Biomedical subjects

Stanley J Watson

Publications and source records attributed to Stanley J Watson.

At least 37 records · Page 2Linked to original sources

PubMed2005

Diurnal rhythmic expression of the rhythm-related genes, rPeriod1, rPeriod2, and rClock, in the rat brain.

High densities of the mRNA of three rhythm-related genes, rPeriod1 (rPer1), rPer2, and rClock, which share high homology in Drosophila and mammals, are found in the rat hypothalamic suprachiasmatic nucleus (SCN). The SCN, however, is not the only brain region that expresses these genes. To understand the possible physiological roles of these rhythm-related genes, we examined expression of these genes in different brain regions at various time points in male Sprague--Dawley rats. Using semi quantitativein situ hybridization with 35S-riboprobes to evaluate mRNA levels, the diurnal rhythmicity of rPer1, and rPer2 mRNA levels was found in the SCN, arcuate nucleus, and median eminence/pars tuberalis. Expression patterns of mRNA for rPer1 and rPer2, however, were not similar in these brain regions. The rhythmicity in these brain regions was specific, because it was not observed in the cerebellum or hippocampus. Moreover, diurnal changes in rClock mRNA expression were not detected in any of the brain regions examined. These findings suggest that the different expression patterns observed for rPer1, rPer2, and rClock mRNAs may be attributed to their different physiological roles in these brain regions, and support previous work indicating that circadian rhythms in the brain are widespread.

Animals↗

PubMed2004

Hippocampal mossy fibre terminal field size is differentially affected in a rat model of risk-taking behaviour.

Individual differences in novelty-induced exploratory activity identify rats which can serve as a model of human sensation-seeking, risk-taking behaviour. Experimentally naïve rats, when exposed to mild stress of a novel environment, exhibit variability in their exploratory activity. Some rats display high rates of locomotor reactivity to novelty (high responders (HR)), and others display low rates (low responders (LR)). The LRHR phenotype is a reliable predictor of drug-taking behaviour and is linked to differences in hippocampal glucocorticoid receptor mRNA expression. In this study, we investigated whether the LRHR phenotype is associated with differences in the quantitative morphology of the hippocampal field CA3, dentate gyrus molecular layer, granule cell layer and mossy fibres. LRs and HRs showed no significant differences in the volumes of CA3 and dentate molecular layer volume or the number of dentate granule cells. However, LRs had a significantly larger suprapyramidal mossy fibre terminal field volume when compared to HRs. The infrapyramidal mossy fibres did not differ between phenotypes. Also, we found a LRHR phenotype-independent significant negative correlation between molecular layer volume per granule cell and the total number of granule cells. These findings implicate the SP-MF in vulnerability for risk-taking behaviour, and we propose that LR and HR hippocampi may differ in the way novelty information is processed.

Animals↗

PubMed2004

Glucocorticoid receptor overexpression in forebrain: a mouse model of increased emotional lability.

The molecular mechanisms that control the range and stability of emotions are unknown, yet this knowledge is critical for understanding mood disorders, especially bipolar illness. Here, we show that the glucocorticoid receptor (GR) modulates these features of emotional responsiveness. We generated transgenic mice overexpressing GR specifically in forebrain. These mice display a significant increase in anxiety-like and depressant-like behaviors relative to wild type. Yet, they are also supersensitive to antidepressants and show enhanced sensitization to cocaine. Thus, mice overexpressing GR in forebrain have a consistently wider than normal range of reactivity in both positive and negative emotionality tests. This phenotype is associated, in specific brain regions, with increased expression of genes relevant to emotionality: corticotropin-releasing hormone, serotonin, norepinephrine and dopamine transporters, and 5-hydroxytryptamine(1A) receptor. Thus, GR overexpression in forebrain causes higher "emotional lability" secondary to a unique pattern of molecular regulation. This finding suggests that natural variations in GR gene expression can contribute to the fine-tuning of emotional stability or lability and may play a role in bipolar disorder.

Affective Symptoms↗

PubMed2004

Effect of agonal and postmortem factors on gene expression profile: quality control in microarray analyses of postmortem human brain.

