Localization of plasminogen activator and inhibitor, LH and androgen receptors and inhibin subunits in monkey epididymis

Epididymis is a site of sperm maturation and storage. Limited and directed-proteolysis regulated by plasminogen activator (PA), plasminogen activator inhibitor type-1 (PAI-1) and other related factors may play an essential role in these processes. Our previous studies have demonstrated that rat epididymis expressed luteinizing hormone receptor (LHR), tissue type (t) and urokinase type (u)PA, mRNAs, and tPA activity was stimulated in vitro by human chorionic gonoadotrophin (HCG). In the present study we further examined localization of mRNAs for tPA, uPA, LHR, androgen receptor (AR), as well as inhibin subunits alpha, betaA and betaB in rhesus monkey epididymis. Using in-situ hybridization with digoxygenin-labelled cRNA probes, we have demonstrated that tPA and PAI-1 mRNAs were localized in epithelial cells of adult monkey epididymis. uPA mRNA was localized in the same areas, but to a much smaller extent. tPA, uPA and PAI-1 mRNAs were greatly expressed in the caput and corpus of adult epididymis than in other regions. In-vitro experiments showed that both tPA and uPA activities in epididymal cells were dramatically stimulated by HCG, but not by follicle stimulating hormone (FSH). LHR (but not FSH receptor) and AR mRNAs were localized in the epithelial cells of the epididymis. However, LHR mRNA was detected in both adult and immature infant monkeys, whereas AR was found only in the adult. Inhibin alpha, betaA and betaB mRNAs were also detected in this organ, betaA mRNA being more strongly expressed in the caput than in other regions of the epididymis. We suggest that LH and androgen may be the key hormones in coordination with the PA-PAI-1 system in regulating epididymal differentiation and sperm maturation.

Temporal expression of urokinase type plasminogen activator, tissue type plasminogen activator, plasminogen activator inhibitor type 1 in rhesus monkey corpus luteum during the luteal maintenance and regression

Proteolytic activity generated by the plasminogen activator (PA) system has been associated with many biological processes. Using a pregnant mare serum gonadotropin (PMSG)/human chorionic gonadotropin (hCG)-induced rhesus monkey corpus luteum (CL) model, we have studied how urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (tPA), and plasminogen activator inhibitor type 1 (PAI-1), are temporally expressed in CL of rhesus monkey at the luteotropic and luteolytic periods. Slot blot analysis and in situ hybridization were performed to analyze the expression and distribution of uPA and PAI-1 messenger RNA (mRNA). Fibrin overlay was used to detect uPA and tPA activities. We found that uPA is the dominating PA in luteotropic CL in the monkey. Abundant expression of PAI-1 mRNA was detected. The highest expression of uPA and PAI-1 mRNA was observed at the luteotropic period, while their expression decreased approximately 50% at early luteal regression defined by considerably decreased serum progesterone levels, and remained at very low levels at the late stage of luteal regression. We also observed an increased tPA activity at the time of luteal regression. Moreover, the exogenous tPA could inhibit the progesterone production in cultured luteal cells from 13-day-old monkey CL. We also used LH receptor mRNA expression as a mark for the luteal phases. A highly expressed, evenly distributed LH receptor mRNA was detected in CL during the luteotropic phase, while its expression decreased at day 13 coinciding with the reduction of progesterone production. We conclude that proteolysis mediated by uPA and regulated by PAI-1 may play a role in the luteal maintenance, while tPA may participate in the luteal regression in the rhesus monkey.

[In vitro stimulation of HTC hepatoma cell growth by recombinant human augmenter of liver regeneration (ALR)]

It was demonstrated that biologically active ALR could be expressed from its cDNA in transient expression experiments in cos-7 cells. The results showed that the cytosolic fraction from the transfected cells with constructed plasmids DNA stimulated of DNA synthesis of in vitro HTC cells in a dose dependent manner. This finding suggests that the HTC hepatoma cell line may be used as a target for bioassay of human ALR in vitro.

