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At least 109 records · Page 6Linked to original sources
PubMed2000

Effect of egg deprivation on sex steroids, gonadotropin, prolactin, and growth hormone profiles during the reproductive cycle of the mouthbrooding cichlid fish Oreochromis niloticus.

Various hormones were analyzed during the course of a reproductive cycle in the cichlid fish Oreochromis niloticus: plasma levels of the gonadal steroids 17beta-estradiol (E2), testosterone (T), 17, 20beta-OH progesterone (17,20beta-P), gonadotropin (taGtH), and plasma and pituitary concentrations of prolactin (tiPRL(I) and tiPRL(II)) and growth hormone (tiGH). Two categories of fish were sampled and sacrificed on days 1 and 3 postspawning and at 3-day intervals thereafter: typical incubating females (INC), and nonincubating females (NI), deprived of their eggs just after spawning. Such deprivation is known to suppress maternal behavior and to accelerate ovarian development and especially vitellogenesis, thus shortening the mean interspawning interval. In both groups, variations of the plasma concentrations of E2 and T appeared to depend on ovarian stages, and differences between groups appeared to reflect underlying differences in the kinetics of ovarian development. The observation of noticeable levels of 17,20beta-P in plasma before spawning, when high values of taGtH could also be detected in NI females, suggests the implication of this progestin in the control of final maturation events, as in some other teleosts. Moreover, 17,20beta-P, which was still detected a few days after spawning, but at low concentrations and only in the plasma of INC females, might play a role at the beginning of the reproductive cycle in incubating females (maternal behavior and/or slowing down of ovarian growth). The pituitary and plasma profiles of both tiPRLs isoforms appeared to depend mainly on the kinetics of ovarian development in each group of fish, suggesting a role during the beginning of vitellogenesis. However, the variance of plasma tiPRL(II), which was significantly enhanced during maternal behavior in INC females, also suggests an implication of this hormone in the control of that behavior. Concerning tiGH, comparison of the plasma profiles in INC and NI fish also suggest an influence on the control of maternal behavior, but a main effect of starvation of INC during mouthbrooding cannot be excluded.

Animals↗
PubMed2002

Factors affecting plasma concentrations of prolactin in the common eider Somateria mollissima.

In the common eider only the females incubate while they fast for 25 days. Thus, since they rely entirely on their body reserves for successful incubation, they can be defined as capital incubators. To assess the potential effects of their initial body mass, the incubation duration, and depletion in body reserves on prolactinemia, blood samples of eiders were analyzed during the breeding cycle and an experimental manipulation of the duration of incubation. Levels of circulating prolactin increased at the onset of incubation and then reached a high and stable level during incubation before increasing sharply before hatching. The prolactin level decreased significantly upon hatching. Captive females deprived from their eggs exhibited a rapid decrease in prolactinemia, suggesting that egg stimuli are necessary to prolactin secretion. Aunts, i.e., helper females caring for conspecific young, presented prolactin levels higher than nonbreeding captive females but not significantly different from those of females at hatching. Plasma prolactin at hatch was directly related to body mass loss. Birds with shortened incubation have higher body masses and showed higher levels of prolactinemia at hatching than the control group, in accordance with the idea that circulant prolactin at hatching is linked to body condition. Females which underwent an extended incubation (and started to eat again) displayed a low body mass and a high prolactinemia. These data therefore suggest that refeeding, albeit increasing the risk of predation, enhances prolactin secretion and allows the bird to continue incubation despite that it has reached a poor body condition.

Animals↗
PubMed1998

The effect of exogenous testosterone on parental behavior, plasma prolactin, and prolactin binding sites in dark-eyed juncos.

Numerous studies have shown that parental behaviors are mediated by prolactin (PRL), while testosterone (T) interferes with their full expression. The limited data available suggest that reduced parental behavior induced by T is not mediated by reduced concentrations of plasma PRL. We hypothesized that T reduces parental behaviors by reducing PRL receptor binding activity at central neural sites that promote the expression of parental behaviors. To test this hypothesis we implanted male dark-eyed juncos (Junco hyemalis) with testosterone-filled or empty implants and measured T and PRL levels, paternal behavior, and specific binding of radio-labeled PRL at selected brain regions that have been implicated in the mediation of parental behaviors. Our findings concurred with previous studies in that T-treated males reduced their parental contributions, had higher levels of T, and had equivalent levels of PRL compared with controls. We found no differences in the capacity to bind 125I-oPRL in three brain regions previously implicated in the mediation of parental care in birds, i.e., the preoptic area, ventromedial nucleus of the hypothalamus, and paraventricular nucleus of the hypothalamus. Thus our findings do not support the hypothesis that T interferes with the expression of parental behavior by reducing PRL receptor binding activity at central sites.

Animals↗
PubMed2005

Carotenoid-based nestling colouration and parental favouritism in the great tit.

