Nicotinic Acid Adenine Dinucleotide Phosphate Potentiates Neurite Outgrowth

Ca2+ regulates a spectrum of cellular processes including many aspects of neuronal function. Ca2+-sensitive events such as neurite extension and axonal guidance are driven by Ca2+ signals that are precisely organized in both time and space. These complex cues result from both Ca2+ influx across the plasma membrane and the mobilization of intracellular Ca2+ stores. In the present study, using rat cortical neurons, we have examined the effects of the novel intracellular Ca 2+-mobilizing messenger nicotinic acid adenine dinucleotide phosphate (NAADP) on neurite length and cytosolic Ca2+ levels. We show that NAADP potentiates neurite extension in response to serum and nerve growth factor and stimulates increases in cytosolic Ca2+ from bafilomycin- sensitive Ca2+ stores. Simultaneous blockade of inositol trisphosphate and ryanodine receptors abolished the effects of NAADP on neurite length and reduced the magnitude of NAADP-mediated Ca2+ signals. This is the first report demonstrating functional NAADP receptors in a mammalian neuron. Interplay between NAADP receptors and more established intracellular Ca2+ channels may therefore play important signaling roles in the nervous system

Cocaine- and Amphetamine-Regulated Transcript Peptide Attenuates Phenylephrine-Induced Bradycardia in Anesthetized Rats

The present study was undertaken to investigate the origin of cocaine- and amphetamine-regulated transcript (CART) peptide immunoreactive (irCART) fibers observed in the nucleus of the solitary tract (NTS) and assess the role of CART peptide on phenylephrine (PE)-induced baroreflex. Immunohistochemical and retrograde tract-tracing studies showed that some of the irCART fibers observed in the NTS may have their cell bodies in the nodose ganglia. In urethane-anesthetized rats, intracisternal or bilateral intra-NTS microinjection of the CART peptide fragment 55-102 (0.1-3 nmol), referred to herein as CARTp, consistently and dose dependently attenuated PE-induced bradycardia. CARTp, in the doses used here, caused no significant changes of resting blood pressure or heart rate. Bilateral intra-NTS injections of CART antibody (1:500) potentiated PE-induced bradycardia. Injections of saline, normal rabbit serum, or concomitant injection of CARTp and CART antiserum into the NTS caused no significant changes of PE-induced baroreflex. The result suggests that endogenously released CARTp from primary afferents or exogenously administered CARTp modulates PE-induced baroreflex

Glutamate Receptor Subunit Immunoreactivity in Neurons of the Rat Rostral Ventrolateral Medulla

Immunohistochemical studies were conducted to assess the subunits of ionotropic and metabotropic glutamate receptor present in the rostral ventrolateral medulla (RVLM) of the rat. Double labeling the medullary sections with polyclonal GluR1, GluR2/3, GluR4, NMDAR1, NMDAR2A/B, mGluR1α, and mGluR2/3 antiserum and monoclonal tyrosine hydroxylase (TH) antiserum revealed nearly all TH immunoreactive (irTH) cells and many TH-negative neurons were immunoreactive to GluR2/3 (irGluR2/3), NMDAR1 (irNMDAR1), and NMDAR2A/B (irNMDAR2A/B). A few RVLM neurons were immunoreactive to GluR1 (irGluR1) and GluR4 (irGluR4), but they were generally TH-negative. Immunoreactivity to mGluR1α (irmGluR1α) appeared to be localized exclusively to fiber-like elements in the RVLM area. Our results show that neurons in the RVLM, including irTH, are endowed mainly with GluR2/3 and NMDAR1 or NMDAR2A/B ionotropic receptor subunits, and that irmGluR1α splice variant appears to be located on nerve fibers ramifying within the RVLM. Moreover, TH-negative neurons in the RVLM appear to bear similar subunits of ionotropic glutamate receptors

Cocaine- and Amphetamine-Regulated Transcript Peptide-Immunoreactivity in Dorsal Motor Nucleus of the Vagus Neurons of Immature Rats

Cocaine- and amphetamine-regulated transcript (CART) peptide, a family of neuropeptides, is shown to inhibit food intake upon intracerebroventricular injection to the rat. CART peptide-immunoreactivity (irCART) was detected in neurons of the dorsal motor nucleus of the vagus (DMNV) of postnatal day one (P1) rats, the earliest day examined. The number of labeled DMNV neurons reached the peak between P5 and P8 rats and gradually declined thereafter. Few irCART neurons were noted in the DMNV between P22 and P90 rats. Double-labeling the medullary sections from P5 and P8 rats with CART-antiserum and choline acetyltransferase (ChAT)-antiserum revealed that irCART neurons in the DMNV were ChAT-immunoreactive (irChAT), but not all irChAT neurons were irCART. Intraperitoneal injection of the retrograde tracer Fluorogold to P3 and P5 rats labeled DMNV neurons, the majority of which were also irCART. The number of irCART neurons in other regions of the brain and spinal cord generally showed an increase in adult rats as compared to that of the same regions in immature rats. Our result suggests that expression of irCART in DMNV neurons undergoes developmental changes such that few neurons appear to contain irCART in mature rats. As a corollary, CART may be a signaling molecule to the gastrointestinal tract during the critical period of early development

