Neurokinin A in the anterior pituitary of female rats: effects of ovariectomy and estradiol.

The effect of acute and chronic ovariectomy and the substitutive treatment with 17-beta estradiol and/or progesterone on anterior pituitary levels of neurokinin A (NKA) was studied in female rats. Acute ovariectomy did not result in significant changes of NKA in the anterior pituitary gland as compared with the levels in diestrous intact rats, but a single injection of 5 micrograms of estradiol in ovariectomized rats significantly decreased NKA levels in the anterior pituitary gland. Progesterone was without effect and did not modify the decrease of NKA in the anterior pituitary gland induced by estradiol. In rats examined 11 to 17 days after ovariectomy, NKA in the anterior pituitary gland was significantly higher than in diestrous intact rats. In the hypothalamus, ovariectomy resulted in decreased levels of NKA in the median eminence-arcuate nucleus. Estradiol significantly reduced NKA stores in the anterior pituitary gland but increased them in the whole hypothalamus and in the median eminence-arcuate nucleus. Thus, estradiol seems to be a powerful regulator of NKA stores in the adenohypophysis and also in the hypothalamus.     

delta 9-Tetrahydrocannabinol suppresses macrophage extrinsic antiherpesvirus activity.

The effect of delta 9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, on macrophage intrinsic and extrinsic antiherpesvirus activities was examined. THC had no effect on the capacity of the macrophage-like cells RAW264.7, J774A.1, and P388D1 to take up virus. In addition, replication of virus within macrophages did not occur regardless of drug treatment, indicating that THC had no effect on macrophage intrinsic antiviral activity. In contrast, the cannabinoid exerted a dose-dependent inhibition of macrophage extrinsic antiviral activity. This activity describes that macrophage function by which these cells suppress virus replication within xenogeneic cells in an interferon-independent manner. The inhibitory effect of THC on extrinsic antiviral activity was greatest on RAW264.7 and J774A.1 cells, followed by P388D1 cells. These macrophage-like cells regained their extrinsic antiviral activity in a time-related fashion following removal of the drug. These results indicate that THC inhibits macrophage extrinsic antiherpesvirus activity, but has no effect on intrinsic antiviral activity. However, the suppressive effect of THC on extrinsic antiviral activity is reversible upon removal of the drug.     

delta 9-Tetrahydrocannabinol elicited ipsilateral circling behavior in rats with unilateral nigral lesion

The present study was designed to examine the influence of delta 9-tetrahydrocannabinol (THC) on the central dopaminergic system using circling behavior. THC 5 mg/kg i.p. produced ipsilateral circling in rats with unilateral nigral lesion by 6-hydroxy-dopamine. THC-induced ipsilateral circling was completely antagonized by 0.2 mg/kg of haloperidol. These findings suggest that THC may cause a presynaptic stimulation of nigrostriatal dopaminergic neurons.     

Sterilization of female rats by neonatal placement of estradiol micropellets in anterior hypothalamus.

A pair of micropellets of a 1% or 10% estradiol (E2)-paraffin mixture (containing 0.2 or 2 mug E2, respectively) or paraffin alone were implanted subcutaneously or intracerebrally in 5-day-old female rats. Animals given 10% E2 pellets became sterilized regardless of loci of the pellets. Of those which had received 1% E2 pellets, only animals with micropellets in the anterior hypothalamus became sterilized. It is suggested that neuronal components which are affected irreversibly by neonatal estrogen treatment are localized in the anterior hypothalamus.     

Temporal changes in serum estradiol and prolactin in immature female rats given a single injection of estradiol benzoate

Serum concentrations of estradiol 17β(E₂) measured by immunoassay reached peak levels (100pg/ml) within one hour in immature female rats given a subcutaneous injection of lug 17βestradiol-3-benzoate (EB). Hypophysectomy did not alter the E₂ concentration, but lower peak levels were found in ovariectomized females. In animals with ovaries a secondary rise in serum E₂ was apparent 12 hours after the injection of EB; from 12 to 48 hours E₂ decreased linearly. A dose of Bug EB caused an abrupt rise in E₂ (180pg/ml) within 30 minutes, but during the next 24 hours rather wide fluctuations in serum levels were found. In animals acclimated to a reversed light schedule and given 5ug EB early in the dark period, E₂ decreased linearly over a period of 72 hours. Prolactin increased in response to the E₂: a rhythm was suggested by the occurrence of increases during the dark periods. The results indicate that statistically significant fluctuations in both E₂ and prolactin occur after a single injection of EB and that measurements at a single point in time are inadequate to determine the true pattern of hormonal changes.     