Induction of vascular endothelial growth factor in balloon-injured baboon arteries. A novel role for reactive oxygen species in atherosclerosis

Neovascularization is a hallmark of neointimal formation in atherosclerotic plaques and restenotic lesions. Vascular endothelial growth factor (VEGF) promotes neovascular growth, whereas oxidative stress is a potent factor in vascular cell proliferation. To investigate the mechanisms of neovascular formation, we treated human and rat vascular smooth muscle cells (VSMCs) with H2O2. Northern blot analysis demonstrated a dose- and time-dependent increase in VEGF mRNA, with a maximum of 4-fold at 3 hours (200 mumol/L). As determined by immunoblotting and enzyme-linked immunosorbent assay, VEGF protein expression and secretion were similarly increased. Human umbilical vein endothelial cells were treated with conditioned medium from VSMCs incubated with 200 mumol/L H2O2. DNA synthesis, measured by thymidine incorporation, was increased 4-fold compared with control, an effect that was blocked by a neutralizing anti-VEGF antibody. The lipid peroxidation product 4-hydroxynonenal (1 mumol/L), an endogenous reactive oxygen species present in human atherosclerotic lesions, also increased VEGF secretion in VSMCs in a similar time-dependent fashion. Immunohistochemical staining and in situ hybridization of aortic sections from balloon-injured baboons demonstrated increased VEGF expression in discrete areas of the neointima and media compared with control sections, and expression correlated with the generation of 4-hydroxynonenal. Regulators of VEGF expression, such as reactive oxygen species, may enhance neovascularization of atherosclerotic and restenotic arteries.

Cellular delivery of human CNTF prevents motor and cognitive dysfunction in a rodent model of Huntington's disease

The delivery of ciliary neurotrophic factor (CNTF) to the central nervous system has recently been proposed as a potential means of halting or slowing the neural degeneration associated with Huntington's disease (HD). The following set of experiments examined, in detail, the ability of human CNTF (hCNTF) to prevent the onset of behavioral dysfunction in a rodent model of HD. A DHFR-based expression vector containing the hCNTF gene was transfected into a baby hamster kidney fibroblast cell line (BHK). Using a polymeric device, encapsulated BHK-control cells and those secreting hCNTF were transplanted bilaterally into rat lateral ventricles. Eight days later, the same animals received bilateral injections of quinolinic acid (QA, 225 nmol) into the previously implanted striata. A third group received sham surgery (incision only) and served as a normal control group. Bilateral infusions of QA produced a significant loss of body weight and mortality that was prevented by prior implantation with hCNTF-secreting cells. Moreover, QA produced a marked hyperactivity, an inability to use the forelimbs to retrieve food pellets in a staircase test, increased the latency of the rats to remove adhesive stimuli from their paws, and decreased the number of steps taken in a bracing test that assessed motor rigidity. Finally, the QA-infused animals were impaired in tests of cognitive function-the Morris water maze spatial learning task, and the delayed nonmatching-to-position operant test of working memory. Prior implantation with hCNTF-secreting cells prevented the onset of all the above deficits such that implanted animals were nondistinguishable from sham-lesioned controls. At the conclusion of behavioral testing, 19 days following QA, the animals were sacrificed for neurochemical determination of striatal choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) levels. This analysis revealed that QA decreased striatal ChAT levels by 35% and striatal GAD levels by 45%. In contrast, hCNTF-treated animals did not exhibit any decrease in ChAT levels and only a 10% decrease in GAD levels. These results support the concepts that implants of polymer-encapsulated hCNTF-releasing cells can be used to protect striatal neurons from excitotoxic damage, produce extensive behavioral protection as a result of that neuronal sparing, and that this strategy may ultimately prove relevant for the treatment of HD.

Preliminary studies on the role of plasminogen activator in seminal plasma of human and rhesus monkey

Two types of plasminogen activators (PA), tissue type (tPA) and urokinase type (uPA), were identified in the seminal plasma of both the human and the rhesus monkey. We studied the possible relationship between PA activities in the seminal plasma and the sperm counts and motility and demonstrated that: (i) PA activity in human seminal plasma from infertile patients was associated with immotile spermatozoa; (ii) the treatment of fertile men with testosterone enanthate (TE) to induce azoospermia was accompanied by an increase in seminal PA activity; (iii) when monomer T4 (isolated from multiglycosides of Tripterygium wilforddi) was administered to fertile male rhesus monkeys to induce azoospermia, PA activities in seminal plasma increased considerably; and (iv) immunocytochemistry studies showed that both uPA and PAI-1 antigens were localized on the surface of human spermatozoa, indicating that human spermatozoa were capable of binding uPA and PAI-1 through their receptors or forming a complex. These data demonstrate that seminal PA activity may be related to azoospermia, and possibly, to the fertilizing capability of spermatozoa in primates.

