The effect of progesterone and its metabolites on the interictal epileptiform discharge in the cat's cerebral cortex

Expression of 5alpha-reductase and 3alpha-hydroxisteroid oxidoreductase in the hippocampus of patients with chronic temporal lobe epilepsy

PURPOSE

The hippocampus is one of the principal target areas for neurosteroidal action, and the major neuroendocrine conversion of progesterone appears to be 5alpha-reduction and 3alpha-hydroxysteroid oxidoreduction, leading to the potent neurosteroid 3alpha,5alpha-tetrahydroxyprogesterone. To investigate whether the human hippocampus is equipped with the enzymes 5alpha-reductase and 3alpha-hydroxysteroid oxidoreductase (3alpha-HSOR), we studied the expression of 5alpha-reductase types 1 and 2 and 3alpha-HSOR types 1 and 2 in the resected hippocampi of patients with medically intractable chronic temporal lobe epilepsy.

METHODS

We studied tissue specimens from the hippocampi of 13 women, 25 men, and four children. Quantification of different mRNAs was achieved by competitive reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

5Alpha-reductase 1 mRNA and 3alpha-HSOR 2 mRNA were expressed in hippocampi of children and adults, whereas 5alpha-reductase 2 mRNA and 3alpha-HSOR 1 mRNA were not expressed. Neither 5alpha-reductase 1 mRNA nor 3alpha-HSOR 2 mRNA concentrations in hippocampal tissue showed any statistically significant differences between women and men or between children and adults.

CONCLUSIONS

This study demonstrates for the first time mRNA expression of the type 1 isozyme of 5alpha-reductase and the type 2 isozyme of 3alpha-HSOR in the human hippocampus. The finding that both 5alpha-reductase and 3alpha-HSOR are present in the hippocampus leads us to assume the synthesis of neuroactive steroids in this human brain area.

Hormonal effects on epilepsy in women

Some female gonadal and adrenal steroid hormones and their related pituitary peptides have neuroactive effects that can influence seizures. These effects may play a significant role in the pathophysiology of epilepsy, the pattern of seizure occurrence, therapeutic interventions using naturally occurring hormones, and the development of hormone-based neuroactive synthetic analogues with potent antiepileptic properties.

Hormonal effects on the brain

Changes in seizure frequency over the course of the menstrual cycle (i.e., catamenial epilepsy) have long been documented. Ovarian steroid hormones have a number of important short- and long-term effects on the brain that may contribute to this phenomenon. In particular, estrogen induces structural and functional changes in hippocampal neurons which may contribute significantly to increasing seizure susceptibility. This article reviews the mechanisms of action of steroid hormones on the basis of findings in animal models, with particular emphasis on the effects of estrogen on the hippocampus.

Effects of neurosteroids on spike-wave discharges in the genetic epileptic WAG/Rij rat

Effects of i.p. administration of the neurosteroids, allopregnanolone and pregnenolone sulfate, were studied in WAG/Rij rats, a genetic model for generalized absence epilepsy. EEG recordings showed that allopregnanolone, a positive modulator of the GABA(A) receptor, in doses ranging from 5 to 20 mg/kg, increased dose-dependently the number- and total duration of spike-wave discharges. Pregnenolone sulfate, a positive modulator of NMDA receptors, also increased those parameters, though only at the highest dose used (100 mg/kg). Significant changes in spike-wave discharges occurred during the first hour post-injection and were not accompanied with behavioral alterations. The obtained data indicate that both these neurosteroids aggravate the spike-wave activity. This finding contrasts with the anti-convulsant effects of some neurosteroids and they point to a different pharmacological profile of epilepsy with convulsive or non-convulsive seizures.

Evaluation of the anticonvulsant profile of progesterone in male amygdala-kindled rats

While there is clinical evidence that progesterone has anticonvulsant activity in women with complex partial seizures, previous studies on the anticonvulsant effect of progesterone in experimental animal models are inconclusive. Moreover, the effect of progesterone on seizure parameters in fully amygdala-kindled rats which best resemble complex partial seizures has not been evaluated. Therefore, in the present work the anticonvulsant effect of progesterone at doses of 10, 30, 60 and 75 mg/kg in fully amygdala-kindled male rats was studied. Only at the high and sedative dose of 75 mg/kg, progesterone suppressed behavioral seizures and afterdischarges elicited 10 min after intraperitoneal (i.p.) administration. Pretreatment with the progesterone antagonist, 17beta-hydroxy-11beta-(4-dimethylaminophenyl)-17alpha-(prop- 1-ynyl)-estra-4,9-dien-3-one (RU 38486) at the dose of 3 mg/kg did not inhibit the anticonvulsant activity of progesterone, while pretreatment with the GABA(A) receptor antagonist, bicuculline (2 mg/kg) blocked the anticonvulsant effect of progesterone. Neither RU 38486 nor bicuculline had any effect on the seizure parameters. These findings suggest that only at large and sedative doses, progesterone has some anticonvulsant activity in male amygdala-kindled rats which may be partly mediated via the GABA(A) receptor complex interaction.

