Early androgen treatment decreases cognitive function and catecholamine innervation in an animal model of ADHD

Relationship between acne vulgaris and attention deficit hyperactivity disorder in adolescent: A cross-sectional study

High androgen hormone exposure in intrauterine life is held to be responsible for the etiopathogenesis of both acne vulgaris (AV) and attention-deficit hyperactivity disorder (ADHD). In this study, we aimed to investigate the prevalence of ADHD in AV patients. Patients between the ages of 12 and 17, diagnosed with AV and a control group were included in the study. The Conners-Wells Adolescent Self-Report Scale-Long Form (CASS-L) was applied to both groups to determine the severity of the ADHD. Ninety-eight patients diagnosed with AV and 96 healthy controls participated in the study. All parameters of the CASS-L were found to be significantly higher in AV patients compared to the control group. In addition, with the severity of the Global Acne Grading System, a positive low level among conduct problems (r = 0.223), cognitive problems (r = 0.271), ADHD index (r = 0.238), inattention (r = 0.238), and a positive moderate level among hyperactivity (r = 0.349), hyperactivity-impulsivity (r = 0.414), and total score (r = 0.429). According to our results, patients diagnosed with AV were more prone to ADHD than the control group. Our study showed that adolescent patients diagnosed with AV were more prone to ADHD than people of similar age and gender without a diagnosis of AV. It should be noted that AV is not only a dermatological disease but may also be accompanied by psychiatric morbidities.

Phasic dopamine signals are reduced in the spontaneously hypertensive rat and increased by methylphenidate

The spontaneously hypertensive rat (SHR) is a selectively bred animal strain that is frequently used to model attention-deficit hyperactivity disorder (ADHD) because of certain genetically determined behavioural characteristics. To test the hypothesis that the characteristically altered response to positive reinforcement in SHRs may be due to altered phasic dopamine response to reward, we measured phasic dopamine signals in the SHRs and Sprague Dawley (SD) rats using in vivo fast-scan cyclic voltammetry. The effects of the dopamine reuptake inhibitor, methylphenidate, on these signals were also studied. Phasic dopamine signals during the pairing of a sensory cue with electrical stimulation of midbrain dopamine neurons were significantly smaller in the SHRs than in the SD rats. Over repeated pairings, the dopamine response to the sensory cue increased, whereas the response to the electrical stimulation of dopamine neurons decreased, similarly in both strains. However, the final amplitude of the response to the sensory cue after pairing was significantly smaller in SHRs than in the SD rats. Methylphenidate increased responses to sensory cues to a significantly greater extent in the SHRs than in the SD rats, due largely to differences in the low dose effect. At a higher dose, methylphenidate increased responses to sensory cues and electrical stimulation similarly in SHRs and SD rats. The smaller dopamine responses may explain the reduced salience of reward-predicting cues previously reported in the SHR, whereas the action of methylphenidate on the cue response suggests a potential mechanism for the therapeutic effects of low-dose methylphenidate in ADHD.

Hippocampus under Pressure: Molecular Mechanisms of Development of Cognitive Impairments in SHR Rats

Data from clinical trials and animal experiments demonstrate relationship between chronic hypertension and development of cognitive impairments. Here, we review structural and biochemical alterations in the hippocampus of SHR rats with genetic hypertension, which are used as a model of essential hypertension and vascular dementia. In addition to hypertension, dysfunction of the hypothalamic-pituitary-adrenal system observed in SHR rats already at an early age may be a key factor of changes in the hippocampus at the structural and molecular levels. Global changes at the body level, such as hypertension and neurohumoral dysfunction, are associated with the development of vascular pathology and impairment of the blood-brain barrier. Changes in multiple biochemical glucocorticoid-dependent processes in the hippocampus, including dysfunction of steroid hormones receptors, impairments of neurotransmitter systems, BDNF deficiency, oxidative stress, and neuroinflammation are accompanied by the structural alterations, such as cellular signs of neuroinflammation micro- and astrogliosis, impairments of neurogenesis in the subgranular neurogenic zone, and neurodegenerative processes at the level of synapses, axons, and dendrites up to the death of neurons. The consequence of this is dysfunction of hippocampus, a key structure of the limbic system necessary for cognitive functions. Taking into account the available results at various levels starting from the body and brain structure (hippocampus) levels to molecular one, we can confirm translational validity of SHR rats for modeling mechanisms of vascular dementia.

Parvalbumin interneuron deficiency in the prefrontal and motor cortices of spontaneously hypertensive rats: an attention-deficit hyperactivity disorder animal model insight

Background

Attention deficit hyperactivity disorder (ADHD) is characterized by impairments in developmental-behavioral inhibition, resulting in impulsivity and hyperactivity. Recent research has underscored cortical inhibition deficiencies in ADHD via the gamma-aminobutyric acid (GABA)ergic system, which is crucial for maintaining excitatory-inhibitory balance in the brain. This study explored postnatal changes in parvalbumin (PV) immunoreactivity, indicating GABAergic interneuron types, in the prefrontal (PFC) and motor (MC) cortices of spontaneously hypertensive rats (SHRs), an ADHD animal model.

Methods

Examining PV- positive (PV+) cells associated with dopamine D2 receptors (D2) and the impact of dopamine on GABA synthesis, we also investigated changes in the immunoreactivity of D2 and tyrosine hydroxylase (TH). Brain sections from 4- to 10-week-old SHRs and Wistar Kyoto rats (WKYs) were immunohistochemically analyzed, comparing PV+, D2+ cells, and TH+ fiber densities across age-matched SHRs and WKYs in specific PFC/MC regions.

Results

The results revealed significantly reduced PV+ cell density in SHRs: prelimbic (~20% less), anterior cingulate (~15% less), primary (~15% less), and secondary motor (~17% less) cortices. PV+ deficits coincided with the upregulation of D2 in prepubertal SHRs and the downregulation of TH predominantly in pubertal/postpubertal SHRs.

Conclusion

Reduced PV+ cells in various PFC regions could contribute to inattention/behavioral alterations in ADHD, while MC deficits could manifest as motor hyperactivity. D2 upregulation and TH deficits may impact GABA synthesis, exacerbating behavioral deficits in ADHD. These findings not only shed new light on ADHD pathophysiology but also pave the way for future research endeavors.

Excess neonatal testosterone causes male-specific social and fear memory deficits in wild-type mice

Neurodevelopmental disorders (ND) disproportionately affect males compared to females, and Autism Spectrum Disorder (ASD) in particular exhibits a 4:1 male bias. The biological mechanisms of this female protection or male susceptibility have not been identified. There is some evidence to suggest that fetal/neonatal gonadal hormones, which play pivotal roles in many aspects of development, may contribute. Here, we investigate the role of testosterone administration during a critical period of development, and its effects on social approach and fear learning in C57BL/6J wildtype mice. Male, but not female mice treated with testosterone on the day of birth (PN0) exhibited deficits in both social behavior and contextual fear conditioning, whereas mice treated with the same dose of testosterone on postnatal day 18 (PN18) did not display such impairments. Testosterone administration did not induce anxiogenic effects or lead to changes in body weight compared to the vehicle-treated group. These impairmeants are relevant to ND and may help identify novel treatment targets.

Sex, hormones and cerebrovascular function: from development to disorder

Proper cerebrovascular development and neurogliovascular unit assembly are essential for brain growth and function throughout life, ensuring the continuous supply of nutrients and oxygen. This involves crucial events during pre- and postnatal stages through key pathways, including vascular endothelial growth factor (VEGF) and Wnt signaling. These pathways are pivotal for brain vascular growth, expansion, and blood-brain barrier (BBB) maturation. Interestingly, during fetal and neonatal life, cerebrovascular formation coincides with the early peak activity of the hypothalamic-pituitary-gonadal axis, supporting the idea of sex hormonal influence on cerebrovascular development and barriergenesis.Sex hormonal dysregulation in early development has been implicated in neurodevelopmental disorders with highly sexually dimorphic features, such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Both disorders show higher prevalence in men, with varying symptoms between sexes, with boys exhibiting more externalizing behaviors, such as aggressivity or hyperactivity, and girls displaying higher internalizing behaviors, including anxiety, depression, or attention disorders. Indeed, ASD and ADHD are linked to high prenatal testosterone exposure and reduced aromatase expression, potentially explaining sex differences in prevalence and symptomatology. In line with this, high estrogen levels seem to attenuate ADHD symptoms. At the cerebrovascular level, sex- and region-specific variations of cerebral blood flow perfusion have been reported in both conditions, indicating an impact of gonadal hormones on the brain vascular system, disrupting its ability to respond to neuronal demands.This review aims to provide an overview of the existing knowledge concerning the impact of sex hormones on cerebrovascular formation and maturation, as well as the onset of neurodevelopmental disorders. Here, we explore the concept of gonadal hormone interactions with brain vascular and BBB development to function, with a particular focus on the modulation of VEGF and Wnt signaling. We outline how these pathways may be involved in the underpinnings of ASD and ADHD. Outstanding questions and potential avenues for future research are highlighted, as uncovering sex-specific physiological and pathological aspects of brain vascular development might lead to innovative therapeutic approaches in the context of ASD, ADHD and beyond.

