Judith K. McQueen

SEX STEROID CONTROL OF MOOD, MENTAL STATE AND MEMORY

1. Sex steroid hormones exert profound effects on mood and mental state. Thus, in women, oestrogen is thought to protect against depression and delay the onset of schizophrenia and Alzheimers disease.

Estradiol-17β increase serotonin transporter (SERT) mRNA levels and the density of SERT-binding sites in female rat brain

The aim of the present study was to determine the effect of estradiol-17 beta (E2), in its positive feedback mode for gonadotropin release, on the serotonin transporter (SERT) in female rat brain. Levels of SERT mRNA were determined by in situ hybridization and SERT-binding sites were measured by quantitative [3H]paroxetine receptor autoradiography. The injection of estradiol benzoate (EB) in acutely ovariectomized rats increased significantly (approximately 50%) the numbers of cells that expressed SERT mRNA in the dorsal raphe nucleus and the density of SERT-binding sites in lateral septum (90%), basolateral amygdala (20%), ventral nucleus of thalamus (250%) and ventromedial hypothalamic nucleus (250%). SERT-binding sites in EB-treated rats were significantly lower in periaqueductal central grey (15%). These findings indicate that effects on SERT gene expression may be involved in the E2-induction of the gonadotropin surge. Together with our previous findings, they also suggest that the sex differences in depression and the apparent psychotropic effect of E2 may be due to the action of E2 on the serotonin transporter as well as 5-HT2A receptors.

Androgen actions on central serotonin neurotransmission: relevance for mood, mental state and memory

Sex steroids exert potent effects on mood and mental state in the human. Our previous experimental findings in female rats suggest that these effects may be mediated, in part, by the action of estrogen on the 5-hydroxytryptamine2A receptor (5-HT(2A)R) and serotonin transporter (SERT) in brain. Here we review our recent findings on the effect of acute (approximately 32 h) testosterone manipulation on central 5-HT(2A)R and SERT in male rats. Castration decreased while testosterone or estrogen, but not 5alpha-dihydrotestosterone (5alpha-DHT), increased significantly the content of 5-HT(2A)R mRNA and SERT mRNA in the dorsal raphe nucleus (DR) and the density of 5-HT(2A)R and SERT binding sites in higher centers of the brain. The lack of effect of 5alpha-DHT, a potent androgen which cannot be converted to estrogen, suggests that the action of testosterone depends upon its conversion to estrogen by aromatase. This may also explain why estrogen, but not testosterone or 5alpha-DHT, increased the density of 5-HT(2A)R binding sites in the caudate-putamen, a brain region where aromatase is scarce. The estrogen induction of SERT mRNA is most prominent in the rostral DR and this together with the correlation between sensitivity of DR serotonin neurons to estrogen and neurotoxic amphetamine derivatives provides a potential topochemical handle with which to investigate testosterone/estrogen regulation of SERT gene expression. These findings are discussed in relation to the possible role of interactions between sex steroids and serotonin mechanisms in mood disorders, schizophrenia and Alzheimers disease.

Serotonin transporter (SERT) mRNA and binding site densities in male rat brain affected by sex steroids

Estrogen increases serotonin transporter (SERT) mRNA and binding sites in female rat brain. In order to determine whether changes in SERT are gender- and steroid-specific we have now carried out studies on adult male Wistar rats which were either intact or castrated (under halothane anesthesia) and injected with arachis oil, estradiol benzoate (EB), testosterone propionate (TP) or the non-aromatizable androgen, 5alpha-dihydrotestosterone (5alpha-DHT). The number of SERT mRNA-expressing cells in the dorsal raphe (DR) nucleus was decreased by castration and increased by treatment (for approximately 32 h) with EB or TP, but not 5alpha-DHT. Sex steroids had no effect on the number of SERT mRNA-expressing cells in the median raphe nucleus. The density of SERT sites, assessed by autoradiography of [3H]paroxetine binding, was significantly reduced in arcuate nucleus and median raphe after castration, and increased in arcuate, basolateral amygdala and ventromedial hypothalamic nucleus by treatment with EB or TP, but not 5alpha-DHT. Estradiol, but not testosterone or 5alpha-DHT reduced the density of SERT sites in midbrain central grey. These data show that testosterone as well as estrogen affects SERT expression in male brain, and that the action of testosterone probably depends upon its enzymatic conversion, by aromatase, to estradiol. Our findings may have implications for sex steroid control of mood and behavior, and the action of neurotoxic derivatives of amphetamine, such as 3, 4-methylenedioxymethamphetamine, in the human.

Gonadal steroids influence neurophysin II distribution in the forebrain of normal and mutant mice