Finasteride blocks the reduction in ictal activity produced by exogenous estrous cyclicity

The purpose of the present study was to examine seizure activity during reduced 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) production. Ovariectomized Long-Evans rats were stereotaxically implanted with bipolar electrodes above the perforant pathway; silastic implants filled with estradiol-17-benzoate (EB) and progesterone were inserted subcutaneously to mimic diestrus. Estrus was then induced in half of these animals by injection of EB (30 microg) and progesterone (2.5 mg), 48 and 4 h, respectively, prior to perforant pathway stimulation. Half of the estrous and diestrous rats also received a 5alpha-reductase inhibitor, finasteride (50 mg/kg), 6 h prior to perforant pathway stimulation. The estrous condition was associated with reduced number and duration of partial seizures, improved performance on a Morris water maze recovery of function test, reduced neuronal loss in the hilar region of the hippocampus, and elevated central and plasma 3alpha,5alpha-THP, compared to estrus+finasteride, diestrus+vehicle and diestrus+finasteride conditions, which did not differ from each another. These data suggest antiseizure effects of estrus may be caused, in part, by the action of 3alpha,5alpha-THP and that the precipitous decline in 3alpha,5alpha-THP may restore seizure threshold to control levels.

Nongenomic effects of neurosteroids

This review summarizes the current knowledge about the synthesis, the mechanism of action, and the effects of neurosteroids in the central nervous system. Particular attention is paid to the nongenomic actions of neurosteroids, which are discussed in relation to their clinical relevance for physiological and pathological states.

Citalopram increases pregnanolone sensitivity in patients with premenstrual syndrome: an open trial

We have investigated the ability of citalopram, a serotonin reuptake inhibitor, to alter the functional sensitivity to a neuroactive steroid during the late luteal phase in twelve women with premenstrual syndrome. Sensitivity to pregnanolone was assessed by comparing the effect of three increasing doses of intravenous pregnanolone on saccadic eye velocity (SEV) and self-rated sedation. Testings were performed in two consecutive menstrual cycles; without treatment and during citalopram treatment. During citalopram treatment, pregnanolone injections induced a significant SEV reduction compared to vehicle, whereas during the pre-treatment cycle there was no significant change in SEV response between vehicle and pregnanolone injections. Citalopram treatment did not alter the self-rated sedation response to pregnanolone compared to vehicle in either study cycle. These findings indicate that treatment with a selective serotonin reuptake inhibitor in the luteal phase increases the pregnanolone sensitivity in patients with premenstrual syndrome.

Progesterone, 5alpha-pregnane-3,20-dione and 3alpha-hydroxy-5alpha-pregnane-20-one in specific regions of the human female brain in different endocrine states

Post-mortem concentrations of progesterone, 5alpha-pregnane-3,20-dione (5alpha-DHP) and 3alpha-hydroxy-5alpha-pregnane-20-one (allopregnanolone) were measured in 17 brain areas and serum in five fertile and five postmenopausal women. Steroid concentrations were measured with radioimmunoassay after extraction of brain tissue with ethanol and purification with celite chromatography. There were regional differences in brain concentrations of all three steroids. The highest progesterone levels were noted in the amygdala, cerebellum and hypothalamus and the highest levels of 5alpha-DHP and allopregnanolone were seen in the substantia nigra and basal hypothalamus. Brain concentrations of all three steroids were significantly higher in the fertile women in luteal phase compared to their postmenopausal controls (P < 0.01). In general, the study showed that there is a variation in brain concentrations depending on ovarian steroid production, indicating that the secretion pattern during the menstrual cycle is reflected in the brain. However, regional differences in brain steroid levels imply local mechanisms for steroid uptake and binding as well. Investigations of gonadal steroid distributions in the human brain might be of importance considering the actions of these steroids in the central nervous system. Such studies could provide information about physiological mechanisms, such as the ovulation, and also form a baseline for comparative studies of normal and pathological conditions involving steroids, for instance, catamenial epilepsy and the premenstrual tension syndrome.

Natural steroids counteracting some actions of putative depressogenic steroids on the central nervous system: potential therapeutic benefits

Psychological similarities in the symptomatology of Cushing's and depressive diseases led to repeated attempts of treatment of the affective disease by suppression of adrenocortical secretion. While successful in many patients, all drugs employed-metyrapone, ketoconazole and aminoglutethimide-carry the danger of inducing adrenal insufficiency. In addition, their undesirable side effects were also a main reason for treatment suspension. In our 1990 proposal for the treatment of depression through control of adrenal steroid levels, we set as one of the goals the identification of steroids which can antagonize each other on their effects on the central nervous system. Specifically, we looked first at steroids that could counter each other's effects on long-term potentiation, a putative memory mechanism in the central nervous system. One reason for this was the consensus that memory mechanisms are affected in both Cushing's and depressive patients. Another was the fact that cortisol-type hormones which underlie, at least in part, the depressogenic actions of adrenal steroids also have inhibitory effects on LTP. We conjectured, then, that a steroid with opposite effects, one that could enhance long-term potentiation and, further, that could counter the depressant effects of corticosterone on long-term potentiation, could be of use in the treatment of depression. Dehydroepiandrosterone sulfate increases long-term potentiation in a dose-related manner, and preliminary data suggest that it also counteracts the depressant effects of corticosterone on long-term potentiation when injected simultaneously on experimental animals. Potentially at least, rather than resort to total suppression of adrenocortical activity, it may be possible to treat depression just by counteracting some of the effects of cortisol-like hormone actions in the central nervous system. Further, both in clinical trials as well as in experimental animals, dehydroepiandro-sterone sulfate has been shown to enhance performance in memory-requiring tasks.

