Polymorphisms in oestrogen and progesterone receptor genes: possible influence on prolactin levels in women.

OBJECTIVE: Oestrogen and progesterone are known to influence the release of human prolactin. The present study was undertaken in order to investigate the possible influence of polymorphisms of the genes encoding the oestrogen receptor (ER)alpha, ERbeta and the progesterone receptor (PGR), on prolactin levels in premenopausal women. DESIGN AND MEASUREMENTS: Serum levels of prolactin were measured in the follicular phase of the menstrual cycle. Subjects were genotyped with respect to a TA repeat polymorphism of the ERalpha gene, a CA repeat polymorphism of the ERbeta gene, and two polymorphisms of the PGR gene: one insertion polymorphism (PROGINS) and one single nucleotide polymorphism (G331A). SUBJECTS: A population-based cohort of 270 42-year-old women. RESULTS: The CA repeat polymorphism of the ERbeta gene and the G331A polymorphism of the PGR gene appeared to be associated with prolactin levels. In contrast, we found no evidence for an influence of the PROGINS polymorphism of the PGR gene or the TA repeat polymorphism of the ERalpha gene on the levels of this hormone. CONCLUSIONS: These data suggest that genetic variants of both the ERbeta and the PGR may influence prolactin release.

Association between a functional polymorphism in the progesterone receptor gene and panic disorder in women.

Although genetic factors are known to be important risk factors for panic disorder there is as yet no conclusive data regarding specific gene variants. Prompted by evidence supporting progesterone to influence the pathophysiology of panic disorder, polymorphisms in the progesterone receptor gene, a single nucleotide polymorphism (G331A) and an insertion/deletion polymorphism (PROGINS) were investigated in 72 patients with panic disorder and 452 controls. The frequency of the A-allele of the G331A polymorphism was higher in panic disorder patients than in controls (p = 0.01). When male and female patients were analyzed separately, the association was observed in female patients only (p = 0.0009), with an odds ratio of 3.5. No differences between groups were observed for the PROGINS polymorphism. In conclusion, these data suggest that the G331A polymorphism in the progesterone receptor gene may influence the risk for panic disorder in women.

Association between estrus cycle-related aggression and tidal volume variability in female Wistar rats.

Premenstrual dysphoria is characterized by symptoms such as irritability and depressed mood, present during the luteal phase of the menstrual cycle, and disappearing shortly after the onset of menstruation. Subjects with premenstrual dysphoria have previously been reported to display enhanced respiratory variability, and to experience anxiety when exposed to panicogens, such as CO2. In the present study, the possible influence of the estrus cycle and estrus cycle-related aggression on respiratory variability was investigated in female rats of the Wistar strain. The rats were subdivided into two groups: those displaying estrus cycle-related aggression, as evaluated using the resident intruder paradigm, and those not showing aggression throughout the estrus cycle. This model has been developed to serve as an animal model of premenstrual irritability. The former group was found to display higher tidal volume variability in diestrus, as compared to the non-aggressive rats. There was no effect of estrus cycle phase on respiratory variability. These results are well in line with the clinical observation that women with premenstrual dysphoria display higher respiratory variability than controls, and the notion that respiratory variability is a parameter of interest in this context. In our opinion, they also strengthen the concept of this animal model as a model of premenstrual irritability.

Association between estrus cycle-related changes in respiration and estrus cycle-related aggression in outbred female Wistar rats.

Premenstrual dysphoric disorder is characterized by irritability surfacing during the luteal phase of the menstrual cycle, and disappearing shortly after the onset of menstruation. Although the cardinal symptoms of premenstrual dysphoria are different from those of panic disorder, the two conditions share a number of traits indicating that they both may be associated with abnormalities in the regulation of respiration. Both subjects with panic disorder and subjects with premenstrual dysphoria are hence reported to display enhanced respiratory variability, and to experience anxiety when exposed to CO(2). In the present study, the possible influence of the estrus cycle on respiratory parameters in outbred female rats of the Wistar strain was investigated. Before being tested with respect to respiration, the rats were subdivided into two groups: those displaying estrus cycle-related variation in aggression, as evaluated using the resident intruder paradigm, and those not showing aggression throughout the cycle. Whereas the former group was found to display higher respiratory rate during the diestrus phase than during the proestrus/estrus phase, no cycle-related variation in respiration was observed in animals not showing cycle-related variation in aggression. The results support previous studies indicating that the estrus cycle exerts an influence on respiration, and suggest that rats prone to cycle-related aggression are more sensitive also to the influence of hormonal cyclicity on respiration. The possible bearing of these findings for the aberration in respiration displayed by subjects with premenstrual dysphoria is discussed.

Increased insulin sensitivity and decreased body weight in female rats after postnatal corticosterone exposure.

