Whole-Exome Sequencing in the Isolated Populations of Cilento from South Italy.

The present study describes the genetic architecture of the isolated populations of Cilento, through the analysis of exome sequence data of 245 representative individuals of these populations. By annotating the exome variants and cataloguing them according to their frequency and functional effects, we identified 347,684 variants, 67.4% of which are rare and low frequency variants, and 1% of them (corresponding to 319 variants per person) are classified as high functional impact variants; also, 39,946 (11.5% of the total) are novel variants, for which we determined a significant enrichment for deleterious effects. By comparing the allele frequencies in Cilento with those from the Tuscan population from the 1000 Genomes Project Phase 3, we highlighted an increase in allele frequency in Cilento especially for variants which map to genes involved in extracellular matrix formation and organization. Furthermore, among the variants showing increased frequency we identified several known rare disease-causing variants. By different population genetics analyses, we corroborated the status of the Cilento populations as genetic isolates. Finally, we showed that exome data of Cilento represents a useful local reference panel capable of improving the accuracy of genetic imputation, thus adding power to genetic studies of human traits in these populations.

Myocardial ß(2) -adrenoceptor gene delivery promotes coordinated cardiac adaptive remodelling and angiogenesis in heart failure.

BACKGROUND AND PURPOSE: We investigated whether ß(2) -adrenoceptor overexpression could promote angiogenesis and improve blood perfusion and left ventricular (LV) remodeling of the failing heart. EXPERIMENTAL APPROACH: We explored the angiogenic effects of ß(2) -adrenoceptor overexpression in a rat model of post-myocardial infarction (MI) heart failure (HF). Cardiac adenoviral-mediated ß(2) -adrenoceptor overexpression was obtained via direct intramyocardial injection 4-weeks post-MI. Adenovirus(Ad)-GFP and saline injected rats served as controls. Furthermore, we extended our observation to ß(2) -adrenoceptor -/- mice undergoing MI. KEY RESULTS: Transgenes were robustly expressed in the LV at 2 weeks post-gene therapy, whereas their expression was minimal at 4-weeks post-gene delivery. In HF rats, cardiac ß(2) -adrenoceptor overexpression resulted in enhanced basal and isoprenaline-stimulated cardiac contractility at 2-weeks post-gene delivery. At 4 weeks post-gene transfer, Ad-ß(2) -adrenoceptor HF rats showed improved LV remodeling and cardiac function. Importantly, ß(2) -adrenoceptor overexpression was associated with a markedly increased capillary and arteriolar length density and enhanced in vivo myocardial blood flow and coronary reserve. At the molecular level, cardiac ß(2) -adrenoceptor gene transfer induced the activation of the VEGF/PKB/eNOS pro-angiogenic pathway. In ß(2) -adrenoceptor-/- mice, we found a ~25% reduction in cardiac capillary density compared with ß(2) -adrenoceptor+/+ mice. The lack of ß(2) -adrenoceptors was associated with a higher mortality rate at 30 days and LV dilatation, and a worse global cardiac contractility compared with controls. CONCLUSIONS AND IMPLICATION: ß(2) -Adrenoceptors play an important role in the regulation of the angiogenic response in HF. The activation of VEGF/PKB/eNOS pathway seems to be strongly involved in this mechanism.

Meta-analysis of genome-wide association studies identifies common variants in CTNNA2 associated with excitement-seeking.

The tendency to seek stimulating activities and intense sensations define excitement-seeking, a personality trait akin to some aspects of sensation-seeking. This trait is a central feature of extraversion and is a component of the multifaceted impulsivity construct. Those who score high on measures of excitement-seeking are more likely to smoke, use other drugs, gamble, drive recklessly, have unsafe/unprotected sex and engage in other risky behaviors of clinical and social relevance. To identify common genetic variants associated with the Excitement-Seeking scale of the Revised NEO Personality Inventory, we performed genome-wide association studies in six samples of European ancestry (N=7860), and combined the results in a meta-analysis. We identified a genome-wide significant association between the Excitement-Seeking scale and rs7600563 (P=2 × 10(-8)). This single-nucleotide polymorphism maps within the catenin cadherin-associated protein, alpha 2 (CTNNA2) gene, which encodes for a brain-expressed α-catenin critical for synaptic contact. The effect of rs7600563 was in the same direction in all six samples, but did not replicate in additional samples (N=5105). The results provide insight into the genetics of excitement-seeking and risk-taking, and are relevant to hyperactivity, substance use, antisocial and bipolar disorders.

