Influence of photoperiod on the time of birth in the rat. IV. Effects of an imposed feeding rhythm

Abstract

Summary. In order to study the respective effects of photoperiod and feeding rhythm on the time of birth in rats, the onset Introduction.

Time of birth and daily activity mediated by feeding rhythms in the pregnant rat

“…These rhythms act by an interaction with the photoperiod, as observed previously in other conditions (Bosc and Nicolle, 1985 fig. 1 b).…”

“…Two definite periods of birth are often observed, depending on the photoperiod (Bosc, 1981) or the feeding regime (Bosc and Nicolle, 1985) (Reynolds, 1965 ;Bosc and Nicolle, 1980). In this experiment, the total activity time decreased as gestation progressed.…”

“…Other environmental cues, such as an imposed feeding rhythm, may affect birth distribution in this nocturnal species (Bosc and Nicolle, 1985). When food and water are given only during the early light phase of a standard light regime, most deliveries occur during the night between the usual last two days of pregnancy.…”

“…The difference in birth time between rats fed at will and those with an imposed feeding rhythm has suggested the existence of an obligatory shift between two types of activity : labor on one hand, and feeding or related activities on the other (Bosc and Nicolle, 1985). The days, 5-6 weeks before the males were introduced.…”

Photoperiod and parturition period in isolated or paired rats : influence of sight deprivation and social conditions

“…Après l'anesthésie, elles ont été gardées isolées (N ou E) ou en paires homogènes (NN et (Mitchell and Yochim, 1970;Plaut et t al., 1970;Lincoln and Porter, 1976;Bosc and Nicolle, 1980a), and therefore the birth mechanism, by endogenous events which are finally integrated at the uterine and cervical levels. Other environmental cues can also modify the time of birth in this species, as in the case of periodic food presentation (Bosc and Nicolle, 1985;Bosc et al, 1986) and probably of social environment (Bosc and Nicolle, 1985). In order to evaluate the possibility of a social influence on the time of parturition, pairs of normal and/or blinded rats were subjected to two different light regimens.…”