Photoperiodic sensitivity of prepubertal female Fisher 344 rats.
TL;DR: It is concluded that the neuroendocrine‐reproductive system of the prepubertal F344 female rat is highly sensitive to light deprivation; light deprivation produces its antigonadotrophic effect through the pineal gland; and olfactory bulbectomy does not potentiate the effects of blinding in the F344 rat.
Abstract: The laboratory rat is thought to be a poor model for study of the photoperiodic control of reproduction; however, this has only been investigated in a few rat strains. The purpose of the present investigation was to determine if the neuroendocrine-reproductive system of the Fisher 344 (F344) rat, an inbred strain, is sensitive to light deprivation. All treatments were performed on 28-day-old female F344 rats and the animals maintained for 8 weeks in a 14:10 light:dark cycle. Blinding resulted in a 65% (P less than 0.01) reduction in uterine weight and a 25% (P less than 0.01) decrease in ovarian weight. Accompanying these reductions in blinded animals were significant inhibitions of anterior pituitary weight, serum prolactin levels, and pituitary prolactin synthesis as measured in vitro. Pinealectomy of the blinded animals prevented all of these effects. Additionally, when olfactory bulbectomy, a procedure known to sensitize rats to the effects of photoperiod, was combined with blinding, the results did not differ significantly from that found with blinding alone. From these data we conclude that 1) the neuroendocrine-reproductive system of the prepubertal F344 female rat is highly sensitive to light deprivation; 2) light deprivation produces its antigonadotrophic effect through the pineal gland; and 3) olfactory bulbectomy does not potentiate the effects of blinding in the F344 rat.
Citations
More filters
TL;DR: Clock genes are highly conserved across species including humans and there is no reason to suggest that they are functionless in humans, so the challenge issued here is for researchers to probe their function and the consequences of their disruption in both animal and human reproduction.
Abstract: Circadian rhythmicity is evident in a wide range of physiological systems including the reproductive axis. The recent discoveries of rhythmic clock gene expression in peripheral tissues, including reproductive tissue, suggests that they may play an important role in optimizing fertility. The evidence for rhythmic control of reproduction from studies in laboratory animals is reviewed and where possible this includes evidence from human studies. Clock genes are highly conserved across species including humans and there is no reason to suggest that they are functionless in humans. The challenge issued here is for researchers to probe their function and the consequences of their disruption in both animal and human reproduction.
112 citations
Cites background from "Photoperiodic sensitivity of prepub..."
...Fisher 344 rats, do retain photo-responsiveness, although the basis for this is not known (Leadem, 1988)....
[...]
...Nevertheless some strains, e.g. Fisher 344 rats, do retain photo-responsiveness, although the basis for this is not known (Leadem, 1988)....
[...]
TL;DR: These data are the first to document dramatic changes in the expression of the Lin28/let-7 axis in the rat hypothalamus during the postnatal maturation and after different manipulations that disturb puberty, thus suggesting the potential involvement of developmental changes in hypothalamic Lin28 / let-7 expression in the mechanisms permitting/leading to puberty onset.
Abstract: Lin28 and Lin28b are related RNA-binding proteins that inhibit the maturation of miRNAs of the let-7 family and participate in the control of cellular stemness and early embryonic development Considerable interest has arisen recently concerning other physiological roles of the Lin28/let-7 axis, including its potential involvement in the control of puberty, as suggested by genome-wide association studies and functional genomics We report herein the expression profiles of Lin28 and let-7 members in the rat hypothalamus during postnatal maturation and in selected models of altered puberty The expression patterns of c-Myc (upstream positive regulator of Lin28), mir-145 (negative regulator of c-Myc), and mir-132 and mir-9 (putative miRNA repressors of Lin28, predicted by bioinformatic algorithms) were also explored In male and female rats, Lin28, Lin28b, and c-Myc mRNAs displayed very high hypothalamic expression during the neonatal period, markedly decreased during the infantile-to-juvenile transition and reached minimal levels before/around puberty A similar puberty-related decline was observed for Lin28b in monkey hypothalamus but not in the rat cortex, suggesting species conservation and tissue specificity Conversely, let-7a, let-7b, mir-132, and mir-145, but not mir-9, showed opposite expression profiles Perturbation of brain sex differentiation and puberty, by neonatal treatment with estrogen or androgen, altered the expression ratios of Lin28/let-7 at the time of puberty Changes in the c-Myc/Lin28b/let-7 pathway were also detected in models of delayed puberty linked to early photoperiod manipulation and, to a lesser extent, postnatal underfeeding or chronic subnutrition Altogether, our data are the first to document dramatic changes in the expression of the Lin28/let-7 axis in the rat hypothalamus during the postnatal maturation and after different manipulations that disturb puberty, thus suggesting the potential involvement of developmental changes in hypothalamic Lin28/let-7 expression in the mechanisms permitting/leading to puberty onset
107 citations
TL;DR: Findings suggested that ELC affect mother–infant interactions and subsequently at least partially alter the neurobehavioral development of offspring.