There are major concerns that specific agonal conditions, including coma and hypoxia, might affect ribonucleic acid (RNA) integrity in postmortem brain studies. We report that agonal factors significantly affect RNA integrity and have a major impact on gene expression profiles in microarrays. In contrast to agonal factors, gender, age, and postmortem factors have less effect on gene expression profiles. The Average Correlation Index is proposed as a method for evaluating RNA integrity on the basis of similarity of microarray profiles. Reducing the variance due to agonal factors is critical in investigating small but validated gene expression differences in messenger RNA levels between psychiatric patients and control subjects.

Adult↗

PubMed2004

Serotonin 5-HT1A, 5-HT1B, and 5-HT2A receptor mRNA expression in subjects with major depression, bipolar disorder, and schizophrenia.

BACKGROUND: Alterations of serotonin neurotransmission are implicated in both mood disorders and schizophrenia. Specific serotonin-receptor-based abnormalities in these psychiatric illnesses have been intensively studied; however, it has been difficult to draw any conclusions because of a lack of consensus. These inconsistencies have most likely arisen from the unavailability of selective ligands. METHODS: Our study used in situ hybridization to quantify 5-HT(1A), 5-HT(1B), and 5-HT(2A) mRNA levels in the hippocampus (HC) and 5-HT(1A) and 5-HT(2A) mRNA levels in the dorsolateral prefrontal cortex (DLPFC) of subjects with a history of major depression disorder (MDD), bipolar disorder (BPD), schizophrenia, and a normal comparison group (15 subjects per group). RESULTS: In the DLPFC, there is a significant decrease in 5-HT(1A) mRNA of subjects with MDD and in 5-HT(2A) mRNA of subjects with BPD. Subjects with MDD have a significant decrease in 5-HT(1A) mRNA in the HC; subjects with BPD and schizophrenia had increased 5-HT(1B) mRNA levels and a significant decrease in 5-HT(2A) mRNA levels in the hippocampal formation. CONCLUSIONS: Alterations in 5-HT(1A,) 5-HT(1B), and 5-HT(2A) mRNA levels in the brains of subjects with both mood disorders and schizophrenia add further support for hypothesis of dysregulation of the serotonergic system in these psychiatric disorders.

Adult↗

PubMed2004

Systematic changes in gene expression in postmortem human brains associated with tissue pH and terminal medical conditions.

Studies of gene expression abnormalities in psychiatric or neurological disorders often involve the use of postmortem brain tissue. Compared with single-cell organisms or clonal cell lines, the biological environment and medical history of human subjects cannot be controlled, and are often difficult to document fully. The chance of finding significant and replicable changes depends on the nature and magnitude of the observed variations among the studied subjects. During an analysis of gene expression changes in mood disorders, we observed a remarkable degree of natural variation among 120 samples, which represented three brain regions in 40 subjects. Most of such diversity can be accounted for by two distinct expression patterns, which in turn are strongly correlated with tissue pH. Individuals who suffered prolonged agonal states, such as with respiratory arrest, multi-organ failure or coma, tended to have lower pH in the brain; whereas those who experienced brief deaths, associated with accidents, cardiac events or asphyxia, generally had normal pH. The lower pH samples exhibited a systematic decrease in expression of genes involved in energy metabolism and proteolytic activities, and a consistent increase of genes encoding stress-response proteins and transcription factors. This functional specificity of changed genes suggests that the difference is not merely due to random RNA degradation in low pH samples; rather it reflects a broad and actively coordinated biological response in living cells. These findings shed light on critical molecular mechanisms that are engaged during different forms of terminal stress, and may suggest clinical targets of protection or restoration.

Adult↗

PubMed2004

Delayed effects of chronic variable stress during peripubertal-juvenile period on hippocampal morphology and on cognitive and stress axis functions in rats.

