Epilepsy, sex hormones, and antiepileptic drugs

Best practice guidelines for the management of women with epilepsy. The Women with Epilepsy Guidelines Development Group

Clinical guidelines for the treatment of epilepsy have been published. A statement on management issues for women with epilepsy has recently been produced by the American Academy of Neurology which has raised awareness of the issues facing women with epilepsy. The communication presented here aims to review current literature on specific issues relating to women with epilepsy, and proposes graded recommendations for its management within a UK health care framework.

Psychoneuroendocrine aspects of temporolimbic epilepsy. Part II: Epilepsy and reproductive steroids

Reproductive dysfunction is unusually common among men and women with epilepsy. Reproductive endocrine disorders are also common and may be causal. The association between particular reproductive endocrine disorders and the laterality and focality of epileptiform discharges suggests an etiologic role for epilepsy. Gonadal steroids are neuroactive and influence seizure occurrence: estrogen is epileptogenic whereas progesterone has antiseizure effects. Fluctuations in the absolute and relative serum levels of these hormones may play a critical role in establishing three distinct patterns of catamenial epilepsy: 1) perimenstrual and 2) preovulatory in women with ovulatory cycles, and 3) entire luteal phase of the cycle in women with anovulatory cycles. Treatment with progesterone reduces seizure frequency by more than half. In men, testosterone effects may depend on the relative concentrations of two major testosterone metabolites that exert opposing influences on neuronal excitability: estrogen potentiates whereas dihydrotestosterone inhibits NMDA-mediated conductance. Combined therapy using an aromatase inhibitor along with testosterone improves sexual function and may reduce seizures in men with epilepsy.

The effects of valproate, carbamazepine, and oxcarbazepine on growth and sexual maturation in girls with epilepsy

OBJECTIVE

Antiepileptic drugs (AEDs) have endocrine effects that may interfere with growth and sexual maturation in children. The aim of this study was to evaluate the effects of AEDs on growth and pubertal development in girls with epilepsy.

STUDY DESIGN

Forty girls taking valproate (VPA), 19 girls taking carbamazepine (CBZ), and 18 girls taking oxcarbazepine (OXC) for epilepsy and 49 healthy control girls participated in the study, which included a cross-sectional clinical examination when the girls were 8 to 18 years old and a longitudinal growth analysis from the age of 1 year.

RESULTS

VPA, CBZ, or OXC did not affect linear growth or pubertal development in girls with epilepsy. However, the patients taking VPA gained weight, and an increase in relative weight was seen in girls who started their medication before as well as during puberty. The body mass index of the VPA-treated girls (19.8 +/- 4.8 kg/m2) was higher than that of the control girls (18.0 +/- 2.5 kg/m2) at clinical examination. The weight of the girls taking CBZ or OXC for epilepsy was similar to that of the control girls. Plasma insulin-like growth factor-I (IGF-I) levels were higher in girls treated with CBZ and OXC than in the control girls, but AEDs did not affect fasting serum insulin, IGF-binding protein-1, or IGF-binding protein-3 concentrations in girls on VPA, CBZ, or OXC medication during the period of exposure (average 2.8, 4.1, and 1.9 years, respectively) in this study.

CONCLUSIONS

AEDs do not seem to have any adverse effects on linear growth or sexual maturation in girls with epilepsy. VPA-related weight gain can be seen already in prepuberty and it is not associated with hyperinsulinemia in these young patients. The clinical significance of high circulating concentrations of IGF-I in patients taking CBZ or OXC remains to be defined.

Effects of menopause on seizures in women with epilepsy

PURPOSE

Although important associations between epilepsy and women's hormonal phases are described, the relation of menopause to epilepsy has received little attention.

METHODS

By using a structured interview, we studied menopausal women with epilepsy seen at the University of Maryland Epilepsy Center over a 1-year period from 1994 to 1995. We analyzed the characteristics and temporal relation of the seizures to menopause and compared the frequency and severity of the seizures with those in a similar group of premenopausal women.

RESULTS

We identified 61 menopausal women (46 who were postmenopausal and 15 perimenopausal) and compared them with 46 premenopausal women. No statistically significant differences were noted in either the frequency or the severity of seizures comparing all menopausal or only postmenopausal with premenopausal women. However, 12 (20%) of the 61 menopausal women noted that their seizures first began during or after menopause, with eight having no proven cause for their seizures. Many individual women described changes in their seizures with menopause. Among the 61 menopausal women, 49 had established epilepsy before the onset of menopause, and 20 (41%) reported worsening of their seizures with menopause, 13 (27%) noted improvement, and 16 (33%) described no changes. These observations were similar for peri- and postmenopausal women. Of the 15 menopausal women taking hormone replacement therapy, the six taking progestin were significantly less likely to report worsening of their seizures.

CONCLUSIONS

These findings support the view that hormonal influences are important in women with seizures. Although, in aggregate, menopausal (combined perimenopausal and postmenopausal) and postmenopausal women's seizures were similar in frequency and severity to those of other women, menopause was associated with changes in seizures for some women. Moreover, menopause may be a previously unrecognized factor for some new-onset seizures. The relations between menopause and epilepsy deserve to be more fully investigated.

Effects of epilepsy on women's reproductive health

Reproductive dysfunctions are common and wide-ranging in women with epilepsy. Menstrual cycle disruption, anovulatory cycles, disturbances in hypothalamic and/or pituitary hormones, and disturbances in gonadal steroids are more common among women with epilepsy. Sexual dysfunction can present as either disorders of desire or physiologic arousal, but the most common dysfunction appears to be an inadequate initial physiologic arousal response. Reproductive dysfunctions may be due to psychologic, pharmacologic, or physiologic factors. Physicians should routinely question all women with epilepsy regarding their reproductive and sexual health. A full history, a complete physical, and laboratory evaluations with endocrinologic work-up should be performed in any woman who reports a reproductive dysfunction. Treatment and/or referral to a gynecologist or endocrinologist should be initiated as appropriate.

Bicuculline-induced rhythmic EEG episodes: gender differences and the effects of ethosuximide and baclofen treatment

PURPOSE

There are gender differences in the expression of seizures. We tested rhythmic EEG episodes induced by low doses of bicuculline in rats for gender differences. To verify the validity of these discharges as a model of absence seizures in both male and female rats, we tested the antiabsence drug ethosuximide (ESM) and a gamma-aminobutyric acid (GABA(B))-receptor agonist, baclofen, which may exacerbate absence seizures.