In utero hypoxic ischemia decreases the cholinergic agonist-stimulated poly-phosphoinositide turnover in the developing rat brain

Perinatal hypoxic-ischemic (HI) insult is known to cause cellular and molecular disturbances leading to functional and behavioral abnormalities during brain development. In this study, we examined the effects of an in utero HI insult on poly-phosphoinositide turnover in vivo in the cerebrum and cerebellum as well as cholinergic-stimulated turnover in cortical slices from developing rat brain. In utero HI treatment was carried out by clamping the uterine blood vessels of near-term fetuses for 5, 10 and 15 min followed by resuscitation of the newborn pups. The in vivo protocol for examining poly-PI signaling activity in 2 week-old pup brain involved intracerebral injection of [3H]inositol for 16 hr and subsequent intraperitoneal injection with lithium (8 meq/kg) for 4 hr prior to decapitation. In the control pups, lithium elicited a 2.6 fold increase in labeled inositol phosphate (IP) in the cerebrum as compared to a 1.3 fold increase in the cerebellum. In utero HI insult (5 to 15 min) resulted in a small increase in labeled IP in the cerebrum but not in the cerebellum. Carbachol stimulation of poly-PI turnover was examined in brain slices prelabeled with [3H]inositol in vivo. Incubation of the prelabeled slices with carbachol in the presence of LiCl (10 mM) resulted in a time-, dose- and age-dependent increase in labeled IP. Brain slices from 2 week-old pups that experienced in utero HI-treatment for 10 and 15 min (but not 5 min) showed a significant decrease in carbachol-stimulation of labeled IP as compared with control pups. These results indicate the effects of in utero HI on the choninergic-stimulated poly-PI signaling pathway and its implication on related functional deficits in the developing brain.

Stimulation of group II phospholipase A2 mRNA expression and release in an immortalized astrocyte cell line (DITNC) by LPS, TNF alpha, and IL-1 beta. Interactive effects

Astrocytes are immunoactive cells in brain and have been implicated in the defense mechanism in response to external injury. Previous studies using cultured glial cells indicated the ability of astrocytes to respond to bacteria endotoxin and cytokines, resulting in the release of phospholipase A2. In this study, we examined the interactive effects of lipopolysaccharides (LPS), interleukin 1 beta (IL-1 beta) and tumor necrosis factor (TNF alpha) to stimulate phospholipase A2 (PLA2) in an immortalized astrocyte cell line (DITNC) with many properties of type I astrocytes. Northern blot analysis using oligonucleotide probes derived from the cDNA encoding the rat spleen group II PLA2 indicated the ability of DITNC cells to respond to all three factors in the induction of gene expression and the release of PLA2. After an initial lag time of 2 h, PLA2 release was proportional to time, reaching a plateau by 12 h. This event occurred at a time period preceding any signs of cell death. Cycloheximide at 1.25 microM completely inhibited cytokine-induced PLA2 release. When suboptimal amounts of TNF alpha were added to the DITNC culture together with IL-1 beta or LPS, a synergistic increase in the induction of PLA2 release could be observed. On the other hand, combination of IL-1 beta and LPS resulted only in an additive increase in PLA2 release. Antibodies to IL-1 beta and TNF alpha completely neutralized the effects of these two agents on PLA2 release. However, neither antibody was able to inhibit the PLA2 release induced by LPS, suggesting that the effect of LPS was not complicated by the release of IL-1 beta or TNF alpha. Taken together, results show that the immortalized astrocyte cell line (DITNC) can be used for studies to elucidate the molecular mechanism underlying the cytokine signaling cascade and subsequent induction of PLA2 synthesis.

Hormonal regulation of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 in cultured monkey Sertoli cells

Sertoli cells play a central role in the control and maintenance of spermatogenesis. Isolated Sertoli cells of mouse and rat testes have been shown to secrete plasminogen activator (PA) and a plasminogen activator inhibitor type-1 (PAI-1) in culture. In this study, we have investigated the hormonal regulation of PA and PAI-1 activities in cultured monkey Sertoli cells. Sertoli cells (5 x 10(5) cells/well) isolated from infant rhesus monkey testes were preincubated at 35 degrees C for 16 h in 24-well plates precoated with poly(D-lysine) (5 micrograms/cm2) in 0.5 ml McCoy's 5a medium containing 5% of fetal calf serum and further incubated for 48 h in 0.5 ml serum-free medium with or without various hormones or other compounds. PA as well as PAI-1 activities in the conditioned media were assayed by fibrin overlay and reverse fibrin autography techniques respectively. The Sertoli cells in vitro secreted only tissue-type PA (tPA), no detectable amount of urokinase-type PA (uPA) could be observed. Monkey Sertoli cells were also capable of secreting PAI-1. Immunocytochemical studies indicated that both tPA and PAI-1 positive staining localized in the Sertoli cells, spermatids and residual bodies of the seminiferous epithelium; Northern blot analysis further confirmed the presence of both tPA and PAI-1 mRNA in monkey Sertoli cells. Addition of follicle-stimulating hormone (FSH) or cyclic adenosine monophosphate (cAMP) derivatives or cAMP-generating agents and gonadotrophin-releasing hormone (GnRH) agonist or phorbol ester (PMA) to the cell culture significantly increased tPA activity.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of prolactin on gonadotropin-induced ovarian estrogen and progesterone production in mouse]