Animal studies on the effects of chronic variable stress during the peripubertal-juvenile period on hippocampal structure and function are lacking. Twenty-eight-day-old Sprague-Dawley rats were subjected to random, variable physical or social stress regimens for 4 weeks. Hippocampal volume was found to continue to grow in all lamina examined during the transition into young adulthood. Our variable physical stress paradigm led to inhibition of this growth in the CA1 pyramidal cell layer (PCL) and in the dentate gyrus-granular cell layer (DG-GCL), which reached full arrest in the CA3-PCL. Volume deficits were first observed after chronic stress exposure when 3 weeks, but not 24 h, of recovery had elapsed. Moreover, these volume deficits were associated with impairments in the Morris water-maze navigation, sustained down-regulation in the basal hippocampal glucocorticoid receptor gene expression, and deficits in the shutdown of acute stress-induced corticosterone secretion. Volume changes both due to normal maturation and after chronic stress exposure were independent of neuron number. Thus, a peripubertal-juvenile chronic stress paradigm that leads to significant alterations in the limbic-hypothalamic-pituitary-adrenal axis can produce robust effects in hippocampal structure and cognitive ability, lasting into adulthood.

Age Factors↗

PubMed2004

Gender-specific gene expression in post-mortem human brain: localization to sex chromosomes.

Gender differences in brain development and in the prevalence of neuropsychiatric disorders such as depression have been reported. Gender differences in human brain might be related to patterns of gene expression. Microarray technology is one useful method for investigation of gene expression in brain. We investigated gene expression, cell types, and regional expression patterns of differentially expressed sex chromosome genes in brain. We profiled gene expression in male and female dorsolateral prefrontal cortex, anterior cingulate cortex, and cerebellum using the Affymetrix oligonucleotide microarray platform. Differentially expressed genes between males and females on the Y chromosome (DBY, SMCY, UTY, RPS4Y, and USP9Y) and X chromosome (XIST) were confirmed using real-time PCR measurements. In situ hybridization confirmed the differential expression of gender-specific genes and neuronal expression of XIST, RPS4Y, SMCY, and UTY in three brain regions examined. The XIST gene, which silences gene expression on regions of the X chromosome, is expressed in a subset of neurons. Since a subset of neurons express gender-specific genes, neural subpopulations may exhibit a subtle sexual dimorphism at the level of differences in gene regulation and function. The distinctive pattern of neuronal expression of XIST, RPS4Y, SMCY, and UTY and other sex chromosome genes in neuronal subpopulations may possibly contribute to gender differences in prevalence noted for some neuropsychiatric disorders. Studies of the protein expression of these sex-chromosome-linked genes in brain tissue are required to address the functional consequences of the observed gene expression differences.

Actins↗

PubMed2004

The delta-opioid receptor agonist (+)BW373U86 regulates BDNF mRNA expression in rats.

delta-Opioid receptor agonists have antidepressant-like effects in behavioral models of depression. Chronic administration of classical antidepressants upregulates mRNA expression of brain-derived neurotrophic factor (BDNF) and its high-affinity tyrosine kinase receptor, TrkB in the frontal cortex and hippocampus of rats. Increases in BDNF and TrkB levels are thought to be important for the therapeutic effects of these drugs. Therefore, we examined the ability of the delta-opioid receptor agonist (+)BW373U86 to regulate BDNF and TrkB mRNA expression in frontal cortex, hippocampus, as well as, basolateral amygdala, endopiriform nucleus, and primary olfactory cortex. At 3 h after a single administration of (+)BW373U86 animals were killed and BDNF and TrkB mRNA levels were examined by in situ hybridization. BDNF mRNA levels produced by (+)BW373U86 were compared to acute administration of the antidepressants desipramine and bupropion. A behaviorally antidepressant dose of 10 mg/kg (+)BW373U86 increased BDNF mRNA expression in all regions examined; a smaller dose of (+)BW373U86 (1 mg/kg) significantly increased BDNF mRNA expression only in frontal cortex. The delta-opioid receptor antagonist naltrindole blocked (+)BW373U86-mediated increases in BDNF mRNA expression. In addition, tolerance developed to increased BDNF mRNA expression with repeated injection, except in frontal cortex. Midazolam was administered to some animals to prevent the convulsions produced by (+)BW373U86, but midazolam did not block delta-opioid receptor-mediated increases in BDNF mRNA expression in frontal cortex, hippocampus, or amygdala. Unlike desipramine and bupropion, (+)BW373U86 upregulated BDNF mRNA expression acutely (within 3 h after a single administration). These data support the concept that delta-opioid receptor agonists may have antidepressant potential, and could be good targets for the development of faster-acting antidepressants.

