Changes of phagocytic biological rhythm by reduction of circadian times and by influences upon hypothalamus.
The circadian oscillations of central temperature and phagocytic activity of blood polymorphonuclears were studied in guinea pigs after circadian times have been reduced, under the effect of chlorpromazine or in animals with bilaterally lesioned hypothalamus in preoptic or in tuberomammillary area. The phagocytic activity was assayed against staphylococcus epidermidis in heparinized blood. In the animals exposed to artificial light in conditions of space restriction (stressed) the phagocytic activity is depressed in the lighting period, the differences light-dark being higher (300%) as in controls (25%). Chlorpromazine lowers both central temperature and phagocytic activity, without changes of their circadian rhythms. Bilateral symmetrical injuries of the preoptic hypothalamic area determined a rise of the central body temperature in the beginning of the dark period. The phagocytic activity of these animals decreases especially at the end of the dark period. Lesions of the tuberomammillary area reduces the phagocytic activity to very low levels and attenuates to a marked extent its circadian oscillations. Body temperature remain unaffected. The circadian biorhythm of the body temperature and of the phagocytic activity, usually concurrently, are controlled by separate hypothalamic mechanisms. After tuberomammillary lesions the phagocytic response of animals to an endovenous injection of a bacterial suspension is very low. The results are discussed on the basis of present data and of prior researches of this laboratory.