Immature mice (21-23 days old) were injected with 8 IU PMSG to stimulate follicle growth and followed 24 h later by either injection of 8 IU hCG alone or hCG plus 100 micrograms of prolactin (PRL). The animals were killed at 3, 12 and 24 h after hCG treatment. The ovaries and blood samples were collected. Granulosa cells were prepared for incubation. Progesterone and estrogen concentrations in both the serum and the culture medium were determined. The results showed that PRL significantly enhanced hCG-induced mouse serum progesterone content, while serum estrogen concentrations were considerably decreased by the co-injection of PRL. Prolactin was also capable of stimulating gonadotropin-induced progesterone secretion in the cultured GC. However, the aromatase activity induced by FSH and hCG was remarkably inhibited by the presence of PRL. These data suggest that PRL inhibition of hCG-induced ovulation may be due to its interference with the gonadotropin-induced estrogen production by the follicular granulosa cells.

[Stereotactic radiosurgery by isocentric linear accelerator]

Stereotactic radiosurgery by isocentric linear accelerator, new technique developed in neurosurgery, was used to treat 92 patients with deeply localized cerebral tumors. Its indications and the techniques of improving its effect, preventing its complication were underlined.

[Prolactin inhibits gonadotropin-induced increase in ovarian plasminogen activator activity and ovulation in mouse]

We have demonstrated in this study that prolactin inhibits hCG-induced ovulation in PMSG-primed mice. At 18 h after the hormone treatment the number of ova in the oviducts was found to be 31.7 +/- 6.7 (mean +/- SE) in hCG treated group. The number was significantly decreased (19.7 +/- 4.9) when 100 micrograms of prolactin was injected simultaneously. The same effect of PRL on hCG induced ovulation could be also observed at 24 h after the hormone treatment; the values reached respectively to 32.3 +/- 10.8 and 20.3 +/- 5.4. Both in vivo and in vitro experiments further showed that the inhibition of the gonadotropin-induced ovulation by PRL is mediated through decreasing in the ovarian plasminogen activator activity.

The possible involvement of tissue type plasminogen activator in luteolysis of rhesus monkey

Changes of plasminogen activators (PA) during different stages of development of the corpus luteum, and their possible physiological role in luteolysis were studied in rhesus monkeys. It was demonstrated for the first time that monkey corpus luteal cells not only produce PA, but that the function of the corpus luteum is also closely related to the activity of this enzyme system. Generally, the life span for a corpus luteum in monkey is approximately 14-16 days, its demise beginning thereafter. In the present study, we found that urokinase in the corpus luteum is higher on day 5 and day 10 after human chorionic gonadotrophin injection, while the tissue type (t) PA is mainly produced on day 13 when luteolysis may take place. Progesterone production remained high on day 5 and day 10 and decreased dramatically from day 13, indicating the important role of tPA but not urokinase (u) PA in suppressing luteal function. When purified tPA (but not uPA) monoclonal antibody was added to luteal cell culture to neutralize endogenously produced tPA activity, progesterone production in the cells was increased significantly. Interestingly, prolactin alone was capable of increasing PA production by luteal cells; prolactin together with luteinizing hormone, however, had a synergistic luteotrophic effect.

Hormonal regulation of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 gene expression in cultured mouse Sertoli cells

We have demonstrated for the first time that (i) mouse Sertoli cells predominantly secrete tPA under the action of FSH and cAMP-generating agents, whereas Leydig cells mainly produce uPA; (ii) Sertoli cells are also capable of secreting PAI-1, as well as FSH, growth factors and GnRH increase PAI-1 gene expression; (iii) the increases in tPA and PAI-1 activities by different hormones in the conditioned media of Sertoli cells correspond to the increases in the levels of tPA and PAI-1 mRNA in the cultured cells, suggesting that the synthesis of the activator-inhibitor in mouse Sertoli cells is regulated at a transcriptional level and the tPA secreted by Sertoli cells may be involved in the spermatogenesis.