Effect of age on synthesis of the GABAergic steroids 5-alpha-pregnane-3,20-dione and 5-alpha-pregnane-3-alpha-ol-20-one in rat cortex in vitro

Progesterone 5-alpha-reductase activity and 3-alpha-hydroxysteroid dehydrogenase activity were determined in the cortex of male and female rats in vitro. Age effects were investigated. The age of the male rats was 3-23 months, and that of the female rats 4-23 months. On addition, we investigated the enzyme 3 beta-hydroxysteroid oxidoreductase, 5-ene-isomerase in rat cortex in order to estimate the local synthesis of progesterone from pregnenolone. We found age-related increases in progesterone 5-alpha-reductase activity in the female rats (r = 0.64, p < 0.01, n = 6) and in the male rats (r = 0.5, p < 0.05, n = 18). 3-alpha-HSDH activity remained constant with age in female and male rats. The ratio of 3-alpha-hydroxysteroid dehydrogenase activity to 5-alpha-reductase activity tended to decrease with age (not significantly) in both male rats (r = -0.45, p = 0.06, n = 19) and the female rats (r = -0.36, p = 0.17, n = 16). We could not detect significant metabolism of pregnenolone to progesterone in rat cortex in vitro. The sensitivity of the assays of 3 beta-hydroxysteroid oxidoreductase, 5-ene-isomerase was calculated from the mean of the blank values + 3SD; the sensitivity of the assay was calculated as 0.103 fmol/mg protein/min. No significant metabolism of pregnenolone could be detected in cortex pooled from several male rats. The mean metabolism of progesterone was 1,200 times higher than the detection threshold of the assay for 3 beta-hydroxysteroid oxidoreductase, 5-ene-isomerase. We conclude that modifications of the inhibitory effects of the GABAergic steroids 5-alpha-pregnane-3,20-dione and 5-alpha-pregnane-3-alpha-ol-20-one via altered progesterone metabolism in rat cortex are possible with aging. A connection with the age-related increase in incidence of epileptic attacks, and with age-related changes in the effects of anticonvulsant and GABAA-active drugs, appears possible.

Progesterone induces changes in sleep comparable to those of agonistic GABAA receptor modulators

There is much evidence that progesterone has hypnotic anesthetic properties. In this vehicle-controlled study, we examined the effects of three doses of progesterone (30, 90, and 180 mg/kg) administered intraperitoneally at light onset on sleep in rats. Progesterone dose dependently shortened non-rapid eye movement sleep (NREMS) latency, lengthened rapid eye movement sleep (REMS) latency, decreased the amount of wakefulness and REMS, and markedly increased pre-REMS, an intermediate state between NREMS and REMS. Progesterone also elicited dose-related changes in sleep state-specific electroencephalogram (EEG) power densities. Within NREMS, EEG activity was reduced in the lower frequencies (< or = 7 Hz) and was enhanced in the higher frequencies. Within REMS, EEG activity was markedly enhanced in the higher frequencies. The effects were maximal during the first postinjection hours. The concentrations of progesterone and the progesterone metabolites 3 alpha-hydroxy-5 alpha-pregnan-20-one and 3 alpha-hydroxy-5 beta-pregnan-20-one, both positive allosteric modulators of gamma-aminobutyric acid A (GABAA) receptors, were determined at different time intervals after vehicle and 30 or 90 mg/kg progesterone. Progesterone administration resulted in dose-dependent initially supraphysiological elevations of progesterone and its metabolites in the plasma and brain, which were most prominent during the first hour postinjection. The effects of progesterone on sleep closely resemble those of agonistic modulators of GABAA receptors such as benzodiazepines and correlate well with the increases in the levels of its GABAA agonistic metabolites. These observations suggest that the hypnotic effects of progesterone are mediated by the facilitating action of its neuroactive metabolites on GABAA receptor functioning.

Progesterone is neuroprotective after transient middle cerebral artery occlusion in male rats

Progesterone (PROG) is a neurosteroid, possessing a variety of functions in the central nervous system. Exogenous PROG has been shown to reduce secondary neuronal loss in conjunction with attenuated brain edema after cerebral contusion and to reduce brain edema after focal cerebral ischemia. In the present study, we assessed the neuroprotective potential of PROG in a model of focal cerebral ischemia in the rat. Forty-eight male Wistar rats were randomly assigned to 4 groups, i.e. pretreatment with water soluble PROG, or dimethyl sulfoxide (DMSO) dissolved PROG, or DMSO as control or delayed treatment with DMSO dissolved PROG. Middle cerebral artery occlusion (MCAO) was induced by insertion of an intraluminal suture and reperfusion was performed by withdrawing the suture. Pretreatments were initiated 30 min before MCAO via intraperitoneal injection. Delayed treatment was initiated upon reperfusion following 2 h of MCAO. Infarct volume, body weight loss, and neurological deficit were measured 48 h after MCAO. Pre- and delayed treatment with DMSO dissolved PROG resulted in a 39% (P < 0.05) and 34% (P < 0.05) reduction in cerebral infarction, respectively, along with decreased body weight loss and improved neurological function as compared to control animals, whereas no statistically significant reduction in infarct volume by water soluble PROG was found. We demonstrated that administration of PROG to the male rat before or 2 hours after onset of MCAO reduces ischemic cell damage and improves physiological and neurological function 2 days after stroke. These results suggests potential therapeutic properties of PROG in the management of stroke.

