Stimulatory response of pineal-thyroid nuclear morphology and function following adrenocortical modulation in rat (Rattus rattus) (original) (raw)
Related papers
Pituitary-adrenal and thyroid effects on melatonin content of the rat pineal gland
Psychoneuroendocrinology, 1989
Based on clinical findings of diminished nocturnal serum melatonin levels in affective illness, we hypothesized that alterations in the pituitary-adrenal or thyroid axes of the rat might alter the nocturnal rise of melatonin content of the pineal gland in that species. Two experiments were conducted to investigate these issues. In the first, rats were injected for nine days with adrenocorticotropic hormone (ACTH) or corticosterone, timed to accentuate and prolong the normal circadian corticosterone rise. Although both these treatments produced significant elevations of serum corticosterone, there was no difference in pineal melatonin content during the day or night from that measured in control rats. In the second experiment, hypothyroidism was induced in rats by thyroid-parathyroidectomy, and hyperthyroidism was produced by injection of triiodotlfyronine (T3) for nine days. Despite clear evidence of metabolic and endocrine effects of these thyroid manipulations, pineal melatonin content was not altered during the day or night. The nocturnal increase of melatonin may have been phaseadvanced in the hypothyroid group, although the experiment was not designed to detect such a shift. There thus is no evidence from this study in the rat to suggest that diminished nocturnal melatonin production in affective illness might be due to associated alterations in the pituitary-adrenal or thyroid systems.
The pineal and melatonin in the regulation of pituitary-thyroid axis
Life Sciences, 1981
Studies of thyroid physiology in rats and hamsters support the view that the pineal gland has an anti-thyrotropic action. While chronic exposure of hamsters to short photoperiod, darkness, or blindness results in a depression of plasma thyroxin and plasma TSH, removal of the pineal gland, which synthesizes melatonin, prevents these effects. Melatonin administration, in the form of daily injections given late in the photoperiod, also results in inhibition of plasma thyroxin and plasma TSH. These anti-thyrotropic effects are similar to the anti-gonadotropic effects of melatonin. The results of a variety of experiments are consistent with the view that melatonin acts on a neuroendocrine control mechanism influencing synthesis or release of hypothalamic thyrotropin releasing hormone (TRH).
International Journal of Biology, 2010
Hormone-induced reponsiveness of the pineal and adrenal glands was studied in post-pubertal male mice (Mus musculus). The influence of steroid hormones (estradiol and testosterone) and non-steroidal antihormones (tamoxifen and flutamide) on pineal and adrenal karyomorphology and cell proliferation activity was analyzed. Estradiol was injected at a dose of 5µg, testosterone 100µg, tamoxifen 500µg and flutamide 2mg per 100g body weight administered intramuscularly in all cases for ten consecutive days. Control mice were similarly injected with 0.3ml of peanut oil vehicle intramuscularly for the same duration. The results indicated that, except testosterone, all other treatments with estradiol, tamoxifen and flutamide caused significant hyperactivity in both the pineal and the adrenal glands, associated with significantly increased cell proliferation activity. On the contrary, testosterone administration was inhibitory to pineal-adrenal karyometric and mitotic incidence values. It was concluded that in male post-pubertal mice both pineal and adrenal glands show antagonistic response towards estradiol and testosterone administration. Although tamoxifen showed estrogen agonistic behaviour, flutamide conversely induced pineal and adrenal cytophysiological stimulation. Such stimulatory response was antagonistic to the inhibitory response shown by pineal and adrenal karyomorphology and cell proliferation following testosterone administration.
Journal of Neural Transmission, 1985
Pineal levels of tryptophan, 5-hydroxytryptophan, serotonin, N-acetylserotonin, melatonin, 5-hydroxyindoleacetic acid and the activities of the enzymes N-acetyltransferase and hydroxyindole-O-methyltransferase were determined in male albino rats and Syrian hamsters that were implanted with the appropriate corticosteroid or adrenalectomized two weeks earlier. Melatonin content and NAT activity were increased at 4 hours (during darkness) in adrenalectomized hamsters; conversely, no alterations in melatonin levels were observed in either adrenalectomized or implanted rats. It is suggested that the changes in adrenal function probably have a minor influence on pineal melatonin production.
Effects of the pineal and melatonin on thyroid activity of male golden hamsters
General and Comparative Endocrinology, 1979
The effects of blinding and pinealectomy in normal and gonadectomized hamsters were studied. Blinding was associated with depressed thyroxin levels and free thyroxin index in normal but not in gonadectomized animals. Pinealectomy, by itself, had no effect on thyroxin levels but reversed the effects of blinding. Pinealectomy of gonadectomized animals had no effect on thyroxin levels but was associated ivith increased thyroxin levels and free thyroxin index in gonadectomized hamsters that were blinded. Different effects of blinding and thiourea treatment suggested different sites of action. Melatonin injections, like blinding, were associated with a depression of thyroxin levels and free thyroxin index. Similar effects of the pineal and melatonin on gonad weights and on thyroxin levels suggest a common site of action of the pineal gland in regulation of pituitary-gonadal and pituitarythyroid axes. Another interpretation of these data is that the effects of the pineal and melatonin on thyroid function are secondary to their effects on the reproductive system.
International Journal of Biology, 2010
The current investigation was undertaken to assess the pineal and thyroid gland cytophysiology and function in response to an exogenously altered steroid milieu following administration of a steroid hormone and non-steroidal antihormones. In the present study male rats (Rattus rattus) were injected with estradiol at a dose of 2 mg, testosterone 100 µg, tamoxifen 100 µg and flutamide 2 mg per 100 g b.w. intramuscularly for 15 consecutive days. Control rats were similarly injected with peanut oil vehicle intramuscularly for the same duration as the treated groups. The results indicated that pineal and thyroid gland response to estradiol and testosterone administration was opposite in nature. Estradiol induced significant hypertrophy of pineal and thyroid cytophysiology as indexed from significantly increased pineal and thyroid karyomorphological and associated parameter values, testosterone contrarily caused significant atrophy of pineal and thyroid cytophysiological parameters. Tamoxifen acted as a true estrogen agonist, whereas flutamide showed an androgen antagonist nature, thereby causing hyperactivity of pineal and thyroid karyomorphological and associated functions similar to that observed in estradiol treated rats, but contrary to that shown by testosterone induction in these rats.
Canadian Journal of Physiology and Pharmacology, 1977
Adrenocol.tica1 function was studied in rats after shampineaIectorny, pinealectomy, or immunization against melatonin and IV-acetylserotonin (NAS). Pineais were stimulated to increase melatonin synthesis by blinding or exposure to 23 h of darkness daily. Blintfing elevated morning corticosterone levels without altering the corticosterone response to novelty stirnulation. Among blinded animals, pinealectomy partially reversed and immunization completely reversed the elevations in morning steroid levels. Exposure to short daily photoperiods flattened the diurnal corticosterone rhythm. Pineaiectomy did not affect morning corticosterone levels but reduced evening corticosterone levels. More importantly, ira~naunization resulted in reduced corticosterone levels throughout the diurnal cycle. These findings suggest that melatonita and (or) NAS may be involved in the regulation of resting diurnal adrenocortical function.