Angiogenesis and biomarkers of cardiovascular risk in adults with metabolic syndrome.

OBJECTIVES: Metabolic syndrome (MetSyn) is associated with an increased risk of atherosclerosis and fatal cardiovascular events. Angiogenesis is thought to contribute to this risk as it might be involved in the progression of atherosclerotic plaques. We investigated the levels of circulating biomarkers of angiogenesis and cardiovascular risk in adults with MetSyn and assessed their association with established metabolic risk factors. DESIGN: The Genetic Park project is a highly inclusive cross-sectional survey (about 80% of residents) conducted in three isolated populations in Southern Italy. A total of 1000 men and women (age range: 18-98 years) were included in the analysis. Anthropometric and blood pressure measurements were recorded. Metabolic and cardiovascular biomarkers included glucose, triglycerides, total cholesterol, HDL, vascular endothelial growth factor, placental growth factor (PlGF), soluble fms-like tyrosine kinase-1, high-sensitivity C-reactive protein, high-sensitivity troponin T (hs-TnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP). RESULT: Subjects with MetSyn had higher levels of PlGF and NT-proBNP after adjustment for age, smoking and body mass index. Circulating levels of PlGF, hs-TnT and NT-proBNP were directly related to the number of criteria of MetSyn, and this association interacted with gender. There was a strong correlation between ageing and cardiovascular risk. CONCLUSIONS: The increase in circulating levels of biomarkers of angiogenesis and cardiac function in subjects with MetSyn mirrors the pathophysiological changes occurring in the cardiovascular system. Over time, these changes might accelerate the formation and progression of atherosclerotic plaques and contribute significantly to cardiovascular morbidity and mortality risk.

Albumin antioxidant capacity is modified by methylglyoxal.

OBJECTIVE: Oxidative stress seems to play a major role in diabetic vascular complication development. Plasma albumin, via its thiol groups, is the main extracellular antioxidant molecule. Methylglyoxal (MG) is a very reactive dicarbonyl compound increased in diabetes which strongly modifies proteins by non-enzymatic glycosylation. The aim of this work was to study if MG could modify albumin antioxidant capacity. METHODS: Bovine serum albumin was incubated with 1 mM MG at 37 degrees C for 7 days (MG-BSA). Albumin physico-chemical changes were evaluated by tryptophan autofluorescence measurement in the presence or in the absence of a quencher (acrylamide). Albumin antioxidant capacity was determined by thiol measurement using Ellman's reagent as well as in a cellular system (HeLa cells stressed by H2O2). RESULTS: MG-BSA exhibited important modifications as shown by conformational changes, decreased tryptophan autofluorescence (30%) and significant thiol loss (40%). MG-BSA led to important modifications resulting in oxidation and loss of albumin antioxidant capacity. MG-BSA modifications were close to the one observed in albumin isolated from diabetic patients. CONCLUSION: Our results suggest that deleterious effects induced by carbonyl stress in diabetes could also originate from a loss of albumin antioxidant capacity by dicarbonyl compound attack. The biological consequences of these findings have now to be investigated.

Organization of the newborn piglets vagal motor complex: insights into integrated autonomic control mechanisms.

