Differential effects of picrotoxin- and pentylenetetrazol-induced convulsions on the secretion of luteinizing hormone and follicle-stimulating hormone in rats

Sex Differences in the Epilepsies and Associated Comorbidities: Implications for Use and Development of Pharmacotherapies

The epilepsies are common neurologic disorders characterized by spontaneous recurrent seizures. Boys, girls, men, and women of all ages are affected by epilepsy and, in many cases, by associated comorbidities as well. The primary courses of treatment are pharmacological, dietary, and/or surgical, depending on several factors, including the areas of the brain affected and the severity of the epilepsy. There is a growing appreciation that sex differences in underlying brain function and in the neurobiology of epilepsy are important factors that should be accounted for in the design and development of new therapies. In this review, we discuss the current knowledge on sex differences in epilepsy and associated comorbidities, with emphasis on those aspects most informative for the development of new pharmacotherapies. Particular focus is placed on sex differences in the prevalence and presentation of various focal and generalized epilepsies; psychiatric, cognitive, and physiologic comorbidities; catamenial epilepsy in women; sex differences in brain development; the neural actions of sex and stress hormones and their metabolites; and cellular mechanisms, including brain-derived neurotrophic factor signaling and neuronal-glial interactions. Further attention placed on potential sex differences in epilepsies, comorbidities, and drug effects will enhance therapeutic options and efficacy for all patients with epilepsy. SIGNIFICANCE STATEMENT: Epilepsy is a common neurological disorder that often presents together with various comorbidities. The features of epilepsy and seizure activity as well as comorbid afflictions can vary between men and women. In this review, we discuss sex differences in types of epilepsies, associated comorbidities, pathophysiological mechanisms, and antiepileptic drug efficacy in both clinical patient populations and preclinical animal models.

Effects of female sex hormones on caffeine-induced epileptiform activity in rats

Research on female sex hormones has demonstrated that estrogen aggravates epileptogenesis. Theoretically, this means that the frequency of epileptic attacks should be decreased in epileptic women during menopause. However, although epilepsy attacks are reported to decrease in some women during menopause, they may not change in others. Increases in attack frequency have even been reported during menopause in some epileptic women. This study has investigated the effects of estrogen, progesterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) on caffeine-induced epileptiform activity in rats. Estrogen was found to increase epileptiform activity in a dose-dependent manner via its own receptors. In contrast, progesterone had no effect on epileptiform activity. FSH and LH suppressed epileptiform activity at low doses; however, at high doses they enhanced it. In conclusion, we suggest that the occurrence or aggravation of epilepsy, despite estrogen deficiency in the menopausal or post-menopausal period, is related to excessive accumulation of FSH and LH.

Regulation of brain function by exercise

The effect of excercise on brain function was investigated through animal experiments. Exercise leads to increased serum calcium levels, and the calcium is transported to the brain. This in turn enhances brain dopamine synthesis through a calmodulin-dependent system, and increased dopamine levels regulate various brain functions. There are abnormally low levels of dopamine in the neostriatum and nucleus accumbens of epileptic mice (El mice strain) and spontaneously hypertensive rats (SHR). The low dopamine levels in those animals were improved following intracerebroventricular administration of calcium chloride. Dopamine levels and blood pressure in SHR were also normalized by exercise. In epileptic El mice, convulsions normalized dopamine levels and physiologic function. These findings suggest that exercise or convulsions affect brain function through calcium/calmodulin-dependent dopamine synthesis. This leads to the possibility that some symptoms of Parkinson's disease or senile dementia might be improved by exercise.

The effect of convulsions on the rectification of central nervous system disorders in epileptic mice

Abnormal behavior in epileptic mice (El mice) may be rectified after convulsive seizures. This mechanism was investigated behaviorally through measurements of ethanol-induced sleeping time and locomotor activity, as well as immunohistochemically using a microphotometry system. Decreased ethanol-induced sleeping time and increased ethanol-dependent locomotor activity in El mice as compared to ddY mice (the mother strain of El mice) were rectified by convulsions as well as the intraventricular (IVT) administration of CaCl2, dopamine, or serotonin. Also, the lower dopamine levels in the neostriatum and nucleus accumbens septi in El mice as compared to ddY mice were improved by convulsions as well as the IVT administration of CaCl2. We have previously observed that a lower level of serum calcium in El mice causes a decrease in central biogenic amine synthesis through a calmodulin-dependent system. This may increase the susceptibility to epileptic convulsions and induce abnormal behavior. Combining the present results with our previous observations, we suggest that the convulsions in El mice will be induced when the balance of physiological functions is lost, as may be seen when the biogenic amine syntheses are decreased. The serum calcium level in El mice is increased by convulsions, and an elevated serum calcium level enhances brain biogenic amine synthesis through a calmodulin-dependent system. Subsequently, biogenic amines rectify physiological disorders in El mice.

Analysis of the Inhibitory Effect of Oestradiol on Functional GABA/5-HT Relationship in the Rat Suprachiasmatic Area

Abstract The purpose of this study was to test the capacity of oestradiol to modulate the stimulating effect of a-aminobutyric acid (GABA) on serotonin (5-HT) metabolism, previously described in the Suprachiasmatic area of the male rat. After an in vivo stimulation of GABA transmission by systemic administration of a GABA-transaminase inhibitor (amino-oxyacetic acid) or a GABA(B) agonist (RS-baclofen), the 5-HT metabolism was studied in the Suprachiasmatic area of ovariectomized, and ovariectomized oestradiol-treated rats. Amino-oxyacetic acid or RS-baclofen treatment increased the endogenous content of 5-HT in the Suprachiasmatic area of males and ovariectomized rats. These two treatments were without effect in ovariectomized oestradiol-treated rats. GABA transmission stimulation induced by amino-oxyacetic acid treatment failed to affect the release and synthesis of 5-HT in ovariectomized oestradiol-treated rats while it increased these two parameters of 5-HT metabolism in the Suprachiasmatic area of male and ovariectomized rats. To investigate the main target of oestradiol effect, comparative studies of the serotoninergic and GABAergic metabolism in the Suprachiasmatic area were performed in the three experimental groups. Under our experimental conditions the endogenous 5-HT metabolism was similar between ovariectomized and ovariectomized oestradiol-treated rats. Nevertheless, 5-HT metabolism was higher in the two female groups than in the male group. Neither GABA metabolism nor GABAergic response to GABA-related drug treatment differed between ovariectomized, and ovariectomized oestradiol-treated rats. However, the turnover of GABA was higher when compared to the two female groups. It is concluded that the lack of 5-HT responsiveness to GABA transmission stimulation in ovariectomized oestradiol-treated rats was not related to an effect of oestradiol on 5-HT metabolism or to an effect of the steroid on GABA turnover. Furthermore, our results suggest a sex difference in the activity of serotoninergic and GABAergic systems in the Suprachiasmatic area.

Sexual dimorphism in the response of the GABAergic system to estrogen administration

Administration of estradiol benzoate to gonadectomized female rats results in up-regulation of CNS gamma-aminobutyric acid (GABA) receptors. The increase of [3H]muscimol binding activity is observed in six of the seven brain areas examined. The same treatment, performed in castrated male or androgenized female rats, induced an increase of [3H]muscimol binding only in the striatum. Evidence is provided suggesting that the dimorphic sensitivity of GABA receptor is not correlated with the difference in spontaneous motor activity reported between male and female rats.