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Some physiological parameters of pineal 5 alpha-dihydrotestosterone receptor in the rat such as ontogeny, circadian rhythm pattern, and its modulation by various neuropeptides and neurotransmitters which have profound influences on the pineal hormone melatonin were examined. Pineal 5 alpha-dihydrotestosterone receptors measured at different ages of the animal revealed that on day 10 both cytosolic receptor (CR) and nuclear receptor (NR) levels were high. With growth and development both groups of receptors declined and during puberty started again to rise. During adulthood both receptors were high; however, NR rose further with full maturation. Both groups of receptors showed circadian rhythmicity. While the CR was significantly higher at 6.00 h than at any time point through 24 h, the NR peaked at 18.00 h when the difference between both groups was maximum. Castration caused significant increment of NR. Treatment of castrated animals with a low dose of testosterone propionate (0.25 mg) significantly stimulated both receptor groups, while treatment with a high dose (2.5 mg) failed to do so. Treatment with various substances such as antiandrogen, opioids, neuropeptides, and neurotransmitters significantly modulated the pineal androgen receptor population: cyproterone acetate and monosodium glutamate suppressed CR; growth hormone releasing hormone increased NR; growth hormone release inhibiting hormone had no significant effects on either group of receptors; exogenous melatonin and norepinephrine increased NR; beta-endorphin increased only NR, but methionine enkephalin stimulated both, and epithalamine had no significant effects on either group of receptors, but thymosin alpha 1 increased NR.(ABSTRACT TRUNCATED AT 250 WORDS)

F. pennanti presented a clear biphasic pineal mediated seasonal sexual cycle. This sexual cycle was essentially characterised by a very short period of sexual quiescence with an arrest of spermatogenesis during October-November. A small but clear decrease in sexual activity was also observed during March-April. This decrease in sexual activity, however, had no quantifiable effect on spermatogenesis. Sexual recrudescence was observed from December-January. The testes remained sexually active from January till September. Almost an inverse relationship was observed between pineal and testicular weight. Pinealectomy, however, prevented naturally induced gonadal regression during both the periods, i.e. September-November and February-April. Exposure of animals to high RH (80 +/- 4%) during sexually active phase induced a steep regression in testicular weight of sham-operated animals even in the presence of gonad stimulatory long photoperiod (16L:8D) and high temperature (40 degrees +/- 5 degrees C) while exposure of animals to moderate RH (65 +/- 5%) during sexual regression phase partially prevented testicular regression even in presence of inhibitory short photoperiod (11L:13D) and normal environmental temperature (30 degrees +/- 5 degrees C). Pinealectomized animals, neither exhibited testicular regression in February-March nor had involuted testes in September-October, thus, suggesting that the effect of humidity is mediated via the pineal gland.

The present study provides evidence that the pineal gland has a physiological role in the proliferation of colony forming units for granulocytes and macrophages (CFU-GM). A biphasic circadian rhythm of CFU-GM proliferation in rat bone marrow cell cultures (BMC) from intact animals peaking at 0600 and 1800 was observed. Pinealectomy (Px) at 1600 obliterated the circadian rhythm patterns of CFU-GM. Afternoon injections of melatonin (1630, 20 micrograms/per day for 10 days) to Px animals restored the rhythmicity. When pinealectomy was done at 0800, the morning peak remained unaltered and the colony number at 1800 was higher than that found in the afternoon Px animals. In conclusion, the pineal gland or its main hormone melatonin seems to have a regulatory role in the proliferation of CFU-GM in rat BMC. Further, the expression of the activity of CFU-GM in rat BMC depends on the time when pinealectomy is done or melatonin is substituted.

The present study provides evidence, for the first time, of a role of the pineal gland in the proliferation of CFU-GM under the influence of different cytokines. The degree of colony formation in different cytokine groups was evaluated after 24 h, 3, 7 and 10 days. The colony growth in the present type of bone marrow cell cultures slows after the 10th day and ceases after the 14th day of incubation. The results show that rGM-CSF and the combination of rGM-CSF with rIl-3 and with rEPO stimulate the colony formation of granulocytes and macrophages. A 50% general reduction in the colony number was noted in the pinealectomy group. Their pattern of response to the different cytokines was similar to that of the intact group. It is suggested that the pineal activity has a physiological role in important aspects of host defence mechanisms, such as the proliferation of CFU-GM.

Recent research has justified the presumption that the pineal gland plays a role in the regulation of the gonadal system in mammals. Evidence also exists for androgen receptors in pinealocytes. In the current study, our approach has been to assess the age- and sex-dependent nature of 5 alpha-DHT receptors in bovine pineal. Although no significant difference was noted between various groups of bulls, cows, peripuberal cows, and calves (male) for pineal weight, the cytoplasmic 5 alpha-DHT binding site/receptor content in the pineal gland differed significantly. While the males had a low androgen receptor concentration in the pineal (46 fmol/pineal), the females showed the highest (442 fmol/pineal). The peripuberal females without calves and calves (male) presented a 5 alpha-DHT receptor content in between (225 fmol/pineal; 138 fmol/pineal). When the data were related to unit weight of pineal tissue, the difference still existed. It is suggested that the concentration of cytoplasmic 5 alpha-DHT receptors reflects the cellular activity and they are inversely related. Further, low cytoplasmic receptors also indicate that most of it is confined to the nuclear sites, as generally suggested for other androgen-dependent tissues. In the light of these suggestions, it is possible that lowest cytosolic 5 alpha-DHT receptor concentration in the males, in reality, reflects a higher degree of cellular function and a high concentration of the receptors in the nuclear site. Similarly, the peripuberal cows and calves perhaps have more cellular activity in the pineal than the mature cows. The current investigation, for the first time, by directly estimating the androgen receptors/binding site in the bovine pineal gland, demonstrates the sex- and age-dependent nature.