METHODS

Adult rats of both sexes were used. Under general anesthesia, EEG electrodes were implanted over frontal and occipital cortex, and some females were ovariectomized. After recovery, male, intact female rats, and female rats ovariectomized and ovariectomized rats with estradiol replacement were compared for occurrence of rhythmic EEG episodes (approximately 6 cycles/ s) induced by 2.5 mg/kg of bicuculline, s.c. Because of gender differences in sensitivity to bicuculline, further pharmacologic effects of ESM (125 and 250 mg/kg, i.p.) and baclofen (2 mg/kg, i.p.) were tested separately in male (3.0 mg/kg of bicuculline), and female (2.5 mg/kg of bicuculline) rats.

RESULTS

After the identical dose of bicuculline, s.c., male and female rats differed in the incidence of rhythmic episodes and in the latency to onset of the first as well as the generalized episode. Female rats with natural or exogenous estrogens (but not ovariectomized rats) developed EEG episodes more often than did males, and this effect could be attributed to the presence of estrogens. ESM pretreatment suppressed the episodes, whereas baclofen enhanced their occurrence, as well as the total duration of episodes without gender-specific differences.

CONCLUSIONS

The study demonstrates gender differences (related probably to the presence of circulating estrogens) in the susceptibility of rats to develop rhythmic EEG episodes induced by threshold doses of bicuculline. This activity has some features of an acute absence seizure model.

Serum sex hormones are altered in patients with chronic temporal lobe epilepsy receiving anticonvulsant medication

PURPOSE

To evaluate the changes in serum sex hormones of gonadal or adrenal origin, the gonadotropic hormones, and sex hormone-binding globulin (SHBG) in men and women with chronic temporal lobe epilepsy (TLE), who are undergoing monotherapy with carbamazepine or receiving carbamazepine in combination with other anticonvulsant drugs.

METHODS

Gonadal hormones (estradiol, testosterone, free testosterone, and inhibin B), adrenal hormones [cortisol, dehydroepiandrosterone sulfate (DHEAS), androstenedione, and 17alpha-hydroxyprogesterone], and gonadotropic hormones (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]) were measured in 22 women and 26 men with TLE. The study also measured prolactin; human growth hormone and its major mediator, insulin-like growth factor-I; thyroid hormones (free thyroxine and free triiodothyronine); thyroid-stimulating hormone (TSH); and SHBG. The results were compared with those obtained from 60 healthy women and 106 healthy men.

RESULTS

In the female patients, TSH, DHEAS, follicular-phase LH, and luteal-phase estradiol were significantly lower than in the control groups, with prolactin and SHBG significantly higher. In the male patients, DHEAS, 17alpha-hydroxyprogesterone, free testosterone, inhibin B, and the testosterone/LH ratio were significantly lower than in the control group, with LH, FSH, and SHBG significantly higher. Increased FSH in 31% of the men indicates an impairment of spermatogenesis; lowered inhibin B in 12% indicates an impaired Sertoli's cell function; and the decreased testosterone/LH ratio in 50% indicates an impaired Leydig's cell function.

CONCLUSIONS

The case patients had endocrine disorders, mainly concerning the gonadotropic and gonadal functions in both sexes; the adrenal function, with lowered DHEAS levels in both sexes; and lowered 17alpha-hydroxyprogesterone levels in the men. SHBG levels were increased in patients taking anticonvulsant medications.

Prenatal morphine exposure alters ovarian steroid hormonal regulation of seizure susceptibility

The present study examined the ovarian hormonal regulation of seizure susceptibility in prenatally morphine- and saline-exposed adult female rats in the flurothyl seizure model in vivo, and in low-magnesium-induced epileptiform activity in brain slices, in vitro. All females were ovariohysterectomized (OVX); some received either estrogen (E) or progesterone (P) replacement, while others were injected with E + P sequentially. In prenatally saline-treated control females, there was an increase in the flurothyl-induced clonic seizure threshold (anticonvulsant effect) in the presence of both hormones (E + P) compared to OVX controls. In morphine-exposed females, there was an increase in the flurothyl-induced clonic seizure threshold after an E injection alone while there was a reduced tonic--clonic seizure threshold in the presence of both hormones (E + P) compared to the hormone treatment-matched group of saline-exposed females. In control females, in low magnesium medium in vitro, the development of two types of epileptiform activity (seizure-like events and status of short discharges) was not affected by the different hormonal conditions. However, prenatal morphine exposure suppressed the development of both types of epileptiform activity in the E-injected females compared to the E-injected, control females. The present data demonstrate that the anticonvulsant effects of P on seizure susceptibility requires the presence of E. Furthermore, prenatal morphine exposure alters ovarian steroid hormone-regulated seizure susceptibility.

Catamenial epilepsy, progesterone and its metabolites

This study was undertaken to determine plasma allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one, A-PREG) and pregnanolone (3alpha-hydroxy-5beta-pregnan-20-one, PREG) concentrations in the luteal phase (22nd to 24th day of the ovarian cycle) in 15 women with partial epilepsy and catamenial exacerbation of the seizures in the intercritical phase and in 15 healthy women matched for age in order to determine if an impaired metabolism of 3alpha-hydroxymetabolites of progesterone (P) occurs in this convulsive disorder. No significant differences between the two groups were found with respect to the mean plasmatic A-PREG and PREG levels. A significant correlation was found instead between P and A-PREG or PREG concentrations.

Sexual behavior and hemispheric laterality of the focus in patients with temporal lobe epilepsy

Various studies have described an unusually common incidence of sexual and reproductive dysfunction in patients affected by temporal lobe epilepsy (TLE). The purpose of the present study was to further investigate, by means of an ad hoc questionnaire, the relationship between sexual disorders and the hemispheric laterality of the epileptic focus in men and women with right (R) TLE and left (L) TLE. The results suggest a reduction of sexual interest in patients with R-TLE as compared with L-TLE in both men and women. This effect was fundamentally observed when sexual interest was implicitly explored. No significant difference was found between R-TLE and L-TLE groups concerning most aspects of sexual performance. Various hypotheses are discussed to interpret this effect of hemispheric lateralization on sexual interest.

