Circadian Rhythms of Brain Temperature in the Chicken, Measured at Different Levels of Constant Illumination

Abstract

Summary 1) Temperature was recorded continuously at various depths in the brain tissue of unanesthetized but moderately restrained chickens. The chickens were kept in a small round arena within a soundproof chamber and exposed to constant illumination for up to 18 days. Activity on a spring-suspended floor in the arena was recorded on print-out counters. Light intensity was varied from 0.05 to 100 lux, but was kept constant for at least 24 hr and in most experiments for several days.2) The brain temperature and most of the activity of all chickens showed clear circadian rhythms. For each condition, the following parameters were computed : mean level of brain temperature, range of circadian oscillation, and amount of activity. 3) Level of brain temperature and amount of activity were positively correlated with light intensity. For the range of brain temperature oscillation, such a correlation was indicated by one statistical test, but the correlation was not significant with increased intensity in two other tests. 4) Range of oscillation seemed to be positively correlated with brain temperature levels at lower values, and negatively correlated at higher values of mean level. 5) The changes in brain temperature in response to changes in light intensity were rather abrupt and simultaneous in all parts of the tissue.In most of the species studied so far, the period of the free-running circadian rhythm depends systematically on light intensity (HOFFMANN, 1965). Little is known about other rhythm parameters' such as range (= difference between maximum and minimum within one period) and mean level (= arithmetic average of all instantaneous values measured within one period). From activity records, the ratio between activity time and rest time, as well as the amount of activity per period, have been computed as subsidiary quantities (ASCHOFF and WEVER, 1962).

Metabolic rate: its circadian rhythmicity in the female domestic fowl.

“…Similar extinctions of rhythmicity were noted for metabolic rate by Kayser in the pigeon kept in darkness (cited by Herring & Brody, 1938) and for locomotor activity and heart rate in the male chicken kept in continuous red light (Winget, Card & Pope, 1968). Also in the male chicken, brain temperature rhythms were smaller in LL conditions than in LD conditions (Aschoff & Von St Paul, 1973). It seems thus possible that a certain lighting intensity is requisite for the maintenance of free-running rhythmicity.…”

“…The nychthemeral cycle in quasinatural lighting may thus act to amplify the free-running circadian rhythm in metabolic rate. This suggestion is also supported by the smaller oscillation range of free-running rhythms as compared to entrained rhythms in brain temperatures (Aschoff & Von St Paul, 1973).…”

Circadian rhythms of urinary excretion: the relationship between the amount excreted and the circadian changes.

“…1965;Mann, 1972;Mann et at. 1976;Wesson, 1964), with other variables, for example reaction time (Mann, Rutenfranz & Wever, 1972), and in other species (Aschoff & von Saint Paul, 1973;Sollberger, 1955). Interestingly, in Fig.…”

Circadian clock in cell culture: I. Oscillation of melatonin release from dissociated chick pineal cells in flow-through microcarrier culture

“…The lengthening of period by constant light treatment is opposite that expected on the basis of empirical data for diurnal birds as described by Aschoff s rule, which shows that constant light treatment shortens the freerunning period in passerine birds (Daan and Pittendrigh, 1976). In intact chickens, however, brain temperature (Aschoff and von Saint Paul, 1973) activity, and oviposition rhythms (Cain and Wilson, 1972) did not show a significant change in period with increasing light intensities over the limited range tested. Therefore, domestic chickens might represent an exception to Aschoff s rule.…”