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Biomedical subjects

Stanley J Watson

Publications and source records attributed to Stanley J Watson.

At least 19 recordsLinked to original sources
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↗
PubMed2003

Binding and GTPgammaS autoradiographic analysis of preproorphanin precursor peptide products at the ORL1 and opioid receptors.

Utilizing agonist-stimulated GTPgammaS autoradiography, we analyzed the ability of preproorphanin FQ (ppOFQ) peptides to stimulate [35S]-GTPgammaS binding in adult rat brain. Orphanin FQ (OFQ) stimulated [35S]-GTPgammaS binding in a pattern similar to that described for [125I]-OFQ at the endogenous opioid receptor-like (ORL1) receptor. The ppOFQ peptides nocistatin and orphanin FQ2 (OFQ II(1-17)) had no effect, suggesting that they do not mediate their reported analgesic effects via a G(i/o)-coupled receptor (i.e. opioid or ORL1). Unlike OFQ II(1-17), high concentrations of its C-terminal extension, OFQ II(1-28), stimulated [35S]-GTPgammaS binding in a mu (mu) opioid receptor-like distribution and the effect was blocked by naloxone. To explore these observations, we evaluated the receptor binding profile of OFQ II(1-28) at the cloned ORL1 and mu opioid receptors. OFQ II(1-28) had no specific binding at either ORL1 or mu opioid receptors at concentrations up to 50 microM. This lack of affinity was not consistent with a mu-mediated effect, as suggested by preliminary observation using functional autoradiography in rat brain sections. Although behavioral studies suggest that OFQ II(1-28) possesses analgesic activity, this effect does not appear to be mediated via direct binding at the mu opioid receptor. Taken together, these findings support the view that (1) OFQ is the only ppOFQ peptide that binds to and activates the ORL1 receptor and (2) OFQ II(1-28) does not bind or stimulate [35S]-GTPgammaS binding in cells expressing the mu opioid receptor.

Animals↗
PubMed2003

Amphetamine-induced c-fos mRNA expression in the caudate-putamen and subthalamic nucleus: interactions between dose, environment, and neuronal phenotype.

When administered in a novel environment relatively low doses of amphetamine induce c-fos mRNA in the subthalamic nucleus (STN) and in preproenkephalin mRNA-containing (ENK+) neurons in the caudate-putamen (CPu). When administered at home, however, low doses of amphetamine do not produce these effects. Environmental novelty also facilitates the behavioral effects of acute and repeated amphetamine, but this is dose-dependent. The purpose of the present experiment therefore was to determine if the effect of context on amphetamine-induced c-fos expression is also dose-dependent. It was found that: (i) No dose of amphetamine tested (1-10 mg/kg) induced c-fos in many ENK+ cells when given at home. (ii) When given in a novel environment low to moderate doses of amphetamine (1-5 mg/kg) induced c-fos in substantial numbers of ENK+ cells, but the highest dose examined (10 mg/kg) did not. (iii) Environmental novelty enhanced the ability of low to moderate doses of amphetamine to induce c-fos in the STN, but the highest dose of amphetamine induced robust c-fos mRNA expression in the STN regardless of context. The results do not support the idea that engaging ENK+ cells, at least as indicated by c-fos mRNA expression, is critical to produce robust behavioral sensitization, but do suggest a possible role for the STN. Furthermore, the results highlight the importance of drug-environment interactions on the neurobiological effects of drugs, and have implications for thinking about the circuits by which context modulates the acute and long-lasting consequences of amphetamine treatment.

Amphetamine↗
PubMed2003

Amphetamine-evoked c-fos mRNA expression in the caudate-putamen: the effects of DA and NMDA receptor antagonists vary as a function of neuronal phenotype and environmental context.

