Naiphinich Kotchabhakdi

Distinct Deactivation and Desensitization Kinetics of Recombinant GABAA Receptors

The functional role of the large heterogeneity in GABAA receptor subunit genes and its role in setting the properties of inhibitory synapses in the CNS is poorly understood. A kinetic comparison between currents elicited by ultra-rapid application with a piezoelectric translator of 1 mM GABA to mammalian cells transfected with cDNAs encoding distinct GABAA receptor subunits revealed that the intrinsic deactivation and desensitization properties depend on subunit combination. In particular, receptors containing alpha 6 with beta 2 gamma 2 subunits were endowed with a significantly slower deactivation as compared to those receptors containing alpha 1 with beta 2 gamma 2 subunits. While desensitization produced by prolonged GABA applications on alpha 1 beta 2 gamma 2 receptors was characterized by a rapid exponential decay followed by a slower decay and a steady state response, alpha 6 beta 2 gamma 2 receptors lacked desensitization. Furthermore, GABAA receptors lacking the gamma 2 subunit were characterized by a much larger non-desensitization component and a very rapid deactivation. Lastly, analysis of GABA-activated currents in cells cotransfected with alpha 1 and alpha 6 together with beta 2 gamma 2 subunit revealed unique kinetic properties. Our results suggest that distinct subunit composition confers specific deactivation and desensitization properties that may profoundly affect synaptic decay kinetics and the capability to sustain high frequency synaptic inputs.

Exercise during pregnancy increases hippocampal brain-derived neurotrophic factor mRNA expression and spatial learning in neonatal rat pup

Physical activities for a few days can increase brain-derived neurotrophic factor (BDNF) mRNA in rat hippocampus. To investigate the influence of maternal exercise during pregnancy on rat pup hippocampal BDNF mRNA, we studied its expression by a semi-quantitative RT-PCR method after young pregnant rats were exercised on a motor driven treadmill. Pups of exercised mothers had significantly increased hippocampal BDNF mRNA expression compared to the control rat pups at birth (on postnatal day 0) (P<0.001). In contrast, hippocampal BDNF mRNA expression in pups of exercised mothers decreased significantly on postnatal day 28 (P<0.002). Spatial learning of rat pups was examined by multiple T maze training for 7 consecutive days between postnatal days 40 and 47. Pups of exercised mothers showed a significant increase in spatial learning ability as demonstrated by significant decreases in total time from starting to target and total number of errors as compared to age-matched control pups during the first 4 days of 7 consecutive days on multiple T maze training (P<0.05). Thus, physical exercise during gestation in pregnant mothers can increase hippocampal BDNF mRNA expression of postnatal pups and result in an improvement in spatial learning in pups from exercised dams.

Postnatal Touch Stimulation Acutely Alters Corticosterone Levels and Glucocorticoid Receptor Gene Expression in the Neonatal Rat

Environmental manipulation early in life can alter the development of the hypothalamic-pituitary-adrenal (HPA) axis by mechanisms that are still unclear. The aim of the present work was to study the acute effects of postnatal touch stimulation, in an attempt to understand the mechanism by which touch stimulation early in life alters the HPA response to stress in adult animals. Rat pups were gently brushed for 15 min daily during the 1st postnatal week. Serum corticosterone levels were determined by radioimmunoassays, while glucocorticoid receptor (GR) gene expression was assayed by semiquantitative reverse transcriptase-polymerase chain reaction. Touch stimulation induced a significant decrease (30–36%) in serum corticosteroid secretion during the 1st and 2nd postnatal day as compared to the unstimulated group. In contrast, GR gene expression in the touch stimulation group was significantly increased in several brain areas such as the hippocampus (19–21%), frontal cortex (26–34%) and midbrain (15–24%). The results thus indicate that neonatal touch stimulation causes acute hormone- secretion and gene-expression changes within the period of stimulation. These changes may be the underlying cause for the permanent changes that have been observed in adult animals touch-stimulated as neonates.