Mood disorders and menopause

Studies of depressive symptoms in menopausal women indicate that menopause is not associated with increased rates of depression, although mild mood and anxiety symptoms may occur in the few years prior to menopause. Women with previous affective disorders that are cyclic or that are associated with reproductive events may be at increased risk for depression at menopause. Because women presenting to menopause clinics are more likely to have affective disorders, the efficacy of estrogen for enhancing mood is an important question. Although some researchers suggest that estrogens have proven mood-elevating and antidepressant properties, others caution that the psychologic benefits of HRT deserve more systematic study before conclusions can be made. It has been suggested that minor psychologic symptoms at menopause or psychologic symptoms accompanied by vasomotor symptoms warrant a trial of HRT before considering psychotropic medication. If the psychologic symptoms do not respond to HRT, are not accompanied by vasomotor symptoms, or are clinically severe, antidepressant medication should be considered first or in addition to HRT. The psychologic effects of progesterone and androgens are less extensively studied than those of estrogen, and further research is needed.

Circulating levels of anticonvulsant metabolites of progesterone in women with partial epilepsy in the intercritical phase

The 3alpha-hydroxy metabolites of progesterone (P), 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone, A-PREG) and 3alpha-hydroxy-5beta-pregnan-20-one (pregnanolone, PREG), have been found to be among the most potent ligands of gamma-aminobutyric (GABA)-A receptors; in experimental animals, they have been found to have anxiolytic, hypnotic and anticonvulsant effects. Similar to those of the benzodiazepines and barbiturates that interact with GABA-A receptors. The present study was undertaken to determine plasma A-PREG and PREG concentrations in the luteal phase in women with partial epilepsy, in order to determine if an impaired metabolism of P occurs in this convulsive disorder. We measured plasma P, A-PREG and PREG levels in 15 women with partial epilepsy in the intercritical phase, and in 15 age-matched healthy women, during the luteal phase of the ovarian cycle (22nd-24th day). The mean plasma +/- S.E. A-PREG levels (three blood samples) were 0.7 +/- 0.6 ng/ml in the epileptic women and 0.5 +/- 0.2 ng/ml in controls, with no significant difference between the two groups (p = NS); the PREG levels were also similar (1.4 +/- 1 ng/ml and 1 +/- 1.1 ng/ml, respectively: p = NS). A significant correlation was found between P levels and both A-PREG and PREG levels (r = 0.72, p < 0.001 and r = 0.79, p < 0.001, respectively). There were no significant differences between the two groups in terms of serum adrenocorticotropic hormone, cortisol, dihydroepiandrosterone-sulfate, follicle stimulating hormone, prolactin, luteinizing hormone or estradiol levels.

Effects of long-term antiepileptic therapy on the catabolism of testosterone

The serum levels of testosterone, sex hormone binding globulin, and free testosterone index were measured in 51 epileptic men (age 18-45) in order to assess the possible effects of antiepileptic drugs on sexual dysfunction. An analytical gas chromatography-mass spectrometry method was developed to assess the urinary excretion of testosterone, epitestosterone, androsterone, etiocholanolone, 11-OH androsterone and 11-OH etiocholanolone and to evaluate if the catabolism of testosterone had been increased. Twenty normal healthy males of similar age, 18-45 years, served as control group. Patients receiving polytherapy (n = 34) or monotherapy with carbamazepine (n = 8) or phenytoin (n = 9) showed higher levels of sex hormone binding globulin and testosterone, and lower levels of free testosterone than did the controls (P < 0.03). Urinary excretion of the metabolites androsterone and 11-OH androsterone was significantly reduced (P < 0.02) in the polytherapy group, while the monotherapy group showed only significant differences (P < 0.02) in the elimination of 11-OH androsterone. Our results suggest that an induction of the hepatic synthesis of sex hormone binding globulin may be the mechanism by which the antiepileptic drugs lower the levels of free testosterone in serum. However, the reduced excretion of androsterone and the normal levels of etiocholanolone show that the antiepileptic drugs do not produce an increase in the main catabolism pathway of testosterone.

Acute effects of 17 beta-estradiol on brain excitability studied in vitro and in vivo

The acute effects of 17 beta-estradiol on brain excitability were studied in vitro and in vivo utilizing rat hippocampal slices and a cat cerveau isolé preparation. The hippocampal slices were perfused with 17 beta-estradiol (10(-7)-10(-10) M) for 30 min. No effects were observed on synaptic activation and inhibition and on the response to iontophoretically applied GABA in intact and ovariectomized female rats (n = 43). In males (n = 32), however, a small (12%) but significant increase in population spike amplitude was observed after 30 min exposure to 10(-9) M 17 beta-estradiol. Higher and lower concentrations were ineffective. In vivo, no acute effects of 17 beta-estradiol on focal epileptic seizure thresholds, evoked potentials, or augmenting response were observed in the visual cortex of non-estrous female cats (n = 11; median dose 1 micrograms/kg, range 0.5 microgram/kg-10 mg/kg).

Effect of phenytoin on semen

Male patients receiving antiepileptic drugs (AEDs) have often complained of hyposexuality. Few studies have been done on semen analysis, which is relevant for assessment of potential and possible reproductive outcome in such cases. We evaluated the effect of epilepsy itself and/or phenytoin (PHT) on the male reproductive system. Fifty-five patients with epilepsy (42 with PHT and 13 untreated) and 28 healthy normal controls were studied by semen analysis. Serum samples from 21 of the 55 patients were also analyzed for testosterone, luteinizing hormone (LH), and follicle-stimulating hormone. Results showed lower volume of seminal fluid, spermatozoa concentration, and total sperm count in untreated and PHT-treated patients as compared with controls, although no difference was evident between the patient groups. Morphologically abnormal sperm were more increased in untreated patients than in PHT treated and control subjects. Hormonal analysis showed lower levels of testosterone in 9 patients. LH levels were increased in one third of the patients. Our results suggests an effect of seizures on the male reproductive system, and PHT may have a slight additive (if any) influence.

How common is catamenial epilepsy?

Forty women of childbearing age with refractory epilepsy were asked to record their seizures, the first and last days of their menstrual periods, and symptoms of premenstrual tension for 3 consecutive months. By defining catamenial epilepsy as the occurrence of at least 75% of seizures each month in the 10-day time frame, which included the 4 days preceding menstruation and the 6 days after its onset, only 5 women (12.5%) were identified who fulfilled the criterion. Nevertheless, after the study was completed, 31 (78%) of these patients claimed that most of their seizures occurred near the time of and were exacerbated by menstruation. The patients with catamenial epilepsy reported no more symptoms of premenstrual tension than did the rest of the group. Clustering outside the menstrual cycle was noted in 4 other patients. Catamenial epilepsy is an uncommon condition. Patient claims about frequency of seizures in relation to menstruation are not always accurate. A standard definition should be adopted because the diagnosis has implications for management.