Pediatric disorders frequently exhibit dysregulation of sympatho-vagal activity, and impaired control of cardiovascular vagal networks. Factors influencing the maturation of vagal networks are of special interest because they normally protect the heart and circulation, facilitate digestion, and preserve visceral metabolism. At present, scant literature exists regarding the development of vagal innervation of the heart. This study in neonatal swine, Sus scrofa, mapped the normal anatomy of vagal motor cell groups, with special focus on the origins of cardiomotor neurons. Right cardiac nerve branches, or the right thoracic vagal trunk were resected, inserted into capillary glass vials filled with 2% FluoroGold (FG) tracer solutions, and sealed to prevent leakage (false positives). Dorsal and ventral vagal complexes were identified on cross-sectioned tissues incubated in a well-characterized specific FG antibody. Thoracic and abdominal vagal motoneurons were cytologically heterogeneous, and predominantly medium-sized, polygonal cell bodies. Discrete longitudinal cell columns were observed, as well as organized arrays of elongate spindle-shaped cells in formation. Long axes and dendrites appeared to orient toward incoming peripheral sensory and central afferents, and were juxtaposed to cerebral microvasculature. The piglets' dorsal vagal complex is: (i) thick and long, comparable to ruminants, in contrast to much shorter lengths in non-ruminants, and (ii) the chief source of vagal motoneurons, forming discrete, topographically organized parasympathetic cell groups with distinct dendritic arbors. The cardiac motor subnucleus is localized to a highly restricted areal subunit of nucleus ambiguus' external formation in the vicinity of the obex. On the other hand, dorsal cardiac vagal motoneurons were few in number and diffusely distributed. Dorsal vagal motoneurons of neonatal swine likely projected primarily to the enteric nervous system, exerting excitatory influence over gastrointestinal activity.

Secretin: hypothalamic distribution and hypothesized neuroregulatory role in autism.

1. This study aims (1) to determine whether secretin is synthesized centrally, specifically by the HPA axis and (2) to discuss, on the basis of the findings in this and previous studies, secretin's possible neuroregulatory role in autism. 2. An immunocytochemical technique with single-cell resolution was performed in 12 age/weight-matched male rats pretreated with stereotaxic microinjection of colchicine (0.6 microg/kg) or vehicle into the lateral ventricle. Following 2-day survival, rats were anesthetized and perfused for immunocytochemistry. Brain segments were blocked and alternate frozen 30-microm sections incubated in rabbit antibodies against secretin, vasoactive intestinal peptide, glucagon, or pituitary-adenylate-cyclase-activating peptide. Adjacent sections were processed for Nissl stain. Preadsorption studies were performed with members of the secretin peptide family to demonstrate primary antibody specificity. 3. Specificity of secretin immunoreactivity (ir) was verified by clear-cut preadsorption control data and relatively high concentrations and distinct topographic localization of secretin ir to paraventricular/supraoptic and intercalated hypothalamic nuclei. Secretin levels were upregulated by colchicine, an exemplar of homeostatic stressors, as compared with low constitutive expression in untreated rats. 4. This study provides the first direct immunocytochemical demonstration of secretinergic immunoreactivity in the forebrain and offers evidence that the hypothalamus, like the gut, is capable of synthesizing secretin. Secretin's dual expression by gut and brain secretin cells, as well as its overlapping central distribution with other stress-adaptation neurohormones, especially oxytocin, indicates that it is stress-sensitive. A neuroregulatory relationship between the peripheral and central stress response systems is suggested, as is a dual role for secretin in conditioning both of those stress-adaptation systems. Colchicine-induced upregulation of secretin indicates that secretin may be synthesized on demand in response to stress, a possible mechanism of action that may underlie secretin's role in autism.

Glycosphingolipid changes induced by advanced glycation end-products.

The effects of advanced glycation end-products (AGEs) on retinal microvascular cell glycosphingolipids were investigated as a potential pathogenic mechanism of diabetic retinopathy. The results obtained showed that, in microvascular retinal endothelial cells and pericytes, AGEs increased the amount of all glycosphingolipids studied (from 25 to 115% depending on the glycosphingolipid species), except for a specific ganglioside, GD3, which decreased by 35% only in pericytes. Glycosphingolipid profiles and GM3 fatty acid analysis did not show any qualitative differences after incubation with AGEs, suggesting that AGEs only induced quantitative changes in cell glycosphingolipids. These results show a new metabolic effect of AGEs, which could be involved in the microvascular alterations observed in diabetic retinopathy.