Dopamine (DA) and glutamate neurotransmission is thought to be critical for psychostimulant drugs to induce immediate early genes (IEGs) in the caudate-putamen (CPu). We report here, however, that the ability of DA and glutamate NMDA receptor antagonists to attenuate amphetamine-evoked c-fos mRNA expression in the CPu depends on environmental context. When given in the home cage, amphetamine induced c-fos mRNA expression predominately in preprodynorphin and preprotachykinin mRNA-containing neurons (Dyn-SP+ cells) in the CPu. In this condition, all of the D1R, D2R and NMDAR antagonists tested dose-dependently decreased c-fos expression in Dyn-SP+ cells. When given in a novel environment, amphetamine induced c-fos mRNA in both Dyn-SP+ and preproenkephalin mRNA-containing neurons (Enk+ cells). In this condition, D1R and non-selective NMDAR antagonists dose-dependently decreased c-fos expression in Dyn-SP+ cells, but neither D2R nor NR2B-selective NMDAR antagonists had no effect. Furthermore, amphetamine-evoked c-fos expression in Enk+ cells was most sensitive to DAR and NMDAR antagonism; the lowest dose of every antagonist tested significantly decreased c-fos expression only in these cells. Finally, novelty-stress also induced c-fos expression in both Dyn-SP+ and Enk+ cells, and this was relatively resistant to all but D1R antagonists. We suggest that the mechanism(s) by which amphetamine evokes c-fos expression in the CPu varies depending on the stimulus (amphetamine vs. stress), the striatal cell population engaged (Dyn-SP+ vs. Enk+ cells), and environmental context (home vs. novel cage).

Amphetamine↗
PubMed2003

Microarray technology: a review of new strategies to discover candidate vulnerability genes in psychiatric disorders.

OBJECTIVE: An international effort is in progress to discover candidate genes and pathways associated with psychiatric disorders, including two of the most serious diseases, schizophrenia and mood disorders, through the use of new technology-microarrays. Instead of studying one gene at a time, microarrays provide the opportunity to analyze thousands of genes at once. METHOD: This article reviews the steps in this discovery process, including the acquisition and characterization of high-quality postmortem brain tissue, RNA extraction, and preparation and use of microarray technology. Two alternative microarray methods and factors affecting the quality of array data are reviewed. RESULTS: New analytical strategies are being developed to process the massive data sets generated by microarray studies and to define the significance of implicated genes. Array results must be validated by other methods, including in situ hybridization and real-time polymerase chain reaction. Identified genes can also be evaluated in terms of their chromosomal locations and possible overlap with regions of suggestive linkage or association identified with genome-wide linkage analysis in psychiatry and in terms of overlap with genes identified by microarray studies in animals administered psychoactive drugs. Microarray studies are only the first major step in the process. Further efforts in the investigation involve multiple strategies for studying function and gene structure, including transgenic and knockout animal studies. CONCLUSIONS: Microarrays present a methodology that can identify genes or pathways for new and unique potential drug targets, determine premorbid diagnosis, predict drug responsiveness for individual patients, and, eventually, initiate gene therapy and prevention strategies.

Brain Chemistry↗
PubMed2002

Correlation of estrogen beta-receptor messenger RNA with endogenous levels of plasma estradiol and progesterone in the female rat hypothalamus, the bed nucleus of stria terminalis and the medial amygdala.

Estrogen receptor beta (ERbeta) has been previously mapped in the rat central nervous system. This study aims to explore the regulation of ERbeta mRNA as it is expressed in the intact and cycling female rat brain. Young adult female rats (90+ day, N=20) were screened for estrous phases via vaginal cytology and sacrificed. Brains and blood were collected and processed for in situ hybridization and estradiol (E2) and progesterone (P4) hormone assays, respectively. ERbeta mRNA levels exhibited significant correlations with ovarian steroid ratios (E2/P4) in various brain regions, including the bed nucleus of stria terminalis, the medial nucleus of amygdala, and the anteroventral periventricular nuclei but not the paraventricular and the supraoptic nuclei or the preoptic area of the hypothalamus. No regulatory changes were detected in the cortex. Specifically, in the affected regions, higher P4 levels were significantly correlated with higher ERbeta mRNA expression. In contrast, there was a tendency for higher E2 levels to be correlated with lower ERbeta mRNA expression, but this tendency reached significance only in the bed nucleus of stria terminalis. These results suggest that ERbeta mRNA is regulated in the intact and cycling female rat hypothalamic as well as extrahypothalamic brain regions, and the circulating ovarian hormones play a critical role.

Amygdala↗
PubMed2002

A 6-hydroxydopamine lesion of the mesostriatal dopamine system decreases the expression of corticotropin releasing hormone and neurotensin mRNAs in the amygdala and bed nucleus of the stria terminalis.

