Effects of estrogen on the basal ganglia

Sex differences in effectiveness and adverse effects of mood stabilizers and antipsychotics: A systematic review

BACKGROUND

Psychiatric disorders differ in their prevalence, symptom profiles, and disease courses in men and women. However, sex differences in psychiatric disorders have not received enough attention to guide treatment recommendations. This systematic review aims to summarize sex differences in the treatment responses and adverse effects of mood stabilizers and antipsychotics transdiagnostically.

METHODS

We conducted a systematic review following the PRISMA 2020 statement (CRD42020212478). A literature search was conducted using MEDLINE, Embase, Cochrane Central, PsycINFO, Web of Science Core Collection, and Scopus databases. Studies comparing mood stabilizer or antipsychotic treatment outcomes in men and women were included. JBI critical appraisal checklists were used to assess bias risk.

RESULTS

Out of 4866 records, 129 reports (14 on mood stabilizers, 115 on antipsychotics) with varying designs were included. Sample sizes ranged from 17 to 22,774 participants (median = 147). The most common psychiatric diagnoses were schizophrenia spectrum (n = 109, 84.5 %) and bipolar disorders (n = 38, 29.5 %). Only four studies explored sex differences in mood stabilizer treatment response. In 40 articles on antipsychotic treatment response, 18 indicated no sex difference, while 16 showed females had better outcomes. Women had more adverse effects with both mood stabilizers and antipsychotics. The risk of bias was low in 84 (65.1 %) of studies.

LIMITATIONS

Substantial heterogeneity among the studies precluded performing a meta-analysis.

CONCLUSION

Number of studies focusing on sex differences in treatment outcomes of mood stabilizers is limited. Women may respond better to antipsychotics than men, but also experience more side effects. The impact of pharmacokinetics on sex differences warrants more attention.

What can epidemiological studies teach on the pathophysiology of adult-onset isolated dystonia?

Several demographic and environmental factors may play an important role in determining the risk of developing adult-onset isolated dystonia (AOID) and/or modifying its course. However, epidemiologic studies have provided to date only partial insight on the disease mechanisms that are actively influenced by these factors. The age-related increase in female predominance in both patients diagnosed with AOID and subjects carrying its putative mediational phenotype suggests sexual dimorphism that has been demonstrated for mechanisms related to blepharospasm and cervical dystonia. The opposite relationship that spread and spontaneous remission of AOID have with age suggests age-related decline of compensatory mechanisms that protect from the progression of AOID. Epidemiological studies focusing on environmental risk factors yielded associations only with specific forms of AOID, even for those factors that are not likely to predispose exclusively to specific focal forms (for example, only writing dystonia was found associated with head trauma, and only blepharospasm with coffee intake). Other factors show biological plausibility of their mechanistic role for specific forms, e.g., dry eye syndrome or sunlight exposure for blepharospasm, scoliosis for cervical dystonia, repetitive writing for writing dystonia. Overall, the relationship between environment and AOID remains complex and incompletely defined. Both hypothesis-driven preclinical studies and well-designed cross-sectional or prospective clinical studies are still necessary to decipher this intricate relationship.

The impact of biological clock and sex hormones on the risk of disease

Molecular clocks are responsible for defining 24-h cycles of behaviour and physiology that are called circadian rhythms. Several structures and tissues are responsible for generating these circadian rhythms and are named circadian clocks. The suprachiasmatic nucleus of the hypothalamus is believed to be the master circadian clock receiving light input via the optic nerve and aligning internal rhythms with environmental cues. Studies using both in vivo and in vitro methodologies have reported the relationship between the molecular clock and sex hormones. The circadian system is directly responsible for controlling the synthesis of sex hormones and this synthesis varies according to the time of day and phase of the estrous cycle. Sex hormones also directly interact with the circadian system to regulate circadian gene expression, adjust biological processes, and even adjust their own synthesis. Several diseases have been linked with alterations in either the sex hormone background or the molecular clock. So, in this chapter we aim to summarize the current understanding of the relationship between the circadian system and sex hormones and their combined role in the onset of several related diseases.

Regulation of Voluntary Physical Activity Behavior: A Review of Evidence Involving Dopaminergic Pathways in the Brain

Physical activity leads to well-established health benefits. Current efforts to enhance physical activity have targeted mainly socioeconomic factors. However, despite these efforts, only a small number of adults engage in regular physical activity to the point of meeting current recommendations. Evidence collected in rodent models and humans establish a strong central nervous system component that regulates physical activity behavior. In particular, dopaminergic pathways in the central nervous system are among the best-characterized biological mechanisms to date with respect to regulating reward, motivation, and habit formation, which are critical for establishing regular physical activity. Herein, we discuss evidence for a role of brain dopamine in the regulation of voluntary physical activity behavior based on selective breeding and pharmacological studies in rodents, as well as genetic studies in both rodents and humans. While these studies establish a role of dopamine and associated mechanisms in the brain in the regulation of voluntary physical activity behavior, there is clearly need for more research on the underlying biology involved in motivation for physical activity and the formation of a physical activity habit. Such knowledge at the basic science level may ultimately be translated into better strategies to enhance physical activity levels within the society.

"Time Slows Down Whenever You Are Around" for Women but Not for Men

What happens when we unexpectedly see an attractive potential partner? Previous studies in laboratory settings suggest that the visualization of attractive and unattractive photographs influences the perception of time. The major aim of this research is to study time perception and attraction in a realistic social scenario, by investigating if changes in subjective time measured during a speed dating are associated with attraction. The duration of the dates was variable and participants had to estimate the time that passed. Among other measures, participants also rated the potential partners in terms of their physical attractiveness before and after the dates and reported if they would like to exchange contact with them. Results showed that, in a real speed dating situation, when there is a perception of the partner as being physically more attractive, women tend to overestimate the duration of that meeting, whereas men tend to underestimate its duration. Such changes may reflect evolutionary adaptations which make the human cognitive system more responsive in situations related to reproductive fitness.