Induction of superovulation in prepubertal female rats by anterior pituitary transplants

Transplants of 26-day-old rats of an anterior pituitary gland from adult intact or castrated male, 20-day-old or adult ovariectomized female donors (all of which contained large amounts of FSH) resulted in superovulation in recipients on the morning of Day 29. Transplants of the gland from 20-day-old males and adult cyclic females could not advance the time of first ovulation or induce superovulation. In the rats in which superovulation could be induced, a marked increase in plasma FSH was noted in recipients shortly after transplantation and the high levels of plasma FSH were maintained until at least 12 h after grafting. These rats also showed preovulatory surges of LH and FSH 54 h after grafting. No obvious elevation of plasma FSH was noted over 72 h in recipients in which superovulation could not be induced. These findings suggest that the final maturation of follicles for superovulation is induced by a transient release of a large amount of FSH from the grafted pituitary gland and that the sex of the pituitary donor has no bearing on this phenomenon.     

The study of properties of immunoreactive estradiol secreted by adrenals and ovaries of immature female rats.

Some properties of immunoreactive estradiol secreted by adrenals and ovaries of immature female rats were studied. It was shown that adrenals and ovaries of 15-day-old animals secrete approximately equal amounts of immunoreactive estradiol, with thin-layer chromatogram of immunoreactive material being identical for both glands. Adrenal- as well as ovarian-derived estradiol can bind to uterine cytosol estradiol receptors with the formation of complexes, which can be activated in the cell-free system. The removal of either adrenals or ovaries causes a decrease of cytosol estradiol receptor levels in the uterus 6 hours after the operation. From these results and previously reported data, nothing suggests that immunoreactive estradiol secreted by the adrenals of immature rats should be regarded as "spurious" hormone.     

Effect of estradiol & testosterone on the pituitary prolactin levels in developing male & female rats

Testosterone priopionate (TP) or estradiol-17 beta (E2) were injected into male and female rats from day of birth to 15 days of age to determine the effect of these steroids on the pituitary prolactin (PRL) level in developing rats. Animals were autopsied on Days 5, 7, 10, 14, 17, 22, 25, 30, 37, 45, 52, and 60 and pituitary PRL estimated by radioimmunoassay. Neonatal administration of TP or E2 markedly increased PRL content in male rats. The peak of PRL was advanced to Days 14 and 23, respectively, in E2- and TP-treated groups. The content of pituitary PRL declined sharply and values increased again by Day 52 in TP-treated rats and Day 37 in E2-treated rats. In the female rat both the steroids advanced the time of PRL peak. Peaks were observed on Days 22 and 30, respectively. Although PRL content declined following these peaks, values remained at a significantly higher level than normal. These results suggest that mechanisms controlling the PRL secretion are functional during the neonatal period. It is also suggested that TP acts to increase PRL levels by 1st being converted to E2.     

delta 9-Tetrahydrocannabinol and cannabidiol: dose-dependent effects on evoked potentials in the hippocampal slice

The effects of (-) trans-delta 9-tetrahydrocannabinol (THC) and its metabolite cannabidiol (CBD) were investigated on evoked responses in the CA1 and dentate gyrus regions of the guinea pig transverse hippocampal slice. In both areas orthodromically evoked responses were enhanced by 10(-7) M THC, while 10(-6) M THC caused depression. Antidromic responses were not significantly affected. Antidromically-evoked inhibition in the CA1 region was decreased at low doses and unaffected at higher doses, while the facilitation by orthodromic interaction was unaffected at both dose ranges. The early part of the orthodromic field potential corresponding to the excitatory postsynaptic potential (EPSP) was enhanced at 10(-7) M in both areas. CBD (10(-6) M) decreased facilitation in CA1, and caused delayed excitation in the dentate granule layer. This study supports the conclusion that the biphasic effects of THC are dose dependent.     

Direct effect of estradiol on the number of dopaminergic receptors in the anterior pituitary, in ovariectomized rats

The effect of estradiol on anterior pituitary dopaminergic receptor content was studied in vivo and in vitro, in relation with the serum PRL secretion. A progressive and significant decrease in the number of these receptors was observed, a few hours before the serum release of PRL induced in ovariectomized females by a sequential treatment with different doses of estradiol benzoate. This decrease in the number of dopaminergic membrane receptors can be obtained as well in vitro, when anterior pituitaries, from ovariectomized rats, are incubated with 17 beta-estradiol. These results suggest that the stimulatory effect of estradiol on PRL secretion may be due, at least in part, to the direct "desensitization" to DA of anterior pituitary cells, which is produced by the decrease of dopaminergic receptor level.     

Intra-striatal estradiol in female rats impairs response learning within two hours of treatment

Estradiol treatment administered systemically or directly to the dorsolateral striatum across two days impairs performance on a response task in which rats learn to make a specific body turn to locate food on a maze. Estradiol can act through both slow and rapid signaling pathways to regulate learning impairments, however it is impossible to dissociate the slow from the rapid contributions of estradiol following long exposures. To assess the rapid effects of estradiol on striatum-sensitive learning, we trained rats on a response learning task after either relatively short or long treatments of estradiol infused directly into the striatum. Three-month-old female rats were ovariectomized 21 days before training and received guide cannulae implanted bilaterally into the dorsolateral striatum. For short duration treatments, rats were given bilateral infusions (0.5 μl) of 17β-estradiol-sulfate (0, 5, 50, or 500 nM in aCSF-vehicle) either 2 h or 15 min prior to training. For long duration treatments, rats received a series of estradiol infusions (500 nM) at 48, 24, and 2 h prior to training. Replicating previous findings (Zurkovsky et al., 2007), intra-striatal estradiol treatments given for two days prior to training impaired response learning. Estradiol-induced impairments in performance were also demonstrated 2 h, but not 15 min, after single infusions. Thus, estradiol acts within hours of exposure in the striatum, a structure lacking classical estrogen receptors, to impair response learning.     