Catecholamine monoamine oxidase a metabolite in adrenergic neurons is cytotoxic in vivo.

3,4-Dihydroxyphenylglycolaldehyde is the monoamine oxidase-A metabolite of two catecholamine neurotransmitters, epinephrine and norepinephrine. This aldehyde metabolite and its synthesizing enzymes increase in cell bodies of catecholamine neurons in Alzheimer's disease. To test the hypothesis that 3,4-dihydroxyphenylglycolaldehyde, but not epinephrine or its major metabolite 4-hydroxy-3-methoxyphenylglycol, is a neurotoxin, we injected 3,4-dihydroxyphenylglycolaldehyde onto adrenergic neurons in the rostral ventrolateral medulla. Injections of epinephrine or 4-hydroxy-3-methoxyphenylglycol were made into the same area of controls. A dose response and time study were performed. Adrenergic neurons were identified by their content of the epinephrine synthesizing enzyme, phenylethanolamine N-methyltransferase, immunohistochemically. Apoptosis was evaluated by in situ terminal deoxynucleotidyl-transferase mediated dUTP nick end label staining. Injection of 3,4-dihydroxyphenylglycolaldehyde in amounts as low as 50 ng results in loss of adrenergic neurons and apoptosis after 18 h. The degree of neurotoxicity is dose and time dependent. Doses of 3,4-dihydroxyphenylglycolaldehyde 10-fold higher produce necrosis. Neither epinephrine nor 4-hydroxy-3-methoxyphenylglycol are toxic. A 2.5 microg injection of 3,4-dihydroxyphenylglycolaldehyde is toxic to cortical neurons but not glia. Active uptake of the catecholamine-derived aldehyde into differentiated PC-12 cells is demonstrated. Implications of these findings for catecholamine neuron death in neurodegenerative diseases are discussed.

A brainstem area mediating cerebrovascular and EEG responses to hypoxic excitation of rostral ventrolateral medulla in rat.

We sought to identify the medullary relay area mediating the elevations of regional cerebral blood flow (rCBF) and synchronization of the electroencephalogram (EEG) in the rat cerebral cortex elicited by hypoxic excitation of reticulospinal sympathoexcitatory neurons of the rostral ventrolateral medulla (RVLM ). In anaesthetized spinalized rats electrical stimulation of RVLM elevated rCBF (laser-Doppler flowmetry) by 31 +/- 6 %, reduced cerebrovascular resistance (CVR) by 26 +/- 8 %, and synchronized the EEG, increasing the power of the 5-6 Hz band by 98 +/- 25 %. Stimulation of a contiguous caudal region, the medullary cerebral vasodilator area (MCVA), had comparable effects which, like responses of RVLM, were replicated by microinjection of L-glutamate (5 nmol, 20 nl). Microinjection of NaCN (300 pmol in 20 nl) elevated rCBF (17 +/- 5 %) and synchronized the EEG from RVLM, but not MCVA, while nicotine (1.2 nmol in 40 nl) increased rCBF by 13 +/- 5 % and synchronized the EEG from MCVA. In intact rats nicotine lowered arterial pressure only from MCVA (101 +/- 3 to 52 +/- 9 mmHg). Bilateral electrolytic lesions of MCVA significantly reduced, by over 59 %, elevations in rCBF and, by 78 %, changes in EEG evoked from RVLM. Bilateral electrolytic lesions of RVLM did not affect responses from MCVA. Anterograde tracing with BDA demonstrated that RVLM and MCVA are interconnected. The MCVA is a nicotine-sensitive region of the medulla that relays signals elicited by excitation of oxygen-sensitive reticulospinal neurons in RVLM to reflexively elevate rCBF and slow the EEG as part of the oxygen-conserving (diving) reflex initiated in these neurons by hypoxia or ischaemia.

Chronic-intermittent hypoxia induces immediate early gene expression in the midline thalamus and epithalamus.

