Abnormally rapid reversal learning and reduced response to antipsychotic drugs following ovariectomy in female rats

Adolescent raloxifene treatment in females prevents cognitive deficits in a neurodevelopmental rodent model of schizophrenia

The existence of sex differences in schizophrenia is a well documented phenomenon which led to the hypothesis that female sex hormones are neuroprotective and hence responsible for the more favorable disease characteristics seen in women. The current study sought to investigate the effects of estrogen-like agents administered during early adolescence on behavioral outcomes in adulthood using the neurodevelopmental maternal immune activation (MIA) rodent model of schizophrenia. Female MIA offspring were administered during the asymptomatic period of adolescence with either 17β-estradiol, raloxifene or saline and were tested in late adolescence and adulthood for schizophrenia-related behavioral performance. We report here that whereas adult female MIA offspring exhibited cognitive deficits in the form of retarded spatial learning, the administration of raloxifene during adolescence was sufficient in preventing these deficits and resulted in intact performance in the MIA group.

Estrogen receptors observed at extranuclear neuronal sites and in glia in the nucleus accumbens core and shell of the female rat: Evidence for localization to catecholaminergic and GABAergic neurons

Estrogens affect dopamine-dependent diseases/behavior and have rapid effects on dopamine release and receptor availability in the nucleus accumbens (NAc). Low levels of nuclear estrogen receptor (ER) α and ERβ are seen in the NAc, which cannot account for the rapid effects of estrogens in this region. G-protein coupled ER 1 (GPER1) is observed at low levels in the NAc shell, which also likely does not account for the array of estrogens' effects in this region. Prior studies demonstrated membrane-associated ERs in the dorsal striatum; these experiments extend those findings to the NAc core and shell. Single- and dual-immunolabeling electron microscopy determined whether ERα, ERβ, and GPER1 are at extranuclear sites in the NAc core and shell and whether ERα and GPER1 were localized to catecholaminergic or γ-aminobutyric acid-ergic (GABAergic) neurons. All three ERs are observed, almost exclusively, at extranuclear sites in the NAc, and similarly distributed in the core and shell. ERα, ERβ, and GPER1 are primarily in axons and axon terminals suggesting that estrogens affect transmission in the NAc via presynaptic mechanisms. About 10% of these receptors are found on glia. A small proportion of ERα and GPER1 are localized to catecholaminergic terminals, suggesting that binding at these ERs alters release of catecholamines, including dopamine. A larger proportion of ERα and GPER1 are localized to GABAergic dendrites and terminals, suggesting that estrogens alter GABAergic transmission to indirectly affect dopamine transmission in the NAc. Thus, the localization of ERs could account for the rapid effects of estrogen in the NAc.

Influence of ovarian hormones on value-based decision-making systems: Contribution to sexual dimorphisms in mental disorders

Women and men exhibit differences in behavior when making value-based decisions. Various hypotheses have been proposed to explain these findings, stressing differences in functional lateralization of the brain, functional activation, neurotransmitter involvement and more recently, sex hormones. While a significant interaction of neurotransmitter systems and sex hormones has been shown for both sexes, decision-making in women might be particularly affected by variations of ovarian hormones. In this review we have gathered information from animal and human studies on how ovarian hormones affect decision-making processes in females by interacting with neurotransmitter systems at functionally relevant brain locations and thus modify the computation of decision aspects. We also review previous findings on impaired decision-making in animals and clinical populations with substance use disorder and depression, emphasizing how little we know about the role of ovarian hormones in aberrant decision-making.

Sex-dependent mental illnesses and mitochondria

The prevalence of some mental illnesses, including major depression, anxiety-, trauma-, and stress-related disorders, some substance use disorders, and later onset of schizophrenia, is higher in women than men. While the higher prevalence in women could simply be explained by socioeconomic determinants, such as income, social status, or cultural background, extensive studies show sex differences in biological, pharmacokinetic, and pharmacological factors contribute to females' vulnerability to these mental illnesses. In this review, we focus on estrogens, chronic stress, and neurotoxicity from behavioral, pharmacological, biological, and molecular perspectives to delineate the sex differences in these mental illnesses. Particularly, we investigate a possible role of mitochondrial function, including biosynthesis, bioenergetics, and signaling, on mediating the sex differences in psychiatric disorders.

Interactions between estradiol and haloperidol on perseveration and reversal learning in amphetamine-sensitized female rats

There are sex differences associated with schizophrenia, as women exhibit later onset of the disorder, less severe symptomatology, and better response to antipsychotic medications. Estrogens are thought to play a role in these sex differences; estrogens facilitate the effects of antipsychotic medications to reduce the positive symptoms of schizophrenia, but it remains unclear whether estrogens protect against the cognitive symptoms of this disorder. Amphetamine sensitization is used to model some symptoms of schizophrenia in rats, including cognitive deficits like excessive perseveration and slower reversal learning. In this experiment female rats were administered a sensitizing regimen of amphetamine to mimic these cognitive symptoms. They were ovariectomized and administered either low or high estradiol replacement as well as chronic administration of the antipsychotic haloperidol, and were assessed in tests of perseveration and reversal learning. Results of these experiments demonstrated that, in amphetamine-sensitized rats, estradiol alone does not affect perseveration or reversal learning. However, low estradiol facilitates a 0.25mg/day dose of haloperidol to reduce perseveration and improve reversal learning. Combined high estradiol and 0.25mg/day haloperidol has no effect on perseveration or reversal learning, but high estradiol facilitates the effects of 0.13mg/day haloperidol to reduce perseveration and improve reversal learning. Thus, in amphetamine-sensitized female rats, 0.25mg/day haloperidol only improved perseveration and reversal learning when estradiol was low, while 0.13mg/day haloperidol only improved these cognitive processes when estradiol was high. These findings suggest that estradiol facilitates the effects of haloperidol to improve perseveration and reversal learning in a dose-dependent manner.