The macrocyclic lactones ivermectin and moxidectin show differential effects on rotational behavior in the 6-hydroxydopamine mouse model of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by motor and cognitive deficits, the result of dopamine (DA)-depletion within the basal ganglia. Currently, DA replacement therapy in the form of Sinemet (L-DOPA plus Carbidopa) provides symptomatic motor benefits and remains the "gold standard" for treatment. Several pharmacological approaches can enhance DA neurotransmission including the administration of DA receptor agonists, the inhibition of DA metabolism, and enhancing pre-synaptic DA release. DA neurotransmission is regulated by several receptor subtypes including signaling through the purinergic system. P2 × 4 receptors (P2 × 4Rs) are a class of cation-permeable ligand-gated ion channels activated by the synaptic release of extracellular adenosine 5'-triphosphate (ATP). P2 × 4Rs are expressed throughout the central nervous system including the dopaminergic circuitry of the substantia nigra, basal ganglia, and related reward networks. Previous studies have demonstrated that P2 × 4Rs can modulate several DA-dependent characteristics including motor, cognitive, and reward behaviors. Ivermectin (IVM) and moxidectin (MOX) are two macrocyclic lactones that can potentiate P2 × 4Rs. In this study, we sought to investigate the role of P2 × 4Rs in mediating DA neurotransmission by exploring their impact on DA-dependent behavior, specifically rotation frequency in the unilateral 6-hydroxydopamine-lesioned mouse model of DA-depletion. While we did not observe any differences in the degree of lesioning based on immunostaining for tyrosine hydroxylase between sexes, male mice displayed a greater number of rotations with L-DOPA compared to female mice. In contrast, we observed that IVM plus L-DOPA increased the number of rotations (per 10 min) in female, but not male mice. These findings highlight the potential role of pharmacologically targeting the purinergic receptor system in modulating DA neurotransmission as well as the importance of sex differences impacting outcome measures.

Cervical dystonia incidence and diagnostic delay in a multiethnic population

BACKGROUND

Current cervical dystonia (CD) incidence estimates are based on small numbers in relatively ethnically homogenous populations. The frequency and consequences of delayed CD diagnosis is poorly characterized.

OBJECTIVES

To determine CD incidence and characterize CD diagnostic delay within a large, multiethnic integrated health maintenance organization.

METHODS

We identified incident CD cases using electronic medical records and multistage screening of more than 3 million Kaiser Permanente Northern California members from January 1, 2003, to December 31, 2007. A final diagnosis was made by movement disorders specialist consensus. Diagnostic delay was measured by questionnaire and health utilization data. Incidence rates were estimated assuming a Poisson distribution of cases and directly standardized to the 2000 U.S. census. Multivariate logistic regression models were employed to assess diagnoses and behaviors preceding CD compared with matched controls, adjusting for age, sex, and membership duration.

RESULTS

CD incidence was 1.18/100,000 person-years (95% confidence interval [CI], 0.35-2.0; women, 1.81; men, 0.52) based on 200 cases over 15.4 million person-years. Incidence increased with age. Half of the CD patients interviewed reported diagnostic delay. Diagnoses more common in CD patients before the index date included essential tremor (odds ratio [OR] 68.1; 95% CI, 28.2-164.5), cervical disc disease (OR 3.83; 95% CI, 2.8-5.2), neck sprain/strain (OR 2.77; 95% CI, 1.99-3.62), anxiety (OR 2.24; 95% CI, 1.63-3.11) and depression (OR 1.94; 95% CI, 1.4-2.68).

CONCLUSIONS

CD incidence is greater in women and increases with age. Diagnostic delay is common and associated with adverse effects. © 2019 International Parkinson and Movement Disorder Society.

Movement disorders in pregnancy

Movement disorders in women during pregnancy are uncommon. Therefore, high quality studies are limited, and guidelines are lacking for the treatment of movement disorders in pregnancy, thus posing a significant therapeutic challenge for the treating physicians. In this chapter, we discuss movement disorders that arise during pregnancy and the preexisting movement disorders during pregnancy. Common conditions encountered in pregnancy include but are not limited to restless legs syndrome, chorea gravidarum, Parkinson disease, essential tremor, and Huntington disease as well as more rare movement disorders (Wilson's disease, dystonia, etc.). This chapter summarizes the published literature on movement disorders and pharmacologic and surgical considerations for neurologists and physicians in other specialties caring for patients who are pregnant or considering pregnancy.

A rapid enhancement of locomotor sensitization to amphetamine by estradiol in female rats

Estradiol moderates the effects of drugs of abuse in both humans and rodents. Estradiol's enhancement of behavioral effects resulting from high (>2.5mg/kg) doses of amphetamine is established in rats; there is less evidence for the role of estradiol in locomotor effects elicited by lower doses, which are less aversive, increase incentive motivation, involve different neural mechanisms than higher doses, and often more readily reveal group differences than do higher doses. Further, the extent to which estradiol is required for the induction versus the expression of sensitization is unknown. To establish a protocol, we replicated the effects of estradiol on locomotor sensitization to amphetamine reported in a previous study that involved a high locomotor-activating dose (1.5mg/kg) of amphetamine, but with a lower dose. Ovariectomized female rats received 5μg of estradiol benzoate (EB) or OIL 30min before each of 5 treatments of 1.0mg/kg amphetamine or saline; all received a 0.5mg/kg challenge dose three days later. Compared with results for OIL, EB enhanced the locomotor-activating effects of repeated 1.0mg/kg amphetamine across treatment days. In contrast, on challenge day, there was no difference between EB-saline and EB-amphetamine to the lower dose (i.e., no sensitization). Experiments 2 and 3 involved a shorter induction (2days) and a lengthier withdrawal (9days) before the challenge test for the expression of sensitization to better differentiate the induction phase from the expression phase. In Expt2, EB-, and not OIL-, treated rats showed sensitization to 0.5mg/kg amphetamine; neither group showed sensitization to 1.5mg/kg amphetamine (ceiling effect?). In Expt3, rats were treated with EB either in both the induction and expression phases, in one of the phases only, or in neither phase. There was an effect of hormone treatment on challenge day and not on induction day; rats given EB on Challenge day showed sensitization to 0.5mg/kg amphetamine; OIL rats did not. The results suggest rapid effects of estradiol on amphetamine sensitization consistent with rapid effects of estradiol reported for other behaviours.

Understanding the broad influence of sex hormones and sex differences in the brain

Sex hormones act throughout the entire brain of both males and females via both genomic and nongenomic receptors. Sex hormones can act through many cellular and molecular processes that alter structure and function of neural systems and influence behavior as well as providing neuroprotection. Within neurons, sex hormone receptors are found in nuclei and are also located near membranes, where they are associated with presynaptic terminals, mitochondria, spine apparatus, and postsynaptic densities. Sex hormone receptors also are found in glial cells. Hormonal regulation of a variety of signaling pathways as well as direct and indirect effects on gene expression induce spine synapses, up- or downregulate and alter the distribution of neurotransmitter receptors, and regulate neuropeptide expression and cholinergic and GABAergic activity as well as calcium sequestration and oxidative stress. Many neural and behavioral functions are affected, including mood, cognitive function, blood pressure regulation, motor coordination, pain, and opioid sensitivity. Subtle sex differences exist for many of these functions that are developmentally programmed by hormones and by not yet precisely defined genetic factors, including the mitochondrial genome. These sex differences and responses to sex hormones in brain regions, which influence functions not previously regarded as subject to such differences, indicate that we are entering a new era of our ability to understand and appreciate the diversity of gender-related behaviors and brain functions. © 2016 Wiley Periodicals, Inc.