Chronic-intermittent hypoxia (CIH) was postulated to activate thalamic regions that are synaptically related to autonomic-related areas of the cerebral cortex. Animals exposed to CIH for 30 days exhibited c-fos labeling in paraventricular thalamic and lateral habenular nuclei. Our findings strongly suggest activation of a diencephalic network that participates in behavioral responses to chronic stress.

In vitro autoradiography of serotonin 5-HT(2A/2C) receptor-activated G protein: guanosine-5'-(gamma-[(35)S]thio)triphosphate binding in rat brain.

Agonist activation of G protein-coupled receptors induces an increase in the binding of guanosine 5'-(gamma-[(35)S]thio)triphosphate ([(35)S]GTPgammaS); this increase in binding has been used as a tool to investigate receptor interaction with the heterotrimer guanine nucleotide-binding regulatory protein (G protein). The present study uses agonist-stimulated [(35)S]GTPgammaS binding to characterize serotonin 5-HT(2A/2C) receptors in rat brain membrane fractions and demonstrate the anatomical localization of the receptors by in vitro autoradiography on slide-mounted sections. The stimulatory effect of the agonist [1-(2,5-dimethoxy-4-iodophenyl)]-2 aminopropane (DOI) is compared to that of serotonin (5-HT). Autoradiography revealed a similar localization of DOI- and 5-HT-stimulated binding of [(35)S]GTPgammaS in distinct areas of prefrontal and parietal cortex, consistent with previously reported 5-HT(2A) receptor distribution. Specific binding was demonstrated in the frontal and parietal cortex, medial prefrontal, and cingular and orbital-insular areas as well as in the hippocampal formation, septal areas, the nucleus accumbens, and the choroid plexus. MDL 100105, a specific 5-HT(2A) antagonist, and ketanserin, an antagonist of 5-HT(2A/2C) receptors, blocked DOI stimulation in all labeled areas, whereas 5-HT stimulation was only partially blocked (70-80%). A small but significant inhibition was observed with the specific antagonist of 5-HT(2C/2B), SB 206553. This autoradiographic technique provides a useful tool for measuring in situ changes in specific receptor-Gq protein coupling in anatomically discrete brain regions, under physiological and pathological conditions.

Chronic-intermittent hypoxia: a model of sympathetic activation in the rat.

This review focuses upon the development of a small animal model that incorporates exposure to chronic-intermittent hypoxia to produce systemic hypertension similar to that experienced by humans with the obstructive sleep apnea syndrome. It has been suggested that experimentally-induced hypertension, like human hypertension, is due to activation of the sympathetic nervous system. That hypothesis is supported by physiological studies carried out in humans with obstructive sleep apnea as well as in animals exposed to chronic-intermittent hypoxia. Furthermore, recent anatomical studies of exposed animals strongly suggested that activation was widespread and included cortical and brainstem components of the sympathetic system. Such findings, while illustrating the complexity of modeling human disease in animals, also demonstrate the heuristic value of chronic-intermittent hypoxia as an experimental approach.

Immediate-early gene expression in cerebral cortex following exposure to chronic-intermittent hypoxia.

Chronic-intermittent hypoxia (CIH) was postulated to evoke c-fos expression in cortical regions that modulate sympathetic discharge. Animals exposed to CIH for 30 days exhibited c-fos labeling in medial prefrontal, cingulate, retrosplenial, and insular cortices. Our findings strongly suggest activation of cortical circuits that adaptively regulate sympathetic and cardiovascular activities.

The human nucleus of the solitary tract: visceral pathways revealed with an "in vitro" postmortem tracing method.

Visceral relay neurons in the nucleus of the solitary tract (NTS) regulate behavior and autonomic reflex functions. NTS projections have been extensively characterized in animal studies but not in humans. For the first time, NTS fiber trajectories in the human medulla oblongata were revealed with an "in vitro" postmortem tracing method. Local intramedullary pathways were labeled by direct pressure injections of free horseradish peroxidase centered on the medial subnucleus at a level adjacent to true obex. Labeled elements were resolved by peroxidase histochemistry as a dark brown intracellular reaction product. A prominent transtegmental system of axons emerged from the NTS injection sites and entered the intermediate reticular zone, a region corresponding to an autonomic reflex center in other mammals. A medial system of axons arched across the dorsomedial reticular formation toward the dorsal medullary raphe and projected ventrally toward the nucleus gigantocellularis. A small lateral fiber trajectory coursed towards the dorsomedial zone of spinal trigeminal nucleus caudalis. Presumptive terminals appeared as dustings of fine punctate processes within the NTS, dorsomotor nucleus and reticular formation. NTS projections in humans resemble those identified in other mammals including primates. Axonal tracing studies predict that visceral impulses in humans may transmit over evolutionarily conserved pathways involved in autonomic feedback control and stress adaptation.