Oestrogens, prolactin, hypothalamic-pituitary-gonadal axis, and schizophrenic psychoses

Interest is growing in the potential effect of gonadal hormones, prolactin, and the hypothalamic-pituitary-gonadal axis in schizophrenic psychoses. Many studies from clinical, epidemiological, and fundamental research have confirmed that oestradiol, the main component of oestrogens, can have protective effects in schizophrenic psychoses. Furthermore, many patients with schizophrenic psychoses-even in the untreated prodromal stages-have hyperprolactinaemia and gonadal dysfunction, with oestrogen deficiency in women and testosterone deficiency in men. The understanding of the pathogenetic mechanisms underlying these findings could contribute to a better understanding of the aetiopathogenesis of schizophrenic psychoses and improve therapeutic approaches. In this Series paper, we aim to review methodologically sound studies in this area, propose a theory to explain these findings in the context of psychosis, and suggest therapeutic strategies and implications for further research.

Adolescent olanzapine sensitization is correlated with hippocampal stem cell proliferation in a maternal immune activation rat model of schizophrenia

Previous work established that repeated olanzapine (OLZ) administration in normal adolescent rats induces a sensitization effect (i.e. increased behavioral responsiveness to drug re-exposure) in the conditioned avoidance response (CAR) model. However, it is unclear whether the same phenomenon can be detected in animal models of schizophrenia. The present study explored the generalizability of OLZ sensitization from healthy animals to a preclinical neuroinflammatory model of schizophrenia in the CAR. Maternal immune activation (MIA) was induced via polyinosinic:polycytidylic acid (PolyI:C) administration into pregnant dams. Behavioral assessments of offspring first identified decreased maternal separation-induced pup ultrasonic vocalizations and increased amphetamine-induced hyperlocomotion in animals prenatally exposed to PolyI:C. In addition, repeated adolescent OLZ administration confirmed the generalizability of the sensitization phenomenon. Using the CAR test, adolescent MIA animals displayed a similar increase in behavioral responsiveness after repeated OLZ exposure during both the repeated drug test days as well as a subsequent challenge test. Neurobiologically, few studies examining the relationship between hippocampal cell proliferation and survival and either antipsychotic exposure or MIA have incorporated concurrent behavioral changes. Thus, the current study also sought to reveal the correlation between OLZ behavioral sensitization in the CAR and hippocampal cell proliferation and survival. 5'-bromodeoxyuridine immunohistochemistry identified a positive correlation between the magnitude of OLZ sensitization (i.e. change in avoidance suppression induced by OLZ across days) and hippocampal cell proliferation. The implications of the relationship between behavioral and neurobiological results are discussed.

The development of psychotic disorders in adolescence: a potential role for hormones

This article is part of a Special Issue "Puberty and Adolescence". The notion that adolescence is characterized by dramatic changes in behavior, and often by emotional upheaval, is widespread and longstanding in popular western culture. In recent decades, this notion has gained increasing support from empirical research showing that the peri- and post-pubertal developmental stages are associated with a significant rise in the rate of psychiatric symptoms and syndromes. As a result, interest in adolescent development has burgeoned among researchers focused on the origins of schizophrenia and other psychotic disorders. Two factors have fueled this trend: 1) increasing evidence from longitudinal research that adolescence is the modal period for the emergence of "prodromal" manifestations, or precursors of psychotic symptoms, and 2) the rapidly accumulating scientific findings on brain structural and functional changes occurring during adolescence and young adulthood. Further, gonadal and adrenal hormones are beginning to play a more prominent role in conceptualizations of adolescent brain development, as well as in the origins of psychiatric symptoms during this period (Walker and Bollini, 2002; Walker et al., 2008). In this paper, we begin by providing an overview of the nature and course of psychotic disorders during adolescence/young adulthood. We then turn to the role of hormones in modulating normal brain development, and the potential role they might play in the abnormal brain changes that characterize youth at clinical high-risk (CHR) for psychosis. The activational and organizational effects of hormones are explored, with a focus on how hormone-induced changes might be linked with neuropathological processes in the emergence of psychosis.

Treating schizophrenia at the time of menopause

The purpose of this review is to optimize treatment for women with schizophrenia during the menopause. Recommendations are based on a relatively sparse literature derived from searching PubMed, PsychINFO, SOCINDEX with appropriate search terms for all years subsequent to 2000. Attention needs to be paid to menopausal symptoms in women with schizophrenia and to the possibility that psychotic symptoms may worsen at this time and that general health may deteriorate. Antipsychotic treatment may need to be modified and cardiac and metabolic health indices closely monitored.