Analysis of Variance↗

PubMed2004

CREB deficient mice show inhibition and low activity in novel environments without changes in stress reactivity.

The ability to respond to unexpected or novel stimuli is critical for survival. Determining that a stimulus is indeed novel requires memory to ascertain its lack of familiarity. As the long-term synaptic changes involved in memory formation require the cAMP response element binding protein (CREB), we examined the extent to which CREB is involved in responses to novel environments. These environments typically trigger an endocrine stress response. Thus, we measured behavioural and stress hormone responses to three novel and one familiar environment in mice with a targeted disruption of the alpha and delta isoforms of the CREB gene (CREB(alphadelta-) deficient mice). We found CREB(alphadelta-) deficient mice to be less active and more inhibited in the elevated plus maze, open field, and light/dark box, without showing differences in anxiety-like behaviour. This inhibition is unique to novel environments because these mice display a normal phenotype in the home cage, a familiar environment. Although CREB(alphadelta-) deficient mice exhibit altered behaviour in novel environments, they show normal reactivity to mild and moderate stress as both basal and stress levels of corticosterone are similar to those of wild-type controls. This is the first report of CREB(alphadelta-) deficient mice to: (i) show altered behaviour, not related to learning and memory-associated behaviours, upon initial exposure to environments and (ii) serve as an animal model that can dissociate locomotor activity from anxiety-like behaviour in novel environments.

Animals↗

PubMed2003

Dexamethasone exposure during the neonatal period alters ORL1 mRNA expression in the hypothalamic paraventricular nucleus and hippocampus of the adult rat.

Dexamethasone is commonly used to limit the severity of chronic lung disease in premature infants with severe respiratory distress syndrome. Recent literature has demonstrated an association between dexamethasone exposure in critically ill premature neonates and later development of cerebral palsy. However, the majority of children exposed to dexamethasone in the neonatal period do not develop cerebral palsy or global developmental delay, and other more subtle effects of early life glucocorticoid exposure may go unnoticed. Presently, little is known regarding possible effects of early dexamethasone exposure on development of neuropeptide systems that are sensitive to glucocorticoid modulation. One such system is the pain-related opioid system that interacts with the stress-related limbic-hypothalamic pituitary adrenal (LHPA) axis. In the present study, a neonatal rat model was used to expose newborn rats to dexamethasone. Using a within-litter design, on postnatal days P3 through P6, pups were either handled, or they received a daily intramuscular injection of saline or dexamethasone. Adult animals were sacrificed on day of life P120, their brains were removed and quick-frozen. Using in situ hybridization histochemistry, mRNA expression of the opioid receptor-like (ORL1) receptor was measured in the paraventricular nucleus of the hypothalamus (PVN) and the hippocampal formation. In dexamethasone-treated adult male rats, ORL1 mRNA expression was increased in the PVN and dentate gyrus, but decreased in area CA1, when compared to handled and vehicle controls. These results suggest that prolonged glucocorticoid receptor (GR) occupation in the neonatal period leads to permanent alterations in ORL1 expression in the LHPA stress axis of the adult rat.

Animals↗

PubMed2003

Syrian hamster proopiomelanocortin cDNA cloning and early seasonal changes in testicular expression.

Beta-endorphin (beta-End) and its precursor, proopiomelanocortin (POMC), are expressed in testis and beta-End stimulates testosterone secretion locally. We measured POMC expression in Syrian hamster testis following transfer from long days (LDs) to short days (SDs). We used RT-PCR to amplify partial-length hamster POMC cDNA to generate a probe for Northern analysis. We also used rat beta-End antiserum for radioimmunoassay analysis. SD exposure for 2 weeks decreased POMC mRNA and beta-End, but not testis weight or testosterone. We conclude that POMC signaling may play a role in seasonal regulation of testicular function.