Derangement of the hypothalamic GnRH pulse generator in women with epilepsy

An increased frequency of reproductive endocrine diseases has been described in women with epilepsy and a subclinical reproductive dysfunction has been suggested in normally menstruating epileptic women. We assessed the reproductive endocrine function in 11 normally menstruating, drug-free epileptic women, evaluating the basal hormonal profile and LH pulsatile secretion during continuous EEG monitoring. A significant LH hyperpulsatility was observed in epileptic women compared with controls; moreover, a significant increase of gonadotropin basal secretions was observed when inter-ictal paroxysmal activity increased. The derangement of the hypothalamic GnRH pulse generator may represent a subclinical condition associated with epilepsy, not necessarily affecting the regularity of menstrual function. However, it is possible that the alteration of LH pulsatile pattern might eventually cause reproductive endocrine diseases. Paroxysmal activity seems to be an important additional factor in the derangement of gonadotropin secretion.

Contraceptive methods for women with neurologic disorders

Sex steroids in oral contraceptives exert several effects on the central nervous system and are therefore of concern when used by neurologically compromised women. In general, oral contraceptives do not aggravate epileptic seizures and are not contraindicated in cases of tension headache. Oral contraceptives can be used in cases of migraine without focal neurologic symptoms as long as headache symptoms do not worsen. Levels of sex steroids can be diminished through enzyme induction by antiepileptic drugs, giving rise to the possibility of contraceptive failure and exposure of the fetus to the teratogenic properties of antiseizure medications. Women with common migraine (without focal neurologic symptoms) who are taking oral contraceptives should be monitored for possible exacerbation of their symptoms. Women who do experience worsening of headache symptomatology when taking the pill should consider alternate means of contraception.

Influence of long-term carbamazepine treatment on thyroid function

We have studied the effects of carbamazepine on thyroid function in sixteen recently diagnosed epileptic children and thirteen epileptic children receiving long-term carbamazepine therapy and compared these findings with the thyroid function of thirteen healthy control subjects. Thyrotropin (TSH), triiodothyronine (T3), thyroxine (T4), free triiodothyronine (FT3) and free thyroxine (FT4) serum levels were determined in both recently diagnosed but as yet untreated epileptic children and normal controls. These hormone levels were determined again after 2 months of treatment and 12 months of treatment in epileptic children. No statistically significant difference was found in the endocrine parameters of untreated epileptic children and the normal control group. After both 2 months and 12 months of carbamazepine therapy, serum levels of T4, FT4 and FT3 were found to be low, but the serum T3 concentration was unaffected. Baseline TSH levels were not changed during carbamazepine therapy either. Serum TSH levels increased rapidly after thyrotropin-releasing hormone stimulation in both the before and 12 months after carbamazepine treatment groups, but the response was higher in the 12 months treatment group. The findings of the present study suggest that accelerated hormone metabolism is responsible for hormonal changes found in patients treated with carbamazepine. Carbamazepine also had effects on the function of the hypothalamo-pituitary axis.

Cortical refractoriness to N-methyl-D,L-aspartic acid (NMA) stimulation in the lactating rat: recovery after pup removal and blockade of progesterone receptors

We have previously reported that lactating rats, unlike cycling rats, are refractory to N-methyl-D,L-aspartic acid (NMA), but not kainate, in terms of behavioral responses and activation of cFos expression in the neocortex and hippocampus. To study the factors involved in the suppression of cortical activation in lactating rats in response to NMA, we examined the effects of removing either the suckling stimulus and/or progesterone. The degree of cFos expression was used as a marker for cortical activation. Whereas control suckled animals exhibited little or no cFos activation in the piriform cortex in response to NMA, cycling rats showed a high degree of activation. Blockade of the effects of progesterone or removal of the pups for 24 h, resulted in a moderate level of cFos intensity in response to NMA. Total recovery was observed only in animals who had their pups removed for 24 h and the effects of progesterone were blocked. In general, similar results were obtained in the hippocampus except that the total recovery of hippocampal activation took longer than the cortex. Thus, the deficits in cortical activation depend on the presence of both the suckling stimulus and progesterone. However, progesterone alone cannot induce these cortical deficits since pregnant rats showed no deficits in cortical activation in response to NMA when compared to cycling rats. Therefore, the suckling stimulus is required for the inhibition of NMDA-receptor mediated activation of the cortex and hippocampus. The effects of progesterone appear to act synergistically with the effects of suckling.

Vive la différence!

Hormonal effects are increasingly recognized as important influences on neuronal function and, ultimately, on animal behavior. Such 'higher' behavioral effects are well studied, particularly in relation to sexually dimorphic behaviors. Yet, somewhat surprisingly, a significant proportion of more basic neuroscience research papers fail to specify the sex of the subjects used. In this brief article Karen Berkley argues that knowledge of, and controlling for, the sex of research animals is important. In addition, if females are used, their reproductive-cycle status could provide a deliberate strategy to investigate the effects of gonadal steroid hormones on biological functions.

Influences of gender, gonadectomy 5 and estrous cycle on GABA/BZ receptors and benzodiazepine responses in rats

Benzodiazepines (BZ) and steroid hormone derivatives can potentiate the inhibitory actions of GABA through interactions with the GABAA/BZ/chloride ionophore complex. The present study examines whether the in vivo hormone milieu of rats modulates GABA/BZ receptors and/or benzodiazepine responses. The influences of gender, estrous cycle, and the diminution of steroid levels on GABA/BZ receptors and BZ anticonvulsant responses were tested by comparing these parameters in groups of intact male, intact female, orchidectomized, and ovariectomized rats. The hormonal milieu appears to modulate the GABA recognition site and possibly GABA-related responses in rats. This is evidenced by the decrease in cortical GABAA receptor affinity seen in females compared with other hormone groups and the gender-related difference observed in susceptibility to seizures induced by the GABA antagonist bicuculline. In cycling females, high circulating levels of progesterone were correlated with heightened seizure thresholds, suggesting that progestins serve a protective role in the control of seizure activity. Although a gender-related difference in cortical BZ binding affinity was observed, BZ receptor parameters in several other brain areas and BZ anticonvulsant responses were unaffected by physiological fluctuations in gonadal hormones.