Spontaneously hypertensive rats vs. Wistar Kyoto and Wistar rats: an assessment of anxiety, motor activity, memory performance, and seizure susceptibility

Spontaneously hypertensive rats (SHRs) are widely accepted for modeling essential hypertension and Attention deficit hyperactivity disorder (ADHD). However, data concerning central nervous system changes associated with behavioral responses of this strain and usage of Wistar Kyoto (WKY) rats as controls are confounding. The objective of the present study was to assess the impact of anxiety and motor activity on the cognitive responses of SHRs compared to Wistar and WKY rats. In addition, the role of brain-derived neurotrophic factor (BDNF) in the hippocampus on cognitive behavior and seizure susceptibility in the three strains was evaluated. In Experiment#1, SHR demonstrated impulsive responses in the novelty suppression feeding test accompanied by impaired spatial working and associative memory in the Y maze and object recognition test compared with the Wistar rat but not WKY rats. In addition, the WKY rats exhibited diminished activity compared to Wistar rats in an actimeter. In Experiment#2, the seizure susceptibility was assessed by 3-min electroencephalographic (EEG) recording after two consecutive injections of pentylenetetrazol (PTZ) (20+40 mg/kg). The WKY rats were more vulnerable to rhythmic metrazol activity (RMA) than the Wistar rats. In contrast, Wistar rats were more prone to generalized tonic-clonic seizures (GTCS) than WKY rats and SHRs. Control SHR had lower BDNF expression in the hippocampus compared to Wistar rats. However, while the BDNF levels were elevated in the Wistar and WKY rats after PTZ injection, no change in this signaling molecule was observed in the SHR in the seizure condition. The results suggest Wistar rats as a more appropriate control of SHR than WKY rats for studying memory responses mediated by BDNF in the hippocampus. The higher vulnerability to seizures in Wistar and WKY rats compared to SHR might be linked to PTZ-induced decreased expression of BDNF in the hippocampus.

Trace amine-associated receptor 1 modulates motor hyperactivity, cognition, and anxiety-like behavior in an animal model of ADHD

Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor that has recently been implicated in several psychiatric conditions related to monoaminergic dysfunction, such as schizophrenia, substance use disorders, and mood disorders. Although attention-deficit/hyperactivity disorder (ADHD) is also related to changes in monoaminergic neurotransmission, studies that assess whether TAAR1 participates in the neurobiology of ADHD are lacking. We hypothesized that TAAR1 plays an important role in ADHD and might represent a potential therapeutic target. Here, we investigate if TAAR1 modulates behavioral phenotypes in Spontaneously Hypertensive Rats (SHR), the most validated animal model of ADHD, and Wistar Kyoto rats (WKY, used as a control strain). Our results showed that TAAR1 is downregulated in ADHD-related brain regions in SHR compared with WKY. While intracerebroventricular (i.c.v.) administration of the selective TAAR1 antagonist EPPTB impaired cognitive performance in SHR, i.c.v. administration of highly selective TAAR1 full agonist RO5256390 decreased motor hyperactivity, novelty-induced locomotion, and induced an anxiolytic-like behavior. Overall, our findings show that changes in TAAR1 levels/activity underlie behavior in SHR, suggesting that TAAR1 plays a role in the neurobiology of ADHD. Although additional confirmatory studies are required, TAAR1 might be a potential pharmacological target for individuals with this disorder.

Maternal polycystic ovary syndrome and attention deficit hyperactivity disorder in offspring at 3 years of age: Odense Child Cohort

INTRODUCTION

Previous data suggested a link between maternal polycystic ovary syndrome (PCOS) and offspring attention deficit hyperactivity disorder (ADHD), which could be mediated by higher prenatal androgen exposure.

MATERIAL AND METHODS

The study was part of the prospective Odense Child Cohort and included 1776 pregnant women, 165 (9%) with PCOS and 1607 (91%) controls. ADHD symptoms at 3 years of age were defined using the parent-reported questionnaire Child Behavior Checklist/1.5-5 (scores >90th centile of Danish national standard). Maternal blood samples were collected in the third trimester measuring total testosterone by mass spectrometry, sex hormone-binding globulin, and calculated free testosterone. Offspring anogenital distance was measured at 3 months of age. Regression models were performed with presence of ADHD symptoms as the dependent variable and adjusted for maternal age, body mass index, parity, smoking status, educational level, and parental psychiatric diagnoses.

RESULTS

ADHD symptoms were present in 105/937 (11%) boys and 72/839 (9%) girls. In boys, maternal PCOS was positively associated with ADHD symptoms (unadjusted odds ratio [OR] 1.91, 95% CI 1.07-3.43, p = 0.03, adjusted OR 2.20, 95% CI 1.20-4.02, p = 0.01), whereas maternal PCOS was not associated with ADHD symptoms in girls. Maternal total testosterone, free testosterone, and offspring anogenital distance were not associated with higher risk of ADHD symptoms in the offspring.

CONCLUSIONS

Higher risk of ADHD in boys born of mothers with PCOS were not associated with maternal third-trimester testosterone levels or offspring anogenital distance.

Testosterone Treatment Mimics Seasonal Downregulation of Dopamine Innervation in the Auditory System of Female Midshipman Fish

In seasonally breeding vertebrates, hormones coordinate changes in nervous system structure and function to facilitate reproductive readiness and success. Steroid hormones often exert their effects indirectly via regulation of neuromodulators, which in turn can coordinate the modulation of sensory input with appropriate motor output. Female plainfin midshipman fish (Porichthys notatus) undergo increased peripheral auditory sensitivity in time for the summer breeding season, improving their ability to detect mates, which is regulated by steroid hormones. Reproductive females also show differences in catecholaminergic innervation of auditory circuitry compared with winter, non-reproductive females as measured by tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholaminergic synthesis. Importantly, catecholaminergic input to the inner ear from a dopaminergic-specific forebrain nucleus is decreased in the summer and dopamine inhibits the sensitivity of the inner ear, suggesting that gonadal steroids may alter auditory sensitivity by regulating dopamine innervation. In this study, we gonadectomized non-reproductive females, implanted them with estradiol (E2) or testosterone (T), and measured TH immunoreactive (TH-ir) fibers in auditory nuclei where catecholaminergic innervation was previously shown to be seasonally plastic. We found that treatment with T, but not E2, reduced TH-ir innervation in the auditory hindbrain. T-treatment also reduced TH-ir fibers in the forebrain dopaminergic cell group that projects to the inner ear, and likely to the auditory hindbrain. Higher T plasma in the treatment group was correlated with reduced-ir TH terminals in the inner ear. These T-treatment induced changes in TH-ir fibers mimic the seasonal downregulation of dopamine in the midshipman inner ear and provide evidence that steroid hormone regulation of peripheral auditory sensitivity is mediated, in part, by dopamine.

Changes in the mesocorticolimbic pathway after low dose reserpine-treatment in Wistar and Spontaneously Hypertensive Rats (SHR): Implications for cognitive deficits in a progressive animal model for Parkinson's disease

Reserpine (RES) is an irreversible inhibitor of VMAT2 used to study Parkinson's disease (PD) and screening for antiparkinsonian treatments in rodents. Recently, the repeated treatment with a low dose of reserpine was proposed as a model capable of emulating progressive neurochemical, motor and non-motor impairments in PD. Conversely, compared to Wistar rats, Spontaneously Hypertensive Rats (SHR) are resistant to motor changes induced by repeated treatment with a low dose of RES. However, such resistance has not yet been investigated for RES-induced non-motor impairments. We aimed to assess whether SHR would have differential susceptibility to the object recognition deficit induced by repeated low-dose reserpine treatment. We submitted male Wistar and SHR rats to repeated RES treatment (15 s.c. injections of 0.1 mg/kg, every other day) and assessed object memory acquisition and retrieval 48 h after the 6^th RES injection (immediately before the appearance of motor impairments). Only RES Wistar rats displayed memory impairment after reserpine treatment. On the other hand, untreated SHR rats displayed object recognition memory deficit, but RES treatment restored such deficits. We also performed immunohistochemistry for tyrosine hydroxylase (TH) and α-synuclein (α-syn) 48 h after the last RES injection. In a different set of animals submitted to the same treatment, we quantified DA, 5-HT and products of lipid peroxidation in the prefrontal cortex (PFC) and hippocampus (HPC). SHR presented increased constitutive levels of DA in the PFC and reduced immunoreactivity to TH in the medial PFC and dorsal HPC. Corroborating the behavioral findings, RES treatment restored those constitutive alterations in SHR. These findings indicate that the neurochemical, molecular and genetic differences in the SHR strain are potentially relevant targets to the study of susceptibility to diseases related to dopaminergic alterations.

