Donald J. Reis - US grants

The Experimental Neurogenic Hypertension Program is a multidisciplinary research program investigating the neurobiology of central neural systems governing arterial pressure (AP), regulating the cerebral circulation, and protecting against cerebral ischemia. The broad objectives of this revised proposal are: (a) to investigate the organization within the rostral ventrolateral medulla (RVL) of neurons controlling regional cerebral blood flow (rCBF), and to characterize the efferent pathway, subcortical relay, and intracortical mechanisms by which electrical, chemical and hypoxic stimulation of the nucleus elevates rCBF; (b) to determine, by anatomical tracing methods, the anatomy of pathways by which visceral signals arising in the nucleus tractus solitarii (NST) ascend to influence the performance of thalamic and forebrain centers involved in processing emotional behaviors; to examine, using techniques of EM immunocytochemistry, the distribution and synaptic relationships of alpha2-2- adrenergic, mu and delta-opiate, and NMDA receptors in and around the perikarya and terminals of sympathoexcitatory reticulospinal neurons of RVL, particularly with respect to sites of action of clonidine; to establish, by similar methods, the sites of and interactions between these, and also the kappa-opioid receptors in NTS in relationship to vagal afferent fibers; (e) to analyze the cellular and genetic mechanisms by which electrical stimulation of the cerebellar fastigial nucleus (FN) can conditionally reduce the volume of focal ischemic infarctions of rat brain, either by modifying Kplus channels, and/or suppressing expression of pro-inflammatory genes, and/or facilitating expression of anti-inflammatory and neuroprotective genes.

Neuropeptide Y (NPY) is a highly bioactive 36-amino acid peptide that occurs abundantly in brain. In preliminary experiments, we found that repeated administration of cocaine elicits substantial, long-lasting, biochemically-selective, and reversible reductions in levels of NPY and NPY mRNA in regions of rat cerebral cortex and nucleus accumbens. Excitotoxic lesions of medial prefrontal cortex, a region thought to be of importance for the expression of some of cocaine's reinforcing properties, did not affect NPY per se but prevented the reduction of NPY elicited by cocaine. Thus, it appears that chronic exposure to cocaine transneuronally reduces, in selected neurons, the biosynthesis of NPY, possibly in response to increases in synaptic dopamine (DA) deriving from mesolimbic/mesocortical neurons; the integrity of the medial prefrontal cortex may be crucial for cocaine's action on this neuronal network. In this study, we seek to determine regional selectivity and kinetics of cocaine/NPY interactions. The hypothesis that DA mediates cocaine's action on transcription of the NPY gene will be tested in vivo and in vitro. Moreover, the reduction in NPY may be reflected in cerebrospinal fluid and by an upregulation of NPY receptors. Finally, we will explore the possibilities that the nucleus accumbens, like the medial prefrontal cortex, is necessary for the effect, and that gestational and/or neonatal cocaine exposure affects NPY systems. We propose that NPY may be a sensitive and selective marker for chronic cocaine use. Its reduction may relate to the anxiety and depression associated with cocaine withdrawal in man.

Project V seeks to establish the mechanisms by which electrical stimulation of the cerebellar fastigial nucleus (FN) reduces the volume of the focal ischemic infarction produced by permanent occlusion of the middle cerebral artery (MCAO) in rat. Specifically, it tests the hypotheses that the central neurogenic protection results from interaction of two events: (a) a reduction in neuronal excitability, and (b) suppression of inflammatory reactions. Study I will determine whether (a) electrical stimulation of FN in anesthetized rats reduces the depolarizing (DC) waves generated in the ischemic penumbra after MCAO (b) FN stimulation in normal rats alters the threshold and pattern of spreading cortical depression; and (c) in case that excitability is altered, if the response can be attributed to alteration in neuronal Kplus channel function. Study II will examine whether (a) MCAO will induce, in brain, expression of the mRNAs and/or protein products for the pro-inflammatory molecules iNOS and lL1-beta; and the endothelial adhesion molecules ICAM and VCAM;(b) FN stimulation reduces the expression of these molecules by MCAO; (c) the inflammatory reactivity of vessels isolated from FN-stimulated brains is reduced compared to non-stimulated brains; (d) FN stimulation reduces the responses to lL-1 injection in brain; (e) FN stimulation modifies the transcription factor NFKbeta, which coordinates expression of inflammatory genes; (f) FN stimulation induces the mRNA and/or proteins for the anti-inflammatory cytokines lL4, lL10, lL-1Ra and/or TGFbeta.