The distribution of arginine vasopressin-associated neurophysin (neurophysin II) immunoreactivity was investigated in normal and mutant house mice during development and after various gonadal steroid manipulations. During postnatal development of normal mice dense networks of neurophysin II immunoreactivity in the lateral septal nucleus and lateral habenular nucleus appeared earlier in male than in female mice, with an adult pattern of immunoreactivity being attained by 8 weeks and 12 weeks of age, respectively. The neurophysin II immunoreactivity in the male was denser than that in female mice. After gonadectomy of adult normal mice there was a gradual loss of neurophysin II immunoreactivity in the lateral septum and lateral habenula over a period of 15 weeks. In hypogonadal mice, a mutant in which gonadal development is arrested postnatally due to a deficiency in hypothalamic gonadotrophin releasing hormone, no immunoreactive neurophysin II could be detected in the lateral septum or lateral habenula. A pattern of neurophysin II immunoreactivity similar to that in normal control mice was observed in hypogonadal mice which had been implanted for 4 weeks with silicone elastomer capsules containing testosterone or oestradiol-17 beta, but not 5 alpha-dihydrotestosterone or progesterone. Stimulation of gonadal development and endogenous steroid production in hypogonadal mice by third ventricular grafts of preoptic area tissue from normal neonatal animals also produced a normal pattern of neurophysin II immunoreactivity in the lateral septum and lateral habenula. In the androgen-insensitive testicular feminized mouse immunoreactive neurophysin II was undetectable in the lateral septum and lateral habenula. Treatment of testicular feminized mice with oestradiol-17 beta, but not progesterone, produced a normal pattern of neurophysin II immunoreactivity. The main immunohistological findings were confirmed by radioimmunoassay of tissue extracts which showed that the concentration of arginine vasopressin in lateral septum was far greater in normal males than females and was undetectable in hypogonadal mice; no oxytocin could be detected in the septum of normal or hypogonadal mice. These results show that the expression of neurophysin II immunoreactivity in the lateral septum and lateral habenula of the mouse brain is dependent on the presence of aromatizeable androgens or oestrogens.

Glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes are increased in the hypothalamus of androgen-insensitive testicular feminized (Tfm) mice

In the hypothalamus of androgen-insensitive testicular feminized (Tfm) mice the normal pattern of immunohistochemical staining for glial fibrillary acidic protein (GFAP) is markedly different from normal. Along the borders of the third ventricle and in the dorsomedial and arcuate nuclei, the numbers of stained astrocytes are increased. The usual ordered array of tanycytic processes is obscured by a tangle of GFAP-stained stellate glial cells. GFAP immunostaining in other regions of the Tfm forebrain is similar to that in normal mice. These results suggest that the distribution of reactive glia in the hypothalamus may have been changed as a consequence of the genetic defect in Tfm mice.

Water deprivation results in increased 2-deoxyglucose uptake by paraventricular neurones as well as pars nervosa in wistar and brattleboro rats

The [14C]2-deoxyglucose (2-DG) technique has been used in conjunction with quantitative autoradiography to determine the metabolic activity of the neurones of the hypothalamo-neurohypophysial system. Water deprivation (4 days) in Wistar rats led to a more than two-fold increase in the metabolic activity of the pars nervosa (PN), and a significant increase in the metabolic activity of paraventricular (PVN) but not supraoptic (SON) neurones. The PN in homozygous Brattleboro rats was significantly more active than that in hydrated Wistar and Piebald Virol Glaxo (PVG) rats; as in Wistar rats, activity of the PN and PVN was significantly increased by 12-15 h water deprivation. The administration of desamino-D-arginine vasopressin (dDAVP) to Brattleboro rats significantly reduced the activity of the PN to that seen in hydrated Wistar and PVG rats. This reduction in activity was accompanied by a significant reduction in plasma osmolality. These results show that (1) in contrast to studies in which the osmotic stimulus was a salt load, water deprivation leads to a significant increase in 2-DG uptake by the perikarya as well as the terminals of neurohypophysial neurones; (2) increased activity of the neurohypophysial neurones occurs even when there is a genetic deficiency of vasopressin and the activity can be increased further by an osmotic stimulus, and (3) the activity of the neurohypophysial neurones can be significantly reduced by the administration of dDAVP.

The Effects of Some Anticonvulsant Drugs on Cobalt-induced Epilepsy

The effects of some anticonvulsant drugs on the development and persistence of cobalt‐induced epileptic foci have been studied in rats. Phenobarbitone produced bilateral polyspikes in control animals and apparently increased the frequency and duration of spike discharges in cobalt rats. Diphenylhydantoin had no discernible effect on the electrocorticogram in either control or cobalt animals. Ethosuximide had no effect in control animals but suppressed spike discharges in cobalt rats for 30–40 min after injection. Chronic administration of ethosuximide slightly delayed but did not prevent the development of the epileptic foci.

RNA and protein metabolism in cobalt-induced epileptogenic lesions in rat brain.

The RNA and protein metabolism of epileptogenic tissue has been studied in rats with cobalt lesions in the motor cortex. At no stage in the development of the primary and secondary epileptic foci were changes in the rate of incorporation of (14C) orotic acid into RNA or (3H) L‐leucine into protein noted. The endogenous levels of RNA and DNA in the epileptogenic lesions were not significantly different from those in control tissue.

Gonadal steroids regulate number of astrocytes immunostained for glial fibrillary acidic protein in mouse hippocampus

The aim of this study was to determine the effect of sex and sex steroids on the distribution of glial fibrillary acidic protein (GFAP) -containing astrocytes in the hippocampal CA1 region of normal, testicular feminized (Tfm/Y) and hypogonadal (hpg) mice. The number of GFAP-immunoreactive (GFAP-IR) cells, assessed by immunohistochemistry, was significantly higher in Tfm/Y and hpg mice than in normal mice. There was no significant sex difference in numbers of GFAP-IR cells in either strain, and no effect of gonadectomy on GFAP-IR cell number in normal mouse hippocampus. In adult male hpg mice, the higher GFAP expression was reduced to normal following treatment with either testosterone or estradiol-17beta, but not 5alpha-dihydrotestosterone. Administration of testosterone from birth significantly reduced the number of hippocampal GFAP-IR cells in both normal and hpg adult mice. These data strongly suggest that the increased number of GFAP-IR astrocytes in the hippocampus is due to the congenital absence of gonadal steroids in hpg mice and androgen insensitivity in Tfm/Y mice. Our findings have important implications for our understanding of the sex steroid modulation of astrocyte reactivity and show that a remarkable degree of plasticity is retained throughout life.