Animals↗

PubMed2003

Interaction between alpha-melanocyte-stimulating hormone and corticotropin-releasing hormone in the regulation of feeding and hypothalamo-pituitary-adrenal responses.

Both central alpha-melanocyte-stimulating hormone and corticotropin-releasing hormone (CRH) have been implicated in feeding and neuroendocrine mechanisms. The anatomical overlap and functional similarities between these two neurotransmitter systems led to the hypothesis that CRH might act as one of the mediators of the central actions of the melanocortin system. By double-labeling in situ hybridization, a subpopulation of CRH neurons in the paraventricular nucleus of the hypothalamus (PVN) were shown to contain the melanocortin-4 receptor (MC4R), concentrated in the ventromedial part of the parvicellular PVN (up to 33%). Intracerebroventricular injection of melanocortin agonist MTII to conscious and freely moving rats induced a rapid induction of CRH gene transcription in the PVN. This effect was accompanied by a rise in plasma corticosterone levels in a dose- and time-dependent manner, with the maximum response observed 30 min after MTII injection. MTII (0.5 nmol)-induced increase in plasma corticosterone was attenuated by the selective MC4R antagonist HS014 (0.25-1.0 nmol) and nonselective CRH receptor antagonist alpha-helical-CRH9-41 (0.125-0.5 nmol) in a dose-dependent manner. Moreover, the anorectic effect of MTII was evaluated at 1, 2, and 24 hr after intracerebroventricular injection. Approximately half of the inhibitory effect of MTII (0.5 nmol) on food intake was reversed by pretreatment with alpha-helical-CRH9-41 at 0.25 and 0.5 nmol doses. Collectively, these results provide evidence that CRH acts as a downstream mediator of melanocortin signaling and contributes to the mechanisms by which the central melanocortin system controls feeding and neuroendocrine responses.

Animals↗

PubMed2003

Brainstem substrates of sympatho-motor circuitry identified using trans-synaptic tracing with pseudorabies virus recombinants.

Previous physiological investigations have suggested the existence of a neural circuit that coordinates activation of motor and autonomic efferents before or at the onset of exercise. Traditionally these circuits have been postulated to involve forebrain areas. However, overlapping populations of medullary reticular formation neurons that participate in motor or autonomic control have been described previously, suggesting that individual pontomedullary reticular formation neurons may coordinate both motor and autonomic responses. We tested this hypothesis by conducting transneuronal retrograde tracing of motor and sympathetic nervous system pathways in rats using recombinant strains of pseudorabies virus (PRV). A PRV strain expressing the green fluorescent protein (PRV-152) was injected into the left gastrocnemius muscle, which was surgically sympathectomized, whereas another recombinant (PRV-BaBlu) was injected into the left adrenal gland. Immunofluorescence methods using monospecific antisera and distinct fluorophores identified neurons infected with one or both of the recombinants. Brainstem neurons coinfected with both PRV recombinants, which presumably had collateralized projections to both adrenal sympathetic preganglionic neurons and gastrocnemius motoneurons, were observed in several areas of the pontomedullary reticular formation. The largest number of such neurons was located in the rostral ventromedial medulla within the ventral gigantocellular nucleus, gigantocellular nucleus pars alpha, raphe obscurus, and raphe magnus. These neurons are candidates for relaying central command signals to the spinal cord.

Adrenal Glands↗

PubMed2003

Socially-induced brain 'fertilization': play promotes brain derived neurotrophic factor transcription in the amygdala and dorsolateral frontal cortex in juvenile rats.

Rough and tumble (R&T) play is assumed to have beneficial effects in developing organisms. To evaluate this idea, brain derived neurotrophic factor (BDNF) gene expression was evaluated in 32-day-old juvenile rats that were allowed to play for 30 min prior to sacrifice. In situ hybridization for BDNF mRNA revealed that the amygdala and dorsolateral frontal cortex had significantly elevated BDNF mRNA expression as a result of play. These effects suggest that play may help program higher brain regions involved in emotional behaviors.