Effects of chlorpromazine on phosphatidylserine biosynthesis in rat pup brain exposed to ethanol in utero

Phosphatidylserine biosynthesis in rat pup brain was examined by assaying the serine base-exchange enzyme activity in the microsomal and plasma membrane fractions, and by measuring the incorporation of [3H]serine into phosphatidylserine in brain slices and in the intact brain. Chlorpromazine, either added in vitro into the incubation system or administered to animals via i.p. injection or feeding a liquid diet, gave rise to an increase in the phosphatidylserine biosynthesis activity. Ethanol administered in the form of a liquid diet to pregnant rats (day 11 birth) resulted in a decrease in phosphatidylserine biosynthesis in the newborn and developing brain. The ethanol-induced decrease in phosphatidylserine biosynthetic activity could be reversed by adding chlorpromazine to the ethanol diet. Results demonstrate that phosphatidylserine biosynthesis in the neonatal brain is affected in opposite directions by chlorpromazine and ethanol. This poses the possibility that chlorpromazine administration may be effective in alleviating the deleterious effects caused by the decreased phosphatidylserine biosynthesis in brain due to in utero ethanol exposure.

An experimental study of trachea anastomosis in rabbits using carbon dioxide laser

A technique of sutureless trachea anastomosis in rabbits using carbon dioxide laser was reported herein. In 6 rabbits with laser-assisted trachea anastomoses, only one was found to have slight anastomotic stenosis after operation, whereas 6 rabbits with conventional sutures all were found to have anastomotic stenosis. Results show that laser-assisted trachea anastomosis has certain advantages over the conventional suturing technique, thereby finding wide application in clinical tracheal reconstruction and lung transplantation.

Interaction of berbamine compound E6 and calmodulin-dependent myosin light chain kinase

The interaction of the berbamine compound E6 and calmodulin (CaM)-dependent myosin light chain kinase (MLCK) has been studied. The experimental results showed that the inhibition of MLCK activity was increased with increasing amounts of E6 and was overcome completely by the addition of excessive CaM. The stimulatory activity of MLCK induced by CaM was gradually inhibited by the increasing concentrations of compound E6, showing that the inhibition of MLCK activity by compound E6 was concentration dependent; and the Ki was 0.95 microM. Compound E6 diminished the fluorescence intensity of dansyl-labeled CaM and the intensity was increased gradually by the addition of different amounts of CaM. Compound E6 had no effect on the activity of MLCK fragments produced by limited trypsinization, and it is a novel and considerably potent calmodulin antagonist.

[Analysis of the treatment with traditional Chinese medicine in chronic glomerulonephritis based on histopathologic type]

The histopathologic type of 189 cases of chronic glomerulonephritis (GN) were confirmed by renal biopsies, they were subdivided into 3 groups. 77 patients of Western medicine (WM) group was treated by conventional WM (prednison or CTX), and after treatment the total effective rate was 55.8%. The TCM-WM group was treated by the same WM plus treatment according to Syndrome Differentiation with Chinese medicinal herbs, and the total effective rate was 86% in 50 patients. The TCM group was treated by Chinese medicinal herbs, and the total effective rate was 67.3% in 62 cases. There was very significant difference (P < 0.01) between the WM and the TCM-WM group. Among the patients of TCM-WM and TCM groups, 67% of 112 cases were manifested as Dampness-Heat Syndrome, so it suggested that one of the important method for GN treatment is clearing away Dampness-Heat. The effects of TCM-WM group is much better than the WM group in treating mesangio-proliferative GN and membranous GN. It was difficult for WM in treating IgA nephropathy, membrano-proliferative GN and focal glomerulosclerosis, but Chinese medicinal herbs were effective with replenishing Qi and strengthening the Spleen, clearing away Dampness-Heat, promoting blood circulation and relieving Stasis, etc.