CO(2)-induced expression of c-fos in the nucleus of the solitary tract and the area postrema of developing swine.

This investigation was performed to determine whether hypercapnic exposure elicited expression of the c-fos protooncogene product, FOS, in nucleus of the solitary tract (NTS) and area postrema (AP) neurons of developing swine. Mean arterial blood pressure (MAP) and heart rate (HR) were also monitored to evaluate whether numbers of neurons containing FOS were related to changes of MAP and HR. In each experiment, two litter-matched piglets were prepared simultaneously, i.e., Saffan anesthesia, paralysis, and artificial ventilation (100% O(2)). One animal was exposed to hypercapnia (1 h of 10% CO(2), balance oxygen), while the other continued to breathe 100% O(2). Animals were studied at three different ages: 5-8 days, 13-15 days, and 26-34 days old. In the NTS, FOS expression was prominent in regions corresponding to the general visceral afferent subdivision; the AP showed no such topographic distribution. The number of NTS and AP neurons with FOS in hypercapnic-exposed animals was significantly greater than those of unexposed animals. However, an age-related increase of FOS was observed only for NTS neurons, with the greatest number observed in 13- to 15-day-old animals. Increases of MAP, not HR, were noted during the early part of hypercapnia in the 5- to 8-day-old group; older animals exhibited no change of MAP. Our findings demonstrated that prolonged hypercapnic stimulation elicited FOS expression in AP and NTS neurons of developing animals, and that such expression was non-uniform, depending upon the region studied.

The area postrema of newborn swine is activated by hypercapnia: relevance to sudden infant death syndrome?

This study was performed to investigate a role of the neonatal area postrema (AP) in the chemoreceptor response to hypercapnia which is defective in sudden infant death syndrome (SIDS). AP responses to CO2 inhalation were monitored in 1 to 5 week old piglets by mapping neurons that were induced to express the c-fos gene product, Fos--a marker of functional activation. Interpretive confounds were minimized by controlling for hypoxia, the effects of surgical procedures and ambient environmental stressors on neuronal activity (c-fos expression). The AP demonstrated a powerful and reproducible response in neonatal swine breathing 10% CO2 for 1 h. Intensely immunolabeled nuclei were detected throughout the longitudinal extent of the circumventricular organ, and were especially heavily concentrated at rostral levels proximal to obex. Quantitative analysis verified statistically significant increases in numbers of cells that were induced to express Fos-like immunoreactivity (FLI) in the AP of CO2- stimulated piglets as compared to control groups. No detectable age-related differences were observed in AP response patterns. Conclusions. The AP responds to hypercapnic stress in the newborn piglet. A mature circumventricular organ response in the neonate may be crucial in defending against common environmental stressors, such as nicotine exposure--an emetic agent acting via the AP and a major risk factor in SIDS. Hence, a defect of the AP or its network may underlie a loss of state-dependent controls over cardiopulmonary reflex function in SIDS.

Corticotropic-releasing hormone and serotonin interact in the human brainstem: behavioral implications.