Behavioral sensitization to ethanol: Neural basis and factors that influence its acquisition and expression

Ethanol-induced behavioral sensitization (EBS) was first described in 1980, approximately 10 years after the phenomenon was described for psychostimulants. Ethanol acts on γ-aminobutyric acid (GABA) and glutamate receptors as an allosteric agonist and antagonist, respectively, but it also affects many other molecular targets. The multiplicity of factors involved in the behavioral and neurochemical effects of ethanol and the ensuing complexity may explain much of the apparent disparate results, found across different labs, regarding ethanol-induced behavioral sensitization. Although the mesocorticolimbic dopamine system plays an important role in EBS, we provide evidence of the involvement of other neurotransmitter systems, mainly the glutamatergic, GABAergic, and opioidergic systems. This review also analyses the neural underpinnings (e.g., induction of cellular transcription factors such as cyclic adenosine monophosphate response element binding protein and growth factors, such as the brain-derived neurotrophic factor) and other factors that influence the phenomenon, including age, sex, dose, and protocols of drug administration. One of the reasons that make EBS an attractive phenomenon is the assumption, firmly based on empirical evidence, that EBS and addiction-related processes have common molecular and neural basis. Therefore, EBS has been used as a model of addiction processes. We discuss the association between different measures of ethanol-induced reward and EBS. Parallels between the pharmacological basis of EBS and acute motor effects of ethanol are also discussed.

Basal Ganglia Volumes: MR-Derived Reference Ranges and Lateralization Indices for Children and Young Adults

SUMMARY - Previous studies indicate rightward asymmetry of the caudate nucleus (CN) volume and leftward asymmetry of the putamen (PN) and globus pallidus (GP). This study aimed to estimate reference ranges for basal ganglia asymmetry in a large cohort of healthy individuals (n= 949), aged seven to 21 years. MRI images of 949 (320 female, mean age 12.6 +/- 3.3, range 7-21) healthy individuals were reviewed. Volumetric measurements of the basal ganglia were obtained using automated segmentation (FreeSurfer). We computed two lateralization indices: (L-R)/(L+R) (LI) and right/left ratio (RLR). Tolerance interval estimates were used to calculate reference ranges. Rightward asymmetry of the CN and leftward asymmetry of the PN and GP were confirmed. PN and GP volume decreased with age, but CN volume did not. The lateralization index decreased with age for PN, but not for CN and GP. RLR increased with age for PN and not for CN or GP. Females were associated with smaller volume, but not with either LI or RLR difference. Reference ranges obtained in this study provide useful resources for power analysis and a reference group for future studies using basal ganglia asymmetry indices.

Sex, stress and the brain: interactive actions of hormones on the developing and adult brain

The brain is a target of steroid hormone actions that affect brain architecture, molecular and neurochemical processes, behavior and neuroprotection via both genomic and non-genomic actions. Estrogens have such effects throughout the brain and this article provides an historical and current view of how this new view has come about and how it has affected the study of sex differences, as well as other areas of neuroscience, including the effects of stress on the brain.

Sex differences in the neurobiology of drug addiction

Epidemiological data demonstrate that while women report lower rates of drug use than men, the number of current drug users and abusers who are women continues to increase. In addition women progress through the phases of addiction differently than men; women transition from casual drug use to addiction faster, are more reactive to stimuli that trigger relapse, and have higher rates of relapse then men. Sex differences in physiological and psychological responses to drugs of abuse are well documented and it is well established that estrogen effects on dopamine (DA) systems are largely responsible for these sex differences. However, the downstream mechanisms that result from interactions between estrogen and the effects of drugs of abuse on the DA system are just beginning to be explored. Here we review the basic neurocircuitry which underlies reward and addiction; highlighting the neuroadaptive changes that occur in the mesolimbic dopamine reward and anti-reward/stress pathways. We propose that sex differences in addiction are due to sex differences in the neural systems which mediate positive and negative reinforcement and that these differences are modulated by ovarian hormones. This forms a neurobehavioral basis for the search for the molecular and cellular underpinnings that uniquely guide motivational behaviors and make women more vulnerable to developing and sustaining addiction than men.

Estrogen and memory system bias in females across the lifespan

Studies in both rodents and humans have made much progress in shedding light on how fluctuations in ovarian hormones can affect memory in women across the lifespan. Specifically, advances in neuroscience have identified multiple memory systems that are each mediated by different brain areas. Two memory systems used to navigate an environment are ‘place’ and ‘response’ memory. They are defined as either using an allocentric strategy: using a spatial or cognitive map of the surroundings, or an egocentric strategy: using habitual-turns/movements, respectively. Studies in neuroendocrinology have shown that estrogen levels can bias a female to use one memory system over another to solve a task, such that high estrogen levels are associated with using place memory and low levels with using response memory. Furthermore, recent advances in identifying and localizing estrogen receptors in the rodent brain are uncovering which brain regions are affected by estrogen and providing insight into how hormonal fluctuations during the menstrual cycle, pregnancy, and menopause might affect which memory system is facilitated or impaired in women at different life stages. These studies can help point the way to improving cognitive health in women.

Eye movements to natural images as a function of sex and personality

Women and men are different. As humans are highly visual animals, these differences should be reflected in the pattern of eye movements they make when interacting with the world. We examined fixation distributions of 52 women and men while viewing 80 natural images and found systematic differences in their spatial and temporal characteristics. The most striking of these was that women looked away and usually below many objects of interest, particularly when rating images in terms of their potency. We also found reliable differences correlated with the images' semantic content, the observers' personality, and how the images were semantically evaluated. Information theoretic techniques showed that many of these differences increased with viewing time. These effects were not small: the fixations to a single action or romance film image allow the classification of the sex of an observer with 64% accuracy. While men and women may live in the same environment, what they see in this environment is reliably different. Our findings have important implications for both past and future eye movement research while confirming the significant role individual differences play in visual attention.

Relevance of animal models to human tardive dyskinesia

Tardive dyskinesia remains an elusive and significant clinical entity that can possibly be understood via experimentation with animal models. We conducted a literature review on tardive dyskinesia modeling. Subchronic antipsychotic drug exposure is a standard approach to model tardive dyskinesia in rodents. Vacuous chewing movements constitute the most common pattern of expression of purposeless oral movements and represent an impermanent response, with individual and strain susceptibility differences. Transgenic mice are also used to address the contribution of adaptive and maladaptive signals induced during antipsychotic drug exposure. An emphasis on non-human primate modeling is proposed, and past experimental observations reviewed in various monkey species. Rodent and primate models are complementary, but the non-human primate model appears more convincingly similar to the human condition and better suited to address therapeutic issues against tardive dyskinesia.

The role of estrogen and testosterone in female rats in behavioral models of relevance to schizophrenia

RATIONALE

The sex steroid hormone, estrogen, may play a protective role in schizophrenia. We previously found that estrogen treatment inhibited serotonin-1A (5-HT(1A)) and dopamine D(2) receptor-mediated disruptions of prepulse inhibition (PPI), a measure of sensorimotor gating which is deficient in schizophrenia.

