DEVELOPMENTAL SODIUM RESTRICTION AND GUSTATORY AFFERENT TERMINAL FIELD ORGANIZATION IN THE PARABRACHIAL NUCLEUS

Dietary sodium restriction instituted early in prenatal development pr oduces physiological, anatomical, and functional changes in the gustat ory system. For trample, a rearrangement of the chorda tympani nerve t erminal field within the nucleus of the solitary tract (NST) is observ ed in rats sodium restricted during development. The altered pattern o f the chorda tympani nerve innervation within the nucleus of the solit ary tract remains even after dietary sodium is restored in the diet at adulthood. In light of these observations, the terminal fields of sec ond-order projections from the nucleus of the solitary tract to the pa rabrachial nucleus (PBn) were examined. To determine the possible rear rangements of the second-order projections, the rostral pole of the NS T in control, restricted, and repleted rats was injected with the fluo rescent tracer Fluoro-Ruby and the terminal fields in the parabrachial nucleus were analyzed. Results show no differences in the size or top ography of the parabrachial nucleus terminal field among control, rest ricted, and repleted rats. These results suggest that the terminal fie ld of second-order gustatory neurons is resistant to dietary sodium re striction during development. The apparent target-dependent effects ma y relate to differences in the developmental processes along the gusta tory pathway. (C) 1998 Elsevier Science Inc.