Ovarian steroids modify the behavioral and neurochemical responses of the central benzodiazepine receptor

The effect of ovarian steroids on the benzodiazepine receptor was assessed in the elevated plus-maze and, after restraint stress, in benzodiazepine receptor binding assays. Vehicle-treated proestrous rats displayed anxiolytic behavior, relative to diestrus or estrous rats. Anxiolytic behavior was observed after 1 or 2 mg/kg diazepam in diestrus and estrus. However, whereas 4 mg/kg increased open arm exploration in diestrus, a decrease in the same measure was found at estrus. At proestrus, a decrease in anxiolytic behavior was observed after 2 and 4 mg/kg. In ovariectomized vehicle-treated rats, restraint stress increased NaCl-induced potentiation of 3H-flunitrazepam binding in cortical and cerebellar, but not in hippocampal membranes. Estradiol benzoate (2 micrograms) prevented the potentiation of flunitrazepam binding by NaCl in nonstressed and stressed animals, whereas progesterone (0.5 mg) increased the NaCl-induced potentiation of flunitrazepam binding in both nonstressed and stressed animals. Combined estradiol benzoate and progesterone treatment produced effects that were intermediate to those seen after injection of either steroid alone. The potentiation of flunitrazepam binding by NaCl observed in vehicle-treated stressed or progesterone-treated nonstressed animals was mimicked in vitro by addition to reaction test tubes of the neuroactive metabolite of progesterone, 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone). These results point to a significant role of ovarian hormones in modifying the stress response of the benzodiazepine receptor.

The neurosteroid 3 alpha, 5 apha-THP has antiseizure and possible neuroprotective effects in an animal model of epilepsy

Some anticonvulsant drugs may suppress seizures by enhancing activity of GABAergic systems. Progesterone (P)'s anti-convulsant and neuroprotective effects may be due to the steroid's actions on GABAA-benzodiazepine receptor complexes (GBRs) rather than intracellular progestin receptors (PRs), as many P metabolites have a greater effect in vitro on benzodiazepine binding and Cl-flux than P, but poor affinity for PRs. If P's actions are due to metabolism to a progestin more potent at GBRs, then systemic administration of one of those P metabolites should also prevent CNS damage. To test this hypothesis male rats were implanted with a bipolar electrode, aimed above the perforant pathway. Experimental animals received the 5 alpha-reduced P metabolite most effective at GBRs, 5 alpha-pregnan-3 alpha-ol-20-one (3 alpha,5 alpha-THP) 2.5 mg/kg s.c., 3 h prior to perforant pathway stimulation, while control animals received sesame oil vehicle. The duration of chewing and drooling and the incidence of wet dog shakes, partial and full seizures were reduced during perforant pathway stimulation in animals pre-treated with 3 alpha,5 alpha-THP compared to vehicle. Two weeks later, animals pre-treated with 3 alpha,5 alpha-THP had shorter latencies and distances to find a hidden platform in a Morris Water maze task. 3 alpha,5 alpha-THP pre-treatment also reduced damage to CA1 and CA3 layers of the hippocampus and preserved the number of neurons in the hilar region. These data indicate that the neurosteroid metabolite of P, 3 alpha,5 alpha-THP, can have anticonvulsant and may have neuroprotective effects in an animal model of epilepsy. Further, these data suggest that the mechanism of P's protective and anticonvulsant effects may be via GBRs rather than PRs.

Interaction between 17 beta-oestradiol and 3 alpha-hydroxy-5 alpha-pregnane-20-one in the control of neuronal excitability in slices from the CA1 hippocampus in vitro of guinea-pigs and rats

The effect of 17 beta-oestradiol and 3 alpha-hydroxy-5 alpha-pregnane-20-one (allopregnanolone) on the action potentials in the Schaffer collateral pathway was investigated in hippocampus CA1. Slices from male and female guinea-pigs and female rats were used. In the rat three groups were studied: (a) untreated prepubertal rats at day 25 after partus; (b) rats injected on day 26 with 10 IU of equine serum gonadotropin studied on day 28, when in the pro-oestrus follicular phase; and (c) on day 32 when in the luteal phase. The allopregnanolone (12.6 microM, 0.5 nL) was applied locally in stratum orienspyramidale. the 17 beta-oestradiol (0.7 nM) was perfused (4 mL min-1) or applied locally. The amplitude of the population spike in stratum pyramidale was increased by oestradiol in guinea-pigs of both sexes and in all the three groups of rats. Allopregnanolone decreased the amplitude of the population spike in the guinea-pigs and in the luteal phase rats. The effect appeared within seconds after the application of the drugs. The allopregnanolone inhibition of the population spike was increased by perfusion with oestradiol in the guinea-pigs and in the luteal phase rats. This effect appeared within 7 min, and improved with increasing length of the perfusion (7-71 min). It remained for 55 min after return to perfusion with artificial cerebrospinal fluid. In prepubertal and follicular phase rats the allopregnanolone inhibition was seen only after perfusion with oestradiol for more than 15 min. The results show that 17 beta-oestradiol increases the allopregnanolone inhibition and that this inhibition is most efficient during the luteal phase of the rat.

Influence of route of administration on progesterone metabolism

While inducing similar progesterone levels, the ratio of 5 alpha- and 5 beta-pregnanolone/progesterone plasma concentrations has been dramatically increased after oral as opposed to vaginal administration, in a cross-over study. The known psychotropic effects of 5 alpha- and 5 beta-pregnanolone lead to different indications and precautions for oral and vaginal administration of progesterone.