Characterization of the Hyperphagic Response to Dietary Fat in the MC4R Knockout Mouse

Defective melanocortin signaling causes hyperphagic obesity in humans and the melanocortin-4 receptor knockout mouse (MC4R(-/-)). The human disease most commonly presents, however, as haploinsufficiency of the MC4R. This study validates the MC4R(+/-) mouse as a model of the human disease in that, like the MC4R(-/-), the MC4R(+/-) mouse also exhibits a sustained hyperphagic response to dietary fat. Furthermore, both saturated and monounsaturated fats elicit this response. N-acylphosphatidylethanolamine (NAPE) is a signaling lipid induced after several hours of high-fat feeding, that, if dysregulated, might explain the feeding behavior in melanocortin obesity syndrome. Remarkably, however, MC4R(-/-) mice produce elevated levels of NAPE and are fully responsive to the anorexigenic activity of NAPE and oleoylethanolamide. Interestingly, additional differences in N-acylethanolamine (NAE) biochemistry were seen in MC4R(-/-) animals, including reduced plasma NAE levels and elevated hypothalamic levels of fatty acid amide hydrolase expression. Thus, while reduced expression of NAPE or NAE does not explain the high-fat hyperphagia in the melanocortin obesity syndrome, alterations in this family of signaling lipids are evident. Analysis of the microstructure of feeding behavior in response to dietary fat in the MC4R(-/-) and MC4R(+/-) mice indicates that the high-fat hyperphagia involves defective satiation and an increased rate of food intake, suggesting defective satiety signaling and enhanced reward value of dietary fat.

Alteration of muscarinic acetylcholine receptors in rabies viral-infected dog brains

Functions of the muscarinic acetylcholine receptor (mAChR) were studied in rabid dog brains using [3H]quinuclidinyl benzilate (QNB) as a radioligand. Of various brain regions, hippocampus and brainstem were the areas mostly affected in terms of impaired specific binding to [3H]QNB, as compared to other regions, as well as to those of controls. Saturation studies of the hippocampus revealed significantly elevated dissociation equilibrium constant (K(d)) values in both furious (n = 5) (9.80 + or - 2.77 nM) and dumb (n = 6) (6.01 + or - 1.08 nM) types of rabies as compared to 11 controls (2.15 + or - 0.31 nM), whereas the maximum number of receptor sites (B (max)) values were comparable among all subgroups of normal (1.38 + or - 0.10 pmol/mg protein), dumb (1.43 + or - 0.17 pmol/mg protein) and furious (1.28 + or - 0.12 pmol/mg protein) rabies types. Hippocampal K(d) values were comparable between high (fluorescent antibody test-FAT and polymerase chain reaction-PCR positive; n = 4) (7.47 + or - 3.27 nM), and low (FAT-negative and PCR-positive; n = 4) virus amount (8.34 + or - 3.93 nM) but these were significantly higher than controls (n = 4) (1.58 + or - 0.17 nM). Our data suggest a functional derangement of mAChR at specific sites of hippocampus and brainstem which is not dependent on the amount of virus.

Amyloid Deposits Show Complexity and Intimate Spatial Relationship with Dendrosomatic Plasma Membranes: An Electron Microscopic 3D Reconstruction Analysis in 3xTg-AD Mice and Aged Canines

Little is known about how amyloid-beta (Abeta) is deposited in relation to the complex ultrastructure of the brain. Here we combined serial section immunoelectron microscopy with 3D reconstruction to elucidate the spatial relationship between Abeta deposits and ultrastructurally identified cellular compartments. The analysis was performed in a transgenic mouse model with mutant presenilin-1, and mutant amyloid-beta protein precursor (AbetaPP) and tau transgenes (3xTg-AD mice) and in aged dogs that develop Abeta plaques spontaneously. Reconstructions based on serial ultrathin sections of hippocampus (mice) or neocortex (dogs) that had been immunolabeled with Abeta (Abeta(1-42)) antibodies showed that the organization of extracellular Abeta deposits is more complex than anticipated from light microscopic analyses. In both species, deposits were tightly associated with plasma membranes of pyramidal cell bodies and major dendrites. The deposits typically consisted of thin sheets as well as slender tendrils that climbed along the large caliber dendritic stems of pyramidal neurons. No preferential association was observed between Abeta deposits and thin dendritic branches or spines, nor was there any evidence of preferential accumulation of Abeta around synaptic contacts or glial processes. Our data suggest that plaque formation is a precisely orchestrated process that involves specialized domains of dendrosomatic plasma membranes.