While elaborate carotenoid-based traits in adult birds may have evolved as honest signals of individual quality in the context of sexual selection or other social interactions, the function of carotenoid-based colours in juveniles is less well understood. We investigated the hypothesis that carotenoid-based nestling colouration has evolved in response to parental preference of intensely coloured offspring during food provisioning. In a field experiment, we manipulated nestling plumage colouration by a carotenoid-supplementation and analysed the parental food provisioning behaviour before feather appearance and at the end of the nestling stage. Carotenoids per se did not influence the nestling's begging behaviour or parental feeding decisions and we found no evidence that carotenoid-based colouration in nestling great tits has a signalling function in parent-offspring interactions. Parents did not discriminate between intensely coloured and control offspring in their food provisioning and in accordance with this finding intensely coloured nestlings were not heavier or larger at the end of the nestling stage. Alternative explanations for the evolution of carotenoid-based colours in nestling birds are discussed.

Animals↗
PubMed1984

Prostaglandin induction of spawning behavior in Cichlasoma bimaculatum (Pisces cichlidae).

Prostaglandin (PG) stimulates female spawning behavior in goldfish and in some other teleosts in which female reproductive behaviors consist of postovulatory oviposition acts. This study examined the effects of PG on female sexual behavior in a teleost fish, Cichlasoma bimaculatum, in which female reproductive behaviors involve both preovulatory courtship and substrate cleaning behaviors, and post-ovulatory oviposition behavior. In females of established pairs, PGF2 alpha injection (5 micrograms, im) at any stage of the spawning cycle, or in the parental phase, rapidly induced substrate cleaning which soon merged into oviposition behavior (without egg release). These results support a role for PG in oviposition behavior of Cichlasoma. However, indomethacin (1 mg, ip), a PG synthesis inhibitor, did not block oviposition in ovulated females which had begun to spawn. Indomethacin may not have lowered PG levels sufficiently. Alternatively, as shown by J.J. Polder (1971, Neth. J. Zool. 21, 265), oviposition behavior may be induced or maintained by other factors associated with the spawning situation.

Animals↗
PubMed1989

Ovarian hormone-induced short-latency maternal behavior in ovariectomized virgin Long-Evans rats.

Two ovarian hormone regimens reported to induce rapid-onset maternal behavior (MB) in maternally naive virgin, ovariectomized Sprague-Dawley (SD) albino rats (R. S. Bridges, 1984, Endocrinology 114, 930-940; A. L. Giordano, 1987, Doctoral Dissertation, Rutgers University, Newark, NJ) were assessed in Long-Evans (LE) hooded rats, a strain which tends to be less maternally responsive in various situations dissociated from parturition. The combination of sufficiently high and long-lasting treatments with estradiol (E, 10-mm Silastic capsule, sc, on Day 1) and progesterone (P, 3 x 30-mm Silastic capsules, Days 3-13) resulted in a mean MB onset latency (after pup presentation on Day 14) of 1.8 days. In contrast, no-hormone or P-only controls had latencies of about 5.5 days. However, the E + P combination was completely ineffective if the E capsule was withdrawn along with the P capsules, unlike the case for SD rats. Also in contrast to the albinos, E alone was ineffective, while E treatment following P withdrawal was only partially effective. The most efficacious regimen, which included a P treatment (injections of 4 mg/day, Days 3-12 or 3-15) known to maintain pregnancy in ovariectomized rats, resulted in mean latencies of less than or equal to 1 day; 39% overall displayed MB rapidly, i.e., retrieval within 15 min of exposure to pups and crouching by 3 hr, and 89% became maternal by the next day. With this regimen, neither duration of 4 mg/day P treatment (10 or 13 days) nor hysterectomy 2 days before testing affected MB latencies. Thus, the essential features of the previously reported ovarian hormone regimens for induction of short-latency MB are efficacious in LE rats, but the hormonal requirements in this strain seem to be more precise. Factors which might contribute to an even higher percentage maternal on the first day of pup exposure are considered.

Animals↗
PubMed1990

Plasma prolactin concentrations in breeding pied flycatchers (Ficedula hypoleuca) with an experimentally prolonged brooding period.

This experiment explored the stimulatory effect of brooding newly hatched young on plasma prolactin concentration in male and female pied flycatchers, Ficedula hypoleuca. By exchanging offspring between nestboxes, one group of parents was exposed to 1- to 3-day-old nestlings for 12 days. Females in this group continued night-time brooding during these 12 days. The females, but not the males (who do not participate in brooding nestlings), after 6 days had higher plasma prolactin concentrations than control birds which had shown a 50% reduction in night-time brooding at this stage. By Day 12, however, prolactin concentration had decreased to the same level as in control birds, even though these females were still brooding 3-day-old nestlings. Female flycatchers given 3-day-old nestlings on the day their own eggs hatched showed an earlier reduction in night-time brooding and an earlier decrease in plasma prolactin than did control birds. An early decrease in prolactin was also seen in the males of this experimental group.

Animals↗