindpaw pinching was abolished by bilateral severance of the SON. Efferent activity of the SON was increased following hindpaw pinching. Thus, the inhibition of ovarian estradiol secretion during noxious physical stress was mainly integrated in the brainstem, and this inhibitory response was due to reflex activation of sympathetic nerves to the ovary. In rats, the sympathetic inhibitory regulation of ovarian estradiol secretion was pronounced when the HPO axis was inhibited by chronic estradiol treatment. Considering the female life cycle, extensive physical stress may inhibit ovarian function, especially before puberty and during old ages when the HPO axis is inactive. Anat Rec, 302:904-911, 2019. © 2019 Wiley Periodicals, Inc.

Modulation of Calcitonin, Parathyroid Hormone, and Thyroid Hormone Secretion by Electrical Stimulation of Sympathetic and Parasympathetic Nerves in Anesthetized Rats

The thyroid and parathyroid glands are dually innervated by sympathetic (cervical sympathetic trunk [CST]) and parasympathetic (superior laryngeal nerve [SLN]) nerve fibers. We examined the effects of electrical stimulation of efferent or afferent nerve fibers innervating the thyroid and parathyroid glands on the secretion of immunoreactive calcitonin (iCT), parathyroid hormone (iPTH), 3,3′,5-triiodothyronine (iT3), and thyroxine (iT4) from the thyroid and parathyroid glands. In anesthetized and artificially ventilated rats, thyroid venous blood was collected. The rate of hormone secretion from the glands was calculated from plasma hormone levels, measured by ELISA, and the flow rate of thyroid venous plasma. SLNs or CSTs were stimulated bilaterally with rectangular pulses with a 0.5-ms width. To define the role of unmyelinated nerve fibers (typically efferent), the cut peripheral segments were stimulated at various frequencies (up to 40 Hz) with a supramaximal intensity to excite all nerve fibers. The secretion of iCT, iT3, and iT4 increased during SLN stimulation and decreased during CST stimulation. iPTH secretion increased during CST stimulation, but was not affected by SLN stimulation. To examine the effects of selective stimulation of myelinated nerve fibers (typically afferent) in the SLN, intact SLNs were stimulated with a subthreshold intensity for unmyelinated nerve fibers. iCT, iT3, and iT4 secretion increased during stimulation of intact SLNs at 40 Hz. These results suggest that excitation of myelinated afferents induced by low intensity and high frequency stimulation of intact SLNs promotes secretion of CT and thyroid hormones from the thyroid gland, potentially via reflex activation of parasympathetic efferent nerve fibers in the SLN.

Mechanism of physical stress-induced inhibition of ovarian estradiol secretion in anesthetized rats

This study examined the site of main integration center in the physical stress-induced inhibition of ovarian estradiol secretion because of ovarian sympathetic nerve (superior ovarian nerve: SON) activation in anesthetized rats. In central nervous system-intact rats, electrical stimulation of the tibial afferent nerve at 10V increased the efferent activity of the SON by 39±13% and reduced the ovarian secretion of estradiol by 34±7%. These responses were observed in decerebrate rats but were abolished in spinal rats. Thus, the main integration center for this ovarian hormonal response is located in the brain stem.

Somatoautonomic reflexes in acupuncture therapy: A review

Oriental therapies such as acupuncture, moxibustion, or Anma, have been used to treat visceral disorders since ancient times. In each of these therapies, stimulation of the skin or underlying muscles leads to excitation of afferent nerves. The sensory information is carried to the central nervous system, where it is transferred to autonomic efferents, thus affecting visceral functions. This neuronal pathway, known as the "somatoautonomic reflex", has been systematically studied by Sato and his colleagues for over a half century. Nearly all their studies were conducted in anesthetized animals, whereas human patients are conscious. Responses in patients or the events following therapeutic somatic stimulation may differ from those observed in anesthetized animals. In fact, it is increasingly apparent that the responses in patients and animals are not always coincident, and the differences have been difficult for clinicians to reconcile. We review the mechanism of the "somatoautonomic reflex" as described in anesthetized animals and then discuss how it can be applied clinically.

Sympathetic regulation of ovarian functions under chronic estradiol treatment in rats

Activation of the sympathetic nerve to the ovary (superior ovarian nerve: SON) decreases ovarian blood flow and estradiol secretion in rats in the estrous phase. The present study examined the effects of long-term estradiol treatment on the sympathetic regulation of both ovarian blood flow and estradiol secretion. Non-pregnant Wistar rats received sustained subcutaneous estradiol (5μg/day) or saline for 4weeks. Chronic estradiol treatment did not affect ovarian blood flow at rest, while changed the basal ovarian estradiol secretion rate, i.e., narrow ranges (4-34pg/min) in estradiol-treated rats, versus wide ranges (3-192pg/min) in saline-treated rats of different estrous cycles. SON was electrically stimulated at different frequencies (2, 5 and 20Hz). Ovarian blood flow was decreased by SON stimulation in a stimulus frequency-dependent manner in both saline- and estradiol-treated rats, but the threshold was shifted from 2Hz to 5Hz after chronic estradiol treatment. Ovarian estradiol secretion rate was not significantly changed by SON stimulation at any frequency in saline-treated rats, while it was markedly decreased by SON stimulation at high frequencies (5 and 20Hz) in estradiol-treated rats. In conclusion, chronic estradiol treatment augments sympathetic inhibition of ovarian estradiol secretion perhaps by inhibiting the hypothalamic-pituitary-ovarian axis.