Calcification of the pineal gland: relationship to laterality of the epileptic foci in patients with complex partial seizures

The right and left temporal lobes differ from each other with respect to the rate of intrauterine growth, the timing of maturation, rate of aging, anatomical organization, neurochemistry, metabolic rate, electroencephalographic measures, and function. These functional differences between the temporal lobes underlies the different patterns of psychopathology and endocrine reproductive disturbances noted in patients with temporolimbic epilepsy. The right hemisphere has greater limbic and reticular connections than the left. Since the pineal gland receives direct innervation from the limbic system and the secretion of melatonin is influenced by an input from the reticular system, I propose that lesions in the right temporal lobe have a greater impact on pineal melatonin functions as opposed to those in the left dominant temporal lobe. Consequently, since calcification of the pineal gland is thought to reflect past secretory activity of the gland, I predicted a higher prevalence of pineal calcification (PC) in epileptic patients with right temporal lobe as opposed to those with left temporal lobe foci. To investigate this hypothesis, the prevalence of PC on CT scan was studied in a sample of 70 patients (43 men, 27 women, mean age: 29.2 years, range 9-58; SD = 10.1) with complex partial seizures, of whom 49 (70.0%) had a right temporal lobe focus. PC was present in 51 patients (72.8%) and was unrelated to any of the historical and demographic data surveyed. In the patients with a focus in the right temporal lobe, PC was present in 46 cases (93.8%) as compared to 5 of 21 patients (23.8%) with left temporal lobe foci.(ABSTRACT TRUNCATED AT 250 WORDS)

Hormones and epilepsy through the lifetime

Hormones influence brain function from gestation throughout life and may affect the seizure threshold by altering neuronal excitability. Estrogen enhances and progesterone diminishes neuronal excitability experimentally, whereas testosterone and corticosteroids have less consistent effects. Hormonal effects in the CNS also depend on the region of brain in which the hormone acts. Sites of action for most steroid hormones include the hypothalamus and limbic cortex, providing a mechanism for modulating behavior and endocrine function. Seizure patterns may change at certain life stages, perhaps as a result of alterations in hormones. At puberty, epilepsy and benign rolandic epilepsy often remit, while juvenile myoclonic and photosensitive epilepsy may arise. Other types of epilepsy do not respond predictably to events in the reproductive life or to advancing age. In some women, fluctuations in hormones over the menstrual cycle appear to increase seizure vulnerability, probably reflecting changes in relative amounts of estrogen and progesterone. Seizure patterns can be altered, for better or worse, during pregnancy. Whether this reflects the effects of hormones or changes in levels of antiepileptic drugs is not resolved. More information is needed about changes in established epilepsy at menopause and in the elderly. Better understanding of endocrine effects on seizures over a lifetime should lead to more effective epilepsy therapies.

Reproductive function in epilepsy

The hypothalamic-pituitary-gonadal axis is a complex system within which both positive and negative feedback occur among its elements and higher brain systems. The occurrence of seizures and changes in the secretion of pituitary hormones can affect the feedback loop. Both seizures and antiepileptic drugs can affect the hypothalamic-pituitary-gonadal axis of males and females and cause changes in hormones and sexuality. Reproductive dysfunction has a social impact because of reduced fertility. Once conception occurs, live birth rates are not diminished. Prospective studies of men and women with epilepsy are needed.

Effects of antiepileptic drugs on hormones

A hormone is an intrinsic substance carried via the blood to a target organ which is then functionally stimulated. Similar to extrinsically administered medications, the metabolism and function of the hormones may be altered by antiepileptic drugs (AEDs). The proposed mechanisms are (a) enhanced metabolism (natural steroids, synthetic steroids, e.g., decadron and birth control pills, thyroxine, and vitamin D3), (b) altered protein bonding (thyroxine, sex hormones), (c) impaired release into the systemic circulation (calcitonin, insulin, vitamin K clotting factors) and (d) altered end-organ effect. The AEDs most likely to interact with hormones are barbiturates, carbamazepine, and phenytoin.

Sexual dysfunction in epilepsy

Sexual dysfunction may arise more frequently in men and women with epilepsy than with other chronic illnesses, manifesting primarily as diminished sexual desire and potency. Studies using retrospective self-report of sexual attitude and behavior find an incidence of sexual dysfunction ranging from 14-66%. Sexual dysfunction may be more common in partial than in generalized epilepsies. Sexual dysfunction in epilepsy may result from a disturbance in social or psychological factors affecting sexual responsiveness. Alternatively, epileptiform discharges may disrupt the function of structures mediating sexual behavior, particularly the limbic cortex, or alter the release of hypothalamic or pituitary hormones. Antiepileptic drugs modulate hormone release from the hypothalamic-pituitary-gonadal axis and may have direct inhibitory effects on sexual behavior. Evidence both supports and refutes each of these etiologies in the sexual dysfunction seen with epilepsy. Specific evaluation and treatment protocols for patients with sexual dysfunction are available.

Reproductive endocrine considerations and hormonal therapy for women with epilepsy

Animal experimental and human clinical investigations show that estrogens lower and progestins raise many seizure thresholds. In women, seizure frequency varies with the serum estradiol to progesterone ratio. The fluctuation of this ratio during the menstrual cycle is a major factor in catamenial epilepsy. A decline in serum antiseizure medication levels premenstrually may be another factor. Estradiol to progesterone ratios are elevated in anovulatory or inadequate luteal phase cycles. This may explain a propensity for seizure onset at the time of menarche and the exacerbation of seizures during the months or years leading up to menopause. It may also be an important factor in the association between reproductive endocrine disorders and epilepsy. Specifically, polycystic ovarian syndrome and hypogonadotropic hypogonadism are significantly overrepresented among women with epilepsy. Epilepsy may promote the development of these disorders. These disorders, in turn, are characterized by inadequate luteal phase cycles that may promote the development or occurrence of seizures. In the setting of catamenial epilepsy or reproductive endocrine disorders, progestins, such as natural progesterone and parenteral medroxyprogesterone, or antiestrogenic agents, such as clomiphene, constitute rational and effective adjuncts to therapy.

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.

A prospective study of serum sex hormones during carbamazepine therapy

This paper reports the results of a 12-month prospective follow-up study on the effects of carbamazepine (CBZ) medication on serum sex and pituitary hormone concentrations in 21 male patients with recently diagnosed epilepsy. The results of the present study indicate that a change occurs in the androgen balance during CBZ medication in male patients with epilepsy: a rise in serum sex hormone binding globulin levels results in decreased free androgen index values, and dehydroepiandrosterone sulfate serum levels decrease. Serum testosterone and free testosterone levels remain unchanged, but estradiol levels decrease. Serum basal prolactin (PRL) levels remain unchanged, but the PRL responses to thyrotropin-releasing hormone and metoclopramide increase slightly during the first year of CBZ medication. Basal and stimulated serum gonadotropin levels remain unchanged. The clinical consequences of these hormonal changes during CBZ medication call for further studies.