OBJECTIVES

The present study aimed to further explore the role of sex steroid hormones in schizophrenia. Part 1 of this study examined whether estrogen could inhibit PPI disruption induced by the N-methyl-D: -aspartate (NMDA) receptor antagonist, MK-801. Part 2 investigated whether the functionally protective effect of estrogen occurs in another animal model of schizophrenia, amphetamine-induced locomotor hyperactivity. Part 3 compared our previous PPI findings in estrogen-treated rats, to treatment with testosterone.

METHODS

Female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated. Some OVX rats received silastic implants filled with either a low (E20) or high dose (E100) of estradiol, or a low (T5) or high dose (T20) of testosterone, for at least 2 weeks before behavioral testing.

RESULTS

The disruption of PPI caused by MK-801 (0.1 mg/kg) was significantly reduced by treatment with estradiol (E20 and E100). However, estradiol treatment did not alter amphetamine-induced (0.25 and 0.5 mg/kg) locomotor hyperactivity, in terms of distance traveled, ambulation, or vertical counts. In contrast to estrogen, testosterone treatment did not affect disruption of PPI after administration of 8-OH-DPAT (0.5 mg/kg) or apomorphine (0.3 mg/kg). Testosterone treatment significantly enhanced the MK-801-induced (0.1 mg/kg) PPI disruption.

CONCLUSIONS

Estrogen is functionally protective against 5-HT(1A)-, dopamine D(2)-, and NMDA receptor-induced PPI disruptions, while testosterone treatment enhances NMDA receptor-mediated PPI disruptions.

Estrogenic regulation of dopaminergic neurons in the opportunistically breeding zebra finch

Steroid-induced changes in dopaminergic activity underlie many correlations between gonadal hormones and social behaviors. However, the effects of steroid hormones on the various behaviorally relevant dopamine cell groups remain unclear, and ecologically relevant species differences remain virtually unexplored. We examined the effects of estradiol (E2) manipulations on dopamine (DA) neurons of male and female zebra finches (Taeniopygia guttata), focusing on numbers of tyrosine hydroxylase-immunoreactive (TH-ir) cells in the A8-A15 cell groups, and on TH colocalization with Fos, conducted in the early A.M., in order to quantify basal transcriptional activity. TH is the rate-limiting enzyme for catecholamine synthesis, and specifically DA in the A8-A15 cell groups. In contrast to other examined birds and mammals, reducing E2 levels with the aromatase-inhibitor Letrozole failed to alter TH-ir neuron numbers within the ventral tegmental area (VTA; A10), while increasing neuron numbers in the central gray (CG; A11) and caudal midbrain A8 populations. Consistent with findings in other birds, but not mammals, we also found no effects of E2 manipulations (Letrozole or Letrozole plus E2 replacement) on TH-Fos colocalization in any location. In accordance with previous observations in both mammals and birds, E2 treatment decreased the number of TH-ir neurons in the A12 population of the tuberal hypothalamus, a cell group that inhibits the release of prolactin. In general, males and females exhibited similar TH-ir neuron numbers, although males exhibited significantly more TH-ir neurons in the A11 CG population than did females. These results suggest partial variability in E2 regulation of DA across species.

Exploration of sex differences in Rhes effects in dopamine mediated behaviors

Studies have shown that Ras homolog enriched in striatum (Rhes) proteins are highly expressed in areas of the central nervous system that have high dopaminergic innervation. In this study, we used Rhes mutant mice (Wild type, Rhes KO, Rhes Heterozygous) of both sexes to explore differences in the effects of Rhes protein levels in basal levels of activity, anxiety, and stereotypy, in relation to sex. Adult male and female mice were evaluated in an open field test for measuring basal levels of activity and anxiety for 5 consecutive days, and they were tested in the apomorphine-induced stereotypy paradigm. Rhes protein levels affected basal levels of activity but it was not found to be related to sex differences. Moreover, a decrease in Rhes protein levels was linked to a nonsignificant anxiolytic effect, mainly in female mice. Finally, a decrease in Rhes protein levels does not affect dopamine D(1) and D(2) receptor (D(1)/D(2)) synergism in female or male mice. Together, these results suggest that Rhes protein levels affect locomotion activity, and have an influence in anxiety depending on sex; Rhes protein levels do not affect D(1)/D(2) synergism in both sexes.

A survey on the impact of the menstrual cycle on movement disorders severity

BACKGROUND

A possible influence of estrogens on the dopaminergic system has been hypothesized and investigated by several studies, and fluctuations in motor symptoms related to the menstrual cycle have been reported in some movement disorders patients. We designed a survey to quantify how frequently female patients with various movement disorders are affected by this phenomenon and its impact on symptom severity.

METHODS

A questionnaire was sent to 104 women between 18- and 60-years-old diagnosed with movement disorders and regularly followed at our centre.

RESULTS

From a total of 65 subjects who completed the questionnaire, 54 women reported the onset of their movement disorders before menopause. Twenty of them (37%) experienced changes in their movement disorders during the menstrual cycle. In particular, there was a significant worsening of symptom severity before (p=0.0005) and during menses (p=0.0004).

CONCLUSIONS

The possible role of such changes should be taken into account when evaluating the efficacy of various therapeutic interventions in movement disorder patients.

Estradiol does not influence strategy choice but place strategy choice is associated with increased cell proliferation in the hippocampus of female rats

Adult neurogenesis occurs in the hippocampus of most mammals. While the function of adult hippocampal neurogenesis is not known, there is a relationship between neurogenesis and hippocampus-dependent learning and memory. Ovarian hormones can influence learning and memory and strategy choice. In competitive memory tasks, higher levels of estradiol shift female rats towards the use of the place strategy. Previous studies using a cue-competition paradigm find that 36% of male rats will use a hippocampus-dependent place strategy and place strategy users had lower levels of cell proliferation in the hippocampus. Here, we used the same paradigm to test whether endogenous or exogenous ovarian hormones influence strategy choice in the cue-competition paradigm and whether cell proliferation was related to strategy choice. We tested ovariectomized estradiol-treated (10 microg of estradiol benzoate) or sham-operated female rats on alternating blocks of hippocampus-dependent and hippocampus-independent versions of the Morris water task. Rats were then given a probe session with the platform visible and in a novel location. Preferred strategy was classified as place strategy (hippocampus-dependent) if they swam to the old platform location or cue strategy (hippocampus-independent) if they swam to the visible platform. All groups showed a preference for the cue strategy. However, proestrous rats were more likely to be place strategy users than rats not in proestrus. Female place strategy users had increased cell proliferation in the dentate gyrus compared to cue strategy users. Our study suggests that 78% of female rats chose the cue strategy instead of the place strategy. In summary the present results suggest that estradiol does not shift strategy use in this paradigm and that cell proliferation is related to strategy use with greater cell proliferation seen in place strategy users in female rats.