Stress, anxiety and peripheral benzodiazepine receptor mRNA levels in human lymphocytes

Peripheral benzodiazepine receptor (PBR) mRNA levels were measured in lymphocytes obtained from a cohort of university students and clinically diagnosed anxious patients. The average level of PBR mRNA was decreased in anxious patients compared to a control group. This data confirms previously published results, but it also indicates that PBR mRNA levels cannot be used as a sole diagnostic measure of anxiety because the range of the individual PBR mRNA levels of the anxious group overlapped the range of the PBR mRNA levels of the control group. PBR mRNA levels in students following academic examinations were increased in some individuals and decreased in others. In the same cohort of students individual levels of cortisol and prolactin were predominantly increased and decreased respectively. There was no correlation between the individual changes in the hormone levels or PBR mRNA, which suggests that each of these parameters is affected by different environmental and physiological factors. Lymphocyte PBR mRNA measurement is a useful additional methodology for studying human stress responses however, its use in clinical studies would require the elucidation of PBRs physiological role.

Epidemiology of sleep-related complaints associated with sleep-disordered breathing in Bangkok, Thailand

BACKGROUND This study assesses the prevalence of and risk factors for sleep-related complaints in Bangkok, Thailand. METHODS A representative sample of the Bangkok population was selected based on results of the 2000 Census. A total of 4680 participants underwent face-to-face interview with a 49-question sleep inventory. RESULTS Four percent of the total sampled (5.3% of men and 3.5% of women) complained of habitual snoring (>3 nights/week) and excessive daytime sleepiness (>3 days/week) for at least 3 months. These subjects were significantly (p<0.0001) older (41.4 vs. 36.7 years), had greater BMI (26.0 vs. 22.8 kg/m(2)), neck size (34.7 vs. 32.5 cms), and waist circumference (88.0 vs. 78.7 cms). They reported significantly shorter nocturnal sleep time, greater frequency of sleep disturbances and awakenings, unrefreshing sleep, choking during sleep, night sweats, nocturia, and bruxism. There was also a greater prevalence of cardiovascular and endocrine diseases. Multivariate analysis showed that male gender; BMI; waist size; and reports of witnessed apneas, unrefreshing sleep and night sweats were significant predictors of snoring and daytime sleepiness. CONCLUSION This is the first epidemiologic study investigating sleep-related complaints and associated health morbidities in the Thai population.

Innervation of the cat pineal gland by neuropeptide Y-immunoreactive nerve fibers : an experimental immunohistochemical study

An immunohistochemical study of the cat pineal gland was performed using a rabbit polyclonal antibody directed against neuropeptide Y (NPY) and an antibody directed against the C-terminal flanking peptide of neuropeptide Y (CPON). Numerous NPY- and CPON-immunoreactive (IR) nerve fibers were demonstrated throughout the gland and in the pineal capsule. The number of IR nerve fibers in the capsule was high and from this location fibers were observed to penetrate into the gland proper via the pineal connective tissue septa, often following the blood vessels. From the connective tissue septa IR fibers intruded into the parenchyma between the pinealocytes. Many IR nerve fibers were observed in the pineal stalk and in the habenular as well as the posterior commissural areas. The number of NPY/CPON-IR nerve fibers in pineal glands from animals bilaterally ganglionectomized two weeks before sacrifice was low. The source of most of the extrasympathetic NPY/CPONergic nerve fibers is probably the brain from where they enter the pineal via the pineal stalk. However, an origin of some of the fibers from parasympathetic ganglia cannot be excluded due to the presence of a few IR fibers in the pineal capsule of ganglionectomized animals. It is concluded that the cat pineal is richly innervated with NPYergic nerve fibers mostly of sympathetic origin. The posttranslational processing of the NPY promolecule results in the presence of both NPY and CPON in intrapineal nerve fibers.

Drug discrimination analysis of pseudoephedrine in rats

Rats were trained to discriminate amphetamine, 1 mg/kg given intraperitoneally, from saline injection in a two-lever operant drug discrimination task. Pseudoephedrine (a sympathomimetic drug with central and peripheral actions) at doses of 10 mg/kg failed to substitute for amphetamine, at 20 mg/kg partial substitution occurred, while at a 40 mg/kg full substitution was seen. The specificity of the amphetamine cue at the training dose used (1 mg/kg) was shown by the finding that a peripherally acting sympathomimetic drug phenylephrine at doses from 0.2 to 0.8 mg/kg failed to substitute for amphetamine. The potential for abuse of pseudoephedrine administered at high doses is discussed.