The objective of this human post mortem study was to determine whether neurons which synthesize corticotropic-releasing hormone and serotonin form circuits implicated in the pathophysiology of major depression and suicide. For the first time, a sensitive, dual immunocytochemical procedure was used to identify circuits formed by corticotropic-releasing hormone-synthesizing and serotonergic cell groups. Corticotropic-releasing hormone-immunoreactive varicose fibers and puncta with morphological characteristics of terminals were labeled in the midline raphe, periventricular gray and pontine parabrachial complex, on single-labeled tissues processed immunocytochemically with a rabbit antibody to rat/human corticotropic-releasing hormone. Presumptive synaptic interactions with monoaminergic neurons were demonstrated with dual labeling techniques. Corticotropic-releasing hormone-immunoreactive terminals apposed neuronal somata and primary dendrites of serotonergic neurons in the pontine raphe. Serotonergic neurons were immunolabeled with a mouse antibody to phenylalanine hydroxylase, an enzyme with substantial sequence homology to tryptophan hydroxylase. Interactions in the lateral parabrachial nucleus were suggested by precise overlap of corticotropic-releasing hormone and serotonergic terminal fields. Corticotropic-releasing hormone projections were confirmed to noradrenergic neurons containing neuromelanin in the locus ceruleus. Maps of corticotropic-releasing hormone fiber trajectories suggest that these pathways may derive from the forebrain and, locally, from the human homologue of Barrington's nucleus--a neurochemically specialized division of the laterodorsal tegmental complex. Chemosensory functions were predicted by novel evidence for corticotropic-releasing hormone- and monoaminergic neurovascular and subependymal fiber plexuses. In conclusion, corticotropic-releasing hormone may influence the activity of two major monoaminergic cell systems implicated in the stress-diathesis model of mental illness, through neural and humoral mechanisms.

Dorsal raphe nucleus serotonergic neurons innervate the rostral ventrolateral medulla in rat.

Stimulation of the dorsal raphe nucleus (DRN) alters arterial pressure, heart rate and cerebral blood flow, yet projections from the DRN to medullary autonomic nuclei have not been described. We examined whether serotonergic (5-HT) projections from the DRN terminate in the rostral ventrolateral medulla (RVL) and if so, whether the projection mediates cardiovascular responses to DRN stimulation. Studies were performed in adult male Sprague-Dawley rats. Horseradish peroxidase or choleratoxin B was injected unilaterally or bilaterally into the RVL. Levels of 5-HT, its precursors L-tryptophan and 5-hydroxytryptophan and the metabolite 5-hydroxyindole acetic acid were measured in the ventral medulla by HPLC three weeks following placement of electrolytic lesions in DRN. Serotonin transporter (3H-cyanoimipramine binding) was quantified by autoradiography in DRN-lesioned animals. Horseradish peroxidase or choleratoxin B injections into the medulla at the level of the RVL resulted in retrogradely labeled neurons bilaterally, with ipsilateral predominance, in the DRN. Labeled cells were preponderant in rostral ventrolateral portions of the DRN, but were also observed in the dorsal, lateral and interfascicular DRN subnuclei; fewer neurons were observed in caudal portions of the DRN. Three weeks following placement of electrolytic lesions in the DRN, the concentrations of 5-HT and 5-hydroxyindole acetic acid, but not L-tryptophan or 5-hydroxytryptophan, were reduced in the medulla by 45 and 48%, respectively, compared to sham-operated or unoperated controls. DRN lesions reduced binding to the 5-HT transporter in the RVL by approximately 30% compared to unlesioned controls. Unilateral lesions of the RVL reduced the evoked blood pressure response by 53+/-15%; bilateral RVL lesions reduced the response by 86+/-9%. The increase in cortical blood flow elicited by DRN stimulation was unchanged after unilateral or bilateral RVL lesions. These studies demonstrate that there is a descending serotonergic projection from the DRN to the RVL. This projection may mediate autonomic changes elicited by DRN stimulation.

Expression of c-fos in the rat brainstem after chronic intermittent hypoxia.

Chronic intermittent hypoxia (CIH) may cause sustained systemic hypertension by increasing sympathetic neural discharge (SND). We hypothesized that CIH alters brainstem circuits modulating SND. After 30 days of CIH exposure in rats, increased c-fos labeling was seen in the nucleus of the solitary tract and ventrolateral medulla as well as other brainstem regions involved in regulation of SND. Increased expression of c-fos after CIH may indicate changes in neuronal genetic transcription which ultimately modulate SND.