Kazuyuki Shinohara

Effects of estrogen and progesterone on the expression of connexin-36 mRNA in the suprachiasmatic nucleus of female rats

To determine the effects of ovarian steroid hormones on gap junction communication in the suprachiasmatic nucleus (SCN), we examined the effects of estrogen and/or progesterone on the expression of connexin-36 mRNA in the SCN and cerebral cortex (CX) of female rats. Ovariectomized adult rats were injected with 20 microg 17beta-Estradiol or sesame oil 48 h before sacrifice and further injected with 1.5 mg progesterone or sesame oil 24 h before sacrifice. Northern blot revealed that estrogen significantly increased the expression of connexin-36 mRNA in the SCN and this increase was inhibited by progesterone. On the other hand, the connexin-36 mRNA level in the CX was not affected by estrogen or progesterone. These results suggest that the gap junction with connexin-36 in the SCN is specifically regulated by ovarian steroid hormones of female rats.

Effect of estrogen on the expression of Cry1 and Cry2 mRNAs in the suprachiasmatic nucleus of female rats.

To determine whether estrogen has an effect on clock genes in the suprachiasmatic nucleus (SCN), we examined the effect of estrogen on the expression of Cry1 and Cry2 mRNAs in the SCN of female rats. Ovariectomized rats were injected with 20 microg 17beta-estradiol at zeitgeber time (ZT) 6 and ZT 18 and killed 24 h after the treatment. Northern blot revealed that the expression of Cry2 mRNA was significantly decreased in the SCN of estrogen-treated rats at both time points [correction]. But estrogen did not affect Cry1 mRNA levels in the SCN at any ZT. These results suggested that Cry1 and Cry2 mRNAs in the SCN were differently regulated by estrogen.

Menstrual and circadian variations in time perception in healthy women and women with premenstrual syndrome

A time production test was performed in seven normal females and seven females with premenstrual syndrome (PMS). We used a time production test for six time intervals (6, 12, 24, 36, 48, 60 s). Time production tests were performed at 08:00, 14:00 and 20:00 h in the follicular, early luteal and late luteal phases (LLP), respectively. The results are as follows. (1) Normal females showed diurnal variations in time production only in the follicular phase (FP). In this phase, they overproduced time at 08:00 h suggesting that the interval clock in normal females was slowest in the morning. (2) Normal females showed menstrual variations in time production only at 20:00 h. They overproduced time in the LLP suggesting that the interval clock in normal females was slowest in the LLP. (3) Neither diurnal nor menstrual variation was found in PMS subjects at any menstrual stage or at any time of the day. These results suggest that the interval timing system in normal females is under the control of ovarian steroid hormones and the circadian clock, but the control of ovarian steroid hormone or the circadian clock does not operate in PMS subjects.

Circadian and photic regulation of cryptochrome mRNAs in the rat pineal gland

Expressions of Cry1 and Cry2 mRNA in the rat pineal gland were examined by Northern blot. The levels of Cry1 and Cry2 transcript had a marked circadian rhythm with peaks at circadian time (CT) 20 in constant darkness. But the amplitude of the Cry1 rhythm was higher than that of the Cry2 rhythm. Furthermore, a significant increase in Cry1 mRNA levels was caused by light pulse given at CT 16 but not at CT 4, but the expression of Cry2 was not significantly induced by light pulses given at either CT 4 or CT 16. These results suggest that Cry1 in the pineal gland is regulated by photic and circadian information but Cry2 is only regulated by circadian information.

Lack of circadian patterns in vasoactive intestinal polypeptide release and variability in vasopressin release in vole suprachiasmatic nuclei in vitro

Organotypic hypothalamic cultures of neonatal rats comprising the suprachiasmatic nuclei (SCN) produce stable 20 h release patterns of vasoactive intestinal polypeptide (VIP) and arginine-vasopressin (AVP). Compared with rats, voles show variably expressed circadian activity patterns. In this study we measured neuropeptidergic release patterns in organotypic SCN cultures of neonatal common voles (Microtus arvalis, n = 6). Slices were prepared at postnatal day 6. After 14 days of incubation, 2 h samples of medium were collected during 50 h. None of the vole SCN slices showed a circadian modulation in VIP release. Peaks in AVP occurred, 20 h apart from each other, in four of six vole SCN slices. These findings contrast with the concurrent release patterns of VIP and AVP in rat SCN slices. The results suggest an independent role of both neuropeptides in the oscillatory output pathways of the circadian pacemaker in the common vole.

Long-term rectal temperature measurements in a patient with menstrual-associated sleep disorder

Abstract The international classification of sleep disorders has proposed menstrual‐associated sleep disorder. However, few studies have investigated its pathophysiological mechanism. A 34‐year‐old woman complaining of insomnia in the late luteal phase underwent continuous rectal temperature measurements and simultaneous actigraphic monitoring for 146u2003days. The acrophase of rectal temperature rhythm was delayed in the luteal phase, compared with that in the follicular phase. Her bedtime and risetime did not differ across the menstrual cycle. These results suggest that her insomnia in the luteal phase may have been a consequence of desynchronization between her temperature rhythm and sleep phase in the luteal phase.

Influences of cholinergic neurotoxin ethylcholine aziridinium ion on circadian rhythms in rats

To investigate whether damages of cholinergic neurons in the brain produce aging-like changes in circadian rhythms, we examined the influences of intracerebroventricular injection of cholinergic neurotoxin ethylcholine aziridinium ion (AF64A, 5 nmol/5 microl) on circadian rhythms in rats, by measuring locomotor activity and body temperature with the automatic behavioral measurement system combined with the telemetry. Daily rhythms in locomotor activity and body temperature were observed in AF64A-treated rats under a 12:12 h light:dark (LD) cycle, however, in AF64A-treated rats, the amplitude of activity and temperature rhythms was significantly decreased, the phase of the both rhythms was advanced and the amount of activity was decreased, compared with control rats. Locomotor activity and body temperature also showed a circadian rhythm in AF64A-treated rats under the constant dark condition with the period similar to that in the control rats. The present findings are in accordance with the observation in aged animals in which cholinergic hypofunction are often observed, suggesting that hypofunctions of the cholinergic systems in the brain might be involved in aging-like changes in the circadian rhythms.