Transcranial direct current stimulation (tDCS) affects neuroinflammation parameters and behavioral seizure activity in pentylenetetrazole-induced kindling in rats

Despite the introduction of new antiepileptic drugs, about 30 % of patients with epilepsy are refractory to drug therapy. Thus, the search for non-pharmacological interventions such as transcranial direct current stimulation (tDCS) may be an alternative, either alone or in combination with low doses of anticonvulsants. This study evaluated the effect of anodal (a-tDCS) and cathodal tDCS (c-tDCS) on seizure behavior and neuroinflammation parameters. Rats were submitted to the kindling model induced by pentylenetetrazole (PTZ) using diazepam (DZP) as anticonvulsant standard. tDCS groups were submitted to 10 sessions of a-tDCS or c-tDCS or SHAM-tDCS. Every 3 days they received saline (SAL), low dose of DZP (alone or in combination with tDCS) or effective dose of DZP 30 min before administration of PTZ, totaling 16 days of protocol. Neither a-tDCS nor c-tDCS reduced the occurrence of clonic forelimb seizures (convulsive motor seizures - stage 3 by the adapted Racine scale we based on). Associated with DZP, c-tDCS (c-tDCS/DZP0.15) increased the latency to first clonic forelimb seizure on the 10th and 16th days. Hippocampal IL-1β levels were reduced by c-tDCS and c-tDCS/DZP0.15. In contrast, these treatments induced an increase in cortical IL-1β levels. Hippocampal TNF-α levels were not altered by c-tDCS or a-tDCS, but c-tDCS and c-tDCS/DZP0.15 increased those levels in cerebral cortex. Cortical NGF levels were increased by c-tDCS and c-tDCS/DZP0.15. a-tDCS/DZP0.15 reduced hippocampal BDNF levels and c-tDCS/DZP0.15 increased these levels in cerebral cortex. In conclusion, c-tDCS alone or in combination with a low dose of DZP showed to affect neuroinflammation, improving central neurotrophin levels and decreasing hippocampal IL-1β levels after PTZ-induced kindling without statistically significant effect on seizure behavior.

Diffusion tensor imaging reveals microstructural alterations in corpus callosum and associated transcallosal fiber tracts in adult macaques with neonatal hippocampal lesions

To investigate the effects of neonatal hippocampal lesions on the microstructural integrity of the corpus callosum (CC) in adulthood, macaque monkeys (n = 5) with neonatal bilateral neurotoxic hippocampal lesion (Neo-Hibo) and sham-operated controls (Neo-C, n = 5) were scanned using magnetic resonance diffusion tensor imaging (DTI) technique at 8-10 years old. CC was segmented into seven regionsgrouped into anterior CC (rostrum, genu, rostral body and anterior midbody) and posterior CC (posterior midbody, isthmus and splenium) for data analysis. Associated transcallosal fiber tracts were delineated using probabilistic tractography and evaluated with tract-based spatial statistics (TBSS). Neo-Hibo lesions resulted in significant increased diffusivity indices (mean, axial and radial diffusivity) in CC posterior segments. Also, significant decreased fractional anisotropy (FA) and increased diffusivity indices were seen in the associated transcallosal fiber tracts proximal to motor, posterior parietal and retrosplenial cortices. In Neo-Hibo animals, increased mean diffusivity (MD) in posterior midbody negatively correlated with reduction of CC surface areaand the magnitude of their memory impairments was significantly correlated with FA in transcallosal fiber tracts across splenium. Although no microstructural changes were observed in CC anterior segments, changes in FA values and diffusivity indices were observed in the white matter fibers of the ventromedial prefrontal cortex. Thus, Neo-H lesions resulted in enduring degradation in transcallosal fibers proximal to parietal and retrosplenial cortices, and hemispheric connections through posterior CC. The findings may provide complementary information for understanding the neural substrate of behavioral and cognitive deficits observed in patients with early insult to the hippocampus.

Differences in serum steroid hormones concentrations in Spontaneously Hypertensive Rats (SHR) - an animal model of Attention-Deficit/Hyperactivity Disorder (ADHD)

Spontaneously hypertensive rats are the most common animal model used to study attention deficit hyperactivity disorder (ADHD). The present study investigated the levels of steroid hormones in the bloodstream of hypertensive rats and its normotensive control strain, Wistar-Kyoto rats, to check if there are any hormonal differences between both strains at the onset of ADHD. Plasma samples were collected from young (5-week-old) and mature (10-week-old) male hypertensive and normotensive rats to determine the serum level of testosterone, 17beta-estradiol, free estriol, progesterone, corticosterone and cortisol using ELISA kits. The results showed statistically significant increases in serum levels of testosterone and free estriol in 10-week-old hypertensive and normotensive rats when compared to 5-week-old animals. Moreover, the concentrations of progesterone, corticosterone and cortisol were significantly elevated in 10-week-old hypertensive rats when compared to 5-week-old animals of both strains as well as 10-week-old normotensive rats. Hormonal differences observed between 10-week-old hypertensive and normotensive rats were also accompanied by differences in the volumes of lateral ventricles as well as the third ventricle and cerebral aqueduct. In conclusion, elevated contents of progesterone, corticosterone and cortisol in hypertensive rats may be associated not only with ADHD but also with developing hypertension. This question needs further study.

Developmental exposures to ultrafine particle air pollution reduces early testosterone levels and adult male social novelty preference: Risk for children's sex-biased neurobehavioral disorders

Epidemiological studies have reported associations of air pollution exposures with various neurodevelopmental disorders such as autism spectrum disorder (ASD), attention deficit and schizophrenia, all of which are male-biased in prevalence. Our studies of early postnatal exposure of mice to the ultrafine particle (UFP) component of air pollution, considered the most reactive component, provide support for these epidemiological associations, demonstrating male-specific or male-biased neuropathological changes and cognitive and impulsivity deficits consistent with these disorders. Since these neurodevelopmental disorders also include altered social behavior and communication, the current study examined the ability of developmental UFP exposure to reproduce these social behavior deficits and to determine whether any observed alterations reflected changes in steroid hormone concentrations. Elevated plus maze, social conditioned place preference, and social novelty preference were examined in adult mice that had been exposed to concentrated (10-20x) ambient UFPs averaging approximately 45 ug/m³ particle mass concentrations from postnatal day (PND) 4-7 and 10-13 for 4 h/day. Changes in serum testosterone (T) and corticosterone where measured at postnatal day (P)14 and approximately P120. UFP exposure decreased serum T concentrations on PND 14 and social nose-to-nose sniff rates with novel males in adulthood, suggesting social communication deficits in unfamiliar social contexts. Decreased sniff rates were not accounted for by alterations in fear-mediated behaviors and occurred without overt deficits in social preference, recognition or communication with a familiar animal or alterations in corticosterone. Adult T serum concentrations were positively correlated with nose to nose sniff rates. Collectively, these studies confirm another feature of male-biased neurodevelopmental disorders following developmental exposures to even very low levels of UFP air pollution that could be related to alterations in sex steroid programming of brain function.

Maternal Polycystic Ovary Syndrome and Risk for Attention-Deficit/Hyperactivity Disorder in the Offspring

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is the most common childhood neurodevelopmental disorder, and boys are two to three times more likely to develop ADHD. Maternal polycystic ovary syndrome (PCOS), a common metabolic disorder associated with excess circulating androgens, has been associated with increased risk for autism spectrum disorder in the offspring. In this study, we aimed to investigate whether maternal PCOS increases the risk for ADHD in the offspring.

METHODS

We conducted a matched case-control study using health and population data registers for all children born in Sweden from 1984 to 2008. Maternal PCOS was defined by ICD-coded register diagnosis. The outcome of ADHD was defined as an ICD-coded register diagnosis of ADHD and/or registered prescription of medications to treat ADHD. A total of 58,912 ADHD cases (68.8% male) were identified and matched to 499,998 unaffected controls by sex and birth month and year.