OBJECTIVE: Glucocorticoids are important for normal brain development. Elevation or removal of these hormones can permanently modify the structure and function of the fetal brain. The purpose of this study was to examine the effects of postnatal corticosterone exposure of female pups on metabolic, endocrine and anthropometric variables in adulthood. DESIGN: Female pups were given subcutaneous injections of corticosterone (5 mg/kg, CORT) or vehicle 3 and 5 days after birth. RESULTS: From 6 weeks of age, the CORT rats weighed significantly less than did controls, with diminished fat depots, decreased serum levels of leptin and reduced food intake. Adult CORT rats showed increased insulin sensitivity, measured by hyperinsulinemic, euglycemic clamp (5 mU/kg/min), as compared with controls. CORT rats had lower basal corticosterone levels and lower corticosterone levels 15 and 90 min after exposure to stress. CONCLUSION: The results indicate that postnatal exposure to corticosterone leads to increased insulin sensitivity, low body weight with diminished fat depots, leptin and food intake. This suggests that postnatal exposure to corticosterone induces specific programming, with consequences in adult life.

Respiratory responses to intravenous infusion of sodium lactate in male and female Wistar rats.

In patients with panic disorder or premenstrual dysphoria, anxiety attacks can be triggered by intravenous administration of sodium lactate. Since respiratory symptoms, such as hyperventilation and shortness of breath, are characteristic features of spontaneous as well as lactate-induced panic, an involvement of central or peripheral chemoreceptors in this reaction has been suggested. In the present study, we examined to what extent intravenous infusion of sodium lactate influences respiratory parameters in freely moving male and female Wistar rats. Prompted by clinical reports suggesting that the susceptibility to spontaneous and lactate-induced anxiety may be influenced by the menstrual cycle, we also investigated if the effect of lactate on respiration in female rats is estrus cycle-dependent. Male and ovariectomized female rats exposed to sodium lactate displayed a larger increase in respiratory rate than rats given an infusion of saline. In intact female rats, the response to lactate infusion was significantly more pronounced in the diestrus phase than in the proestrus/estrus phase of the cycle. It is concluded that sodium lactate is a respiratory stimulant in rat, and that this effect is influenced by female sex steroids.

Diagnosis and treatment of premenstrual dysphoria.

Premenstrual dysphoria (PMD) is a severe form of premenstrual syndrome afflicting 5% to 10% of all fertile women. Cardinal symptoms--appearing regularly between ovulation and menstruation and disappearing within a few days after the onset of the bleeding--are depressed mood, tension, affect lability, and irritability. Of these symptoms, irritability is often the most prominent. Serotonin reuptake inhibitors (SRIs), but not nonserotonergic antidepressants, reduce the symptoms of PMD effectively. The onset of action of SRIs is much shorter when used for PMD than when used for depression, enabling women with PMD to restrict medication use to the luteal phase of the cycle (so-called intermittent treatment). The findings that SRIs are effective for PMD--and that sexual dysfunction is the most frequent side effect during long-term treatment--both lend support for the hypothesis that a major role for brain serotonin is to modulate sex steroid-driven behavior.

Postnatal endotoxin exposure results in increased insulin sensitivity and altered activity of neuroendocrine axes in adult female rats.

OBJECTIVES: Severe postnatal infection leads to a systemic inflammatory response with release of cytokines and glucocorticoids, representing a stressful event for the newborn child. The purpose of this study was to mimic this situation and to study the effects of early postnatal endotoxin exposure of female rat pups on metabolic, endocrine and anthropometric variables in adulthood. DESIGN: Female pups were given subcutaneous injections of lipopolysaccharides (LPS; Salmonella enteriditis, 0.05 mg/kg) or vehicle 3 and 5 days after birth. RESULTS: Six hours after injection, LPS-treated rats had higher corticosterone levels than controls. As adults, LPS-exposed female rats showed increased insulin sensitivity (P<0.05), measured with the hyperinsulinemic euglycemic clamp (5 mU/kg per min). They exhibited a higher locomotor activity (P<0.05) and increased skeletal muscle mass in comparison with controls (P<0.05). Basal ACTH and corticosterone levels in LPS-treated rats were elevated (P<0.05), as were corticosterone levels after exposure to a novel environment stress (P<0.05). The adrenals were morphologically changed and enlarged (P<0.05) in LPS-exposed rats at 11 weeks of age, and a higher density of hypothalamic but not hippocampal glucocorticoid receptor protein was found in the LPS-treated rats (P<0.05). Furthermore, circulating progesterone levels were lower (P<0.05) and testosterone tended to be higher. CONCLUSION: The results indicate that postnatal exposure to LPS leads to increased insulin sensitivity in the adult female rat. In addition, LPS-treated rats showed changes in the regulation of hypothalamic-pituitary-adrenal and hypothalamic-pituitary-gonadal axes. This study suggests that postnatal exposure to an endotoxin such as LPS can induce specific programming of neuroendocrine regulation, with long-term consequences in adult life.