Anxiolytic effect of progesterone is mediated by the neurosteroid allopregnanolone at brain GABAA receptors

Previous studies from this laboratory have shown that progesterone (PROG) treatment in ovariectomized rats produces an anti-anxiety response similar to that observed after the administration of prototypical anxiolytic benzodiazepine (BDZ) compounds. The PROG-induced anxiolytic response was highly correlated with an increased level of 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone) in the blood and brain, and was also associated with a facilitation of GABA-stimulated chloride ion (Cl-) influx in cortical synaptoneurosomes. This correlative evidence suggested that the anxiolytic effect of PROG was a result of its in vivo reduction to the neuroactive steroid, allopregnanolone. In this report, a series of studies was conducted to determine the mechanism(s) by which PROG alters behavior in animal models of anxiety. In the first experiment, ovariectomized rats were injected with PROG (1 mg/0.2 ml, SC) 4 h prior to a test in the elevated plus-maze. Some animals also received an injection of picrotoxin (0.75 mg/kg, IP), a GABAA receptor-gated Cl- channel antagonist, whereas other animals were pretreated with RU 38486 (5 mg/0.2 ml, SC), a progestin receptor antagonist. PROG elicited anxiolytic behavior in the plus-maze, an effect that was blocked by picrotoxin administration. Pretreatment with RU 38486 was not effective in altering PROG-induced anxiolytic behavior in the plus-maze. In a second experiment, the effect of PROG on behavior in the plus-maze was determined in the presence of N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxamide (4-MA; 10 mg/0.2 ml, SC), a 5 alpha-reductase inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Orally administered progesterone enhances sensitivity to triazolam in postmenopausal women

An endogenously formed metabolite of progesterone, 3 alpha-hydroxy-5 alpha-dihydroprogesterone (3 alpha-OH-5 alpha-DHP) modulates the gamma-aminobutyric acid receptor complex and plays a physiologic role in brain excitability regulation. On the basis of in vitro observations of 3 alpha-OH-5 alpha-DHP-enhanced [3H]flunitrazepam binding, we investigated the potential clinical effect of coadministering oral progesterone and triazolam. Sixteen postmenopausal women were randomly assigned to receive either intravenous triazolam plus oral progesterone 300 mg (TRZPROG) or intravenous triazolam plus oral placebo (TRZ). Triazolam was infused until 0.5 mg was given or until a predetermined maximal response was attained. Pharmacodynamic evaluation included DSST, continuous performance test, hand-eye coordination, short-term memory, and sedation. Effect ratios were calculated as the ratio of area under the effect-time curve to area under the curve (AUC). Variants of the sigmoid Emax model were fit to the data from the three psychomotor performance tests. A triazolam dose of less than 0.5 mg was administered to seven of eight subjects in the TRZPROG and five of eight subjects in the TRZ group, resulting in lower triazolam AUC values for the TRZPROG than for the TRZ group (p = 0.0275). There was clear evidence for a pharmacodynamic interaction. Mean effect ratios for all tests were greater in the TRZPROG group than in the TRZ group (DSST, p = 0.0097; continuous performance test, p = 0.0338; hand-eye coordination, p = 0.0041). The TRZPROG group had lower EC50 values than the TRZ group (DSST, p = 0.0435; continuous performance test, p = 0.0381; hand-eye coordination, p = 0.0154).(ABSTRACT TRUNCATED AT 250 WORDS)

The progesterone metabolite 5 alpha-pregnan-3 alpha-ol-20-one reduces K(+)-induced GABA and glutamate release from identified nerve terminals in rat hippocampus: a semiquantitative immunocytochemical study

5 alpha-Pregnan-3 alpha ol-20-one (3 alpha-OH-DHP) reduced the depolarization-induced loss of GABA and, to a lesser extent, the glutamate-like immunoreactivities from nerve terminals in the in vitro hippocampal slice. Phenobarbital (PB) had similar effects. These results suggest that 3 alpha-OH-DHP affects presynaptic transmitter release, possibly in a barbiturate-like manner.

Pro- and anticonvulsant effects of stress: the role of neuroactive steroids

The present review deals with findings related to the contribution of pro- and anticonvulsant effects of "neuroactive" steroids and the role of the gamma-aminobutyric acid (GABA) receptor as a physiological target for naturally occurring steroids. Ways are discussed via which GABAergic neurotransmission can be enhanced or reduced following maneuvers that inflict stress. The duality of stress effects is emphasized in conjunction with different types of epileptogenesis (e.g., grand mal vs petit mal) that undergo dissimilar evolution. Among the issues covered are steroid-induced sedation and epileptogenicity, excitatory steroids, stress and epilepsy, GABA and respiratory functions, asymmetric brain injury, and psychopathology and stress.