RESULTS

Maternal PCOS increased the odds of offspring ADHD by 42% after adjustment for confounders (odds ratio [OR], 1.42; 95% confidence interval [CI], 1.26-1.58). Exclusion of ADHD cases with comorbid autism spectrum disorder attenuated but did not explain the relationship (OR, 1.34; 95% CI, 1.18-1.52). The risk was somewhat elevated for ADHD with comorbid autism spectrum disorder (OR, 1.76; 95% CI, 1.37-2.26). The risk for ADHD was higher among obese mothers with PCOS (OR, 1.68; 95% CI, 1.31-2.17) and was highest among obese mothers with PCOS and other features of metabolic syndrome (OR, 2.59; 95% CI, 1.02-6.58).

CONCLUSIONS

This study provides evidence that maternal PCOS may subtly influence the neurodevelopment of the offspring, resulting in increased risk for neurodevelopmental disorders such as ADHD.

Maternal salivary testosterone in pregnancy and fetal neuromaturation

Testosterone exposure during pregnancy has been hypothesized as a mechanism for sex differences in brain and behavioral development observed in the postnatal period. The current study documents the natural history of maternal salivary testosterone from 18 weeks gestation of pregnancy to 6 months postpartum, and investigates associations with fetal heart rate, motor activity, and their integration. Findings indicate maternal salivary testosterone increases with advancing gestation though no differences by fetal sex were detected. High intra-individual stability in prenatal testosterone levels extend into the postnatal period, particularly for pregnancies with male fetuses. With respect to fetal development, by 36 weeks gestation higher maternal prenatal salivary testosterone was significantly associated with faster fetal heart rate and less optimal somatic-cardiac integration. Measurement of testosterone in saliva is a useful tool for repeated-measures studies of hormonal concomitants of pregnancy. Moreover, higher maternal testosterone levels are associated with modest interference to fetal neurobehavioral development.

Masculinization in Parents of Offspring With Autism Spectrum Disorders Could Be Involved in Comorbid ADHD Symptoms

OBJECTIVE

People with autism spectrum disorders (ASD) often have comorbid ADHD symptoms. ASD and ADHD are both associated with high intrauterine testosterone (T) levels. This study aims to investigate whether masculinization predicts inattention symptoms in parents, and in their ASD-affected offspring.

METHOD

The sample consisted of 32 parents with ASD-affected children (13 male, 19 female) and 32 offspring individuals (28 male, 4 female). Masculinization of parents was measured by 2D:4D finger ratio, and current T levels. Inattention in both parents and in their offspring was measured with behavior questionnaires.

RESULTS

The results indicated that masculinized 2D:4D explains inattentive ADHD symptoms in ASD parents and in their offspring. These predictions are mediated by T and inattention symptoms of ASD parents, respectively.

CONCLUSION

These findings suggest the existence of a masculinized endophenotype in ASD parents, which may be characterized by high attentional sensitivity to T effects.

Postnatal testosterone may be an important mediator of the association between prematurity and male neurodevelopmental disorders: a hypothesis

Children born premature are at risk for neurodevelopmental disorders, including autism and schizophrenia. This piece advances the hypothesis that altered androgen exposure observed in premature infants is an important mediator of the neurodevelopmental risk in males associated with prematurity. Specifically, the alterations of normative physiologic postnatal activations of the hypothalamic-pituitary-gonadal axis that occur in preterm males are hypothesized to contribute to the risk of neuropsychiatric pathology of prematurity through altered androgen-mediated organizational effects on the developing brain. The physiology of testosterone and male central nervous system development in full-term births is reviewed and compared to the developmental processes of prematurity. The effects of the altered testosterone physiology observed within prematurity outside of the central nervous system are reviewed as a segue into a discussion of the effects within the nervous system, with a special focus on autism spectrum disorders and attention deficit hyperactivity disorder. The explanatory power of this model is reviewed as a supplement to the preexisting models of prematurity and neurodevelopmental risk, including infection and other perinatal central nervous system insults. The emphasis is placed on altered androgen exposure as serving as just one among many mediators of neurodevelopmental risk that may be of interest for further research and evidence-based investigation. Implications for diagnosis, management and preventative treatments conclude the piece.

Innervation of the medial prefrontal cortex by tyrosine hydroxylase immunoreactive fibers during adolescence in male and female rats

Adolescence is associated with continued maturation of the cerebral cortex, particularly the medial prefrontal cortex (mPFC). We have previously documented pruning in the number of neurons, dendrites, and synapses in the rat mPFC from preadolescence to adulthood, with the period of pubertal onset being particularly important. We hypothesized that dopaminergic innervation of this region, critical for executive functions, would also be influenced by pubertal onset. Here, we measured changes in the volume of tyrosine hydroxylase (TH) immunoreactive axons in all layers of the male and female mPFC from preadolescence to adulthood (postnatal Day (P) 25, 35, 45, 60, and 90) as a marker of dopaminergic innervation. Assessing both total fiber volume and length, TH fibers were quantified by multiplying the mPFC volume by fiber density. While there were subtle layer-specific changes, TH fiber volume and length increased between P25 and P90 in both males and females. Contrary to our hypothesis, a role for pubertal onset in TH innervation of this region was not discernable. In summary, axons immunoreactive for TH increase with similar trajectories in the mPFC of male and female rats from pre-puberty to young adulthood.

Spontaneously Hypertensive Rats (SHR) Are Resistant to a Reserpine-Induced Progressive Model of Parkinson's Disease: Differences in Motor Behavior, Tyrosine Hydroxylase and α-Synuclein Expression

Reserpine is an irreversible inhibitor of vesicular monoamine transporter-2 (VMAT2) used to study Parkinson’s disease (PD) and screening for antiparkinsonian treatments in rodents. Recently, the repeated treatment with a low-dose of reserpine was proposed as a progressive model of PD. Rats under this treatment show progressive catalepsy behavior, oral movements and spontaneous motor activity decrement. In parallel, compared to Wistar rats, spontaneously hypertensive rats (SHR) are resistant to acute reserpine-induced oral dyskinesia. We aimed to assess whether SHR would present differential susceptibility to repeated reserpine-induced deficits in the progressive model of PD. Male Wistar and SHR rats were administered 15 subcutaneously (s.c.) injections of reserpine (0.1 mg/kg) or vehicle, every other day and motor activity was assessed by the catalepsy, oral movements and open field tests. Only reserpine-treated Wistar rats presented increased latency to step down in the catalepsy test and impaired spontaneous activity in the open field. On the other hand, there was an increase in oral movements in both reserpine-treated strains, although with reduced magnitude and latency to instauration in SHR. After a 15-day withdrawn period, both strains recovered from motor impairment, but SHR animals expressed reduced latencies to reach control levels. Finally, we performed immunohistochemistry for tyrosine hydroxylase (TH) and α-synuclein (α-syn) 48 h after the last injection or 15 days after withdrawn. Reserpine-treated animals presented a reduction in TH and an increase in α-syn immunoreactivity in the substantia nigra and dorsal striatum (dSTR), which were both recovered after 15 days of withdraw. Furthermore, SHR rats were resistant to reserpine-induced TH decrement in the substantia nigra, and presented reduced immunoreactivity to α-syn in the dSTR relative to Wistar rats, irrespective of treatment. This effect was accompanied by increase of malondaldhyde (MDA) in the striatum of reserpine-treated Wistar rats, while SHR presented reduced MDA in both control and reserpine conditions relative to Wistar strain. In conclusion, the current results show that SHR are resilient to motor and neurochemical impairments induced by the repeated low-dose reserpine protocol. These findings indicate that the neurochemical, molecular and genetic differences in the SHR strain are potential relevant targets to the study of susceptibility to PD.

