Monoaminergic dysregulation on diestrus-2 and estrus through high emotional reactivity.

Rats with great differences in emotional reactivity, during weighing and handling for vaginal smear screening were examined on diestrus-2 (DE-2), proestrus (PE), and estrus (E). Rats with high emotional reactivity (HR), interpreted as trait anxiety, had different serotonergic and dopaminergic profile in hypothalamus-preoptic area (HY-PA) and striatum (Str) and thymus weight lower than that found in rats with low emotional reactivity (LR). In HY-PA of rats with HR when compared to rats with LR, increased 5-hydroxyindoleacetic acid (5-HIAA), 5-HIAA/serotonin (5-HT) ratio, and 3,4-dihydroxyphenylacetic acid (DOPAC) and in Str increased DOPAC and DOPAC/dopamine (DA) ratio were found only on DE-2, paralleled by increased adrenal weight and decreased thymus weight. In Str, a significant effect of HR on 5-HIAA was found only on E, in parallel with increased 5-HT and decreased DOPAC and DOPAC/DA ratio when compared to rats with LR. The results suggest that activation of 5-HT and DA in HY-PA and DA in Str through HR is apparent only on DE-2 while, conversely, on E suppression of striatal DA it is apparent with 5-HT dysregulation. These findings might have some relevance to the predisposition of women with trait anxiety to premenstrual syndrome.

Relationship between the thymus and neurochemical changes in the hypothalamus-preoptic area and prefrontal cortex in female rats with delayed puberty.

In female rats, aged 55-58 days with delayed puberty due to deficient growth and environmental stress, 5-hydroxyindoleacetic acid levels and serotonin turnover rate in the hypothalamus-preoptic area as well as body weight, body weight gain and relative weight of ovaries, uterus, adrenals and preputial glands were lower while serotonin and 5-hydroxyindoleacetic acid levels in the prefrontal cortex were higher when compared to normal rats with the latest onset of puberty aged 42-52 days. In rats with delayed puberty, multiple regression analysis revealed a significant negative dependence on dopamine turnover in the hypothalamus-preoptic area for body weight gain and, of all organs, for the relative weight of the thymus. A similar negative significant dependence on serotonin turnover rate in the prefrontal cortex was also found for the relative weight of thymus and spleen. The same analysis in the opposite direction revealed a significant negative dependence of 3,4-dihydroxyphenylacetic acid levels and dopamine turnover rate in the hypothalamus-preoptic area as well as serotonin turnover rate in the prefrontal cortex only on thymus weight. After separation of delayed pubertal rats into two groups, based on absolute ovarian weight, the rats in the low ovarian weight range and no signs of puberty exhibited: lower body weight gain, lower body weight, and lower relative weight only of thymus, ovaries and preputial glands in parallel with an increased dopamine turnover rate in the hypothalamus-preoptic area and serotonin turnover rate in the prefrontal cortex compared to the delayed pubertal rats in the high ovarian weight range and early signs of puberty. The results suggest that in rats with delayed puberty: (1) serotonergic activation in the hypothalamus-preoptic area is lower compared to normal puberty rats; (2) dopaminergic activation in the hypothalamus-preoptic area negatively affects body weight gain, thymus weight and initiation of puberty and (3) thymus weight is negatively implicated in dopaminergic activation in the hypothalamus-preoptic area and serotonergic activation in the prefrontal cortex and positively related to ovarian weight and early signs of puberty.

Stress through handling for vaginal screening, serotonin, and ACTH response to ether.

The effect of duration of handling for vaginal smear screening on the adrenal weight and acute ACTH response to ether were examined in 4-day-cycling female rats, sacrificed at 97-103 days of age on diestrus-2 after evaluation of resistance to handling, thymus weight, and hypothalamic serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). Prolonged handling paralleled increased resistance (behavioral response) to handling and adrenal weight but was inversely related to thymus weight. The hypothalamic 5-HT, 5-HIAA, and 5-HIAA/5-HT ratio, compared to controls with similar conditions of handling, were not modified after 2.5 min of ether despite the ACTH rise. In ether-stressed rats, the ACTH response to ether was lower after prolonged handling compared to short handling paralleling decreased thymus weight. In contrast, 5-HT, 5-HIAA, and the 5-HIAA/5-HT ratio were higher, paralleling increased resistance and adrenal weight. The results suggest chronic activation of the hypothalamo-pituitary-adrenal axis with positive serotonergic involvement after prolonged handling and resistance during vaginal screening and a negative implication of this activation on the acute ACTH response to ether.