Membrane estrogen receptors activate the metabotropic glutamate receptors mGluR5 and mGluR3 to bidirectionally regulate CREB phosphorylation in female rat striatal neurons

Along with its ability to directly regulate gene expression, estradiol influences cell signaling and brain functions via rapid, membrane-initiated events. In the female rat striatum, estradiol activates membrane-localized estrogen receptors to influence synaptic neurotransmission, calcium channel activity, and behaviors related to motor control. Yet, the mechanism by which estradiol acts to rapidly affect striatal physiology has remained elusive. Here we find that membrane estrogen receptors (ERs) couple to the metabotropic glutamate receptors mGluR5 and mGluR3, providing the framework to understand how membrane estrogen receptors affect striatal function. Using CREB phosphorylation as a downstream measure of ER/mGluR activation, membrane-localized estrogen receptor α (ERα) activates mGluR5 signaling to mediate mitogen-activated protein kinase (MAPK)-dependent CREB phosphorylation. Further, ERα and estrogen receptor β (ERβ) activate mGluR3 to attenuate L-type calcium channel-dependent CREB signaling. Interestingly, while this fundamental mechanism of ER/mGluR signaling was initially characterized in hippocampal neurons, estrogen receptors in striatal neurons are paired with a different set of mGluRs, resulting in the potential to functionally isolate membrane-initiated estrogen signaling across brain regions via use of specific mGluR modulators. These results provide both a mechanism for the rapid actions of estrogens within the female striatum, as well as demonstrate that estrogen receptors can interact with a more diverse set of surface membrane receptors than previously recognized.

Oromandibular dystonia and hormonal factors: twelve years follow-up of a case report

Oromandibular dystonia (OMD) is a focal neurological movement disorder characterized by involuntary sustained and often painful muscle contraction, usually producing repetitive movements or abnormal positions of the mouth, jaw and/or tongue. We report on a 30-year-old woman affected with OMD with a 12-year follow-up. Focal dystonia involved an involuntary activity of the lateral pterygoid muscles causing forceful jaw displacement in the maximal protrusive position. These episodes initially occurred during jaw function and increased up to an open-lock with bilateral pre-auricular pain. Dystonic spasms were absent during sleep and were reduced temporarily by sensory tricks. Treatment with botulinum toxin type A (BTX) was performed during three different sessions over a 1-year period. Electromyographic-guided BTX injections into the lateral pterygoid muscles were given with cannula electrodes. Botox reduced the involuntary activity of the muscles. Recurrence and exacerbation of dystonic symptoms occurred during the two pregnancies and completely disappeared immediately after both deliveries with prolonged symptom-free periods. During the last 8 years, the patient had a slight relapse of symptoms during flu attacks, periods of stress and during menses. The temporal pattern of these symptoms indicates a possible relationship between OMD and hormonal factors.

Enhanced latent inhibition in dopamine receptor-deficient mice is sex-specific for the D1 but not D2 receptor subtype: implications for antipsychotic drug action

Latent inhibition (LI) is reduced learning to a stimulus that has previously been experienced without consequence. It is an important model of abnormal allocation of salience to irrelevant information in patients with schizophrenia. In rodents LI is abolished by psychotomimetic drugs and in experimental conditions where LI is low in controls, its expression is enhanced by antipsychotic drugs with activity at dopamine (DA) receptors. It is however unclear what the independent contributions of DA receptor subtypes are to these effects. This study therefore examined LI in congenic DA D1 and D2 receptor knockout (D1 KO and D2 KO) mice. Conditioned suppression of drinking was used as the measure of learning in the LI procedure. Both male and female DA D2 KO mice showed clear enhancement of LI reproducing antipsychotic drug effects in the model. Unexpectedly, enhancement was also seen in D1 KO female mice but not in D1 KO male mice. This sex-specific pattern was not replicated in locomotor or motor coordination tasks nor in the effect of DA KOs on baseline learning in control groups indicating some specificity of the effect to LI. These data suggest that the dopaminergic mechanism underlying LI potentiation and possibly antipsychotic action may differ between the sexes, being mediated by D2 receptors in males but by both D1 and D2 receptors in females. These data suggest that the DA D1 receptor may prove an important target for understanding sex differences in the mechanisms of action of antipsychotic drugs and in the aetiology of aberrant salience allocation in schizophrenia.

Sex differences in nicotine action

Accumulating evidence suggests that the antecedents, consequences, and mechanisms of drug abuse and dependence are not identical in males and females and that gender may be an important variable in treatment and prevention. Although there has been a decline in smoking prevalence in developed countries, females are less successful in quitting. Tobacco use is accepted to be a form of addiction, which manifests sex differences. There is also evidence for sex differences in the central effects of nicotine in laboratory animals. Although social factors impact smoking substantially in humans, findings from nonhuman subjects in controlled experiments provide support that sex differences in nicotine/tobacco addiction have a biological basis. Differences in the pharmacokinetic properties of nicotine or the effect of gonadal hormones may underlie some but not all sex differences observed. Laboratory-based information is very important in developing treatment strategies. Literature findings suggest that including sex as a factor in nicotine/tobacco-related studies will improve our success rates in individually tailored smoking cessation programs.

Introduction: the end of sex as we once knew it

This special issue of Physiology and Behavior is devoted to papers summarizing sex differences that are now recognized to include not only reproductive behaviors, but also non-reproductive processes and phenomena such as feeding, thirst, pain, sensory processes, mood, cognitive function, the effects of stress, and the propensity for drug abuse. The purpose of this brief introduction is to trace some of the main themes and historical highlights in the discovery that the entire nervous system appears to be a target of reproductive hormones, as well as being subject to developmentally programmed sex differences.

Functional alterations of the nigrostriatal dopamine system in estrogen receptor-alpha knockout (ERKO) mice

Estrogen represents an important factor for the development and function of the nigrostriatal dopamine system. Estrogen also controls sex-specific differentiation and activity of the nigrostriatal dopaminergic system. We used an estrogen receptor-alpha knockout (-/-) model (ERKO) to study the influence of this particular receptor subtype on the regulation of functional characteristics of the male and female nigrostriatal dopamine system. On the striatal level, we found a sex-specific regulation of dopamine D1 receptors (D1) and dopamine receptor-interacting protein 78 (Drip78). In female (-/-) mice D1 receptor expression levels were increased compared to wild type (wt) animals, whereas in male (-/-) mice Drip78 mRNA levels were decreased compared to wt. In the midbrain, expression of tyrosine hydroxylase (TH) and brain-derived neurotrophic factor (BDNF) was reduced in (-/-) mice of both sexes. Glial cell line-derived neurotrophic factor (GDNF) expression was not affected. These data demonstrate that the integrity of estrogen receptor-alpha (ERalpha) signalling is necessary for the regulation of gene expression of proteins known to be important for the function of the nigrostriatal system at the postsynaptic striatal and presynaptic midbrain level.