Abstract: Rodent studies have revealed that the early rearing environment plays an important role in the development of stress vulnerability, memory and cognition. Although early lighting conditions (ELC) are involved in these neuronal developments through both maternal and offspring behavior, their influence has not been fully elucidated. Thus, by using Sprague-Dawley rats, we examined whether ELC affected maternal care by the dam and the subsequent neurodevelopment of the offspring. Prolonged dark phase conditions (PDC) (light/dark, 6/18 h) and prolonged light phase conditions (light/dark, 18/6 h) were administered from postnatal day 2 to postnatal day 14. Throughout this period, maternal care and the circadian rhythmicity of dams were investigated. In adolescence and adulthood of the offspring, we measured anxiety-like behavior, social interaction, object recognition memory, activity rhythm and corticosterone response to stress with hippocampal expression of N-methyl-D-aspartate and glucocorticoid receptor mRNAs. PDC altered maternal care and circadian rhythmicity in the dam compared with normal lighting conditions and prolonged light phase conditions. PDC markedly increased anxiety-like behavior, decreased social interaction and object recognition memory, and inhibited corticosterone feedback in offspring later in life. Furthermore, hippocampal levels of glucocorticoid receptor mRNA and N-methyl-D-aspartate receptor 2B mRNA in rats subjected to PDC were significantly lower than in animals subjected to normal lighting conditions. In the adult offspring, the circadian rhythm of locomotor activity was not affected. These findings suggested that ELC affect mother-infant interactions and subsequently at least partially alter the neurobehavioral development of offspring.
65 citations
Cites background from "Photoperiodic sensitivity of prepub..."
...tend to avoid rearing pups under the harsh conditions that would decrease their chance of survival (Leadem, 1988; Heideman & Sylvester, 1997; Lorincz et al., 2001)....
[...]
...Particularly in female rats, the duration of light exposure regulates the prolactin surge and subsequently controls reproduction (Pieper & Gala, 1979; Leadem, 1988; Nelson et al., 1994; Sterner & Cohen, 1995)....
[...]
...Laboratory rats are sensitive to reproductive inhibition by exposure to a short photoperiod alone and tend to avoid rearing pups under the harsh conditions that would decrease their chance of survival (Leadem, 1988; Heideman & Sylvester, 1997; Lorincz et al., 2001)....
[...]
TL;DR: The F344 strain of laboratory rats is the first in which unmanipulated animals have been found to be robustly affected byPhotoperiod, indicating that this strain could be a valuable new model for the study of reproductive regulation by photoperiod.
Abstract: Laboratory rats are considered to be reproductively unresponsive to photoperiod because photoperiod treatments do not induce robust reproductive responses. Groups of 15 young male Fischer 344 (F344) rats were tested for effects of long (16L:8D) and short (8L:16D) photoperiods on testicular development and body mass. Two weeks of short photoperiod inhibited testicular growth, spermatogenesis, and increases in body weight. Testis size became refractory to short photoperiod after 8 wk, but the body weight was lower in short photoperiod for the full 10 wk of the study. In young Harlan Sprague-Dawley rats, in contrast, long and short photoperiod had no effect on either body weight or testis size. Pinealectomized F344 rats had significantly higher body weights and larger testes than did sham-operated controls, suggesting that the effects of photoperiod are mediated, at least in part, by the pineal gland. The F344 strain of laboratory rats is the first in which unmanipulated animals have been found to be robustly affected by photoperiod, indicating that this strain could be a valuable new model for the study of reproductive regulation by photoperiod.
62 citations
TL;DR: Results suggest that differential responses of the Dio2 gene to photoperiod may determine the strain-dependent differences inPhotoperiod sensitivity in laboratory rats.
Abstract: The molecular basis of seasonal or nonseasonal breeding remains unknown. Although laboratory rats are generally regarded as photoperiod-insensitive species, the testicular weight of the Fischer 344 (F344) strain responds to photoperiod. Recently, it was clarified that photoperiodic regulation of type 2 iodothyronine deiodinase (Dio2) in the mediobasal hypothalamus (MBH) is critical in photoperiodic gonadal regulation. Strain-dependent differences in photoperiod sensitivity may now provide the opportunity to address the regulatory mechanism of seasonality by studying Dio2 expression. Therefore, in the present study, we examined the effect of photoperiod on Dio2 expression in photoperiod-sensitive F344 and photoperiod-insensitive Wistar rats. A statistically significant difference was observed between short and long days in terms of testicular weight and Dio2 expression in the F344 strain, while no difference was observed in the Wistar strain. These results suggest that differential responses of the Dio2 gene to photoperiod may determine the strain-dependent differences in photoperiod sensitivity in laboratory rats.