Comparison of 5 alpha-pregnan-3 alpha-ol-20-one and phenobarbital on cortical synaptic activation and inhibition studied in vitro

The effects of 5 alpha-pregnan-3 alpha-ol-20-one (3 alpha-OH-DHP) and phenobarbital (PB) on synaptic excitation and inhibition in rat hippocampal slices in vitro were compared. Stimulations were made orthodromically and antidromically while we recorded extracellularly from the dendritic and the somatic layer of the CA1 region. Perfusion with 5 micrograms/ml of 3 alpha-OH-DHP for 30 min significantly increased the recurrent inhibition evoked by antidromic stimulation. The effect was most pronounced at short interstimulus intervals. The duration of the recurrent inhibition also was prolonged. There was no effect on the conditioned population spike after orthodromic paired-pulse stimulation. Furthermore, no effect was observed on the amplitude of the orthodromic fiber volley, the rate of increase in the field excitatory postsynaptic potential (EPSP) and the latency and amplitude of the CA1 population spike. Qualitative and quantitative similar findings were observed during perfusion with PB 0.1 mg/ml, (i.e., a concentration 20 times higher than that of 3 alpha-OH-DHP). Higher concentrations of PB also affected synaptic excitation. The findings suggest a similar effect of 3 alpha-OH-DHP and PB on recurrent GABA-ergic inhibition; however, 3 alpha-OH-DHP appears to be much more potent.

The effect of progesterone and its metabolite 5 alpha-pregnan-3 alpha-ol-20-one on focal epileptic seizures in the cat's visual cortex in vivo

The acute effects of progesterone and its brain metabolite 5 alpha-pregnan-3 alpha-ol-20-one (3 alpha-OH-DHP) on focal epileptic seizures in the cat's visual cortex was studied in vivo using an unanesthetized cervaux-isolé preparation. This model made it possible to study in parallel the effect of the drugs on ictal activity and synaptic transmission. A dose-dependent increase in seizure threshold was observed after i.v. injections of both 3 alpha-OH-DHP and progesterone, 3 alpha-OH-DHP being about 20 times as potent as the latter. I.v. injections of 3 alpha-OH-DHP 1.0 mg/kg increased the median seizure threshold to 265% of baseline. While 3 alpha-OH-DHP exerted an immediate effect on seizure thresholds, the maximal effect of progesterone was delayed about 20 min. Concerning the mechanisms underlying the antiepileptic effect, three changes occurred within the effective dose range: (1) a small, but significant reduction in the presynaptic nerve volleys, (2) a reduction in the postsynaptic excitatory field potentials in the dorsal lateral geniculate nucleus and cortex, and (3) an enhanced postsynaptic inhibition. Taken together, these observations point to both pre- and postsynaptic effects, supporting the hypothesis of a barbiturate-like mechanism of action of progesterone and its brain metabolites.

Premenstrual syndrome--psychiatric or gynaecological disorder?

The premenstrual syndrome (PMS) is a combination of mental and physical symptoms arising in the luteal phase of the menstrual cycle. The symptoms disappear after the onset of menstruation. During the rest of the follicular phase the patient is free from symptoms. The cyclical nature of the symptom variations is characteristic of the syndrome. The lack of a commonly accepted definition and a way to diagnose PMS has led to contradictory results in the search for its aetiology and treatment. The diagnosis of PMS should be based on prospective daily ratings of symptoms and defined criteria of subgroups. In our studies three subgroups can be identified. The "Pure PMS" group with significant cyclical symptoms being worse during the luteal phase and no symptoms during the follicular phase. A "Premenstrual aggravation" group with symptoms always present but with an aggravation premenstrually. A "Non-PMS" group of women who do not suffer from menstrual cycle related symptoms. These three groups show significant differences in the number of patients with an earlier psychiatric history and are different in the extent of neurosis on a personality test. The Pure PMS group had less neurosis and a lower frequency of patients with an earlier psychiatric history. In anovulatory cycles, whether induced or spontaneous, the cyclical nature of symptoms disappeared. This shows the important role that the corpus luteum has in precipitating symptoms in PMS. GnRH-agonists can be used to induce anovulation and this will stop the cyclical changes. Postmenopausal women receiving oestradiol/progestagen sequential treatment develop PMS-like symptoms when progestagen is added to the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Pregnanolone (3 alpha-hydroxy-5 alpha-pregnane-20-one), a progesterone metabolite, facilitates inhibition of synaptic transmission in the Schäffer collateral pathway of the guinea pig hippocampus in vitro

Pregnanolone (3 alpha-hydroxy-5 alpha-pregnane-20-one, a metabolite of progesterone) caused a significant depression of the amplitude of the population spike evoked in stratum pyramidale in CA1 of the guinea pig hippocampus in vitro. Local application of pregnanolone on the surface of the slice in stratum oriens depressed the population spike without effects on the presynaptic spike and the population excitatory postsynaptic potential simultaneously recorded in stratum radiatum. The depression was dose-dependent and was observed with a minimum latency of 10 s after application of a 0.5-nl droplet of 3.1 microM pregnanolone. The concentration at the recording site was computed to be 0.2 microM. The duration of the depression was 20-30 min. The depression was significantly reduced during perfusion of the slice bath with 100 microM picrotoxin in artificial cerebrospinal fluid. When pregnanolone was applied locally in stratum radiatum, the amplitudes of the presynaptic spike, the population excitatory postsynaptic potential and the population spike were depressed. The effects on the presynaptic spike and the population excitatory postsynaptic potential vanished with different time courses. It is concluded that the depression of the population spike was caused by GABAA-mediated inhibition of the pyramidal neurones. The role of pregnanolone as a positive modulator of the GABAA receptor and the effect of this modulation on the complex mechanisms underlying catamenial epilepsy are discussed.