Progesterone administration attenuates excitatory amino acid responses of cerebellar Purkinje cells

We have previously shown that the sex steroid progesterone plays a modulatory role in amino acid physiology by suppressing excitatory responses of cerebellar Purkinje cells to glutamate and augmenting inhibitory responses of these neurons to GABA. In the present study using the rat, progesterone effects on neuronal responses to the specific excitatory amino acid agonists quisqualate, kainate and N-methyl-D-aspartate were tested using iontophoretic, extracellular single unit recording techniques. In addition, the effect of systemic administration of progesterone on quisqualate-evoked excitation was evaluated in the presence of the GABAA blocker bicuculline. Progesterone consistently attenuated excitatory neuronal responses to local application of all three excitatory amino acids by 40-51%, but exerted variable effects on combined administration of quisqualate and N-methyl-D-aspartate which were dependent on temporal and dose-related factors. Progesterone-induced attenuation of the quisqualate response was found to be mediated primarily by a non-N-methyl-D-aspartate receptor. In addition, bicuculline application did not block progesterone effects on quisqualate excitation, suggesting that the observed steroidal modulation of excitatory amino acid function is not secondary to progesterone-induced potentiation of GABA inhibition.

Lack of enzyme induction with oxcarbazepine (600 mg daily) in healthy subjects

1. Oxcarbazepine (OXC), the 10-keto analogue of carbamazepine (CBZ), has similar anticonvulsant efficacy and possibly improved patient tolerability. Unlike CBZ, it is metabolised by reduction and may not induce hepatic monooxygenase enzymes. 2. Serum concentrations of OXC and its active metabolite 10-OH-carbazepine (10-OH-CZ) were followed after a single 300 mg dose and during and after 300 mg OXC twice daily for 29 doses in eight healthy male volunteers. 3. Antipyrine metabolism, urinary 6-beta-hydroxycortisol excretion, sex hormone binding globulin (SHBG) levels and circulating androgens were measured as indices of hepatic enzyme induction before, during and after treatment with OXC. 4. Elimination half-lives (mean +/- s.e. mean) of 10-OH-CZ were unaltered by 2 weeks' therapy with OXC (before 11.3 +/- 1.1 h; after 13.9 +/- 3 h). Trough plasma concentrations of 10-OH-CZ at steady-state (31 +/- 2.2 mumol l-1) were higher than predicted (16.5 +/- 4 mumol l-1). 5. Antipyrine metabolism, urinary 6-beta-hydroxycortisol excretion, SHBG levels and circulating androgens were unaltered by treatment with OXC. 6. OXC (600 mg daily) does not induce hepatic monooxygenase enzymes and so is likely to have more predictable dose-concentration relationships and to produce fewer physiological and pharmacological interactions than CBZ.

Selected neurologic complications of pregnancy

Many neurologic disorders, such as eclampsia, pseudotumor cerebri, stroke, obstetric nerve palsies, subarachnoid hemorrhage, pituitary tumors, and choriocarcinoma, can develop in the pregnant patient. Maternal mortality from eclampsia, which ranges from 0 to 14%, can be due to intracerebral hemorrhage, pulmonary edema, disseminated intravascular coagulation, abruptio placentae, or failure of the liver or kidneys. Associated fetal mortality ranges from 10 to 28% and is directly related to decreased placental perfusion. Pseudotumor cerebri can be associated with serious visual complications; thus, the therapeutic goal is to prevent loss of vision. The risk of stroke in the pregnant patient is 13 times the risk in the nonpregnant patient of the same age. The major causes of stroke in pregnant patients are arterial occlusion and cerebral venous thrombosis. Lumbar disk prolapse is common in pregnant patients, and lumbosacral plexus injuries can occur during labor or delivery. In addition, peripheral nerve compression or entrapment syndromes are thought to be caused by the retention of fluid during pregnancy. The incidence of subarachnoid hemorrhage during pregnancy is 1 in every 10,000 patients, a rate 5 times higher than in nonpregnant women. Because of a proliferation of prolactin-secreting cells, the pituitary gland can enlarge dramatically during pregnancy, a change that can disclose a previously unknown tumor or cause a known pituitary tumor to become symptomatic. The incidence of choriocarcinoma is 1 in 50,000 full-term pregnancies but 1 in 30 molar pregnancies. This malignant tumor has a high rate of cerebral metastatic lesions. In addition to these disorders that develop during pregnancy, the pregnant state can affect numerous preexisting neurologic conditions, including epilepsy, headaches, multiple sclerosis, myasthenia gravis, spinal cord injury, and brain tumors. We discuss advice for patients with such conditions who wish to become pregnant, recommendations for medical and surgical management, and surgical considerations for neurologic complications during pregnancy.

Serum steroid hormones and pituitary function in female epileptic patients during carbamazepine therapy

Ten regularly menstruating women with epilepsy were studied in a 12-month prospective follow-up study to evaluate the short-term effects of carbamazepine (CBZ) on serum sex hormone balance and pituitary function. Thirteen female epilepsy patients receiving long-term CBZ monotherapy (mean medication duration 5.3 years) were also studied. Controls were 17 regularly menstruating healthy volunteers. Untreated patients had higher free testosterone (FT) and luteinizing hormone (LH) serum concentrations than control subjects, whereas the other parameters did not differ between these two groups. However, serum sex hormone binding globulin (SHBG) levels increased and dehydroepiandrosterone sulfate (DHEAS) levels decreased during CBZ treatment. Although calculated free androgen index (FAI) decreased during CBZ therapy, the directly measured FT levels remained unaltered. These changes were found after 2 months and continued after 12 months of CBZ treatment. Moreover, patients with long-term CBZ also had high SHBG levels, low serum DHEAS levels, and low FAI values. Basal LH serum levels decreased during the first year of CBZ treatment and luteinizing hormone-releasing hormone (LH-RH)-stimulated LH concentrations were lower after 2 months of CBZ treatment. Although the serum basal follicle-stimulating hormone (FSH) and prolactin (PRL) levels were unaffected during the first year of CBZ therapy, the LH-RH-stimulated FSH concentrations and metoclopramide (MC)-stimulated PRL concentrations were lower after 12 months of CBZ treatment than before CBZ. Both basal and stimulated gonadotropin and PRL serum levels of long-term CBZ patients were unaffected. No changes were found in estradiol (E2), testosterone (T), or cortisol (C) serum concentrations during short or long-term CBZ treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Progesterone enhances inhibitory responses of cerebellar Purkinje cells mediated by the GABAA receptor subtype

