Release of antidiuretic hormone from neurohypophysis in response to hemorrhage and infusion of hypertonic saline in dogs

Influence of alpha-receptor blocking agents upon metabolic activity in nuclei involved in central control of blood pressure

The energy metabolism of the central nervous structures involved in the regulation of blood pressure was examined by means of the autoradiographic 2-deoxy-D-[14C]glucose method in normal, awake rats during hypotension induced by the alpha-adrenergic blockers, phentolamine, phenoxybenzamine, and yohimbine. Administration of these alpha-blockers produced a dose-dependent increase of glucose consumption in the medial nucleus of the solitary tract (NTSm), the dorsal motor nucleus of the vagus (DMX), the nucleus ambiguus (NA), and the paraventricular (PAVH) and supraoptic (SO) hypothalamic nuclei. However, in the external cuneate nucleus and in the paramedian reticular nucleus there was a decrease in glucose utilization. These changes appear to be at least partly due to the hypotension produced by the drugs in addition to their central effects; when the hypotension was prevented by administration of the plasma expander, dextran, in phenoxybenzamine-treated rats, the effects were less than those observed in animals with hypotension not limited by dextran infusion.

Anatomical evidence of direct projections from the nucleus of the solitary tract to the hypothalamus, amygdala, and other forebrain structures in the rat

Ascending projections from the caudal (general-visceroceptive) part of the nucleus of the solitary tract (NTS) were studied experimentally in the rat by the aid of the anterograde autoradiographic and the retrograde horseradish peroxidase (HRP) tracer techniques. Microelectrophoretic deposits of tritiated proline and leucine which involved the caudal part of the NTS, the dorsal motor nucleus of the vagus (dmX), and portions of the hypoglossal nucleus, nucleus intercalatus and/or nucleus gracilis were found to label ascending fibers that, besides going to numerous brain stem territories that included prominently the parabrachial area, could also be traced to serveral forebrain structures, namely, the bed nucleus of the stria terminalis (BST), the paraventricular (PA), dorsomedial (HDM) and arcuate (ARC) nuclei of the hypothalamus, the central nucleus of the amygdaloid complex (AC), the medial preoptic area (PM) and the periventricular nucleus of the thalamus (TPV). Smaller isotope injections almost completely confined to the NTS and dmX resulted in lighter labeling of a similar set of parabrachial and forebrain projections, whereas in another case, in which the deposit was almost exclusively limited to the nucleus gracilis, no label was seen in the aforementioned structures. In another series of experiments, aimed at further localizing the neurons of origin of the prosencephalic projections under consideration, small microelectrophoretic HRP injections confined almost totally to BST, PA, HDM, AC, PM or TPV, as well as both small and large injections involving ARC, resulted in labeled neurons situated in the dorsal medullary region, mainly in the medial portion of the NTS at the level of and caudal to the area postrema. Taken together, these observations indicate for the first time the existence of relatively direct conduction lines by which interoceptive information might be conveyed to limbic forebrain structures; some of the possible physiological correlates of these anatomical findings are discussed.