Age Factors↗

PubMed2003

Colocalization of estrogen beta-receptor messenger RNA with orphanin FQ, vasopressin and oxytocin in the rat hypothalamic paraventricular and supraoptic nuclei.

The functional significance of the novel estrogen receptor beta in brain areas that exclusively contain the ERbeta receptor subtype such as the paraventricular (PVN) and the supraoptic (SON) nuclei of the hypothalamus is not yet fully understood. The present study attempts to characterize the peptidergic nature of the ERbeta-containing neuronal population in the PVN and the SON using the double in situ histochemistry method in the female rat. Using this method, the ERbeta mRNA coexpressions with the novel opioid neuropeptide (orphanin FQ and its receptor ORL1) mRNA in addition to the previously reported neuropeptide (arginine vasopressin-AVP, oxytocin-OXY, corticotropin releasing hormone-CRH, enkephalin-ENK) mRNAs were assessed. In the PVN, roughly half of the ERbeta expression was colocalized with the prepro-orphanin FQ mRNA, which was comparable to the colocalization observed between the ERbeta and AVP mRNAs in the same region. In addition, there was 20% overlap between the ERbeta and ORL1 receptor mRNAs, and 10% overlap between the ERbeta and OXY mRNAs in the PVN. By contrast, the coexpression between the prepro-orphanin FQ and ERbeta mRNAs was less striking in the SON. Potential interactions between the ERbeta and the well-characterized AVP-OXY neurosecretory system as well as the novel OFQ-ORL1 opioid neuropeptide system may provide new leads for the functional significance of ERbeta, specifically in stress/autonomic responses.

Animals↗

PubMed2003

Spongiform degeneration in mahoganoid mutant mice.

mahoganoid is a mouse coat-color mutation whose pigmentary phenotype and genetic interactions resemble those of Attractin (Atrn). Atrn mutations also cause spongiform neurodegeneration. Here, we show that a null mutation for mahoganoid causes a similar age-dependent neuropathology that includes many features of prion diseases but without accumulation of protease-resistant prion protein. The gene mutated in mahoganoid encodes a RING-containing protein with E3 ubiquitin ligase activity in vitro. Similarities in phenotype, expression, and genetic interactions suggest that mahoganoid and Atrn genes are part of a conserved pathway for regulated protein turnover whose function is essential for neuronal viability.

Alleles↗

PubMed2003

Mineralocorticoid receptor function in major depression.

BACKGROUND: Negative feedback regulation of the hypothalamic-pituitary-adrenal axis occurs through a dual-receptor system of mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Their affinity for cortisol and their distribution in the brain differ. Studies using an MR antagonist have demonstrated that MR is active throughout the circadian rhythm. Because major depression is accompanied by increased glucocorticoid secretion and insensitivity to glucocorticoid feedback, and because glucocorticoids are capable of down-regulating MR and GR, we expected that major depression would be accompanied by decreased MR activity. METHODS: To test this hypothesis, we administered spironolactone, an MR antagonist, to individuals with major depression and matched control subjects and assessed levels of corticotropin and cortisol secretion in response to this acute challenge. Studies were conducted in the morning, the time of peak activation of the hypothalamic-pituitary-adrenal axis. All patients were currently depressed and free of all medications. All controls were free of all psychiatric diagnoses and of all medications. RESULTS: Spironolactone treatment resulted in a significant increase in cortisol secretion levels in both groups. Depressed patients demonstrated higher cortisol secretion levels than control subjects. In addition, depressed patients demonstrated a different pattern of increase in cortisol secretion levels after spironolactone administration. Furthermore, a significant effect of spironolactone treatment on corticotropin secretion levels can be observed in depressed patients, whereas controls show no such effect. CONCLUSIONS: Despite high baseline cortisol levels, patients with major depression show high functional activity of the MR system. Paired with the body of evidence regarding decreased sensitivity to GR agonists, these data suggest an imbalance in the MR/GR ratio. The balance of MR and GR is known to affect brain serotonin systems and may play an etiologic role in serotonin receptor changes observed in patients with major depression.

Adult↗