Previous studies from this laboratory have indicated that the sex steroid progesterone (P) is able to augment inhibitory responses of cerebellar Purkinje cells to the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) in the urethane anesthetized adult female rat. Because both GABAA and GABAB receptors are localized in this CNS area, agonist/antagonists for these receptors were utilized in the present evaluation in order to delineate the specific receptor subtype involved in P-GABA interactions. Systemically administered P was found to augment GABA-mediated inhibition by an average of 80%. Concomitant application of the GABAA blocker, bicuculline, greatly reduced this modulatory effect of the steroid. In contrast, P administration had no effect on baclofen-induced inhibition. These data suggest that P effects on GABA physiology are mediated predominantly at the GABAA receptor.

Pregnancy and epilepsy

In a prospective study, 30 pregnant epileptic patients were followed through their pregnancy to determine the effect of seizures on pregnancy and its outcome and the effect of pregnancy on seizures. An attempt was made to correlate the serum hormone and anticonvulsant drug levels with seizure frequency, complications of pregnancy, occurrence of status epilepticus and teratogenicity. In 14 patients seizure frequency increased, in 15 it remained unchanged and in 1 patient it decreased. There were 2 spontaneous abortions, 2 patients had status epilepticus and 1 offspring of a patient had a ventricular septal defect. This patient was receiving carbamazepine and diphenylhydantoin. Patients with increased seizures frequency had significantly higher oestrogen levels, lower level of progesterone and lower level of anticonvulsant drugs as compared with those with no change in seizures. Patients who had abortions and those who developed status epilepticus had high serum oestrogen levels.

Effects of puberty on seizure frequency

Seizure frequency was documented before, during and in some cases after puberty for 12 patients with continuing generalised tonic-clonic seizures (GTCS) and for 14 with complex partial seizures (CPS) who were receiving anti-epileptic drugs. For the patients with GTCS there was a significant increase in seizure frequency during the pubertal growth-spurt, with a subsequent decrease after growth ceased. There appeared to be no relationship between puberty and the frequency of CPS. Both groups were more likely to have suboptimal plasma drug-levels during puberty, suggesting that medication was not the cause of the increased GTCS frequency. Further examination of hormonal levels in relation to frequency of GTCS during puberty could provide a better understanding of the influence of hormones.

Unbalanced progesterone and estradiol secretion in catamenial epilepsy

Ten women with a documented history of catamenial epilepsy underwent a hormonal study to evaluate hypophyseal-gonadal function. Baseline values of luteinizing hormone, follicle-stimulating hormone and prolactin were similar in catamenial seizure patients and in control groups throughout a complete menstrual cycle. Stimulated secretions of the same hypophyseal hormones in catamenial seizure patients overlapped those of the controls. The luteal secretion ratio of progesterone to estradiol was significantly reduced in catamenial seizure patients versus normal controls. In a subgroup of catamenial seizure patients on antiepileptic therapy, luteal progesterone levels were remarkably decreased compared to normal and epileptic controls. These results indicate that catamenial epilepsy is characterized by an imbalance in ovarian steroid secretion and emphasize the need for an endocrinological assessment in these patients.

Steroid hormone effects on picrotoxin-induced seizures in female and male rats

Picrotoxin (1 mg/kg, i.p.), evoked a single generalized seizure in 75% of ovariectomized rats. Pretreatment of matched pairs with silastic implants containing 100% estradiol had an anticonvulsant effect; it protected all rats against such seizures. Implants containing 10% estradiol in cholesterol were less effective in protecting against picrotoxin-induced seizures. With 2 mg/kg picrotoxin, 85% of the seizure-affected ovariectomized controls had multiple seizures. The incidence of seizures and the ratio of single to multiple seizures induced by the higher dose of picrotoxin were unaffected by estradiol silastic implants, intraperitoneal injections of progesterone (0.5 mg, 4-5 h before convulsant) or the combination of both hormones. At the 2 mg/kg dose, 8/8 intact males had no seizures while all paired ovariectomized females had seizures. By contrast, the incidence of seizures in pairs of gonadectomized males and females did not differ. Testosterone treatment improved the ratio of single to multiple seizures in males but not in females. Males had statistically fewer multiple seizures than did females after testosterone treatment. The distribution of latencies to a single seizure is statistically different from the distribution of latencies to the first of multiple seizures irrespective of dose, sex and hormone treatment. This suggests that the population of rats responding with a single seizure at the higher dose of picrotoxin have a higher threshold for acquiring multiple seizures and that testosterone predisposes males but not females to this population.

Effects of carbamazepine therapy on serum sex hormone levels in male patients with epilepsy

The effects of carbamazepine (CBZ) therapy and epilepsy on sex hormone plasma levels in male patients with epilepsy were evaluated by measuring the levels of testosterone (T), free testosterone (FT), sex hormone binding globulin (SHBG), estradiol (E2), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin (PRL), and dehydroepiandrosterone sulfate (DHEAS) and by calculating the free androgen index (FAI) in 23 male patients with epilepsy receiving CBZ medication, in 18 untreated male patients with epilepsy, and in 19 healthy age-matched control subjects. No significant differences in the mean T or FT levels were found between the three groups, but the CBZ-treated patients had significantly higher SHBG levels and their FAI values and DHEAS concentrations were lower. The LH, FSH, PRL, or E2 levels in CBZ-treated and untreated male patients with epilepsy did not differ from the controls. CBZ monotherapy does not significantly change the serum balance of sex hormones; however, CBZ clearly affects the serum levels of SHBG and DHEAS.

