Thackery S. Gray - US grants

The central nucleus of the amygdala (CNA) and the bed of nucleus of the stria terminalis (BNST) have been implicated in gastric secretory functions and in the etiology of stress-induced gastric ulcers and hemorrhages. The studies of this proposal are intended to provide data clarifying the role of the CNA and BNST in gastric functions by using anatomical, histochemical and immunocytochemical techniques. These methods will be applied in studying the organization and the possible neurotransmitters used by CNA and/or BNST pathways to vagal gastric regions in the medulla of the rat. Information provided by the study of the biochemical and anatomical substrates mediating the development of stress-induced ulcers may aid in the clinical treatment of such problems. The topography of the CNA and BNST axonal projections to the vagal autonomic nuclei (dorsal motor nucleus of the vagus nerve, nucleus ambiguus and nucleus tractus solitarius) will be analyzed using anterograde and retrograde tracing techniques. The hypothesis that certain neuropeptides are contained within these efferent pathways will be tested using various combinations of intracranial lesions, retrograde tracers and immunocytochemistry. The hypothesis that the CNA and/or BNST are connected monosynaptically with vagal motor neurons innervating the stomach will be tested using electron microscopic and anterograde and retrograde pathway tracing techniques.

Anatomical and physiological evidence indicates that discrete regions of the amygdala, specifically the central nucleus and the bed nucleus of the stria terminalis, are responsible for activating cardiovascular, respiratory, gastric, and nociceptive responses that occur during stressful or aversive conditions. These responses are mediated through descending pathways from the amygdala to the brainstem and spinal cord. It is hypothesized that these pathways are organized according to both their neuropeptide content and their anatomical relationship to central catecholamine-containing neurons and preganglionic autonomic neurons. Studies are proposed that will examine amygdalar axon terminal topography within sympatho-activating, catecholamine containing, and respiratory regions of the brainstem and spinal cord. Amygdalar axonal terminal zones to be studied include the midbrain central gray, locus coeruleus, parabrachial nucleus, A5 catecholaminergic neurons, dorsal vagal complex, ventrolateral medulla and cervical spinal cord. Also, the anatomic relationship of amygdalar terminals to catecholaminergic neurons and cells projecting to preganglionic sympathetic regions of the spinal cord will be examined. A new highly sensitive anterograde tracer, Phaseolis vulgaris leucoagglutinin lectin, will be combined with catecholamine immunocytochemical and fluorescent dye retrograde tracing methods to accomplish these experiments. Experiments are also proposed to identify the neuropeptide content and intra-amygdalar organization of neurons which innervate the above regions of the brainstem and spinal cord. A modification of the combined fluorescent retrograde tracing and immunocytochemical technique will be employed to perform these experiments. The data will be analyzed using both quantitative and qualitative methods. The amygdala, its putative transmitters and interconnected brainstem/spinal regions participate in the development and expression of cardiovascular disease (e.g., hypertension and cardiac arrhythmias) and gastric disorders (e.g., stress-induced gastric ulcers). Therefore, the data collected by this proposal should aid in the clinical treatment and further basic scientific study of central autonomic-related diseases.