Diazepam modulates the period of locomotor rhythm in mice (Mus booduga) and attenuates light-induced phase advances

Chronic ethanol intake alters circadian phase shifting and free-running period in mice

Chronic alcohol intake is associated with widespread disruptions in sleep and circadian rhythms in both human alcoholics and in experimental animals. Recent studies have demonstrated that chronic and acute ethanol treatments alter fundamental properties of the circadian pacemaker--including free-running period and responsiveness to photic and nonphotic phase-shifting stimuli--in rats and hamsters. In the present work, the authors extend these observations to the C57BL/6J mouse, an inbred strain characterized by very high levels of voluntary ethanol intake and by reliable and stable free-running circadian activity rhythms. Mice were housed individually in running-wheel cages under conditions of either voluntary or forced ethanol intake, whereas controls were maintained on plain water. Forced ethanol intake significantly attenuated photic phase delays (but not phase advances) and shortened free-running period in constant darkness, but voluntary ethanol intake failed to affect either of these parameters. Thus, high levels of chronic ethanol intake, beyond those normally achieved under voluntary drinking conditions, are required to alter fundamental circadian pacemaker properties in C57BL/6J mice. These observations may be related to the relative ethanol insensitivity displayed by this strain in several other phenotypic domains, including ethanol-induced sedation, ataxia, and withdrawal. Additional experiments will investigate chronobiological sensitivity to ethanol in a range of inbred strains showing diverse ethanol-related phenotypes.

Diazepam affects both level and amplitude of rat locomotor activity rhythm but has no effect on core body temperature

The present study investigates the effects of a chronic administration of diazepam, a benzodiazepine widely used as an anxiolytic, on locomotor activity and body core temperature rhythms in male Wistar rats housed under 12 : 12 light : dark (LD) cycle conditions. Diazepam was administered subcutaneously for 3 wks in a dosage of 3 mg/kg body weight/day, 1 h before the onset of darkness. Diazepam increased the level of locomotor activity from the first day until the end of treatment, and also increased the amplitude of the activity circadian rhythm, but only on the third wk of treatment. Diazepam exerted no effects on the length of the period and did not affect the phase of the locomotor activity rhythm. The body temperature rhythm of rats was affected neither by short-term (a single injection) nor by long-term (every day for 3 wks) diazepam treatment. Diazepam lacked effect on body core temperature even on the first day of administration, thereby ruling out the possibility of drug tolerance development. The fact that diazepam affects locomotor activity, but not core body temperature, suggests that different mechanisms mediate the actions of diazepam on locomotor activity and on core body temperature.

Circadian variation of core body temperature in Parkinson disease patients with depression: a potential biological marker for depression in Parkinson disease

BACKGROUND

The biological rhythm in comorbidity of depression and Parkinson disease (PD) is still unclear. For early diagnosis or clarification of the pathologic condition of comorbidity of depression and PD, the present study investigated the presence of circadian rhythm abnormalities in patients with depression.

METHODS

We measured the rectal temperature (RT) in 30 PD patients with or without depression during 48 consecutive hours using the maximum entropy method (MEM) and least-squares method (COSINOR). The presence of major or minor depression was evaluated by the Mini International Neuropsychiatric Interview based on the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders, and the Hamilton Depression Scale.

RESULTS

The RT rhythms of patients without depression predominately showed a circadian rhythm. However, 2 of 6 patients with depression showed an infradian rhythm using MEM. COSINOR revealed that PD patients with depression showed lower amplitudes of core body temperature (p = 0.012) and higher minimum RT (p = 0.031) relative to those of patients without depression.

CONCLUSION

PD patients with depression show an altered RT circadian rhythm. The results suggest that the characteristics of core body temperature could be potentially used as a biological marker for depression in PD.

Effect of melatonin and diazepam on the dissociated circadian rhythm in rats

The main structures involved in the circadian system in mammals are the suprachiasmatic nuclei (SCN) of the hypothalamus. The SCN contain multiple autonomous single-cell circadian oscillators that are coupled among themselves, generating a single rhythm. However, under determined circumstances, the oscillators may uncouple and generate several rhythmic patterns. Rats exposed to an artificially established 22-h light-dark cycle (T22) express two stable circadian rhythms in their motor activity that reflect the separate activities of two groups of oscillators in the morphologically well-defined ventrolateral and dorsomedial SCN subdivisions. In the experiments described in this paper, we studied the effect of melatonin and diazepam (DZP) administration in drinking water on the dissociated components of rat motor activity exposed to T22, to deduce the possible mechanism of these drugs on the circadian system. In order to suppress the endogenous circadian rhythm of melatonin, in some of the rats the pineal gland or the superior cervical ganglia were removed. The results show that melatonin or DZP treatment increased the manifestation of the light-dependent component to the detriment of the manifestation of the non-light-dependent component and that melatonin, but not DZP, shortens the period of the non-light-dependent component. These findings suggest that both DZP and melatonin favor entrainment to external light, and that melatonin could also act on the SCN, producing changes in the period of the circadian cycle.

