Significance of measured elevation of skin temperature induced by calcitonin gene-related peptide in anaesthetized rats

Is calcitonin gene-related peptide a modulator of menopausal vasomotor symptoms?

PURPOSE

Calcitonin gene-related peptide (CGRP) is a neuropeptide widely distributed in the central and peripheral nervous systems, which is known as a potent vasodilator. Postmenopausal women who experience hot flushes have high levels of plasma CGRP, suggesting its involvement in menopausal vasomotor symptoms.

METHODS

In this review, we describe the biochemical aspects of CGRP and its effects associated with deficiencies of sexual hormones on skin temperature, vasodilatation, and sweating as well as the possible peripheral and central mechanisms involved in these events.

RESULTS

Several studies have shown that the effects of CGRP on increasing skin temperature and inducing vasodilatation are potentiated by a deficiency of sex hormones, a common condition of postmenopausal women. Additionally, the medial preoptic area of the hypothalamus, involved in thermoregulation, contains over 25-fold more CGRP-immunoreactive cells in female rodents compared with male rodents, reinforcing the role of female sex hormones on the action of CGRP. Some studies suggest that ovarian hormone deficiency decreases circulating endogenous CGRP, inducing an upregulation of CGRP receptors. Consequently, the high CGRP receptor density, especially in blood vessels, amplifies the stimulatory effects of this neuropeptide to raise skin temperature in postmenopausal women during hot flushes.

CONCLUSIONS

The duration of the perception of each hot flush in a woman is brief, while local reddening after intradermal administration of α-CGRP persists for 1 to 6 h. This contrast remains unclear.

Effects of the traditional Japanese medicine Tokaku-jyoki-to in rat-models for menopausal hot flash

AIM OF STUDY

Luteinizing hormone-releasing hormone (LH-RH) has been suggested as an inducer of centrally mediated elevation of skin temperature, and calcitonin gene-related peptide (CGRP) is one of the potent vasodilator neuropeptides that has been suggested as an inducer of peripherally mediated elevation of skin temperature. We investigate the effect of the Japanese herbal medicine Tokaku-jyoki-to using two rat-models for menopausal hot flash.

MATERIALS AND METHODS

Tokaku-jyoki-to used in present study was prepared as a spray-dried powder from hot-water extract. Skin temperature was measured by thermister thermometer. Estrogen receptor (ER) binding assay of Tokaku-jyoki-to extract was performed using human recombinant ERalpha or ERbeta.

RESULTS

Oral Tokaku-jyoki-to (1000 mg/kg) restored skin temperature rise induced by LH-RH or CGRP in ovariectomized (OVX) rats as well as subcutaneous 17beta-estradiol (0.010 mg/kg) did. Tokaku-jyoki-to did not affect the lower concentration of plasma estradiol and the decreased uterine weight due to ovariectomy, although the hormone replacement of 17beta-estradiol restored them. In estrogen receptor ligand-binding study, Tokaku-jyoki-to extract bound to human ERalpha poorly and did not bound to human ERbeta.

CONCLUSIONS

These results suggest that Tokaku-jyoki-to, which appears to contain organ-specific selective estrogen receptor modulator, may be useful for the treatment of hot flashes in patients for whom estrogen replacement therapy is contraindicated as well as menopausal women.

Involvement of cytokine-induced neutrophil chemoattractant in hypothalamic thermoregulation of luteinizing hormone-releasing hormone

We demonstrated in a previous study that serum IL-8 concentrations were significantly higher in women with hot flashes than without hot flashes. To clarify the role of IL-8 in the pathoetiology of menopausal hot flashes, we examined the effect of rat cytokine-induced neutrophil chemoattractant (CINC), a member of the IL-8 family, on thermoregulation using ovariectomized (OVX) rats treated with intracerebroventricular (i.c.v.) injection of LHRH agonist (LHRHa) as a model of hot flashes. We found that: 1) expression of CINC mRNA was increased around the periventricular area in the hypothalamus at 1 h, and the serum CINC concentration was increased at 2 h after i.c.v. injection of LHRHa; 2) the increase in serum CINC concentration in hypophysectomized rats was significantly lower than that in sham-operated rats; 3) i.c.v. but not iv injection of CINC elevated the rectal temperature of OVX rats; 4) i.c.v. injection of LHRHa into OVX rats produced a rapid rise (maximal increase: 10-25 min) in tail skin temperature, and the elevation was augmented by injection of an anti-CINC antibody; and 5) changes in serum CINC concentration and skin temperature after i.c.v. injection of LHRHa were reversed by replacement of estradiol. In conclusion, the production of CINC in the hypothalamus due to LHRHa injection in OVX rats was increased after elevation of skin temperature, suggesting that CINC plays a key role in the homeostasis of body temperature. Disturbance of the thermoregulatory mechanism involving LHRH and CINC may be related to the pathoetiology of hot flashes.

Acupuncture reduces experimental renovascular hypertension through mechanisms involving nitric oxide synthases

OBJECTIVE

To test the hypothesis that acupuncture on stomach 36 point (ST-36) reduces hypertension by activating nitric oxide synthase signaling mechanisms.

METHODS

The authors used the two-kidney, one-clip renal hypertension (2K1C) hamster model with electroacupuncture treatment.

RESULTS

Thirty-minute daily electroacupuncture treatment for 5 days reduced mean arterial pressure from 160.0 +/- 7.6 to 128.0 +/- 4.3 mmHg (mean +/- SEM), compared to 115.0 +/- 7.2 mmHg in sham-operated hamsters. Electroacupuncture increased periarteriolar NO concentration from 309.0 +/- 21.7 nM to 417.9 +/- 20.9 nM in the 2K1C hamster cheek pouch microcirculation when measured with NO-sensitive microelectrodes. Hypertension reduced endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) proteins relative to the sham-operated control, as measured by Western blotting. Electroacupuncture prevented the reduction of eNOS and nNOS associated with hypertension and showed even higher eNOS and nNOS expressions than sham-operated control in stomach and cheek pouch tissues, which are on the stomach meridian. Analysis of liver tissue, a non-stomach-meridian organ, indicated that electroacupuncture did not have a significant benefit in terms of enhanced expressions of eNOS and nNOS in the treated 2K1C hypertensive group.

CONCLUSIONS

Activation of eNOS and nNOS is one of the mechanisms through which ST-36 electroacupuncture reduces blood pressure; this reduction works through the stomach meridian.

Breast and infant temperatures with twins during shared Kangaroo Care

Kangaroo Care has been shown to keep a singleton preterm infant warm by body heat generated in maternal breasts that is conducted to the infant. No studies have examined whether twins simultaneously receiving Kangaroo Care, called Shared Kangaroo Care, are sufficiently warm and how the breasts respond to twin presence. Two case studies were done to determine the temperatures of twins being simultaneously kangarooed and the temperatures of maternal breasts during Shared Kangaroo Care. Two sets of premature twins were held in Shared Kangaroo Care for 1.5 hours. Infant temperatures were recorded from incubators; breast temperatures were recorded from thermistors. Infant temperatures remained warm and increased during Kangaroo Care, and each breast appeared to respond to the thermal needs of the infant on that breast. Physiological explanations for thermal synchrony exist. These data suggest that twins can be simultaneously held in Kangaroo Care without thermal compromise because each breast responds individually to the infant's thermal needs.