S. Sorrentino

Interactions of the Pineal Gland, Blinding, and Underfeeding on Reproductive Organ Size and Radioimmunoassayable Growth Hormone

Restricting male rats to one-half normal food intake from day 25 until day 60 of life significantly delayed all aspects of normal growth that were measured. Body weights were reduced by 50% and pituit

A Method for Measurement of Prolactin in the Hamster by Means of Radioimmunoassay

Pituitary and plasma prolactin levels have been measured in the golden hamster (Mesocricetus auratus) by means of a double antibody radioimmunoassay (RIA) using the NIAMD rat prolac

Role of the pineal gland in growth restraint of adult male rats by light and smell deprivation.

The effects of various surgical manipulations in adult male rats were studied in order to determine what effect reductions in sensory stimuli (i.e., light and smell) would have on parameters of growth

Central and peripheral neural pathways necessary for pineal function in the adult female rat.

Reproductive involution produced by surgical removal of the olfactory bulbs and of the eyes from adult female rats was prevented by pinealectomy, superior cervical ganglionectomy or by bilateral trans

Pineal-induced alteration of estrous cycles in blinded hamsters

Abstract Estrous cycles, as evaluated by vaginal smears of adult hamsters, were examined under a variety of experimental conditions. Normal females cycled regularly with oval and elongate nucleated epithelial cells usually observed one of every four days. Cycles of blinded hamsters did not vary from those of normal or blinded-pinealectomized hamsters until approximately 7 weeks after eye removal. Thereafter, blinded hamsters became acyclic, exhibiting a vaginal smear which contained cornified cells predominantly and varying numbers of leukocytes. An absence of follicles and corpora lutea also was observed in the ovaries of blinded hamsters. In addition, blinded hamsters possessed smaller than normal uteri. Cycles of blinded-pinealectomized hamsters never varied from those of normal hamsters; in each of these groups approximately 25% of the smears were routinely of the estrous type. Bilateral ovariectomy in animals blinded for 7 weeks had no effect on pattern of vaginal smears. Ovariectomy in normal and blinded-pinealectomized hamsters induced a cessation of cyclic epithelial changes and thereafter the smears appeared similar to those obtained from blinded or blinded-ovariectomized hamsters.

Pineal regulation of growth hormone synthesis and release in blinded and blinded-anosmic male rats.

Removal of eyes from young male rats led to slight retardation in body weight gain, tibial length, and tail length compared with respective parameters measured in normal rats. Young rats lacking eyes and pineal glands presented body weights, tibial lengths, and tail lengths that approached normal. Pituitary levels of radio-immunoassayable growth hormone (GH) were significantly lower in blinded rats with intact pineal glands compared with levels in normal or blinded-pinealectomized rats. Plasma levels of GH tended to be lower in blinded and blinded- pinealectomized rats relative to normal levels; however, due to the wide range of GH levels in all groups, no statistically significant differences were observed. Blindness and anosmia in young male rats severely retarded body weight gain, tibial length, and tail length relative to respective parameters of normal, blinded, blinded-pinealectomized, and blinded-anosmic-pinealectomized rats. Blinded-anosmic-pineal-ectomized rats grew subnormally, with body weights equal to those of blinded rats. Plasma GH concentrations were low in blinded-anosmic rats, but due to the overlapping values, statistical significance was not attained. In general, the size of reproductive organs correlated well with inhibition of body growth, being moderately smaller in blinded rats and markedly so in blinded-anosmic rats. These differences in the size of the reproductive organs were not observed if pinealectomy was performed simultaneously with blinding and olfactory bulb removal. It is concluded that, in young male rats that are deprived of light by blinding, there is a dramatic inhibition of GH production and release by the pituitary gland. This response, like the response of the reproductive organs, is enhanced when rats are deprived of both smell and light. These phenomena only occur in the presence of the pineal gland. Therefore, the pineal gland plays an important role in these processes. It is further concluded that anosmia or perhaps non-specific surgical stress may alter GH synthesis and/or release from the pituitary gland.

Interaction of photic and olfactory stimuli in mediating pineal-induced gonadal regression in adult female rats.

Abstract Whereas neither blinding nor olfactory bulb removal alone appreciably altered the reproductive organs of adult female rats, when animals were subjected to both operations, the sexual organs were macroscopically and microscopically hypotrophic within 8 weeks; the frequency of pregnancy also was reduced greatly in the doubly deprived rats. Furthermore, adrenal and pituitary weights were characteristically smaller in rats deprived of their eyes and olfactory bulbs. Pinealectomy reversed all the effects which followed dual sensory deprivation. No statistically significant differences in the pineal levels of hydroxyindole- O -methyltransferase activity were found.

Plasma Growth Hormone and Corticosterone Levels in the Hypothyroid and Athyroid Rat

Resting plasma levels of growth hormone (GH) and corticosterone (B) were examined in the thyroid-deficient rat. Plasma GH was found to be lowered in thyroparathyroidectomized (TPTx) and 6-methylthiour

Ovulation in PMS-treated rats with gonadotropin releasing hormone after pentobarbital and melatonin block.

The immature rat that has been induced to ovulate with pregnant mare serum (PMS) has proven to be a valuable model for the study of antiovulatory compounds. This paper describes an extension of this model in order to attempt to study the site of action of substances such as pentobarbital and a pineal compound, melatonin. A first experiment was designed to define a specific time for injecting pentobarbital in order to inhibit ovulation. In this study immature female rats were given injections with 25 IU PMS; pentobarbital was given at various times after PMS treatment. This study showed that sodium pentobarbital (35 mg/kg, i.p.) inhibits LH release and ovulation when rats have been anesthetized between 2 and 6 p.m. on day 2 after PMS treatment. In a second experiment ovulation was blocked with pentobarbital (35 mg/kg, i.p., beginning at 12 noon and at 2 p.m. on day 2 after PMS treatment) and completely restored to normal with the s.c. injection of 2 mug GnRH at 2 and 4 p.m. on day 2 after PMS treatment. In the third experiment, varying doses of GnRH were studied for their capacity to overcome the pentobarbital block. This study showed that 2 mug, 1 mug, 500 ng, and 250 ng of GnRH at 2 and 4 p.m. on day 2 after PMS treatment were equipotent in causing ovulation. In a fourth experiment ovulation was blocked with melatonin and this block was overcome with exogenous GnRH. In the last study exogenous GnRH was shown to restore ovulation after being blocked by both melatonin and pentobarbital. This evidence suggests that pentobarbital and melatonin inhibit ovulation by inhibiting the secretion of endogenous GnRH.

Lack of pineal-induced gonadal regression in dark-exposed or blind hamsters after surgical isolation of the medial-basal hypothalamus

Abstract Blinding or exposing hamsters to increased dark periods (L:D::1:23) caused involution of the reproductive organs. Involution of reproductive organs was absent in hamsters that were pinealectomized or subjected to complete surgical isolation of the medial-basal hypothalamus. This observation suggests that isolation of the medial-basal hypothalamus may have destroyed pathways which serve to transmit photic information to the pineal (e.g., medial forebrain bundle) or the site of action of the substance secreted by the pineal in blind or dark-exposed hamsters is outside of the cut, located in a neural structure responsible for inhibition of gonadotropin release.