Programming of Dopaminergic Neurons by Neonatal Sex Hormone Exposure: Effects on Dopamine Content and Tyrosine Hydroxylase Expression in Adult Male Rats

We sought to determine the long-term changes produced by neonatal sex hormone administration on the functioning of midbrain dopaminergic neurons in adult male rats. Sprague-Dawley rats were injected subcutaneously at postnatal day 1 and were assigned to the following experimental groups: TP (testosterone propionate of 1.0 mg/50 μL); DHT (dihydrotestosterone of 1.0 mg/50 μL); EV (estradiol valerate of 0.1 mg/50 μL); and control (sesame oil of 50 μL). At postnatal day 60, neurochemical studies were performed to determine dopamine content in substantia nigra-ventral tegmental area and dopamine release in nucleus accumbens. Molecular (mRNA expression of tyrosine hydroxylase) and cellular (tyrosine hydroxylase immunoreactivity) studies were also performed. We found increased dopamine content in substantia nigra-ventral tegmental area of TP and EV rats, in addition to increased dopamine release in nucleus accumbens. However, neonatal exposure to DHT, a nonaromatizable androgen, did not affect midbrain dopaminergic neurons. Correspondingly, compared to control rats, levels of tyrosine hydroxylase mRNA and protein were significantly increased in TP and EV rats but not in DHT rats, as determined by qPCR and immunohistochemistry, respectively. Our results suggest an estrogenic mechanism involving increased tyrosine hydroxylase expression, either by direct estrogenic action or by aromatization of testosterone to estradiol in substantia nigra-ventral tegmental area.

Attention deficit-hyperactivity disorder symptoms in women with polycystic ovary syndrome

OBJECTIVES

Several studies suggest that androgens are involved in the etiology of attention deficit-hyperactivity disorder (ADHD). In this study, we investigated the ADHD symptoms in women with polycystic ovary syndrome (PCOS), a complex endocrine, hormonal, and metabolic condition associated with hyperandrogenism.

METHODS

Forty women between the ages of 18 and 35 years with PCOS were recruited for the study group. For comparison, 40 healthy women who had regular menses were included. Current and childhood ADHD symptoms were assessed by using the Adult ADHD Self-Report Scale and Wender-Utah Rating Scale, respectively.

RESULTS

Women with PCOS had higher total Adult ADHD Self-Report Scale and total Wender-Utah Rating Scale scores than controls. According to the Wender-Utah Rating Scale, the frequency of childhood ADHD was significantly higher in PCOS group than the control. Adult ADHD Self-Report Scale: Hyperactivity-Impulsivity and Wender-Utah Rating Scale: Behavioral Problems/Impulsivity scores were significantly higher in women with PCOS. However, there were no significant differences between groups in both current and childhood inattention scores. We found no correlations between ADHD symptoms and serum hormone levels including testosterone in women with PCOS.

CONCLUSIONS

These results suggest that women with PCOS have higher ADHD symptoms. Further studies are needed to investigate the association between PCOS and ADHD.

On the effects of testosterone on brain behavioral functions

Testosterone influences the brain via organizational and activational effects. Numerous relevant studies on rodents and a few on humans focusing on specific behavioral and cognitive parameters have been published. The results are, unfortunately, controversial and puzzling. Dosing, timing, even the application route seem to considerably affect the outcomes. In addition, the methods used for the assessment of psychometric parameters are a bit less than ideal regarding their validity and reproducibility. Metabolism of testosterone contributes to the complexity of its actions. Reduction to dihydrotestosterone by 5-alpha reductase increases the androgen activity; conversion to estradiol by aromatase converts the androgen to estrogen activity. Recently, the non-genomic effects of testosterone on behavior bypassing the nuclear receptors have attracted the interest of researchers. This review tries to summarize the current understanding of the complexity of the effects of testosterone on brain with special focus on their role in the known sex differences.

Sex differences in attention Deficit Hyperactivity Disorder: candidate genetic and endocrine mechanisms

Attention Deficit Hyperactivity Disorder (ADHD) is a developmental condition characterised by severe inattention, pathological impulsivity and hyperactivity; it is relatively common affecting up to 6% of children, and is associated with a risk of long-term adverse educational and social consequences. Males are considerably more likely to be diagnosed with ADHD than females; the course of the disorder and its associated co-morbidities also appear to be sensitive to sex. Here, I discuss fundamental biological (genetic and endocrine) mechanisms that have been shown to, or could theoretically, contribute towards these sexually dimorphic phenomena. Greater understanding of how and why the sexes differ with respect to ADHD vulnerability should allow us to identify and characterise novel protective and risk factors for the disorder, and should ultimately facilitate improved diagnosis, prognosis and treatment.

Spatial memory in spontaneously hypertensive rats (SHR)

The spontaneously hypertensive rat (SHR) is an established animal model of ADHD. It has been suggested that ADHD symptoms arise from deficits in executive functions such as working memory, attentional control and decision making. Both ADHD patients and SHRs show deficits in spatial working memory. However, the data on spatial working memory deficits in SHRs are not consistent. It has been suggested that the reported cognitive deficits of SHRs may be related to the SHRs’ locomotor activity. We have used a holeboard (COGITAT) to study both cognition and activity in order to evaluate the influence of the activity on the cognitive performance of SHRs. In comparison to Wistar-Kyoto (WKY) rats, SHRs did not have any impairment in spatial working memory and reference memory. When the rats’ locomotor activity was taken into account, the SHRs’ working memory and reference memory were significantly better than in WKY rats. The locomotor activity appears to be a confounding factor in spatial memory tasks and should therefore be controlled for in future studies. In the SHR model of ADHD, we were unable to demonstrate an impairment of working memory which has been reported in patients with ADHD.

Fetal programming effects of testosterone on the reward system and behavioral approach tendencies in humans

BACKGROUND

Sex differences are present in many neuropsychiatric conditions that affect emotion and approach-avoidance behavior. One potential mechanism underlying such observations is testosterone in early development. Although much is known about the effects of testosterone in adolescence and adulthood, little is known in humans about how testosterone in fetal development influences later neural sensitivity to valenced facial cues and approach-avoidance behavioral tendencies.

METHODS

With functional magnetic resonance imaging we scanned 25 8-11-year-old children while viewing happy, fear, neutral, or scrambled faces. Fetal testosterone (FT) was measured via amniotic fluid sampled between 13 and 20 weeks gestation. Behavioral approach-avoidance tendencies were measured via parental report on the Sensitivity to Punishment and Sensitivity to Rewards questionnaire.

RESULTS

Increasing FT predicted enhanced selectivity for positive compared with negatively valenced facial cues in reward-related regions such as caudate, putamen, and nucleus accumbens but not the amygdala. Statistical mediation analyses showed that increasing FT predicts increased behavioral approach tendencies by biasing caudate, putamen, and nucleus accumbens but not amygdala to be more responsive to positive compared with negatively valenced cues. In contrast, FT was not predictive of behavioral avoidance tendencies, either through direct or neurally mediated paths.

CONCLUSIONS

This work suggests that testosterone in humans acts as a fetal programming mechanism on the reward system and influences behavioral approach tendencies later in life. As a mechanism influencing atypical development, FT might be important across a range of neuropsychiatric conditions that asymmetrically affect the sexes, the reward system, emotion processing, and approach behavior.

Intra-orbitofrontal cortex injection of haloperidol removes the beneficial effect of methylphenidate on reversal learning of spontaneously hypertensive rats in an attentional set-shifting task

Numerous studies suggest that attention-deficit/hyperactivity disorder (ADHD) is caused by deficits in catecholaminergic systems. Furthermore, dysfunctions of prefrontal cortex can impair inhibitory controls of ADHD patients, resulting in their impulsive behaviors. Researchers also find that rats with lesions in the orbitofrontal cortex show deficits in the reversal learning of attentional set-shifting task (ASST), a behavioral test frequently used in human studies to asses the inhibition system. However, the role of orbitofrontal dopamine system in the mechanism responsible for the dysfunctions of inhibitory controls in ADHD patients and animal models remains unknown. In the present study, we manipulated orbitofrontal dopamine activities of spontaneously hypertensive rats (SHR), a widely used ADHD animal model, through intra-peritoneal injection of methylphenidate (MPH) and central infusion of haloperidol, and observed their performances in ASST. The results show that juvenile SHRs learned slower than Wistar controls in the first and second reversal learnings of ASST. The deficits could be removed by intra-peritoneal injections of MPH. Furthermore, central infusions of haloperidol in the orbitofrontal cortex blocked the effects of MPH. In conclusions, dopamine activity in orbitofrontal cortex might play a crucial role in the neural mechanism of reversal learning deficits in this animal model of ADHD.

The role of motivation and reward neural systems in vocal communication in songbirds

Many vertebrates are highly motivated to communicate, suggesting that the consequences of communication may be rewarding. Past studies show that dopamine and opioids in the medial preoptic nucleus (mPOA) and ventral tegmental area (VTA) play distinct roles in motivation and reward. In songbirds, multiple lines of recent evidence indicate that the roles of dopamine and opioid activity in mPOA and VTA in male birdsong differ depending upon whether song is used to attract females (sexually-motivated) or is produced spontaneously (undirected). Evidence is reviewed supporting the hypotheses that (1) mPOA and VTA interact to influence the context in which a male sings, (2) distinct patterns of dopamine activity underlie the motivation to produce sexually-motivated and undirected song, (3) sexually-motivated communication is externally reinforced by opioids released as part of social interactions, and (4) undirected communication is facilitated and rewarded by immediate opioid release linked to the act of singing.