Modulation by female sex hormones of the cannabinoid-induced catalepsy and analgesia in ovariectomized mice

Cannabinoids are psychoactive compounds with many pharmacological properties such as analgesia, sedation and catalepsy most of which are mediated by cannabinoid CB1 receptors. In the present study, we evaluated whether the ovarian sex hormones are involved in the cannabinoid-induced catalepsy and analgesia in ovariectomized female mice. Female NMRI mice (weighing 25-30 g) were divided into 3 main groups: unoperated, sham-operated and ovariectomized. Both the catalepsy and analgesia induced by different doses of the synthetic cannabinoid WIN 55,212-2 (2 and 4 mg/kg, i.p.) were examined in the groups in the presence or absence of the cannabinoid CB1 antagonist AM251 (0.5 mg/kg). We also evaluated effects of estradiol valerate (10 mg/kg) and progesterone (25 mg/kg) on catalepsy and analgesia induced by WIN 55,212-2 in ovariectomized mice. The antinociceptive effect of WIN 55,212-2 was significantly (P<0.01) enhanced in ovariectomized mice, which was prevented by pretreatment with estradiol but not by progesterone. There was no significant difference in the cannabinoid-induced catalepsy between control and ovariectomized mice. However, pretreatment with progesterone but not estradiol potentiated the cataleptic effect of low dose of WIN 55,212-2 (2 mg/kg) in ovariectomized mice (P<0.01). The present data demonstrated for the first time that ovarian sex steroids could modulate both cannabinoid-induced catalepsy and analgesia in female ovariectomized mice.

In vitro effects of 17 beta-oestradiol on the sensitivity of receptors coupled to adenylate cyclase on striatal neurons in primary culture

Pretreatment of intact striatal neurons from the mouse embryo in primary culture with 17 beta-oestradiol (10(-9) M), 24 hours) enhanced the stimulation of adenylate cyclase activity induced by either dopamine (D1 receptors), isoproterenol, serotonin or 2-chloroadenosine (maximal effective concentrations) but suppressed inhibitory responses evoked by agonists of D2-dopaminergic or enkephalin (mu and delta) receptors. Binding studies indicated that some of these effects are (beta 1) or are not (D1 and D2) associated with changes in the number of receptors. Similar effects were partially seen with testosterone but not with 17 alpha-oestradiol, progesterone or dexamethasone and those induced by 17 beta-oestradiol were abolished when cells were exposed to inhibitors of mRNA transcription (alpha-amanitin) or protein synthesis (cycloheximide). Modifications in the properties of Gs or Go,i proteins were postulated because the number of adenylate cyclase catalytic subunits was not affected by 17 beta-oestradiol pretreatment. Results of ADP-ribosylation experiments with cholera toxin or pertussis toxin and of immunoblot experiments with anti-G alpha o and anti-G beta sera led us to suggest that 17 beta-oestradiol induces qualitative modifications in Go,i proteins leading to a stabilization of the associated form of the heterotrimer G alpha o,i beta gamma. In fact, pretreatment with pertussis toxin (which impairs G alpha o,i beta gamma dissociation) mimics the effects of 17 beta-oestradiol on responses of adenylate cyclase to stimulatory and inhibitory agonists.

Estrogen abolishes latent inhibition in ovariectomized female rats

Estrogen is frequently prescribed as a method of birth control and as hormone replacement therapy for post-menopausal women with varied effects on cognition. Here the effects of estrogen on attention were examined using the latent inhibition (LI) behavioral paradigm. Ovariectomized (OVX) female rats were given either estrogen benzoate (EB, 10 or 100 microg/ml/kg; SC) or sesame oil vehicle. Males and OVX females receiving vehicle displayed normal LI. In contrast, LI was abolished in OVX females receiving EB. The lack of LI in OVX females receiving EB was a result of low suppression ratios, reflecting strong conditioning between the tone and the shock in these subjects even if they were pre-exposed to the tone. Thus, estrogen impaired the ability of OVX females to ignore irrelevant stimuli. Since different cognitive tasks vary in their required ability to ignore irrelevant stimuli, these results may account for some of the variations in the current literature on estrogen and cognition.

Implications for estrogens in Parkinson's disease: an epidemiological approach

Evidence from experimental and epidemiological studies suggests a role of sex hormones in the pathogenic process leading to neurodegenerative diseases, (i.e., Alzheimer's and Parkinson's disease). The effects of sexual steroid hormones are complex and vary with the events of women's fertile life. Estrogens are supposed to influence dopamine synthesis, metabolism, and transport; however, there is no consensus regarding the direction, locus, and mechanism of the effect of estrogens on the dopaminergic system. A neuroprotective effect of estrogens has been demonstrated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-animal models of Parkinson's disease (PD). Epidemiological studies indicate gender differences regarding the onset and the prognosis of PD. Most of the analytical studies explored the relationship between PD and exogenous estrogens. Only three studies investigated the role of endogenous estrogens in the risk of developing PD. These studies reported an increased risk of PD in conditions causing an early reduction in endogenous estrogens (early menopause, reduced fertile life length). Longer cumulative length of pregnancies has also been associated with an increased PD risk. A lack of consensus still exists on the effect of the type of menopause (surgical vs. natural) on PD risk. Finally, the effect of postmenopausal estrogen replacement therapy is still debated. Inconsistencies across studies are in part explained by the complexity of the mechanisms of action of sexual hormones and by the paucity of analytical studies.

Changes in the content of estrogen alpha and progesterone receptors during differentiation of mouse embryonic stem cells to dopamine neurons

Embryonic stem cells (ESC) can differentiate to derivatives of the three embryonic germ layers. Dopamine neurons have been produced from mouse and human ESC. This in vitro induction mimics the developmental program followed by dopaminergic cells in vivo. Production of dopamine neurons might have clinical applications for Parkinson's disease, which has a higher incidence in men than in women, suggesting a protective role for sex hormones, particularly progesterone and estradiol. These hormones exert many of their effects through the interaction with their nuclear receptors. In this study, we used a described 5-stage protocol for dopamine neuron differentiation of ESC, allowing neuronal commitment as evidenced by specific markers and by behavioural recovery of hemiparkinsonian rats after grafting. We studied the expression of steroid hormone receptors by immunoblot during this procedure and found an increase in the content of both A and B isoforms of progesterone receptor (PR) and a decrease in estrogen receptor alpha (ER-alpha) when cells were at the neural/neuronal stages, when compared with the amount found in initial pluripotent conditions. We also found the same pattern of PR and ER-alpha expression by immunocytochemistry. Ninety-two percent of dopamine neurons expressed progesterone receptors and only 19% of these neurons co-expressed tyrosine hydroxylase and ER-alpha. These results show a differential expression pattern of ER-alpha and PR isoforms during neuronal differentiation of ESC.