The mesostriatal dopamine (DA) system is known to play a vital role in extrapyramidal motor responses, and animals with a unilateral 6-hydroxydopamine (6-OHDA) lesion of this system have proved useful in studying the behavioral and neurobiological effects of DA depletion. Less is known about the role of this system in modulating emotional responses, although a number of lines of evidence suggest that dopamine influences emotional behavior. During the course of a study involving rats that had a unilateral 6-OHDA lesion, we discovered a hemispheric asymmetry in the levels of corticotropin releasing hormone (CRH) mRNA in the central nucleus of the amygdala (CEA). The present study was performed in order to determine (1) if the lesion resulted in a decrease in CRH mRNA, and/or if there was upregulation on the intact side, (2) if a similar imbalance in CRH mRNA was observed in other brain regions and (3) if levels of other neuropeptide mRNAs were affected by the lesion. Adult male Sprague-Dawley rats were left unoperated or were pretreated with desipramine and then injected unilaterally with 6-OHDA into the medial forebrain bundle to lesion the ascending mesostriatal DA neurons. Animals were killed 15-31 days following surgery and brain sections processed for CRH, neurotensin and enkephalin mRNAs by in situ hybridization. Levels of CRH and neurotensin mRNAs were decreased on the lesioned side in the CEA and oval nucleus of the BST (BSTov) relative to the intact side and to unoperated controls. Levels of enkephalin mRNA in these regions were not affected by the lesion. These effects appeared specific, because the lesion did not alter CRH mRNA expression in the ventral BST, paraventricular nucleus of the hypothalamus or cortex or neurotensin mRNA expression in the CA1 region of the hippocampus. In contrast, and consistent with previous reports, levels of neurotensin and enkephalin mRNAs were upregulated on the lesioned side of the striatum. This study provides evidence that the mesostriatal DA system regulates CRH and neurotensin mRNA in the BSTov and CEA, suggesting that dopamine may be an important modulator of CRH and neurotensin function within these nuclei. Although the precise mechanisms are not clear, and the involvement of noradrenergic systems cannot be precluded, data are consistent with the idea that dopamine, released in response to a stressful experience for example, interacts with CRH and neurotensin in the extended amygdala to affect emotional responsiveness.

Amygdala↗
PubMed2002

Nociceptin/orphanin FQ and opioid receptor-like receptor mRNA expression in dopamine systems.

Although nociceptin/orphanin FQ (N/OFQ) influences dopamine (DA) neuronal activity, it is not known whether N/OFQ acts directly on DA neurons, indirectly by means of local circuitry, or both. We used two parallel approaches, dual in situ hybridization (ISH) and neurotoxic lesions of DA neurons by using 6-hydroxydopamine (6-OHDA), to ascertain whether N/OFQ and the N/OFQ receptor (NOP) mRNA are expressed in DA neurons in the ventral tegmental area (VTA) and substantia nigra compacta (SNc). In the VTA and SNc, small populations (approximately 6-10%) of N/OFQ-containing neurons coexpressed mRNA for tyrosine hydroxylase (TH), the rate-limiting enzyme for DA synthesis. Similarly, very few (1-2%) TH-positive neurons contained N/OFQ mRNA signal. A majority of NOP-positive neurons (approximately 75%) expressed TH mRNA and roughly half of the TH-containing neurons expressed NOP mRNA. Many N/OFQ neurons (approximately 50-60%) expressed glutamic acid decarboxylase 65 and 67 mRNAs, markers for gamma-aminobutyric acid (GABA) neurons. In the 6-OHDA lesion studies, NOP mRNA levels were nearly 80 and 85% lower in the VTA and SNc, respectively, on the lesioned side. These lesions appear to lead to compensatory changes, with N/OFQ mRNA levels approximately 60% and 300% higher in the VTA and SNc, respectively, after 6-OHDA lesions. Finally, N/OFQ-stimulated [(35)S]guanylyl-5'-O-(gamma-thio)-triphosphate levels were decreased in the VTA and SNc but not the prefrontal cortex after 6-OHDA lesions. Accordingly, it appears that N/OFQ mRNA was found largely on nondopaminergic (i.e., GABA) neurons, whereas NOP mRNA was located on DA neurons. N/OFQ is in a position to influence DA neuronal activity by means of the NOP located on DA neurons.