Laser-evoked cortical responses in freely-moving rats reflect the activation of C-fibre afferent pathways

The limited success of translating basic animal findings into effective clinical treatments of pain can be partly ascribed to the use of sub-optimal models. Murine models of pain often consist in recording (1) threshold responses (like the tail-flick reflex) elicited by (2) non-nociceptive specific inputs in (3) anaesthetized animals. The direct cortical recording of laser-evoked potentials (LEPs) elicited by stimuli of graded energies in freely-moving rodents avoids these three important pitfalls, and has thus the potential of improving such translation. Murine LEPs are classically reported to consist of two distinct components, reflecting the activity of Aδ- and C-fibre afferent pathways. However, we have recently demonstrated that the so-called "Aδ-LEPs" in fact reflect the activation of the auditory system by laser-generated ultrasounds. Here we used ongoing white noise to avoid the confound represented by the early auditory response, and thereby comprehensively characterized the physiological properties of C-fibre LEPs recorded directly from the exposed surface of the rat brain. Stimulus-response functions indicated that response amplitude is positively related to the stimulus energy, as well as to nocifensive behavioral score. When displayed using average reference, murine LEPs consist of three distinct deflections, whose polarity, order, and topography are surprisingly similar to human LEPs. The scalp topography of the early N1 wave is somatotopically-organized, likely reflecting the activity of the primary somatosensory cortex, while topographies of the later N2 and P2 waves are more centrally distributed. These results indicate that recording LEPs in freely-moving rats is a valid model to improve the translation of animal results to human physiology and pathophysiology.

Asymmetric steroidogenic response by the ovaries to the vasoactive intestinal peptide

In vitro the vasoactive intestinal peptide (VIP) stimulates progesterone, androgens, and estradiol secretion, and the effects are time-dependent. The present study analyzed the acute (1 h) and sub-acute (24 h) effects of unilateral injection of VIP into the ovarian bursa on each day of the estrous cycle on progesterone, testosterone, and estradiol serum levels. Cyclic 60-day-old virgin female rats on diestrus-1, diestrus-2, proestrus, or estrus were injected with saline or VIP 10(-6) M into the left or right ovarian bursa. One hour after saline injection on each day of estrus cycle, progesterone levels were higher than in control animals. The acute effects of saline solution on testosterone and estradiol levels were asymmetric and varied during the estrous cycle. In comparison with saline groups, the effects of VIPergic stimulation on progesterone, testosterone, and estradiol serum levels depend on the time elapsed between treatment and autopsy and vary during the estrous cycle. An acute asymmetric response from the ovaries to the VIP was observed at diestrus-1, diestrus-2, and proestrus on progesterone and estradiol levels. The asymmetries on testosterone levels were observed at diestrus-1, diestrus-2, and estrus days. The present results suggest that in the cyclic rat, each ovary has different sensitivities to VIPergic stimulation which depends on the endocrine status of the animal.

Autonomic nervous regulation of ovarian function by noxious somatic afferent stimulation

It is well known that ovarian function is regulated by hypothalamic-pituitary-ovarian hormones. However, although several histological studies have described the autonomic innervation of the ovary, the involvement of these autonomic nerves in ovarian function is unclear. Recently, it has been shown that both the superior ovarian nerve (SON) and the ovarian nerve plexus (ONP) induce vasoconstrictor activity by activation of alpha 1-adrenoceptors, whereas the SON, but not the ONP, inhibits ovarian estradiol secretion by activation of alpha 2-adrenoceptors. Furthermore, reflex activation of these ovarian nerves by noxious cutaneous stimulation of the rat hindpaw results in ovarian vasoconstriction and inhibition of estradiol secretion. Thus, in addition to long-term regulation of ovarian function by hormones, ovarian autonomic innervation may be involved in rapid regulation of ovarian function by responding to either internal or external environmental changes.

Sympathetic regulation of estradiol secretion from the ovary

It is well known that hormone secretion from endocrine glands is regulated by hierarchical feedback mechanisms. However, although Cannon revealed in the 1920s that sympathoadrenal medullary function increased during emergency situations, no studies on the autonomic nervous regulation of hormone secretion have been undertaken for many years. In the past 40 years, the autonomic nervous regulation of insulin secretion from the pancreas, gastrin secretion from the stomach, glucocorticoid secretion from the adrenal cortex, etc., has been demonstrated. Estradiol secretion from the ovary is strongly controlled by the hypothalamic-pituitary-ovarian axis, and its possible regulation by autonomic nerves has been largely unnoticed. Some histological studies have revealed rich adrenergic sympathetic innervation in the ovary. Recently, it has been demonstrated that the activation of the sympathetic nerves to the ovary directly reduces estradiol secretion from the ovary. This article reviews physiological and morphological studies, primarily in rats, on the sympathetic regulation of estradiol secretion from the ovary.