Dystonia gravidarum: A new case with a long follow-up

We report a case of cervical dystonia occurring in a 33-year-old without personal history of movement disorder but with family history of essential tremor, primigravid, primiparous woman at 1 weeks' amenorrhea, resolved completely after delivery in the course of 3 months. Dystonia never recurred in the following 5 years. Several neurological disorders are known to occur or worsen during pregnancy. As far as we know, this is the second reported case of dystonia occurring during pregnancy, thus confirming that dystonia gravidarum represents a new entity and should be considered in women of reproductive age affected by dystonia, especially when presenting with rapid-onset cervical dystonia.

Estrogen and the development and protection of nigrostriatal dopaminergic neurons: concerted action of a multitude of signals, protective molecules, and growth factors

The nigrostriatal dopamine system comprises the dopaminergic neurons located in the ventral midbrain, their axonal connections to the forebrain, and their direct cellular target cells in the striatal complex, i.e. GABAergic neurons. The major function of the nigrostriatal dopaminergic unit is the coordination and fine tuning of motor functions at the extrapyramidal level. Numerous biologically active factors including different types of growth factors (neurotrophins, members of the TGFbeta family, IGFs) and peptide/steroid hormones have been identified in the past to be implicated in the regulation of developmental aspects of this neural system. Some of these developmentally active determinants have in addition been found to play a crucial role in the mediation of neuroprotection concerning dopaminergic neurons. Estrogen was identified as such a compound interfering with embryonic neuronal differentiation and cell survival. The physiological mechanisms underlying these effects are very complex and include interactions with other developmental signals (growth factors), inflammatory processes as well as apoptotic events, but also require the activation of nonneuronal cells such as astrocytes. It appears that estrogen is assuming control over or at least influences a multitude of developmental and protective cellular mechanisms rather than taking over the part of a singular protagonist.

Dystonia gravidarum: A new entity?

We describe cervical dystonia occurring in a 31-year-old, previously well, primigravid, primiparous Chinese woman at 4 weeks' amenorrhea, which was ameliorated with low-dose clonazepam and disappeared completely by the end of the second trimester without recurring despite her being tapered off benzodiazepine therapy. Investigations were unremarkable for structural and biochemical causes of dystonia. Chorea, paraballismus, and restless legs syndrome are known to occur during pregnancy, attributable to high estrogen levels. Dystonia, on the other hand, has not been described to occur de novo in pregnancy. This association should be considered in women of reproductive age who present with cervical dystonia.

The neurobiology of postpartum depression

Postpartum psychiatric changes can range from maternity blues to psychosis. Causality is still undetermined, but explanations for these disturbances often focus on hormonal changes and dysregulation. Researchers have begun the process of delineating what neurobiological factors may be associated with depressive disorders in pregnancy and the postpartum. This article reviews the current literature on the roles of gonadal and pituitary hormones in the psychopathophysiology of postpartum mood disorders. Other biological factors, such as biogenic amines, neuroactive steroids, cholesterol, and fatty acids, are also discussed. The potential benefits of neuroimaging to aid in understanding neuropsychiatric changes that occur in the context of postpartum depression are also considered.

Gender and the Parkinson's disease phenotype

OBJECTIVES

To determine whether there are gender differences in the Parkinson's disease (PD) phenotype using a large clinic-based cohort.

METHODS

We examined gender differences in demographic, historical and clinical characteristics in a consecutive clinical series of 1,264 individuals diagnosed with PD.

RESULTS

The majority of individuals in the sample were male (67 %). Comparative analyses showed males and females were not significantly different on most demographic and historical characteristics. For both genders, the mean age and the mean age at symptomatic onset were about 70 and 63 years, respectively and, thus, disease duration was not significantly different between genders. The proportion of individuals with a positive family history of PD (15 %) was similar for both genders. A positive history of depression was significantly higher in females (35 % vs. 24 %). The UPDRS instability score was significantly worse among females, whereas the rigidity score was significantly worse for males. Females showed significantly worse ADL capacity and a more advanced H&Y stage. The proportion of individuals receiving antiparkinsonian medication (about 66 %) and time between the last dose and the clinical evaluation (about 4 hours) was similar for both genders. There was a trend for lower daily levodopa equivalence dosage and more severe dyskinesia score among females but these differences did not reach statistical significance after Bonferroni correction.

CONCLUSIONS

The majority of comparisons tended to highlight the commonalities in the PD phenotype between genders, particularly in reference to historical and early disease stage characteristics. However, gender may be an important factor related to the expression of PD features during the symptomatic disease course.

Sex differences in cytochrome P450 1B1, an estrogen-metabolizing enzyme, in the rhesus monkey telencephalon

The metabolic enzyme CYP1B1 is a recently cloned member of the cytochrome P450 superfamily, expressed widely throughout primate tissue, including the CNS. Although CYP1B1 protein is known to metabolize estradiol to catecholestrogens in the uterus, its localization and function in brain have not yet been described. To better understand CYP1B1 distribution, we have combined in situ hybridization (ISH) for its mRNA with immunohistochemistry (IHC) for the CYP1B1 protein in selected brain regions of male and female adult rhesus monkeys (Macaca mulatta). Blocks of formalin-fixed tissue obtained from the frontal cortex, hippocampus, thalamus, and amygdala were processed and embedded in paraffin. They were then sectioned and stained as described for human tissue [Muskhelishvili, L., Thompson, P.A., Kusewitt, D.F., Wang, C., Kadlubar, F.F., 2001. In situ hybridization and immunohistochemical analysis of cytochrome P450 1B1 expression in human normal tissues. J. Histochem. Cytochem. 49, 229-236]. Results indicated widespread distribution of CYP1B1 mRNA in both male and female monkey frontal cortex, hippocampus, thalamus, and amygdala. In contrast, although CYP1B1 protein was co-localized with its mRNA in the female brains, it was primarily restricted to hippocampal pyramidal neurons in the male brains. These results suggest that CYP1B1 may subserve widespread metabolic functions in the female primate brain but have more restricted actions within the hippocampal pyramidal neurons of the male.

