Circadian rhythms in rat mid‐brain and caudate nucleus biogenic amine levels

Abstract

SUMMARY1. The circadian rhythms of rectal temperature and biogenic amine levels in mid-brain and caudate nucleus have been measured in normal and adrenalectomized rats adapted to and maintained under fixed illumination cycle.2. Rectal temperature reaches a peak value between 24.00 hr and 06.00 hr during the dark phase of the illumination cycle at a time when motor activity is maximal. In adrenalectomized rats, the pattern is similar but the peak is significantly lower.3. Highest histamine levels in the caudate nucleus and mid-brain of normal and adrenalectomized rats are found at the time when body temperature and motor activity is maximal.4. Similarly, caudate nucleus and mid-brain noradrenaline levels reach their peak during the dark phase of the illumination cycle. These levels are significantly different from those found during the light phase of the illumination cycle. The rise in noradrenaline in the mid-brain of adrenalectomized rats, however, was not significant.5. Peak 5-hydroxytryptamine (5-HT) levels in the caudate nucleus of normal rats and the mid-brain of adrenalectomized rats were found to be 12 hr out of phase with peak values obtained for other parameters that were measured.6. The significance ofthese circadian rhythms in relation to states of sleep and wakefulness, general metabolism, and motor activity is discussed.

Sedation and histamine H1‐receptor antagonism: studies in man with the enantiomers of chlorpheniramine and dimethindene

“…Further, administration of histamine or drugs which enhance histaminergic transmission leads to desynchronization of the EEG and wakefulness (Wolf & Monnier, 1973;Monti et al, 1986;Lin et al, 1988), and histamine may also modulate the activity of medullary neurones (Jones et al, 1983;Bradley et al, 1984). Circadian rhythms in the level of histamine have been found in various regions of the brain (Friedman & Walker, 1968;Orr & Quay, 1975), and the rate of formation of histamine is elevated in rodents during the period of darkness when spontaneous activity is maximal (Schwartz et al, 1976). Nevertheless, it is possible that pharmacological activity other than H1 antagonism may give rise to sedation with antihistamines, and the drugs used in the present study, in particular chlorpheniramine, are not specific H1-receptor antagonists.…”

Diurnal Variation of Corticotropin-Releasing Activity in the Rat Hypothalamus

“…This pattern of change, therefore, differs from that of the CRF rhythmicity observed in the present experiment not only in its magnitude of change but also in the time phase relation to the lighting regimen employed. On the other hand, daily change in the serotonin content in the rat caudate nucleus and mid-brain (Friedman and Walker, 1968) as well as in the whole brain (Scheving et al, 1968) appears rather to resemble the pattern of CRF rhythmicity reported herein. But, the rise of serotonin content over its nadir was only 18% (Scheving et al, 1968) or at best 65 % (Friedman and Walker, 1968).…”

“…On the other hand, daily change in the serotonin content in the rat caudate nucleus and mid-brain (Friedman and Walker, 1968) as well as in the whole brain (Scheving et al, 1968) appears rather to resemble the pattern of CRF rhythmicity reported herein. But, the rise of serotonin content over its nadir was only 18% (Scheving et al, 1968) or at best 65 % (Friedman and Walker, 1968). Furthermore, we have already shown (Hiroshige et al, 1968a) that not only norepinephrine but also serotonin is virtually devoid of CRF-like activity when tested by our intrapituitary microinjection method.…”

“…As already reported (Hedge et al, 1966;Hiroshige et al, 1968a), this amount of vasopressin as well as oxytocin, when placed directly into the adenohypophysis, was proved quite ineffective in eliciting ACTH release. As to the biogenic amines present in the hypothalamus, daily rhythms were observed in the norepinephrine content of the rat hypothalamus (Manshardt and Wurtman, 1968) and also in the noradrenaline and histamine content in the caudate nucleus and mid-brain of the rat (Friedman and Walker, 1968). This pattern of daily change, however, showed the peak value during the dark period, usually early in the morning, and the minimum at 18: 00 or 24: 00 with the magnitude of daily fluctuation of 50 to 100% over the minimum.…”

The effects of hallucinogenic drugs on maze exploration in the rat over a 24 hour period

“…In the rat, a 24 h rhythm has been reported for such functions as motor activity (Richter, 1922;Peacock, Hodge & Thomas, 1966), body temperature (Halberg, 1960;Friedman & Walker, 1968) and brain concentration of biogenic amine (Scheving, Harrison, Gordon & Pauly, 1968 ; Davies, Ancill & Redfern, 1972).…”