Animals↗
PubMed2002

The ability of amphetamine to evoke arc (Arg 3.1) mRNA expression in the caudate, nucleus accumbens and neocortex is modulated by environmental context.

The ability of amphetamine or cocaine to induce the expression of c-fos mRNA in a number of brain regions is greatly enhanced when these drugs are administered in a distinct and relatively novel environment, relative to when they are given in the home cage. The purpose of this study was to determine if environmental context has a similar effect on the ability of amphetamine to induce the expression of arc (also known as Arg 3.1), an "effector" immediate early gene (IEG) thought to play a direct role in cellular plasticity. Rats were administered either saline or amphetamine (0.5 mg/kg, i.v.), in their home cage or in a distinct test environment. Fifty minutes later, they were decapitated and their brains processed for in situ hybridization histochemistry. In the prefrontal cortex, caudate-putamen and core of the nucleus accumbens, amphetamine significantly increased arc mRNA expression under both conditions, but the level of expression was significantly enhanced when amphetamine was given in a distinct environment. In the shell of the nucleus accumbens amphetamine significantly increased the expression of arc mRNA only when it was administered in the distinct environment. Thus, the ability of amphetamine to induce the expression of arc varies as a function of the environmental context in which it is administered. This could contribute to the ability of environmental context to modulate forms of drug experience-dependent neuroplasticity, including behavioral sensitization.

Amphetamine↗
PubMed2002

Evaluation of Affymetrix Gene Chip sensitivity in rat hippocampal tissue using SAGE analysis. Serial Analysis of Gene Expression.

DNA microarrays are a powerful tool for monitoring thousands of transcript levels simultaneously. However, the use of DNA microarrays in studying the central nervous system faces several challenges. These include the detection of low-abundance transcripts in highly complex tissue as well as estimating relatively low-magnitude changes in transcript levels in response to experimental manipulation. Many transcripts important to brain function have low expression levels or are expressed in relatively few cells, making them difficult to detect in the complex background of brain tissue. The aim of the present study is to evaluate the sensitivity of Gene Chip detection of transcripts in brain by using results from serial analysis of gene expression (SAGE) studies. The results of this comparison indicate that Affymetrix Gene Chips, like SAGE, only reliably detect medium- to high-abundance transcripts and that detection of low-abundance transcripts, many of which have great relevance to biological function in brain, is inconsistent. Specifically, we estimate that Gene Chips reliably detect no more than 30% of the hippocampal transcriptome when using a gross hippocampal dissection as the source tissue. This report provides the first broad evaluation of Affymetrix Gene Chip sensitivity relevant to studying the brain.

Animals↗
PubMed2002

c-fos mRNA induction in acute and chronic audiogenic stress: possible role of the orbitofrontal cortex in habituation.

To study putative brain circuits involved in habituation to stress, rats were exposed daily (30 min for 15 days) to an environment in the presence (Chronic) or absence (Acute) of loud noise (105 dB sound pressure level--SPL A Scale). Behavioral and endocrine measures of stress were taken throughout this habituation period, and both measures displayed strong habituation in the Chronic group. All rats were killed immediately after the day 16 exposure, constituting an acute stressor for the Acute group, and regional brain activity was assessed using c-fos mRNA induction with in situ hybridization. Hearing damage could not easily explain these results because additional rats exposed to a similar stress protocol exhibited no changes in auditory brainstem evoked potentials. c-fos mRNA induction in the central auditory system was similar between the Acute and Chronic groups, particularly at lower auditory processing levels, also arguing against a simple reduction in auditory processing in the chronically stressed rats. However, c-fos mRNA expression was reduced in chronically, as compared to acutely, stressed rats in several regions previously implicated in audiogenic stress (lateral septum, bed nucleus of the stria terminalis, some preoptic areas, and the paraventricular hypothalamic nucleus). Interestingly, the orbitofrontal cortex was the only region displaying higher c-fos mRNA induction in the chronically as compared to acutely stressed rats. This region has connections to several stress-responsive areas and may thus be a critical region actively inhibiting stress.

Animals↗