Functional changes in GABAA receptor stimulation during the oestrous cycle of the rat

1. Slices of rat cuneate nucleus were used to study whether or not gonadal steroids influence the gamma-aminobutyric acid (GABA) system in vivo. Females in different stages of the oestrous cycle as well as steroid-treated (oestrogen, progesterone or both) ovariectomized animals were used. 2. Functional changes in the GABAA receptors were assayed using the effects of potentiators (benzodiazepine, barbiturate) and antagonists (picrotoxin) on the muscimol control dose-response curves. 3. The potentiating effect of the benzodiazepine, flurazepam was unchanged during the oestrous cycle, and the hormone treatments did not alter this effect. 4. During oestrus, an increase was seen in the potentiating effect of the barbiturate (pentobarbitone). This suggests a synergistic effect between barbiturates and gonadal steroids. Progesterone treatment also increased the effect of pentobarbitone. 5. The antagonistic action of picrotoxin was unaffected during the oestrous cycle. However, progesterone (or progesterone and oestrogen) treatment reduced the potency of picrotoxin. 6. This study supports the idea that endogenous steroids (presumably progesterone) affect the GABAA receptors during the oestrous cycle by a mechanism associated with the barbiturate site of the GABAA receptor complex.

Some substances with proposed digitalis-like effects evaluated on platelet functions sensitive for cardiac glycosides

1. The effects of progesterone, corticosterone 21-acetate, chlormadinone acetate, dehydroepiandrosterone 3-sulfate and lysophosphatidylcholine were tested on 86Rb-uptake, 3H-5-HT-uptake, ADP-induced aggregation and 5-HT-induced shape change in human platelets. Ouabain and digoxin were used for reference. 2. Ouabain and digoxin 10(-5) M inhibited 86Rb-uptake by more than 85%, and chlormadinone acetate 10(-5) M by 20%. The other substances had no effects. 3. Ouabain and digoxin were potent inhibitors on 3H-5-HT-uptake, whereas chlormadinone acetate had no effect. 4. Ouabain and digoxin increased ADP-induced aggregation but chlormadinone acetate decreased it. 5-HT-induced shape change was decreased by ouabain and digoxin, and to a lesser extent by chlormadinone acetate and its vehicle (ethanol 1.0%).

Anticonvulsant steroids and the GABA/benzodiazepine receptor-chloride ionophore complex

The ability of steroids to influence brain excitability is well documented. Certain 3 alpha-hydroxylated pregnanes are known to possess anticonvulsant and sedative-hypnotic/anesthetic properties. It has been observed that the seizure susceptibility in menstruating women with catamenial epilepsy appears to be correlated with changes in ovarian steroid levels. However, the underlying mechanism of these steroid influences on brain activity has only been recently revealed by pharmacological studies. These studies have provided compelling evidence for the presence of a novel steroid recognition site on the GABAA-benzodiazepine receptor complex (GBRC). Steroids may interact with this site with high affinity and stereospecificity to enhance chloride channel conductance in a manner similar to that produced by benzodiazepines (BZs) or barbiturates. The existence of such a steroid site on the GBRC is further supported by recent experiments involving the transfection of GABAA receptor cDNAs into a human embryonic kidney cell line. Based on the knowledge of the structure-activity requirements for the interaction of steroids with this novel recognition site, it is conceivable that the development of new anticonvulsant steroids with high therapeutic indices can be achieved.

Mechanisms involved in the control of punished responding in mother rats

In a previous study we found that mother rats show more drinking responses than virgins in the punished drinking paradigm, an animal model for anxiety. The present investigation was carried out to determine the possible mechanisms underlying this naturally occurring anticonflict effect. In Experiment 1, we investigated whether the induction of maternal behavior in virgin females (by long-term estrogen and progestin treatment in combination with pup exposure) enhances punished drinking. However, no release from shock-induced (0.25 mA) suppression of drinking was observed in maternally responsive virgins deprived of water for 24 hr. Unlike natural mothers, then, no anticonflict effect is seen in maternal virgins. A considerable body of evidence suggests that facilitation of gamma-aminobutyric acid (GABA) activity in the brain increases punished responding in rats. In the second experiment, therefore, lactating females were injected with pentylenetetrazol, a GABA antagonist, before being monitored for punished drinking. The drug attenuated the enhanced acceptance of shock in mothers, the effect being observed at a dose level that did not reliably affect unpunished responding. Experiment 3 addressed the possible influence of ovarian and adrenal hormones on punished drinking in lactating females. No significant behavioral effects were observed in mothers subjected to adrenalectomy or ovariectomy 4 days before testing.

Regional distribution of progesterone and 5 alpha-pregnane-3,20-dione in rat brain during progesterone-induced "anesthesia"

Progesterone and 5 alpha-pregnane-3,20-dione (5 alpha-DHP) concentrations were measured in seven brain areas and in plasma during "anesthesia" induced by progesterone (1-2 mg IV) in female rats. The highest levels of progesterone were detected in the striatum and hypothalamus (23.3 +/- 5.27 and 22.7 +/- 4.30 micrograms/g +/- SEM, respectively); these concentrations were approximately 1000 times higher than those during the post-ovulatory phase. Highest levels of 5 alpha-DHP were detected in the striatum and hippocampus (11.5 +/- 1.74 and 10.4 +/- 3.15 micrograms/g +/- SEM, respectively). The ratio of 5 alpha-DHP to progesterone was approximately 100 times higher in brain tissue than in plasma. We conclude that a conversion of progesterone to 5 alpha-DHP occurs in the brain during the course of progesterone-induced "anesthesia". This metabolic step may be an important contributory factor to the anesthetic potency of progesterone.

