Blind-anosmic Rats Research Articles

Corpus luteum progesterone secretion in rats undergoing pineal-mediated reproductive regression.

In nonseasonal breeders, such as the laboratory rat, the potentiation of the antigonadal action of light deprivation by olfactory bulbectomy is manifested, among other things, by a diminished secretion of testosterone in males and estradiol in females. Little is known about the actions of the pineal gland on progesterone secretion. Since secretion of the luteotrophic hormones (LH and PRL) decreases in blind-anosmic rats and because the rat corpus luteum exhibits different degrees of LH and/or PRL dependency, the purpose of these experiments was to study the corpus luteum progesterone secretion in both pseudopregnant and pregnant blinded-bulbectomized rats. Female rats blinded and bulbectomized at the age of 25 d showed at adulthood (75 d old) (1) estrous cycles longer than the regular 4-5 d in length exhibited by intact rats: 82.3 vs. 9.0% (P less than .01); (2) a decreased paired ovarian weight, 24.1 +/- 3.7 (nine) vs. 37.3 +/- 2.2 (ten) mg/100 gm BW (P less than .05), and lower plasma levels of LH on metestrus: 15.9 +/- 1.7 vs. 26.2 +/- 3.4 ng/ml (P less than .01). Pinealectomy, as previously reported, completely reversed the effects of dual sensory deprivation. In contrast to the clear antigonadal action of the pineal gland, which seems to affect the follicular component of the ovary through modifications in the rate of LH secretion, the production of progesterone by the corpus luteum remained almost unaffected. Although the duration of the diestrous phase in both pseudopregnancy and pregnancy was significantly longer in blind-anosmic rats than in intact ones (P less than .01), the serum levels of progesterone throughout both corpus luteum phases were identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible involvement of the hypothalamic dopaminergic system in the prolactin-inhibitory effects of the pineal gland in blind-anosmic male rats.

The purpose of the present study was to assess whether the pineal-induced suppression of prolactin (PRL) cell activity in blind-anosmic (BA) rats was possibly mediated via the hypothalamic dopaminergic system. Prepubertal male rats were divided into the following groups: sham-operated (Sham), BA and blind-anosmic-pinealectomized (BAP). Animals from each group were sacrificed 1, 4 and 8 weeks after the operations. Blinding and anosmia resulted in pineal-dependent decreases in the weight of the testes, accessory organs and anterior pituitaries at 4 and 8 weeks but not 1 week after the operations. Likewise serum PRL levels were significantly decreased in BA rats at 4 and 8 weeks but this effect was not prevented in BAP rats. Hypothalamic dopamine (DA) turnover in BA rats at 1 week was twice that seen in either the Sham or BAP groups at that time; this effect ended by 4 weeks. There were no effects of any treatment on DA turnover at 8 weeks. Finally, PRL cell sensitivity to DA inhibition was determined by measuring the release of PRL from pituitaries incubated in vitro with either vehicle or 5 x 10(-7) M DA. None of the treatments caused significant alterations in the response to DA, though this must be interpreted with caution since only one dose of DA was used. From these data we conclude that: (1) there is an increase in DA neuron activity that precedes the inhibition of both PRL secretion and the reproductive system in BA rats, and (2) the inhibition of PRL cell activity in these animals is apparently not due to an increase in sensitivity to DA.

Pineal-induced inhibition of pubertal prolactin cell development in blind-anosmic female rats

Pineal-induced inhibition of pubertal prolactin cell development in blind-anosmic female rats

Immunocytochemical and ultrastructural correlates of the pineal inhibition of prolactin cell activity in blind-anosmic female rats.

The effects of the pineal gland on the light microscopic-immunocytochemical and ultrastructural appearance of pituitary mammotrophs were studied in female rats eight weeks after prepubertal blinding and olfactory bulbectomy. Blinding and anosmia resulted in a marked decrease in the size of the pars distalis concomitant with a reduction in the apparent number and size of PRL cells as compared with intact animals. Ultrastructurally, these cells appeared much less active than those of intact rats. The small and angular-shaped mammotrophs of blind-anosmic rats characteristically exhibited scant arrays of rough endoplasmic reticulum, small Golgi complexes with few immature secretory granules, few mature secretory granules and rare exocytosis patterns. Pinealectomy tended to reverse the effects of blinding and anosmia on pars distalis size and PRL cell size, apparent number and ultrastructure. In fact, the mammotrophs of blind-anosmic-pinealectomized rats were quite similar in ultrastructural appearance to those of intact rats. From these data we conclude that the pineal causes mammotroph hypotrophy and hypoplasia in blind-anosmic female rats.

