Photoperiodic regulation of the time of birth in rats: Involvement of circadian endogenous mechanisms

Bosc, M. J.

doi:10.1016/0031-9384(90)90341-z

Cited by 18 publications

(7 citation statements)

References 28 publications

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“…Pups were estimated to have been born between 0700 and 1000 h, within 3 h of lights-on, comparable to that in previous reports [42][43][44][45]. By contrast, births were delayed in 91% of PnX rats, 73% of VnX rats, and 86% of PnXþVnX rats.…”

Section: Effects Of Neurectomy On Timing Of Birth and Hormones In Cirmentioning

confidence: 81%

Transection of the Pelvic or Vagus Nerve Forestalls Ripening of the Cervix and Delays Birth in Rats1

Clyde

Lechuga

Ebner

et al. 2011

Biology of Reproduction

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Innervation of the cervix is important for normal timing of birth because transection of the pelvic nerve forestalls birth and causes dystocia. To discover whether transection of the parasympathetic innervation of the cervix affects cervical ripening in the process of parturition was the objective of the present study. Rats on Day 16 of pregnancy had the pelvic nerve (PnX) or the vagus nerve (VnX) or both pathways (PnX+VnX) transected, sham-operated (Sham) or nonpregnant rats served as controls. Sections of fixed peripartum cervix were stained for collagen or processed by immunohistochemistry to identify macrophages and nerve fibers. All Sham controls delivered by the morning of Day 22 postbreeding, while births were delayed in more than 75% of neurectomized rats by more than 12 h. Dystocia was evident in more than 25% of the PnX and PnX+VnX rats. Moreover, on prepartum Day 21, serum progesterone was increased severalfold in neurectomized versus Sham rats. Assessments of cell nuclei counts indicated that the cervix of neurectomized rats and Sham controls had become equally hypertrophied compared to the unripe cervix in nonpregnant rats. Collagen content and structure were reduced in the cervix of all pregnant rats, whether neurectomized or Shams, versus that in nonpregnant rats. Stereological analysis of cervix sections found reduced numbers of resident macrophages in prepartum PnX and PnX+VnX rats on Day 21 postbreeding, as well as in VnX rats on Day 22 postbreeding compared to that in Sham controls. Finally, nerve transections blocked the prepartum increase in innervation that occurred in Sham rats on Day 21 postbreeding. These findings indicate that parasympathetic innervation of the cervix mediates local inflammatory processes, withdrawal of progesterone in circulation, and the normal timing of birth. Therefore, pelvic and vagal nerves regulate macrophage immigration and nerve fiber density but may not be involved in final remodeling of the extracellular matrix in the prepartum cervix. These findings support the contention that immigration of immune cells and enhanced innervation are involved in processes that remodel the cervix and time parturition.

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Section: Effects Of Neurectomy On Timing Of Birth and Hormones In Cirmentioning

confidence: 81%

Transection of the Pelvic or Vagus Nerve Forestalls Ripening of the Cervix and Delays Birth in Rats1

Clyde

Lechuga

Ebner

et al. 2011

Biology of Reproduction

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“…The doe emits a pheromone at her ventrum that guides a highly stereotyped nipple search behavior of the pups (Schley, 1977(Schley, , 1981 Regular anticipation of nursing would require the doe to have a predictable nursing rhythm and the pups to have the capability to measure time, by means of either an interval timer or an oscillator system. Since parturition most frequently occurs during resting time (Lincoln and Porter, 1976;Gattermann, 1983;Reppert et al, 1987;Bosc, 1989), the rabbit, which is predominantly nocturnally active under undisturbed conditions (Jilge, 1991b), should give birth during the light phase (L). Because in the natural habitat as well as in the laboratory, the doe has to visit the pups outside her &dquo;housing area&dquo; in order to nurse them, she should synchronize nursing with major activity by shifting nursing to the time of nocturnally elevated activity.…”