The effect of two different conditions of humidity (80 +/- 5% and 40 +/- 5%) under stimulatory photoperiod (14L/10D) and high temperature (38 +/- 2 degrees C) was studied on the testes and accessory sex organs of the Indian palm squirrel, Funambulus pennanti, during the sexually active phase. High humidity (80 +/- 5%) reduced significantly the testes weight of the sham-operated animals as compared to the controls under natural environmental conditions but had no effect on that of pinealectomized animals. Moderate humidity (40 +/- 5%) did not affect the testes of sham-operated as well as pinealectomized animals, as compared to the respective controls. The seminal and prostatic weights showed no significant difference in high or moderate humidity conditions. However, the epididymal weight of the animals exposed to high humidity was significantly reduced in sham-operated animals only. Thus, these results indicate that the pineal gland may be implicated in mediating the humidity information to control the male gonadal function in the Indian palm squirrel, Funambulus pennanti.

Bioassay of the pineal extract of F. pennanti was performed in immature female mice which was previously sensitized with human chorionic gonadotrophin. Reduction of ovarian and uterine weights indicated an antigonadotropic nature of the pineal gland of this animal.

Melatonin (aMT) implantation during testicular inactive phase (January-March) brought an early initiation of testicular development in Perdicula asiatica. However, during the recrudescence (March-May), active (April-June), and regressive (May-July-September) phases both aMT and 5-methoxytryptamine (MT) implantation had inhibited testicular weight and activity significantly. Subcutaneous injections of aMT, MT and 5-methoxytryptophol (ML) during morning (7.30 a.m.-8.00 a.m. and evening (4.30 p.m.-5.00 p.m.) could not bring about any significant effect on the weight or activity of the testes during the inactive (January-February) phase, while inhibited testicular weight and activity during the active (May-June) phase when administered in the morning as well as in the evening hours.

Chronohaematological study was performed on the blood of pinealectomized and sham-operated lizards over a 48 hrs. time scale. Pineal removal significantly inhibited leucocytopoisis, erythropoiesis and led to hypoglycemia, as evident from lowered circulating number of cells and level of glucose respectively. However existence of circadian rhythm in WBC, RBC and glucose level of sham-operated lizards was evident. Influence of pineal extirpation on chronohaemotology varied with time scale (Time X Pinealectomy P less than 0.01).

The general plan of the development of the organ in Calotes versicolor in no way differs from that of Sphenodon and Lacerta. The lens of the parietal eye of Calotes appears at a comparatively later state of development than in Sphenodon and Lacerta. The papaphysis in the embryos of Calotes versicolor is a simple structure. Histologically all the structures resemble the wall of the brain from which they arose.

The present study reveals that the annual Harderian gland weight cycle of P. asiatica has a direct relationship with the testicular cycle and an inverse relationship with the pineal gland cycle. Pinealectomy resulted in a significant decrease of the Harderian gland weight during the recurdescence (March-May) and active (April-June) phases. Subcutaneous implantation of melatonin (aMT) and 5-methoxytryptamine (MT) brought about a significant reduction during the recrudescence and active phases whereas subcutaneous injections of aMT, MT and 5-methoxytryptophol (ML) reduced Harderian gland weight effectively during the morning as well as in the evening hours in the active and inactive phases.

Effects of melatonin (aMT) and 5-methoxytryptamine (MT) were studied on the testicular activity cycle of the fresh-water snake, Natrix piscator. The subcutaneous implantation and the injections (morning as well as evening) of these two methoxyindoles prevented testicular recrudescence, retarded the testicular active phase, and accelerated the rate of regression of testes, while having no effect on the inactive testes. Contrary to this, these two compounds increased the pineal gland weight during different reproductive phases. These results revealed that both aMT and MT, whether they were continuously released through silastic capsule implants or administered through daily periodic injections, produced inhibitory effects on the testicular function.

Pinealectomy for 60 days (noted every month of the year), in the tropical Indian chequered water snake. Natrix piscator, caused inhibition of testicular growth during late progressive and active phases and retarded the rate of regression during regressive phase; during sexually inactive phase the testes remain partially active. The weight of the accessory sex organs, vas deferens, and kidney (along with the renal sex segment activity) followed the same pattern as that of the testes. Thus, it may be concluded that the pineal gland of this ophidian participates in the regulation of seasonal testicular cycle, probably via the hypothalamo-hypophyseal axis, and hence the effects of pinealectomy are seasonal and a reproductive phase-dependent phenomenon.