Alcohol consumption and the body's biological clock

This review summarizes new findings on the bidirectional interactions between alcohol and the clock genes, underlying the generation of circadian rhythmicity. At the behavioral level, both adult and perinatal ethanol treatments after the free-running period and light response of the circadian clock in rodents; genetic ethanol preference in alcohol-preferring rat lines is also associated with alterations in circadian pacemaker function. At the neuronal level, it has been shown that ethanol consumption alters the circadian expression patterns of period (per) genes in various brain regions, including the suprachiasmatic nucleus. Notably, circadian functions of beta-endorphin-containing neurons that participate in the control of alcohol reinforcement become disturbed after chronic alcohol intake. In turn, per2 gene activity regulates alcohol intake through its effects on the glutamatergic system through glutamate reuptake mechanisms and thereby may affect a variety of physiological processes that are governed by our internal clock. In summary, a new pathologic chain has been identified that contributes to the negative health consequences of chronic alcohol intake. Thus, chronic alcohol intake alters the expression of per genes, and as a consequence, a variety of neurochemical and neuroendocrine functions become disturbed. Further steps in this pathologic chain are alterations in physiological and immune functions that are under circadian control, and, as a final consequence, addictive behavior might be triggered or sustained by this cascade.

Chronic ethanol intake alters circadian period-responses to brief light pulses in rats

Although chronic alcohol intake is associated with widespread disruptions of sleep-wake cycles and other daily biological rhythms in both human alcoholics and experimental animals, the extent to which the chronobiological effects of alcohol are mediated by effects on the underlying circadian pacemaker remains unknown. Nevertheless, recent studies indicate that both adult and perinatal ethanol treatments may alter the free-running period and photic responsiveness of the circadian pacemaker. The present experiment was designed to further characterize the effects of chronic ethanol intake on the response of the rat circadian pacemaker to brief light pulses. Ethanol-treated and control animals were exposed to 15-min light pulses during either early or late subjective night on the first day of constant darkness following entrainment to a 12:12 light-dark cycle. Relative to pulses delivered during early subjective night and to "no-pulse" conditions, light pulses delivered during late subjective night resulted in period-shortening after-effects under constant darkness, but only in control animals, not in ethanol-treated animals. These results indicate that chronic ethanol intake reduces the responsiveness of the circadian pacemaker to acute photic stimulation, and suggest that the chronobiological disruptions seen in human alcoholics are due in part to alterations in circadian pacemaker function.

Effect of chronic ethanol ingestion on biochemical circadian rhythms in Wistar rats

Chronic ingestion of ethanol for 60 days was known to alter the characteristics of biochemical circadian rhythms in Wistar rats. Peak times of glucose, potassium and lactic acid rhythms were delayed by 18 h, 3 h, and 3 h respectively, whereas peak times of cholesterol and malondialdehyde rhythms were advanced by 3 h and 9 h respectively during ethanol treatment. Significant changes in range (p < 0.001 expect in calcium) and 24 h mean (p < 0.001) of all the biochemical circadian rhythms studied were observed during ethanol treatment. The alterations in the characteristics of these biochemical circadian rhythms could be principally due to the alterations on the hepatic cellular architecture; other plausible underlying reasons are also discussed.

Lithium modulates biochemical circadian rhythms in Wistar rats

We studied the effects of chronic lithium treatment on circadian rhythms of glucose, cholesterol, calcium, potassium, malondialdehyde (MDA), and lactic acid in Wistar rats. Lithium altered the peak time, range, and 24h mean of these biochemical rhythms. Peak times of the circadian rhythms of glucose, calcium, and potassium were delayed by 3h, 6h, and 6h, respectively, whereas circadian rhythms of MDA and lactic acid were advanced by 9h and 3h, respectively, in lithium-treated rats. Delays observed in our experiments would support the hypothesis that lithium's therapeutic effect is to delay overtly fast circadian rhythms. Advances of peak times owing to lithium treatment are discussed.