Sex matters during adolescence: testosterone-related cortical thickness maturation differs between boys and girls

Age-related changes in cortical thickness have been observed during adolescence, including thinning in frontal and parietal cortices, and thickening in the lateral temporal lobes. Studies have shown sex differences in hormone-related brain maturation when boys and girls are age-matched, however, because girls mature 1–2 years earlier than boys, these sex differences could be confounded by pubertal maturation. To address puberty effects directly, this study assessed sex differences in testosterone-related cortical maturation by studying 85 boys and girls in a narrow age range and matched on sexual maturity. We expected that testosterone-by-sex interactions on cortical thickness would be observed in brain regions known from the animal literature to be high in androgen receptors. We found sex differences in associations between circulating testosterone and thickness in left inferior parietal lobule, middle temporal gyrus, calcarine sulcus, and right lingual gyrus, all regions known to be high in androgen receptors. Visual areas increased with testosterone in boys, but decreased in girls. All other regions were more impacted by testosterone levels in girls than boys. The regional pattern of sex-by-testosterone interactions may have implications for understanding sex differences in behavior and adolescent-onset neuropsychiatric disorders.

Acute administration of vinpocetine, a phosphodiesterase type 1 inhibitor, ameliorates hyperactivity in a mice model of fetal alcohol spectrum disorder

BACKGROUND

Maternal alcohol use during pregnancy causes a continuum of long-lasting disabilities in the offspring, commonly referred to as fetal alcohol spectrum disorder (FASD). Attention-deficit/hyperactivity disorder (ADHD) is possibly the most common behavioral problem in children with FASD and devising strategies that ameliorate this condition has great clinical relevance. Studies in rodent models of ADHD and FASD suggest that impairments in the cAMP signaling cascade contribute to the hyperactivity phenotype. In this work, we investigated whether the cAMP levels are affected in a long-lasting manner by ethanol exposure during the third trimester equivalent period of human gestation and whether the acute administration of the PDE1 inhibitor vinpocetine ameliorates the ethanol-induced hyperactivity.

METHODS

From postnatal day (P) 2 to P8, Swiss mice either received ethanol (5g/kg i.p.) or saline every other day. At P30, the animals either received vinpocetine (20mg/kg or 10mg/kg i.p.) or vehicle 4h before being tested in the open field. After the test, frontal cerebral cortices and hippocampi were dissected and collected for assessment of cAMP levels.

RESULTS

Early alcohol exposure significantly increased locomotor activity in the open field and reduced cAMP levels in the hippocampus. The acute treatment of ethanol-exposed animals with 20mg/kg of vinpocetine restored both their locomotor activity and cAMP levels to control levels.

CONCLUSIONS

These data lend support to the idea that cAMP signaling system contribute to the hyperactivity induced by developmental alcohol exposure and provide evidence for the potential therapeutic use of vinpocetine in FASD.

Why are autism spectrum conditions more prevalent in males?

Autism Spectrum Conditions (ASC) are much more common in males, a bias that may offer clues to the etiology of this condition. Although the cause of this bias remains a mystery, we argue that it occurs because ASC is an extreme manifestation of the male brain. The extreme male brain (EMB) theory, first proposed in 1997, is an extension of the Empathizing-Systemizing (E-S) theory of typical sex differences that proposes that females on average have a stronger drive to empathize while males on average have a stronger drive to systemize. In this first major update since 2005, we describe some of the evidence relating to the EMB theory of ASC and consider how typical sex differences in brain structure may be relevant to ASC. One possible biological mechanism to account for the male bias is the effect of fetal testosterone (fT). We also consider alternative biological theories, the X and Y chromosome theories, and the reduced autosomal penetrance theory. None of these theories has yet been fully confirmed or refuted, though the weight of evidence in favor of the fT theory is growing from converging sources (longitudinal amniocentesis studies from pregnancy to age 10 years old, current hormone studies, and genetic association studies of SNPs in the sex steroid pathways). Ultimately, as these theories are not mutually exclusive and ASC is multi-factorial, they may help explain the male prevalence of ASC.

No association between the 2D:4D fetal testosterone marker and multidimensional attentional abilities in children with ADHD

AIM

It has been suggested that high levels of prenatal testosterone exposure are implied in the aetiology of attention-deficit-hyperactivity disorder (ADHD). This study examined the association between the ratio of the length of the second and fourth digits (2D:4D ratio), a marker of fetal testosterone exposure, and the presence of ADHD-related cognitive and behavioural problems in children with ADHD and in typically developing comparison individuals.

METHOD

A clinically referred group of 64 children who fulfilled DSM-IV-TR criteria for ADHD (47 males, 17 females; mean age 8 y 8 mo, SD 1 y 8 mo, range 7-12 y) and 46 comparison children (25 males, 21 females; mean age 9 y 2 mo; SD 1 y 10 mo, range 7-12 y) were included in the study. The length of the second and fourth digits was measured by two independent raters. The Child Behaviour Checklist (CBCL) and the Test of Everyday Attention for Children (TEA-Ch) were used to assess behavioural problems and different aspects of attention.

RESULTS

No group differences in 2D:4D ratio were observed between children with (combined, inattentive, or hyperactive-impulsive subtype of) ADHD and comparison children. The ratio did not show the postulated relation with cognitive and behavioural aspects of ADHD.

INTERPRETATION

These findings challenge the hypothesis that fetal testosterone exposure plays a prominent role in the aetiology of ADHD.

A novel function of microRNA let-7d in regulation of galectin-3 expression in attention deficit hyperactivity disorder rat brain

In this study we investigated the locomotor activity and non-selective attention in spontaneously hypertensive rats (SHR) with control Wistar-Kyoto (WKY) rats, which were employed as an attention deficit hyperactivity disorder (ADHD) model. In open-field test and làt maze, SHR rats were found to be much more spontaneously active than WKY rats. As compared with WKY rats, a lower level of galectin-3 was observed in SHR brain prefrontal cortex (PFC), which was the major affected brain area of ADHD. Through miRNA microarray screening, rno-let-7d was noted to be solely upregulated in SHR PFC. Interestingly, rno-let-7d had a binding site at galectin-3 mRNA and was shown to regulate galectin-3 3' untranslated region (UTR) directly. Mutation of galectin-3 3'UTR by one nucleotide of the seed sequence prevented rno-let-7d regulation of the 3' UTR completely. Although rno-let-7d did not directly regulate tyrosine hydroxylase (TH) 3'UTR, the level of galectin-3 was important for cAMP response element binding protein, the major transcript factor for TH gene. Either overexpression or downexpression of galectin-3 could result in modulation of TH expression in both PC12H and PC12L cells. In conclusion, our data suggested a novel function of rno-let-7d in regulation of galectin-3 and in ADHD development. Rno-let-7d, which is increased in the PFC of SHR brain, negatively regulated galectin-3, which is coupled with TH expression regulation.

Mineralocorticoid and glucocorticoid receptors in hippocampus: their impact on neurons survival and behavioral impairment after neonatal brain injury

Glucocorticoids (GC) exert multiple effects within the central nervous system via mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) activation. MR expression is associated with a neuroprotective phenotype, whereas GR activation is implicated in the induction of an endangered neural phenotype and the opposite actions are most evident in hippocampus, where these receptors are predominantly present. Hippocampus has an overall inhibitory influence on the activity of the hypothalamic-pituitary-adrenal (HPA) axis and it has been suggested that efficient learning and adequate stress response depend on the appropriate functioning of the axis brought by coordinated activation of MR and GR in this region. There is a growing body of evidence that perinatal asphyxia causes irreversible damage to the brain leading to neurons loss in regions vulnerable to oxygen shortage especially in hippocampus. In the present review, some aspects of recently acquired insight in the role of GC receptors in promoting neuronal death and survival after hippocampal injury are discussed. Since the unbalance of MR and GR in hippocampus creates a condition of disturbed neuroendocrine regulation their potential impact on behavioral impairment will also be reviewed.