Intrahypothalamic injection of RU486 antagonizes the lordosis induced by ring A-reduced progestins

We explored the possibility that ring A-reduced progestins facilitate lordosis in estrogen primed rats through their interaction with an intracellular progestin receptor (PR) by using RU486. This drug binds with high affinity to the PR, thus preventing the action of progesterone (P). Ovariectomized estrogen-primed rats (2 micrograms estradiol benzoate 40 hr earlier) were bilaterally injected into the ventromedial hypothalamic nucleus (VMHN) with 1 microgram of: P, 5 alpha-pregnanedione or 3 beta,5 beta-pregnanolone in 1 microliter oil. All three progestins effectively facilitated lordosis, tested at four and eight hours after intrahypothalamic injections. The ability of RU486 to counteract progestin-induced lordosis was assessed by infusing 10 micrograms of this agent into the VMHN along with any of the progestins. RU486 antagonized the lordosis induced not only by P (67% reduction) but also that induced by 5 alpha-pregnanedione and by 3 beta,5 beta-pregnanolone (47% and 93% reductions, respectively). Results suggest that ring A-reduced progestins may act through the PR mechanism to facilitate lordosis, i.e., in a fashion similar to P.

Anticonvulsant profile of the progesterone metabolite 5 alpha-pregnan-3 alpha-ol-20-one

5 alpha-Pregnan-3 alpha-ol-20-one (3 alpha-OH-DHP) is a naturally occurring metabolite of progesterone that can modulate brain excitability through a specific steroid recognition site on the GABA/benzodiazepine receptor-chloride ionophore complex. The anticonvulsant properties of 3 alpha-OH-DHP were determined using standardized anticonvulsant screening tests in mice. This steroid was found to be effective against metrazol-, (+)-bicuculline- and picrotoxin-induced seizures. The steroid has maximum potency against (+)-bicuculline-induced convulsions and no activity against maximal electroshock and strychnine-induced seizures. These findings support the hypothesis that therapeutically useful anticonvulsant steroids active at the putative steroid recognition site associated with the GABA/benzodiazepine receptor-chloride ionophore complex can be identified.

Lordosis facilitation in estrogen primed rats by intrabrain injection of pregnanes

Progesterone (P) and nine of its natural metabolites were bilaterally injected (5 micrograms in 0.5 microliter oil) into either the ventromedial hypothalamus (VMH) or the medial preoptic area (MPOA) of estrogen primed rats to assess their relative potencies for stimulating lordosis. P, 5 alpha-pregnanedione and 5 beta, 3 beta-pregnanolone elicited lordosis when injected at either VMH or MPOA. By contrast, 5 alpha, 3 beta-pregnanolone as well as 20 alpha-OH and 20 beta-OH-pregnenone were much more effective in stimulating lordosis when implanted in the MPOA. Finally, 5 beta-pregnanedione and 5 beta,3 alpha-pregnanolone did not stimulate lordosis at neither VMH nor MPOA. The observation that lordosis was induced in estrogen primed rats both by pregnanes that bind to the P receptor (i.e., P; 5 alpha-pregnanedione; 20 alpha- and 20 beta-OH-pregnenone) and by pregnanes that do not (i.e., 5 alpha, 3 beta-; 5 beta,3 beta- and 5 alpha,3 alpha-pregnanolone) indicates that diverse cellular mechanisms are involved in the facilitation of lordosis by pregnanes.

Progesterone, some progesterone derivatives and urinary digoxin-like substances from pregnant women in radioimmuno- and 86Rb-uptake assays of digoxin

Progesterone and some derivatives were tested in a radioimmunoassay (RIA) of digoxin and in a bioassay measuring the 86Rb-uptake into red blood cells as an index of Na+, K+-ATPase activity. The digitalis-like activity of the hormones was compared with that found in chromatographic fractions of material extracted from the urines of pregnant women at term. Progesterone at concentrations greater than 10(-6) M cross-reacted in the RIA, and at 10(-3) M it decreased 86Rb-uptake by 18%. The anaesthetic progesterone derivates 5 alpha-pregnane-3 alpha-ol-20-one and 5 alpha-pregnane-3,20-dione crossreacted to a lesser degree in the RIA and lacked effect in the bioassay. Similar results were obtained with pregnandiol-glucuronide, the major urinary metabolite of progesterone. In contrast, several fractions of the urinary material had significant effects in both assays. It is concluded that the digitalis-like activity of progesterone is not coupled to properties associated with its anaesthetic effects. Furthermore, although progesterone may account for a part of the endogenous digoxin-like substances in serum of neonates and pregnant women, neither progesterone proper nor pregnandiol-glucuronide explains the great amount of digoxin-like substances found in the urines.

Effects of 5 alpha-dihydrocorticosterone on evoked responses and long-term potentiation

The effect of a Ring A-reduced metabolite of corticosterone, 5 alpha-dihydrocorticosterone (DHB) on long-term potentiation (LTP) in the dentate gyrus (DG) of the rat were studied in barbiturate-anaesthetised animals. It was observed that DHB significantly impairs the development of LTP, more particularly the population spike (PS) component of the evoked potential (EP) to perforant path (PP) stimulation. Nutralipid, an inert control solvent of the steroid, did not affect LTP development. We argue that both, membrane and intracellular effects of DHB, are involved in the mechanisms responsible for DHB blocking of LTP.