Neuropeptide W-Immunoreactivity in the Hypothalamus and Pituitary of the Rat

Neuropeptide W-23 (NPW23) and neuropeptide W-30 (NPW30) are 23- and 30-amino acid peptides recently isolated from the porcine hypothalamus. Immunohistochemical studies using a rabbit polyclonal antiserum against the rat NPW23 peptide revealed a limited distribution in the rat brain. NPW23-immunoreactive (irNPW) cells were detected in the paraventricular nucleus (PVH), mainly in the parvocellular division, supraoptic nucleus (SO), accessory neurosecretory nuclei, dorsal and lateral hypothalamic areas, perifornical nucleus, arcuate nucleus, and anterior and posterior pituitary; whereas, irNPW fibers were noted in the PVH and SO, retrochiasmatic nucleus, dorsal and lateral hypothalamic areas, median eminence, amygdala, and posterior pituitary. The pattern of distribution of irNPW in the hypothalamus corroborates a possible role of NPW on prolactin release and feeding behavior reported by others

Pressor Response to Microinjection of Orexin/Hypocretin Into Rostral Ventrolateral Medulla of Awake Rats

Orexin A (or hypocretin 1)-immunoreactive neurons in the rat lateral hypothalamus project to several areas of the medulla oblongata that are closely associated with cardiovascular regulation. The present study was undertaken to further strengthen the hypothesis that orexin A accelerates cardiovascular response by activating sympathoexcitatory neurons in the rat rostral ventrolateral medulla (RVLM). First, immunohistochemical studies revealed the presence of orexin A-immunoreactive fibers in the RVLM. Double labeling the sections with orexin A- and tyrosine hydroxylase (TH)-antisera further showed that orexin A-immunoreactive fibers are in close proximity with TH-immunoreactive neurons, some of which may be barosensitive, bulbospinal neurons in the RVLM. Second, microinjection of orexin A (6.35, 12.7 and 38.1 μM) into the RVLM, which was verified later by histological examination, caused a significant increase of mean arterial pressure (MAP) and a moderate increase of heart rate (HR) in awake rats. L-glutamate (33.3 mM) injected into the same sites, caused a larger increase in MAP, but a decrease in HR; whereas, saline injection was without significant effect. Results from this study suggest that orexin A, which may be released from the nerve fibers originating from the neurons in the lateral hypothalamus, acting on RVLM neurons in the medulla, increases sympathetic outflow targeted to the heart and blood vessels in awake animals

Apelin-Immunoreactivity in the Rat Hypothalamus and Pituitary

With the use of an antiserum against human apelin-36, apelin-immunoreactivity (irAP) was detected in neurons and cell processes of the supraoptic nucleus (SO), paraventricular nucleus (PVH), accessory neurosecretory nuclei (Acc) and suprachiasmatic nucleus. Strongly labeled cells/processes were noted in the internal layer of the median eminence, infundibular stem, anterior and posterior pituitary. Double-labeling the sections with goat polyclonal neurophysin I-antiserum and rabbit polyclonal apelin-antiserum revealed a population of magnocellular neurons in the PVH, SO and Acc expressing both irAP and neurophysin I-immunoreactivity (irNP), the latter being a marker of oxytocin-containing neurons. By inference, the AP-positive but irNP-negative magnocellular neurons could be vasopressin-containing. The presence of irAP in certain hypothalamic nuclei and pituitary suggests that the peptide may be a signaling molecule released from the hypothalamic-hypophysial axis

Beacon-Like Immunoreactivity in the Hypothalamus of Sprague-Dawley Rats

Distribution of the novel peptide beacon in the hypothalamus of Sprague-Dawley rats was examined by immunohistochemical methods. Beacon-immunoreactive (irBC) neurons were found in the paraventricular, supraoptic, and accessory neurosecretory nuclei, and intensely labeled fibers in the median eminence and infundibulo-pituitary stalk. Scattered cells and/or fibers were noted in the suprachiasmatic nucleus, arcuate nucleus, retrochiasmatic area, lateral and medial preoptic area, as well as anterior and lateral hypothalamic area. The wide distribution of irBC in the hypothalamus of Sprague-Dawley rats suggests that the peptide may influence, in addition to a proposed role in feeding, a multitude of biological activities associated with the hypothalamic-pituitary axis