Effects of estrogen replacement therapy on cholinergic basal forebrain neurons and cortical cholinergic innervation in young and aged ovariectomized rhesus monkeys

Estrogen modulates the function of cholinergic basal forebrain neurons in aged female rats. The present study tested the hypothesis that estrogen enhances the phenotype of cholinergic basal forebrain neurons and their cortical cholinergic innervation in young adult and aged ovariectomized rhesus monkeys. Sixteen monkeys (9 young and 7 aged) received two injections of estradiol cypionate or vehicle separated by 3 weeks. All monkeys were killed 1 day after the last injection. Quantitative immunofluorescence in the vertical limb of the diagonal band (VLDB) revealed enhanced optical density for choline acetyltransferase (ChAT) in both young and aged monkeys treated with estrogen. In contrast, optical density for low-affinity p75 neurotrophin receptor immunoreactivity in the VLDB did not change after estrogen treatment in either aged or young animals. Quantitative immunofluorescence for either ChAT or the low-affinity p75 neurotrophin receptor in the nucleus basalis Meynert failed to reveal differences between vehicle and estrogen treatment in either age group. Quantitative estimates of acetylcholinesterase (AChE) fiber density revealed that estrogen-treated aged monkeys but not their younger counterparts had decreased numbers of AChE-positive fibers in layer II of frontal, insular, and cingulate cortices. These data indicate that estrogen administered in a manner simulating natural hormonal cyclicity produces modest age-specific chemical phenotypic and regional changes in select neuronal subfields of the cholinergic basal forebrain and their cortical projection sites in nonhuman primates.

Effect of Bak Foong pills on enhancing dopamine release from the amygdala of female rats

To investigate whether Bak Foong Pills (BFP), a well-known gynaecological tonic, has a direct effect on the central nervous system, we employed the in vivo electrochemical detection technique, fast cyclic voltammetry (FCV), to measure the dopamine release from the mesolimbic structure-amygdala of both male and female rats. The results showed that intracerebroventricular BFP (0.75, 1.5 microg) treatment promoted dopamine release from the amygdala in both female and ovariectomized female rats. The BFP-induced response appeared within 5 min after addition of BFP and lasted for at least 40 min. However, no effect of BFP was observed in male rats for an observed period of up to 60 min. The results suggest that BFP may have gender-specific beneficial effect on dopaminergic functions of the amygdala.

Estrogen as neuroprotectant of nigrostriatal dopaminergic system: laboratory and clinical studies

In this review, we relate both laboratory and clinical evidence associated with the capacity for estrogen to function as a modulator of nigrostriatal dopaminergic pathology. To accomplish this goal, we have divided this review into three parts. In Part 1, we provide a brief historical perspective of studies that have laid the groundwork for demonstrating the existence of hormonal- nigrostriatal interactions. In Part 2, we focus specifically on laboratory data that show the ability and conditions by which estrogen may function as a neuroprotectant of the nigrostriatal dopaminergic system. Finally, in Part 3, we review the clinical literature related to this issue as a means for consideration of estrogen as a modulator, neuroprotectant, and therapy for Parkinson disease.

Menstrual cycle effects on hypothalamic dopamine receptor function in women with a history of puerperal bipolar disorder

Neuroendocrine challenge tests of hypothalamic dopamine receptor function in the early postpartum period suggest that the sensitivity of these receptors is increased in women with a history of bipolar disorder after childbirth. We tested the hypothesis that, in women predisposed to bipolar disorder in the puerperium, hypothalamic dopamine receptor function is more sensitive to changes in circulating ovarian hormone concentrations than in women without such histories. Eight fully recovered and drug-free women who had had at least one episode of bipolar illness following childbirth were compared with nine normal controls. Growth hormone (GH) responses to apomorphine (APO 0.005 mg s.c.) were measured in the early follicular phase, when plasma concentrations of ovarian hormones are low, and in the mid-luteal phase, when they are relatively high. The recovered bipolar subjects and the controls did not differ from each other in their follicular and midluteal oestrogen and progesterone concentrations. In the midluteal phase, both groups had increased oestrogen and progesterone levels. The recovered bipolar subjects did not differ from controls in baseline concentrations of GH in either of the menstrual phases. The APO-GH responses of the two groups did not differ in the follicular phase, but in the midluteal phase, when female sex steroids are relatively increased, the recovered group had significantly enhanced APO-GH responses [MANOVA for repeated measures: (i) area under the curve, group by phase effect: p < 0.04; (ii) GH peak rise after APO, group by phase effect: p < 0.056] and the responses were not related to concurrent measures of mood. The results of this small study of women predisposed to bipolar disorder in the puerperium shows an increased dopaminergic receptor sensitivity in the luteal phase of the menstrual cycle. It suggests that their dopaminergic systems have increased sensitivity to changes in circulating female sex steroids. This may be aetiologically relevant to the pathogenesis of puerperal bipolar disorder.

Prepulse inhibition of acoustic startle in aromatase knock-out mice: effects of age and gender

Estrogen has been suggested to play a neuromodulatory and neuroprotective role on the brain dopamine system. We used aromatase knockout (ArKO) mice that lack a functional aromatase enzyme and are unable to convert testosterone into estrogen, and assessed prepulse inhibition of acoustic startle, locomotor hyperactivity to amphetamine treatment and rotarod performance. Mice were tested at either 1 month, 4-5 months or 12-18 months of age. In male, but not female ArKO mice, there was an age-related reduction of prepulse inhibition. The 12-18 months old male ArKO mice also showed significantly greater amphetamine-induced hyperactivity. Mice heterozygous for the mutation showed no deficits or were in-between wildtype mice and ArKO mice. We postulate that these data indicate a neuroprotective role of estrogen, particularly in male mice, on ageing of brain mechanisms involved in pre-pulse inhibition and locomotor activity regulation. It is likely that these brain mechanisms are or include dopaminergic activity.

Gender-related differences in the effects of nitric oxide donors on neuroleptic-induced catalepsy in mice

It has been suggested that nigrostriatal dopaminergic transmission is modulated by nitric oxide (NO). Since there is evidence that gonadal hormones can affect extrapyramidal motor behavior in mammals, we investigated the effects of isosorbide dinitrate (ISD), linsidomine (SIN-1) and S-nitroso-N-acetylpenicillamine (SNAP), three pharmacologically different NO donors, on neuroleptic-induced catalepsy in 60- to 80-day-old male and female albino mice. Catalepsy was induced with haloperidol (1 mg/kg, ip) and measured at 30-min intervals by means of a bar test. Drugs (or appropriate vehicle) were injected ip 30 min before haloperidol, with each animal being used only once. ISD (5, 20 and 50 mg/kg) caused a dose-dependent inhibition of catalepsy in male mice (maximal effect 120 min after haloperidol: 64% inhibition). In the females only at the highest dose of ISD was an attenuation of catalepsy observed, which was mild and short lasting. SIN-1 (10 and 50 mg/kg) did not significantly affect catalepsy in female mice, while a significant attenuation was observed in males at the dose of 50 mg/kg (maximal inhibition: 60%). SNAP (20 mg/kg) significantly attenuated catalepsy in males 120 min after haloperidol (44% inhibition), but had no significant effect on females. These results basically agree with literature data showing that NO facilitates central dopaminergic transmission, although the mechanisms are not fully understood. They also reveal the existence of gender-related differences in this nitrergic modulation in mice, with females being less affected than males.