Pineal gland inhibition of prolactin cell activity is independent of gonadal regression.

In order to determine whether the inhibitory effect of the pineal gland on the PRL cells of blind-anosmic female rats is a result of the attendant gonadal regression observed in these animals, mammotroph activity was compared between intact and ovariectomized rats eight weeks after prepubertal blinding and olfactory bulbectomy. PRL synthesis was evaluated by measuring the amount of 3H-leucine incorporated into PRL by interior pituitaries in vitro. PRL synthesis was reduced by 47% in blind-anosmic rats, an effect which was reversed by pinealectomy. Although ovariectomy itself led to a 64% decrease in PRL synthesis, dual-sensory deprivation in these animals resulted in a further 59% suppression of PRL production. PRL storage, as estimated by measuring total immunoreactive PRL in vitro also appeared to be significantly depressed in blind-anosmic female rats. Once again, ovariectomy had no effect on this reduction. PRL release, as assessed by monitoring serum levels of the hormone, was decreased in blind-anosmic rats. Ovariectomy also caused a reduction in serum PRL levels; however, the combination of blinding and olfactory bulbectomy had no further depressive effect on circulating PRL titers in these animals. Correlated with the decrease in PRL cell activity in both intact and ovariectomized blind-anosmic rats was a pineal-induced decrease in anterior pituitary weight and DNA content in both sets of animals. From these data we conclude that the pineal's inhibition of the PRL cell in blind-anosmic female rats is largely independent of the gonads and, therefore, could not be secondary to gonadal involution.

Evidence for an Inhibitory Influence of the Pineal on Prolactin in the Female Rat

The effect of the pineal gland on prolactin (PRL) synthesis, storage and release was tested in female rats. To do this, we incubated in vitro hemi-anterior pituitaries from 80-day-old female rats that had been rendered, 8 weeks previously, either blind-anosmic, blind-anosmic and pinealectomized or left intact. Reproductive organ weights, pituitary weights and pituitary DNA content were decreased in animals rendered both blind and anosmic. These effects were reversed by removal of the pineal gland. Additionally, the serum levels of PRL were diminished in blind-anosmic rats from that of intact controls. The synthesis of PRL in vitro was dramatically reduced in the pituitaries of blind-anosmic rats as evidenced by a 63% decrease in [3H]leucine incorporation into PRL from that observed in the intact group. Likewise, the total amount (medium + pituitaries) of radioimmunoassayable PRL in vitro was depressed by 26% in the blind-anosmic group as compared with intact controls. Pinealectomy reversed the reductions in de novo synthesized and total immunoreactive PRL in vitro. From these studies we conclude that in the blind-anosmic female rat the pineal chronically inhibits PRL synthesis and storage in the pituitary and, possibly, its release into the blood. These pineal-induced effects could be accounted for by a reduction in the pituitary mammotroph as might be indicated by the decrease in pituitary DNA content observed in dual-sensory deprived rats.

Influence of pinealectomy on serum estrogen and progesterone levels in blind-anosmic female rats.

Previous studies show that the suppression of gonadal function in blind-anosmic rats is dependent on the pineal gland. The present results demonstrate that in young female rats both the pineal gland and dual sensory deprivation have additional independent antigonadal effects.

Pituitary and plasma LH and prolactin levels in female rats rendered blind and anosmic: influence of the pineal gland.