Adolescent female rats are more resistant than males to the effects of early stress on prefrontal cortex and impulsive behavior

We tested the hypothesis that adolescent Sprague-Dawley females may be more resistant than males to display impulsive behavior and lower prefrontal cortex thickness after mother-infant separation (MS). Starting at postnatal day 2 (P2), the MS group was separated 6 hr/day and the early handled (EH) group 15 min/day for 10 days, and another group was standard facility reared (SFR). Subjects were examined for novel open-field activity (P28), light-dark apparatus (P29), familiar open-field (P30) and frontal cortical thickness. This protocol resulted in impulsive behavior in MS rats relative to EH and SFR, but this effect was less pronounced in females than males. MS affected the two sexes differently in terms of decreased prefrontal cortex dorsoventral thickness, with this effect being significant in males but not females. Neuroanatomical and behavioral documentation that adolescent females are more resistant than males to ADHD-like effects of maternal separation have not been previously reported.

Gene expression of synaptosomal-associated protein 25 (SNAP-25) in the prefrontal cortex of the spontaneously hypertensive rat (SHR)

Dopamine is believed to play an important role in the etiology of attention-deficit/hyperactivity disorder (ADHD). In our previous study, we showed that gene expression of dopamine D4 receptor decreased in the spontaneously hypertensive rat (SHR) in the prefrontal cortex (PFC). In the present study, we explored the potential causes of dysfunction in the dopamine system in ADHD. It is the first time that neuronal activities in both juvenile SHR and WKY rats have been measured by functional MRI (fMRI). Our results showed that in PFC the Blood Oxygenation Level Dependent (BOLD) signal response in SHR was much higher than WKY under stressful situations. We tested the effects of acute and repeated administration of amphetamine on behavioral changes in SHR combined with the expression of the neuronal activity marker, c-fos, in the PFC. Meanwhile dopamine-related gene expression was measured in the PFC after repeated administration of amphetamine. We found that potential neuronal damage occurred through deficit of D2-like receptor protective functions in the PFC of the SHR. We also measured the expression of synaptosomal-associated protein 25 (SNAP-25) in SHR in PFC. The results showed decreased expression of SNAP-25 mRNA in the PFC of SHR; this defect disappeared after repeated injection of D-AMP.

Potential hormonal mechanisms of attention-deficit/hyperactivity disorder and major depressive disorder: a new perspective

Hormonal influences on the organization of behavior are apparent to neuroendocrinologists but under-examined in relation to childhood and adolescent mental disorders. A central mystery in the field of developmental psychopathology is the preferential male vulnerability to behavior disorders in childhood and female vulnerability to emotional disorders in adolescence. Relative neglect of a hormonal explanation may be due to lack of simple or unifying conceptual paradigms to guide studies. This paper seeks to stimulate research in this area by drawing upon clinical psychology and neuroscience literatures to offer a heuristic paradigm for clinical research. Two syndromes are selected here for illustration: Attention-Deficit/Hyperactivity Disorder (ADHD) and Major Depressive Disorder (MDD), because they have opposite gender risk profiles. Two guiding theories are evaluated. First, prenatal organizational effects of testosterone may modulate striatally-based dopaminergic circuits in such a way as to place boys at greater risk for early developing inattention and disruptive behavioral disorders. Second, activational effects of estradiol at puberty may modulate amygdalar and other circuitry, with particular effects on serotonergic pathways, in such a way as to place girls at greater risk for internalizing and mood disorders. Hypotheses from these theories are evaluated based on the current available literature, and limitations of, and future directions for, this literature are discussed.

Evidence that dopamine within motivation and song control brain regions regulates birdsong context-dependently

Vocal communication is critical for successful social interactions among conspecifics, but little is known about how the brain regulates context-appropriate communication. The neurotransmitter dopamine (DA) is involved in modulating highly motivated, goal-directed behaviors (including sexually motivated singing behavior), and emerging data suggest that the role of DA in vocal communication may differ depending on the context in which it occurs. To address this possibility, relationships between immunolabeled tyrosine hydroxylase (TH, the rate-limiting enzyme in catecholamine synthesis) and song produced within versus outside of a breeding context were explored in male European starlings (Sturnus vulgaris). Immunocytochemistry for dopamine beta-hydroxylase (DBH; the enzyme that converts DA to norepinephrine) was also performed to provide insight into whether relationships between song and TH immunoreactivity reflected dopaminergic or noradrenergic neurotransmission. Measures of TH and DBH were quantified in song control regions (HVC, Area X, robust nucleus of the acropallium) and regions implicated in motivation (medial preoptic nucleus (POM), ventral tegmental area (VTA), and midbrain central gray). In Area X, POM, and VTA measures of TH correlated with song produced within, but not outside of a breeding context. DBH in these regions did not correlate with song in either context. Together, these data suggest DA in both song control and motivation brain regions may be more tightly linked to the regulation of highly goal-directed, sexually motivated vocal behavior.

Juvenile male rats display lower cortical metabolic capacity than females

The juvenile brain undergoes marked maturational changes accompanied by major sex hormone changes. In particular, sex differences in neural substrates could underlie male-specific dysfunction in behavioral responses related to the prefrontal cortex. Sex differences in regional metabolic capacity of the cerebral cortex were investigated in juvenile Sprague-Dawley rats. At 6 weeks of age the brains were processed for quantitative histochemistry of cytochrome oxidase, a rate-limiting enzyme in cellular respiration, which is an index of brain metabolic capacity. Quantitative image analysis revealed a main effect of sex with males displaying lower regional metabolic capacity than females in the dorsolateral and orbital prefrontal cortex and in the posterior parietal cortex. In addition, males separated for 6 h/day from their mothers as pups showed greater ambulatory behavior in the novel open field and higher metabolism in the posterior parietal cortex relative to males separated for 15 min/day. This is the first study to show sex differences in brain metabolic capacity in regions such as the prefrontal cortex that may be hypometabolic in juvenile males relative to females.

Effects of sex hormones on associative learning in spontaneously hypertensive rats

Pavlovian conditioning of a visual stimulus paired with food was examined in spontaneously hypertensive rats (SHR), which are a commonly used model for Attention-Deficit/Hyperactivity Disorder (ADHD), and in Wistar rats (normoactive control). In gonadally intact rats of both strains, males spent more time in the food cup following onset of the light than did females, indicating a stronger association of the conditioned stimulus (CS) with reward. Gonadectomy carried out in adulthood affected conditioning differently in the two strains. In Wistar rats, gonadectomy had no effect on conditioned responding in females, but reduced conditioned responding in males, effectively eliminating the sex difference in behavior. This result suggests that circulating androgens in male Wistar rats normally aid conditioning in this task. In contrast, gonadectomy enhanced conditioning in both sexes in the SHR rats, indicating that androgens and/or estrogens impair conditioned associations in this strain. These data indicate that gonadal steroids can influence conditioning in rats and that the valence of steroid action on this behavior is strain-dependent. To the extent that SHR serves as a model of ADHD in humans, the influence of steroids on associative learning may play a role in the expression of ADHD-like behaviors.

Attention deficit/hyperactivity disorder (ADHD) symptoms and digit ratios in a college sample

Diagnosticians recognize three subtypes of attention deficit/hyperactivity disorder (ADHD) if there are developmentally inappropriate levels (six or more symptoms) of Hyperactive-Impulsive behavior, or Inattentive behavior, or both (Combined), respectively. ADHD may partly reflect androgen dysfunction, and an arguable proxy for prenatal androgen exposure is the 2D:4D finger ratio set at least as early as week 9 in the fetus; this is lower in men than in women. We examined the relationship between digit ratios and ADHD symptoms representing the three phenotypes: ADHD/Combined as measured by "summarized" (Rasched) scales, i.e., 1) the short version of the Wender Utah Rating Scale (WURS) and a total symptom list derived from the DSM IV, and the subdivided DSM IV into 2) ADHD/Inattentive and 3) ADHD/Hyperactive-Impulsive inventories, in a sample of European-descent college students (135 female, 52 male) not selected for ADHD. All digit ratios were calculated excluding the thumb. There were significant sex differences for the 2D:4D digit ratios of both hands (RH and LH), and between the RH 3D:4D and between the LH 2D:3D ratio. In females, the more masculine the LH 2D:4D ratio, the more the ADHD/Combined symptoms (both WURS and DSM) and the more the ADHD/Inattentive symptoms and ADHD/Hyperactive-Impulsive symptoms. More masculine ratios also correlated between the total WURS and RH 2D:3D, RH 2D:4D, and LH 2D:3D; and between the inattentive DSM symptoms and LH 2D:5D, and between the ADHD/Hyperactive and Impulsive symptoms and RH 3D:4D.