52 citations
Cites background or result from "Photoperiodic sensitivity of prepub..."
...This result was consistent with previous reports that the Wistar strain is a reproductively nonphotoperiodic strain, while the F344 strain is sensitive to photoperiod (11, 12, 14, 17, 28)....
[...]
...Gonadal development of F344 rats is also inhibited by blinding (17) or by melatonin injection (12)....
[...]
References
More filters
TL;DR: By the usual criteria in endocrinology, the pineal now fulfills all the qualifications of an organ of internal secretion.
Abstract: ONLY A LITTLE over a decade ago, any discussion of the function of the pineal gland included qualifying adjectives such as alleged, supposed, and putative. In the same vein, since it connoted a hormonal function, rather than referring to the pineal as a gland, the phrase pineal organ was usually employed to describe this portion of the epithalamus. However, this is no longer the case, at least in mammals. By the usual criteria in endocrinology, the pineal now fulfills all the qualifications of an organ of internal secretion. Several major discoveries revolutionized ideas concerning the function of the pineal gland. Certainly, as noted frequently in other reviews, the isolation and identification of N-acetyl-5-methoxytryptamine (melatonin), a pineal hormone, from bovine pineal tissue by Lerner et al. (1, 2) provided a strong impetus for subsequent investigations on this sometimes exasperating organ. At least as important as this discovery, however, were the observations that light and darkness govern both ...
1,229 citations
TL;DR: The pituitary response to chronic estrogen treatment was studied in two strains of rats, the Fischer 344 (F344) and the Holtzman, and these two strains differ dramatically in their pituitsary growth response to DES.
Abstract: The pituitary response to chronic estrogen treatment was studied in two strains of rats, the Fischer 344 (F344) and the Holtzman. Silastic tubing implants containing diethylstilbestrol (DES) were placed in weanling animals. Uterine and pituitary growth and protein synthesis were monitored over an 8-week period. The incorporation of [3H]leucine into PRL and GH was measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both F344 and Holtzman strains respond to chronic DES with an increase in PRL synthesis. PRL synthesis is 7% of the total protein synthesis in ovariectomized female controls of both strains and increases to 40–50% in 8-week DEStreated F344 rats and to 35–45% in Holtzman rats. The uterine growth responses were similar in both strains and reached a plateau after approximately 2 weeks. Despite their similarity in PRL synthesis and uterine growth, these two strains differ dramatically in their pituitary growth response to DES. In the F344 strain, pituitaries from treated animals a...
228 citations
TL;DR: The effect of light on a polyestrous mammal was investigated and it was found that the normal diurnal variations associated with estrus in the rat were reversed when the day-night rhythm of light was artificially shifted.
Abstract: THE FACT that light stimulates many vertebrates, hastening the onset of the breeding season or inducing precocious sexual maturity, has already been es-il_ tablished. It has also been shown that this stimulation of the gonads and accessories is mediated through the anterior pituitary. For a review of the subject see Bissonette (1). The effect of light on a polyestrous mammal was investigated by Hemmingsen and Krarup (2), who found that the normal diurnal variations associated with estrus in the rat were reversed when the day-night rhythm of light was artificially shifted. They further reported a prolonged cornification of the vagina in rats kept under continuous light. Browman (3), confirmed the effect of light on the vaginal smear and also found no significant change in the age at which vaginal introitus occurred.
164 citations
TL;DR: Giving the extract of a protein-free bovine pineal extract to intact animals caused effects varying with the dose, which reversed changes in ovarian hypertrophy, pituitary hyperTrophy, and adrenalhypertrophy.
Abstract: Fifty-four 26-day-old female rats of the CD strain were divided into four groups of 10 or 11 each, i.e. 1) controls; 2) animals given 0.3 ml of a protein-free bovine pineal extract daily intraperitoneally for 28 days; 3) sham-operated animals; 4) pinealectomized animals. In a second experiment two groups of six each were divided into a ) control animals given a diet restricted with respect to Na, K and phosphate, and b) animals on the same diet, given 1.0 ml/day of the pineal extract. Pinealectomy caused ovarian hypertrophy ( P < .001), pituitary hypertrophy ( P < .001), and adrenal hypertrophy ( P < .05). The extract reversed these changes. Giving the extract to intact animals caused effects varying with the dose. The dose of 0.3 ml given daily caused gonadal atrophy ( P < .05), pituitary atrophy ( P < .001) and insignificant adrenal activity. The dose of 1.0 ml caused further gonadal atrophy ( P < .001) and significant adrenal atrophy ( P < .05).
126 citations
92 citations