Reproductive endocrine disorders in women with primary generalized epilepsy

It is known that women suffering from temporal lobe epilepsy may frequently present reproductive endocrine disorders (REDs). We hypothesized that a high occurrence of REDs could be found also in primary generalized epilepsy (PGE), and therefore investigated the hormonal and ovarian echographic profiles in 20 PGE female patients of reproductive age. Fourteen reported normal menstrual cycles, while 6 complained of longstanding menstrual irregularities. All but three patients were receiving antiepileptic drug (AED) therapy. In all subjects, the basal levels of gonadotropins, prolactin, and gonadal steroids were assayed. The response of luteinizing hormone (LH) to gonadotropin-releasing hormone was also investigated and ovarian ultrasonographic findings were evaluated. In five of six patients with menstrual problems (25% of the group), a well-defined RED was diagnosed (polycystic ovarian disease in three cases and hypothalamic ovarian failure in two). The 14 patients with normal menstrual cycles showed an elevation of mean basal follicle-stimulating hormone and prolactin, and a blunting of mean LH response. Our results suggest that a high occurrence of REDs may be found also in PGE. We hypothesize that a neurotransmitter dysfunction might be the common pathogenetic mechanism resulting in both REDs and PGE. The hormonal alterations observed in the patients with normal menstrual cycles seem to support our hypothesis. Previous data seem to rule out a possible AED effect accounting for the hormonal findings observed in our series. However, further studies are needed to confirm our preliminary results.

Circulating hormones and pituitary responsiveness in young epileptic men receiving long-term antiepileptic medication

Impairment of libido and sexual potency are commonly reported by male epileptic patients. This may be partly a consequence of medication. Circulating hormones were measured in 53 postpubertal male epileptic patients less than 45 years of age and in an age-matched control group (n = 40), consisting of 14 untreated epileptic patients and 26 unmedicated healthy subjects. A subgroup also underwent a combined gonadotrophin- and thyrotrophin-releasing hormone (LH-RH/TRH) pituitary stimulation test. Untreated patients did not differ from healthy subjects for any parameter, and their data were combined for comparison with the treated epileptic patients. Total testosterone (T), androstenedione, and basal follicle-stimulating hormone concentrations were similar in all patient groups. Patients receiving more than one drug had higher sex hormone binding globulin (SHBG) (p less than 0.01) and lower free T and dehydroepiandrosterone sulphate (DHAS) levels (both p less than 0.001) than controls. Carbamazepine (CBZ) monotherapy also reduced free T (p less than 0.05) and DHAS (p less than 0.001) and increased basal prolactin (p less than 0.01). In these two groups of patients, basal luteinising hormone (LH) was elevated (p less than 0.01), presumably as a pituitary response to increased T catabolism. There was a negative correlation between free T and circulating CBZ (r = -0.54, p less than 0.05) in the monotherapy patients. Phenytoin (PHT) was associated with a rise in SHBG (p less than 0.01) and a fall in DHAS (p less than 0.001). Basal LH was also elevated, but this just failed to reach statistical significance (p less than 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Sex steroid effects on extrahypothalamic CNS. I. Estrogen augments neuronal responsiveness to iontophoretically applied glutamate in the cerebellum

The purpose of this study was to test whether 17 beta-estradiol (E2) could alter neuronal activity or responsiveness to iontophoretically applied amino acid neurotransmitters in an area not reported to contain classical E2 receptors. Such a region is the cerebellum, which was selected as a model system for these studies because it has been well characterized electrophysiologically. Extracellular activity of cerebellar Purkinje neurons was recorded from urethane-anesthetized, adult, ovariectomized rats using multibarrel glass micropipets. Spontaneous firing rate and responses of single units to microiontophoretic pulses (10 s pulses every 40 s) of GABA (10-50 nA) or glutamate (GLUT, 3-40 nA) were examined before, during and after iontophoretic (0.25 mM 17 beta-estradiol hemisuccinate) or jugular i.v. (100, 300 or 1000 ng/kg 17 beta-estradiol) administration of E2. Both modes of E2 administration resulted in a significant increase in Purkinje cell excitatory responses to GLUT, independent of the direction of change in spontaneous firing rate. This effect was seen as early as one minute after iontophoretic application of E2 and 10-40 min following i.v. E2. In all cases, recovery to the control level of response was not observed by 2 h following E2 administration. 17 alpha-E2 (300 ng/kg) resulted in a less pronounced, transient increase in GLUT response, while a lower dose (100 ng/kg) did not have any effect. Prior administration of the anti-estrogen tamoxifen did not prevent any of the observed E2 effects. In addition, estrogen-priming did not alter E2-induced potentiation of GLUT responses. In contrast to the effect of E2 on GLUT responsiveness, GABA-mediated inhibition of Purkinje cells was either increased, antagonized or unchanged following E2 application. In summary, this study suggests the hypothesis that circulating levels of E2 may alter neuronal sensitivity to specific neurotransmitter substances within the cerebellar circuitry.

Sex steroid effects on extrahypothalamic CNS. II. Progesterone, alone and in combination with estrogen, modulates cerebellar responses to amino acid neurotransmitters

In a preliminary report we have shown that both intravenous and local application of progesterone (P) are capable of increasing cerebellar Purkinje cell responsiveness to microiontophoretically applied gamma-aminobutyric acid (GABA) and decreasing responsiveness to glutamate (GLUT) in the urethane-anesthetized, ovariectomized adult rat. In the present study we have examined the time course of effects of several doses of P and different combinations of both E2 and P on responses of individual Purkinje cells to GABA and GLUT. Extracellular activity of single Purkinje neurons was recorded using multibarrel glass micropipets. Spontaneous firing rate and responses of neurons to microiontophoretic pulses (10 s pulses every 40 s) of GABA (10-50 nA) and GLUT (3-40 nA) were examined before and after jugular i.v. administration of P or E2/P combinations to ovariectomized rats. In some cases animals received s.c. injections of E2 (2 micrograms) at 24 and 48 h before the day of recording. This injection schedule results in maximal reproductive effects of P. Within 5-15 min after P administration (5,50 or 500 micrograms) to ovariectomized rats, Purkinje cell responses to GLUT were decreased by 87%, and inhibitory responses to GABA were increased by 50%, with no associated change in spontaneous firing rate. In addition, the magnitude of the change in amino acid response was directly proportional to the dose of P. In most cases, complete recovery was observed 20-45 min after P administration. E2 pretreatment did not alter these P-induced effects. Combinations of E2 (300 ng/kg) and P (50 or 500 micrograms) injected simultaneously resulted in effects on GLUT responsiveness which were similar to those seen with P alone, while effects similar to E2 alone were observed with administration of E2 plus P at 5 micrograms. The administration of a protein synthesis inhibitor, anisomycin (30 mg/kg, i.v.), 20 min before the recording session did not prevent any of the above steroid effects. These results indicate that sex steroids can act to alter neuronal responsiveness to putative neurotransmitters in a CNS region not known to contain steroid receptors and that the particular combination of steroids will determine the neuronal response. These findings further suggest that the observed steroid-induced alterations in Purkinje cell responsiveness do not appear to require genomic mechanisms.