Effects of afternoon injections of O-acetyl-5-methoxytryptophol, melatonin or 5-methoxytryptophol in female syrian hamsters

Abstract

Female Syrian hamsters were maintained in a 14:10 light: dark photoperiod (lights on 6 a.m.) and injected each afternoon between 4 p.m. and 6 p.m. with diluent or with 25 micrograms melatonin, O-acetyl-5-methoxytryptophol (aML) or 5-methoxytryptophol (ML). After 7 or 12 weeks of treatment, only the melatonin-treated hamsters were acyclic. Gross inspection of their ovaries revealed that they were smooth, brown, and devoid of corpora lutea and large follicles. Progesterone levels of the acyclic animals were midway between the high levels observed during estrus and postestrus and the low levels observed on cycle days 2 and 3. Additionally, the melatonin-treated hamsters had significantly reduced uterine weights and pituitary and plasma levels of prolactin. Hamsters treated with aML had significantly lower pituitary prolactin and plasma and pituitary levels of LH only at the 7 week timepoint. ML-treated hamsters had lower pituitary prolactin levels also at 7 weeks. The endocrine changes wrought by injections of aML and ML, however, were insufficient to ultimately affect vaginal cyclicity. In conclusion, it would appear that at the dose used and the time administered melatonin is the more active of the indoles tested in the female hamster, at least in terms of alterations in reproductive physiology.

Splenic hypertrophy and extramedullary hematopoiesis induced in male Syrian hamsters by short photoperiod or melatonin injections and reversed by melatonin pellets or pinealectomy

“…Essentially, this is what was observed in the present set of experiments. Melatonin injections inhibit estrous cyclicity and fecundity in female hamsters; the large, brown ovaries of these acyclic females are full of interstitial tissue (Richardson et al, 1982) but still produce some progesterone (Little et al, 1986). The observed depression in relative spleen weights associated with small uteri conforms to the paradigm of hypogonadism also in that sex.…”

Melatonin Metabolism in the Central Nervous System

“…This almost forgotten metabolite (Fig. 2) was reported to inhibit nicotinic and muscarinic acetylcholine receptors [26] and, in Syrian hamsters, to decrease pituitary prolactin and LH levels [76], but again, these effects are presumably only of pharmacological nature. This compound is very unstable in the presence of ubiquitously abundant esterases [72].…”

SARS-CoV-2 Infection and Lung Regeneration

“…Studies have also suggested that pulmonary capillary endothelial cells can stimulate epithelial progenitor cells, including bronchoalveolar stem cells and alveolar epithelial cells, to proliferate, promoting alveolar regeneration by producing paracrine growth factors ( 238 ). EPC therapy is also considered a potential treatment for cell-based pulmonary hypertension ( 239 , 240 ). These cell-based therapy strategies may inspire the treatment of COVID-19.…”