Female rats at 25 days of age were left intact or rendered either blind, blind-pinealectomized. blind-anosmic or blind-anosmic-pinealectomized. At 60 days of age blind-anosmie rats had depressed body weights and markedly hypotrophic uteri, ovaries and adrenal glands. Pituitary LH levels were significantly elevated in blind-anosmic rats whereas pituitary prolactin levels were significantly depressed. Plasma LH levels in blind and blind-anosmic animals were significantly depressed: plasma prolactin levels were unaffected by either of these treatments. Pinealectomy was effective in reversing the effects of combined blinding and anosmia on body, reproductive organ and adrenal weights as well as on pituitary LH and prolactin and plasma LH levels. For unknown reasons, compared to that of the hamster the neuroendocrine-reproductive

The pineal gland of the blind-anosmic female rat: its influence on medial basal hypothalamic lrh, pif and/or prf activity in vivo.

25-day-old female rats were left intact, or rendered either blind-anosmic or blind-anosmic-pinealectomized. Five weeks later, blind-anosmic animals were found to possess significantly depressed body, anterior pituitary, uterine and ovarian weights. The pituitary levels of LH were elevated while pituitary prolactin was depressed in the dual sensory-deprived rats. Blind-anosmic animals also had significantly depressed plasma levels of LH and elevated plasma levels of prolactin. The effects of blinding and anosmia were effectively reversed by pinealectomy. Ovariectomized, estrogen and progesterone-treated (OVX, EP-treated) rats that received an intracarotid injection of a medial basal hypothalamic (MBH) extract from intact or from blind-anosmic-pinealectomized female rats exhibited a marked rise in plasma LH to a peak at 10 min after injection. This peak was followed by a steady decline in plasma LH concentration. Animals injected with MBH extract from blind-anosmic rats also demonstrated a rise in plasma LH with the levels remaining more or less constant for the 10 and 20-min samples. Rather than declining, the plasma LH levels in 3 out of 4 rats exhibited a further increase until the 40-min sample. The injection of either cortical extract or saline had no effect on plasma LH levels. OVX, EP-treated rats receiving either MBH extracts from intact or blind-anosmic rats or cortical extract exhibited a depression in plasma prolactin titers 5 min following injection. This response was followed by a slight increase in plasma prolactin at 10 and 20 min with a subsequent decrease. Each of the OVX, EP-treated recipients injected with MBH extract from blind-anosmic-pinealectomized rats responded with an obvious increase in plasma prolactin levels within 5 min after injection, followed by a decrease. It was concluded that the MBH of the blind-anosmic rat was high in LRH activity while PIF appeared to predominate over PRF activity. On the other hand, in the MBH of the blind-anosmic-pinealectomized rat, LRH activity was lower while PRF appeared to predominate over PIF activity.

Pituitary and plasma prolactin levels in male rats as influenced by the pineal gland.

Rendering 21-day-old male rats blind (by bilateral orbital enucleation) and anosmic (by removal of the olfactory bulbs) resulted in severely depressed body weights and anterior pituitary gland weights and in reduced pituitary levels of prolactin until the animals were 125 days of age. Pinealectomy in blind anosmic rats returned all parameters toward those in controls although body weights and absolute pituitary weights were still slightly lower (p < 0.05 vs. intact controls) than normal in the animals autopsied at 75 and 100 days of age. By 125 days of age all rats had equivalent body and organ weights and also by this time pituitary prolactin levels had returned to the levels of those found in intact and pinealectomized control animals. Only in blind anosmic rats killed at 75 days of age were plasma levels of prolactin found to be significantly depressed.

Pituitary-Adrenal Function in Photic and Olfactory Deprived Rats

SummaryThe effect of photic and/or olfactory deprivation on pituitary-adrenal function was determined in female rats subjected to bilateral optic enucleation and/or olfactory bulb removal. Morning (09:00) and afternoon (16:00) nonstress levels of corticosterone of sensory-deprived rats appeared normal, and in all cases nonstress levels were completely suppressed with dexamethasone (100 μg/kg). Stress mechanisms of blind and/or anosmic rats, in the absence of dexamethasone, were intact. Stress-induced increments in plasma corticosterone of experimentals did not differ from those of intact controls. However, in the presence of dexamethasone, blind and blind-anosmic rats failed to show a plasma corticosterone response to ether stress. These data suggest that pituitary-adrenal function, unlike pituitary-ovarian function, is not markedly affected by photic and/or olfactory deprivation. Absence of the stress response in blind and blind-anosmic dexamethasone-treated rats may reflect changes in ovarian function a...