Intra-striatal estradiol in female rats impairs response learning within two hours of treatment

Estradiol treatment administered systemically or directly to the dorsolateral striatum across two days impairs performance on a response task in which rats learn to make a specific body turn to locate food on a maze. Estradiol can act through both slow and rapid signaling pathways to regulate learning impairments, however it is impossible to dissociate the slow from the rapid contributions of estradiol following long exposures. To assess the rapid effects of estradiol on striatum-sensitive learning, we trained rats on a response learning task after either relatively short or long treatments of estradiol infused directly into the striatum. Three-month-old female rats were ovariectomized 21 days before training and received guide cannulae implanted bilaterally into the dorsolateral striatum. For short duration treatments, rats were given bilateral infusions (0.5 μl) of 17β-estradiol-sulfate (0, 5, 50, or 500 nM in aCSF-vehicle) either 2 h or 15 min prior to training. For long duration treatments, rats received a series of estradiol infusions (500 nM) at 48, 24, and 2 h prior to training. Replicating previous findings (Zurkovsky et al., 2007), intra-striatal estradiol treatments given for two days prior to training impaired response learning. Estradiol-induced impairments in performance were also demonstrated 2 h, but not 15 min, after single infusions. Thus, estradiol acts within hours of exposure in the striatum, a structure lacking classical estrogen receptors, to impair response learning.     

Selenium complexes in the anterior pituitary of rats exposed to L-selenomethionine

Selenium precipitates were demonstrated histochemically by silver amplification at light and electron microscopic levels in the anterior pituitary of rats exposed to L-selenomethionine (SeMeth). By electron microscopy (EM), the silver amplified selenium complexes were identified in somatotrophs, corticotrophs and gonadotrophs. Precipitates were observed mainly in the secretory granules and to a lesser extent in the lysosomes. The staining intensity increased with increasing amounts of SeMeth. Following a single injection of 3.7 mg Se/kg a substantial increase in staining was observed during the first 48 h after injection and precipitates could still be observed in the anterior pituitary after 2 weeks. During a long-term study where the rats were exposed to selenium contained in the drinking water (3.0 mg Se/l drinking water for 1, 2 or 4 weeks) an increasing amount of precipitates were observed during the first 2 weeks followed by a small decrease in staining intensity. Organic selenium, or rather a metabolite, is suggested to form bands with endogenous metal, primarily zinc, as has been suggested in the brain and anterior pituitary after exposure to sodium selenite.     

Discrete early changes in cellular subpopulations of rat uterine and anterior pituitary estrogen receptors in response to acute exposure to exogenous estradiol

Distribution of estrogen receptors among ligand-occupied and unoccupied species in cytosolic and nuclear subcellular compartments has been analyzed as an acute response to administration of 5 micrograms of estradiol in adult female rats. Patterns of anterior pituitary and uterine receptor turnover were monitored at intervals over a 5-h period, using either intact or 2-weeks ovariectomized animals. In terms of total cellular receptor content, initial levels were higher in castrate animals, but rapidly fell to intact levels within an hour following estradiol injection. Cycloheximide given shortly before estradiol had no effect on total pituitary receptor patterns, but appeared to result in an elevation in total uterine receptor content at early intervals. Unoccupied cytosol receptors were rapidly depleted and, with the exception of castrate pituitary samples, showed some replenishment within 5 h, all of which was cycloheximide-sensitive. Initially, occupied cytosol receptors were low in intact rats, but were present at levels approaching those of the unoccupied cytosol receptor forms in the ovariectomized rat tissues. Occupied cytosol receptor levels fluctuated in response to estradiol. Subpopulations of nuclear receptors, especially the unoccupied species, showed significant tissue specificity. In the uterus, unoccupied nuclear forms were initially present in high amounts, and the levels did not change in response to estradiol administration. In the pituitary, the levels of these receptors rose and subsequently fell over the 5-h interval. Cycloheximide conferred a similar biphasic response to estradiol upon the otherwise insensitive unoccupied nuclear forms of the uterus. Occupied nuclear receptors turned over completely during the 5-h study interval, with the kinetics being faster in the castrate than the intact tissues. Cycloheximide affected occupied nuclear forms of the uterus only, dramatically increasing their levels in response to estrogen and causing prolonged retention in the castrate animal model. Collectively, the cycloheximide effects on this system are consistent with early estrogen induction or stimulation of a protein which inhibits accumulation of occupied or unoccupied receptor species within the nucleus. This re-examination of all forms of cellular estrogen receptors as they fluctuate acutely in response to exogenous estrogen has revealed several heretofore undetected responses which must be incorporated into the overall scheme of early estrogen action.