mentioning

confidence: 99%

The Ontogeny of Circadian Rhythms in the Rabbit

Jilge

1993

J Biol Rhythms

100

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The nursing rhythms of 14 rabbit does and the activity of 18 litters from birth to days 14-16 were monitored continuously, as were the circadian rhythms of different behavioral functions of 10 young rabbits from weaning until day 380 of life. The does gave birth 2 hr, 26 min +/- 2 hr, 8 min after lights-on in a light-dark cycle (LD 12:12). The first nursing occurred 20 hr, 30 min +/- 2 hr, 21 min after parturition. Does that had continuous access to the next boxes exhibited a regular once-a-day nursing rhythm; the nursing visits to the litters occurred during the dark phase (D). The nursing visits lasted 3 min, 42 sec +/- 25 sec. Nursing advanced during the first 10 days of lactation by an average of 42 +/- 16 min/day, and thus shifted to the first half of D. The pups anticipated nursing by a significant increase of activity, which was established between days 1 and 5 of life. In two does, the nursing rhythm split into two nursing visits per day, one during D and one during the light phase (L). When scheduled to nurse at an "artificial" phase in L with T = 24 hr, the pups' anticipatory activity was entrained by the 24-hr nursing rhythm. During a 48-hr fast, the elevated activity persisted around the phase of prior nursing time, demonstrating that it was controlled by an endogenous oscillator entrained by the zeitgeber of maternal nursing. Of 10 weanlings, 6 first exhibited a trimodal rhythm, which turned bimodal within 3-6 days. Stable entrainment by the external LD zeitgeber was attained by about days 45-80, and full nocturnality was attained by about days 200-250 after weaning. Having attained steady-state conditions, 7 of 10 rabbits exhibited a stable unimodal, nocturnal rhythm in each of the five functions, while the other 3 retained a bimodal rhythm.

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“…32, 54, 56; reviewed in Ref. 36) and in sensitivity of the myometrium to OT (5,34,36), and that there is a direct relationship between these rhythms and the light-dark cycle (7,18). The findings are also consistent with the fact that rabbits usually give birth during the day but nurse their young at night (Refs.…”

Section: Discussionmentioning

confidence: 79%

Effect of photoperiod on the mechanical response of the pregnant rabbit uterus to oxytocin

Ninomiya-Alarcon

Hudson²,

Reyes-Guerrero³

et al. 2004

American Journal of Physiology-Regulatory, Integrative and Comp

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We present findings suggesting that photoperiod is important in determining the sensitivity of the late-pregnant rabbit uterus to oxytocin (OT). Longitudinal myometrial strips were taken from term-pregnant and estrous rabbits and mounted in an organ bath for isometric myographic recording at different times during a 16:8-h light-dark cycle (lights on 0600 -2200; n ϭ 5/group), and the strength of contractions was registered in response to the application of OT or KCl. Strength of contractions was dose dependent and was up to 200 times greater at doses three to four orders of magnitude lower in tissue taken from pregnant animals during the light phase (0700 and 1300) than during the dark phase (2400 and 0400). Strips from nonpregnant estrous females also showed greater sensitivity and contractile force when taken in the light (0700) than in the dark (0400), although the differences were not significant. Consistent with the influence of photoperiod on uterine sensitivity to OT, strips taken from two groups of pregnant females (n ϭ 5/group) maintained on a light-dark cycle advanced 12 h showed significantly greater sensitivity and force in response to OT during the new subjective light than during the new subjective dark phase. The photoperiod-dependent contractile response to OT was specific and not simply the result of a change in general mechanical properties of the muscle, because administration of KCl resulted in dose-dependent contractions of similar magnitude in both the light and dark phase. These results are consistent with the fact that rabbits, like other nocturnal mammals, typically give birth during the day. parturition; electromyographic uterine recording; circadian rhythmicity MUCH EFFORT HAS BEEN DIRECTED to understanding the processes triggering parturition, and although this is still not completely understood, some common features are emerging. One is that parturition has a strong diurnal component such that mammals usually give birth during their species-typical rest period (reviewed in Refs. 14,35,36,54): nocturnal mammals such as the rat during the day (28, 39, 52, 61) and diurnal mammals such as sheep (Ref. 30; own observations), monkeys (15,16,56), and humans (9,10,29,49,55,64) during the night. Moreover, in humans, births occurring at night are typically of shorter duration, require fewer interventions, and have an obstetrically better outcome than births occurring during the day (Refs. 3,9,55,60; reviewed in Ref. 36).A second common feature is the importance of the hormone oxytocin (OT), released at the time of parturition from the posterior pituitary into the bloodstream, in helping to initiate and sustain the uterine contractions necessary for expulsion of the fetus(es) (1, 11, 12, 17, 19, 23-25, 31, 33, 50, 67). In those species in which it has been studied, principally macaque monkeys and humans, there is a diurnal rhythm in circulating levels of OT, with the highest levels at night (18,20,33,34,36,65). This rhythm becomes more pronounced as gestation progresses and is most marked at the...

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Photoperiodic regulation of the time of birth in rats: Involvement of circadian endogenous mechanisms

Cited by 18 publications

References 28 publications

Transection of the Pelvic or Vagus Nerve Forestalls Ripening of the Cervix and Delays Birth in Rats1

Transection of the Pelvic or Vagus Nerve Forestalls Ripening of the Cervix and Delays Birth in Rats1

The Ontogeny of Circadian Rhythms in the Rabbit

Effect of photoperiod on the mechanical response of the pregnant rabbit uterus to oxytocin

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