Studies on the maternal transfer of photoperiodic information in mammals indicate that the daily photoperiod perceived by the mother during the gestation‐lactation period is communicated to the fetus either through the placenta or via the milk. However, the impact of photoperiodic exposures during gestation and lactation on the maternal pineal and reproductive physiology has not been reported for any tropical rodent. The exposure of pregnant female Indian palm squirrels (Funambulus pennanti) to constant light (24 h light:0 h dark), constant dark (0 h light: 24 h dark), long daylength (14 h light: 10 h dark) or short daylength (10 h light: 14 h dark) during early gestation ( 30 days), it did not interfere with the maintenance of pregnancy. Alterations in photoperiodic condition during late gestation and lactation altered the postpartum recovery process. Pineal gland activity, as assessed by pineal mass, protein content and plasma melatonin, was lowest during the breeding phase, but increased gradually after parturition until the next breeding phase. During gestation and lactation, constant light, long daylength and short daylength conditions were less effective, while constant dark condition had a profound effect in depressing pineal gland activity, which subsequently advanced postpartum recovery. Hence, lactating females under constant darkness prepare themselves for next mating much earlier than females under natural daylength (12 h light:12 h dark) conditions. Therefore, photoperiodic information, mediated via the pineal gland, may be important for maintaining gestation physiology as well as postpartum recovery in female rodents.

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Impact of photoperiodic exposures during late gestation and lactation periods on the pineal and reproductive physiology of the Indian palm squirrel, Funambulus pennanti

5-methoxytryptophol (5-ML) is a pineal indoleamine derived from serotonin shown to be biologically active in a number of species This indolamine exhibits a circadian pattern synchronized with the day–night cycle with significant increases during daylight, already recognized in vertebrates The multiplicity of physiological and endocrine functions of 5-ML is remarkable; it is involved in circadian rhythms, reproduction and sexual processes Furthermore, a number of pharmacological benefits of 5-ML have been reported, including immunomodulatory, antitumor and antioxidative activities However, the molecular mechanisms of these pharmacological effects remain unclear The purpose of this article is to provide an overview on the general properties and physiological functions of 5-ML An attempt has been made to fully document all studies performed using 5-ML In addition, this article aims to gain insight into the current state of knowledge regarding pharmacological and therapeutic effects of this indoleamine

Physiological and pharmacological properties of 5-methoxytryptophol

The parametric or tonic effects of light were studied in a recently established diurnal circadian model-the Indian palm squirrel, Funambulus pennanti. Sixteen squirrels (7 female, 9 male) were housed individually under varying constant light conditions (0.1 lux to 46 lux) with gross locomotor activity continuously monitored. Free-running period (tau), amplitude, mesor and day-to-day stability of the activity rhythm were determined using modified periodogram and iterative harmonic analyses, while the ratio of activity to rest time was estimated by eye-fit. The main findings were as follows: 1) tau did not vary between sexes or between light conditions, although a trend for tau to lengthen when light intensity was increased was noted; 2) amplitude and mesor did not show sex differences, but both sexes showed a decrease in amplitude and mesor when light intensity was decreased; 3) the stability of the activity rhythm was greater in males than in females, and a trend was observed for rhythm stability to decrease when light intensity was reduced. These descriptive data contribute to the growing literature on this diurnal species.

Circadian locomotor activity rhythms of the diurnal Indian palm squirrel in constant light.

To elucidate the role of photoperiodically modulated endogenous melatonin and its receptor MT1 in the ovary of a diurnal rodent, adult Indian palm squirrel Funambulus pennanti were exposed ...

Photoperiodic regulation of ovarian steroidogenesis in a tropical rodent, Funambulus pennanti: role of melatonin and MT1

Effects of gonadal steroids on pineal morphogenesis and cell differentiation of the embryonic quail studied under cell culture conditions.

We studied the effects of four indolamines (melatonin, 5-methoxytryptamine, 5-methoxytryptophol, and 5-methoxytryptophan) on ovarian activity in a tropical rodent, the Indian palm squirrel (Funambulus pennati), during the sexually active phase. Injection of the four 5-methoxyindoles at a dose of 20 μg/0.1 mL per animal every evening for 30 days reduced ovarian mass in both intact and pinealectomized animals. Intact animals treated with 5-methoxyindoles had a lower uterine mass than the intact controls. On the other hand, the uterine mass of pinealectomized animals treated with 5-methoxyindoles did not differ from that of their respective controls. Plasma estradiol levels showed a similar pattern to ovarian masses. We conclude that the effect of 5-methoxyindoles in the female palm squirrel is independent of the pineal gland and that 5-methoxytraptophol and 5-methoxytryptophan are more potent than melatonin.

Savita Singh

Papers

Modulation of ovarian function by various indolamines during the sexually active phase in the Indian palm squirrel, Funambulus pennanti