In utero ethanol exposure decreases the biosynthesis of phosphatidylserine in rat pup cerebrum

Phosphatidylserine is enriched in the brain and has been implicated to play a role in regulating neuronal membrane functions. In this study, three experimental protocols were used to examine the effects of in utero ethanol exposure on phosphatidylserine biosynthesis in rat pup brain, namely, (1) assay of the serine base-exchange enzyme activity in brain microsomes, (2) incubation of brain slices with [3H] serine, and (3) incorporation in vivo of [3H]serine into phosphatidylserine as well as serine-related phospholipids in brain. Results from all three protocols point to a decrease in phosphatidylserine biosynthesis in newborn rat pup cerebrum on exposure to ethanol in utero compared with the pair-fed controls. When in utero ethanol-exposed pups were nursed by mothers given a chow diet, the differences gradually returned to control levels by 17 days of age. The decrease in phosphatidylserine biosynthesis may be important in explaining some of the neuronal deficits associated with in utero ethanol exposure.

Paradoxical effect of a GnRH agonist on steroidogenesis in cultured monkey granulosa cells

In this study we demonstrate: (i) The GnRH agonist exerts a direct dose-dependent stimulative effect on the aromatase activity and progesterone production in cultured monkey granulosa cells; (ii) the stimulative effect on steroidogenesis can be completely blocked by concomitant treatment with a GnRH antagonist, suggesting that the actions of GnRH are mediated through stringent stereospecific recognition sites; (iii) in addition to the stimulative effect, the GnRH agonist in the presence of gonadotropins also exerts an inhibitory effect, even though the peptide by itself is more effective in the stimulation of steroidogenesis, and the stimulation of gonadotropin on steroidogenesis could be gradually restored by decreasing the concentration of the GnRH agonist in the culture; and (iv) paradoxical effect can also be observed in the presence of cAMP-inducing agents, suggesting that the inhibitory action of the peptide on gonadotropin-induced steroidogenesis is localized at a step distal to the stringent recognition sites.

The protective effect of hyperbaric oxygen on hearing during chronic noise exposure

A series of experiments were conducted on guinea pigs to study the protective effect of hyperbaric oxygen (HBO) on hearing during chronic repeated noise exposure. A 1/3 octave band of noise centered at 1000 Hz was used (126 dB SPL, 1 h daily for 5 d; or 108 dB SPL, 1 h daily, 5 d/week for 4 weeks). Some groups of animals were treated with HBO (2-3 ATA, 1 h duration) before noise exposure. The results indicate that inhalation of HBO (every other day) can markedly reduce noise-induced threshold shift and relieve cochlear damage. The mechanism responsible for HBO protection against noise-induced hearing damage is discussed.

Neurosteroids: biosynthesis, metabolism and function of pregnenolone and dehydroepiandrosterone in the brain

Pregnenolone (P) and dehydroepiandrosterone (D) accumulate in the brain as unconjugated steroids and their sulfate (S) and fatty acid (L) esters. The microsomal acyl-transferase activity is highest in immature (1-3 weeks old) male rats. The immunocytochemical and biochemical evidence for P biosynthesis by differentiated oligodendrocytes is reviewed. The importance of P synthesis for its brain accumulation is assessed by the intracysternal injection of the inhibitor aminoglutethimide. Primary glial cell cultures convert P to 20-OH-P, PL, progesterone, 5 alpha-pregnane-3,20-dione and 3 alpha-hydroxy-5 alpha-pregnane-20-one (Polone). Astroglial cell cultures also produce these metabolites, whereas neurons from 17-day mouse embryos only form 20-OH-P. P and D are converted to the corresponding 7 alpha-hydroxylated metabolites by a very active P-450 enzyme from rat brain microsomes. Several functions of neurosteroids are documented. P decreases in olfactory bulb of intact male rats exposed to the scent of estrous females. D inhibits the aggressive behavior of castrated male mice towards lactating female intruders. The D analog 3 beta-methyl-androst-5-en-17-one, which cannot be metabolized into sex steroids and is not demonstrably androgenic or estrogenic is at least as efficient as D. Both compounds elicit a marked decrease of PS in rat brain. The Cl- conductance of gamma-aminobutyric (GABAA) receptor is stimulated by GABA agonists, an effect which is enhanced by Polone and antagonized by PS. Thus, P metabolites in brain as well as steroids of extraencephalic sources may be involved physiologically in GABAA receptor function. The neurosteroids accumulated in brain may be precursors of sex steroid hormones and progesterone receptors have been localized in glial cells. P and D do not bind to any known intracellular receptor. A heat stable P binding protein has been found in brain cytosol with distinct ligand specificity. A binding component specific for steroids sulfates, including Polone S, DS and PS, in the order of decreasing affinity is localized in adult rat brain synaptosomal membranes. Its relationship to the GABAA receptor is under current investigation.