Early androgen treatment influences the pattern and amount of locomotion activity differently and sexually differentially in an animal model of ADHD

Higher testosterone level in males is one of the most obvious possibilities for the development of a clear gender difference in ADHD. The present study focused on the influence of excessive androgen exposure in the developmental stage on the hyperactivity feature of ADHD. The study used the spontaneously hypertensive rat (SHR) as an animal model. The amount of locomotion activity previously used as an over-activity measure in the SHR has resulted in a complicated picture. While the general activity level of SHR was significantly higher than its progenitor-the Wistar Kyoto rat (WKY), comparative differences with the Wistar rat could be observed only under certain experimental conditions. The present study applied the scaling approach to assess open field behaviors from a qualitative aspect. Although SHR and Wistar rats showed similar locomotion amounts, movement patterns differed significantly, as indicated by the spatial scaling exponent. Androgen treatment during the early postnatal developmental stage significantly increased total path lengths only in the male SHR. Effects of the hormone manipulation were not expressed in the scaling measurement. The scaling approach conclusively provides a different aspect of open field behaviors and also reacts differently as the total path length to excessive early testosterone exposure.

Delayed P300 latency correlates with abnormal Test of Variables of Attention (TOVA) in adults and predicts early cognitive decline in a clinical setting

Delayed P300 latency identifies dementia better than the Mini-Mental Status Exam and, in some cases, the Wechsler Memory Scale (WMS-III). The purpose of this study was to determine whether the outcome of an objective Test of Variables of Attention (TOVA) correlates with the findings of an electrophysiologic test-P300 latency-in patients 40 y of age or older. Adult attention deficit disorder may be an important premorbid marker of memory dysfunction or dementia. In males, the means for P300 latency and age-adjusted P300 latency were significantly greater for patients classified as SD-BL (significantly deviant or borderline: TOVA<-1.0) than for those categorized as normal (TOVA(3)0) for attention failure (ie, omissions [P<.010] and commissions [P<.005]) but not for response time or for variability. Males with >2 SD-BL quarters had significantly delayed P300 latency and age-adjusted P300 latency compared with males who had 0 SD-BL quarters (P<.020) and 1 SD-BL quarter (P<.005). In females, the means for P300 latency and age-adjusted P300 latency were significantly delayed for those grouped as SD-BL than for those labeled normal for response time (P<.001) and variability (P<.010), but not for omissions or for commissions. Females with >2 SD-BL quarters had significantly delayed P300 latency and age-adjusted P300 latency compared with females who had 0 SD-BL quarters (P<.005) and 1 SD-BL quarter (P<.010). Results suggest that TOVA abnormalities may be an indicator of delayed P300 and attention disorder. Recent research correlates TOVA abnormalities with impaired WMS scores of early dementia. Coupling of TOVA assessment findings with results of P300, Mini-Mental Status Exam, and WMS-III may allow for enhanced accuracy in the diagnosis and evaluation of the complex pathway of failing attention, memory, and cognition that leads to dementia.

Learning deficits expressed as delayed extinction of a conditioned running response following perinatal exposure to vinclozolin

Vinclozolin (Vz) is one member of a group of fungicides whose metabolites are androgen receptor antagonists. These fungicides have been shown to block androgen-driven development and compromise reproductive function. The current study sought to determine if Vz also affects learning following exposure to low doses during the perinatal period. To test this, an androgen-dependent behavior was examined, the extinction of a previously reinforced running response. Pregnant Long-Evans rats were administered a daily oral dose of 0, 1.5, 3, 6 or 12 mg/kg Vz from the 14th day of gestation through postnatal day 3. After reaching adulthood, male and female offspring were trained to run through a short alleyway for food reinforcement. Acquisition of the response was not affected by Vz exposure. However, males required more trials than females for response extinction once food was no longer available in the apparatus. Males exposed to 6 or 12 mg/kg Vz failed to show any extinction by the end of the procedure, while the lowest dose of Vz appeared to facilitate extinction in both male and female offspring. These results demonstrate that endocrine disrupting antiandrogens can alter nervous system development in addition to the reproductive system.

Association between symptoms of attention-deficit/hyperactivity disorder and bulimic behaviors in a clinical sample of severely obese adolescents

OBJECTIVE

Preliminary evidence suggests a comorbidity between attention-deficit/hyperactivity disorder (ADHD) and obesity. This study was carried out to identify the clinical characteristics of obese adolescents with a higher probability of ADHD and advance the understanding of the potential factors underlying the comorbidity between obesity and ADHD. We evaluated the association between ADHD symptoms and bulimic behaviors, depressive and anxiety symptoms, degree of obesity, pubertal stage, age and gender in a clinical sample of obese adolescents.

DESIGN

Cross-sectional study.

SUBJECTS

Ninety-nine severely obese adolescents aged 12-17 years.

MEASUREMENTS

Subjects filled out the Bulimic Investigatory Test, Edinburgh, the Beck Depression Inventory and the State-Trait Anxiety Inventory for Children. Their parents completed the Conners Parent Rating Scale, which assesses ADHD symptoms. The degree of overweight was expressed as body mass index-z score. Puberty development was clinically assessed on the basis of Tanner stages.

RESULTS

Bulimic behaviors were significantly associated with ADHD symptoms after controlling for depressive and anxiety symptoms. The degree of overweight, pubertal stage, age and gender were not significantly associated with ADHD symptoms.

CONCLUSION

Obese adolescents with bulimic behaviors may have a higher probability to present with ADHD symptoms independently from associated depressive or anxiety symptoms. The degree of overweight, pubertal stage, age and gender might not be useful for detecting obese adolescents with ADHD symptoms. Therefore, we suggest systematic screening for ADHD in obese adolescents with bulimic behaviors. Further studies are needed to understand which specific dimension of ADHD primarily accounts for the association with bulimic behaviors. Future research should also investigate the causal link between bulimic behaviors and ADHD and explore potential common neurobiological alterations. This may lead to a better understanding of the effectiveness of stimulants for the treatment of bulimic behaviors in obese subjects.

An intermittent, controlled-rate, slow progressive degeneration model of Parkinson's disease: antiparkinson effects of Sinemet and protective effects of methylphenidate

The causes of nigrostriatal neuron degeneration in Parkinson's disease (PD) are not known, but it has been suggested that exogenous or endogenous factors or neurotoxins may play a role. The degree of vulnerability to neurotoxins or other potential mediators of nigral dopamine cell death is thought to be important in understanding Parkinson's disease. In most animal models, the rate of terminal degeneration and corresponding functional impairment is too rapid to investigate effectively either cell vulnerability or the potential benefits of some neuroprotective treatments. In the present study, a new model of Parkinson's disease is described that might help in addressing the issue of nigral cell vulnerability and to evaluate interventions with clinical potential. 6-Hydroxydopamine (6-OHDA) was infused in escalating, intrastriatal doses over several weeks. Control animals received multiple infusions of vehicle at the same volume. Behavioral testing was carried out between each infusion, including forelimb-use and somatosensory function. A symptomatic threshold was established for each animal, indicating the amount of neurotoxin required to induce a stable deficit. Oral administration of L-DOPA (Sinemet) ameliorated limb-use asymmetries acutely. An immunocytochemical assay for tyrosine hydroxylase, a dopamine cell marker, revealed a partial loss of immunoreactive cells in the substantia nigra. Animals that were co-administered methylphenidate (MPH), a dopamine transport inhibitor, along with the 6-OHDA were spared from the behavioral and neurochemical effects of 6-OHDA, despite receiving more than twice as much neurotoxin as controls. These data suggest that establishing a symptomatic threshold preclinically may help researchers evaluate potential treatments and model individual and group resistance to nigrostriatal insults.

Testing the prenatal hormone hypothesis of tic-related disorders: gender identity and gender role behavior

The hypothesis that prenatal masculinization of the brain increases risk of tic disorders in postnatal life was tested by measuring gender and gender role behavior in 89 children and adults with a clinical diagnosis of Tourette syndrome or obsessive compulsive disorder and 67 healthy, unaffected children and adults. Consistent with this hypothesis, a tic disorder in females was associated with more gender dysphoria, increased masculine play preferences, and a more typically "masculine" pattern of performance on two sex-typed spatial tasks. Males with tic disorders reported increased masculine play preferences, and the strength of these preferences was positively associated with the severity of tic symptoms. In addition, unlike their female counterparts, males with tic disorders showed a relative impairment in mental rotation ability. These behavioral profiles are consistent with those of children who have verifiable elevations in prenatal androgen levels. These findings therefore support the hypothesis that an altered androgen-dependent process of sexual differentiation during prenatal life may contribute to the development of tic-related disorders.