NEUROANATOMICAL ALTERATIONS IN THE RAT NUCLEUS OF THE SOLITARY TRACT FOLLOWING EARLY MATERNAL NACL DEPRIVATION AND SUBSEQUENT NACL REPLETION

Restricting the NaCl content in the rat maternal and preweaning diet r esults in a significant and specific reduction (60%) of chorda tympani nerve responsiveness to sodium stimuli in the offspring. Repletion of dietary sodium at any time during postnatal development results in a complete and persistent recovery of chorda tympani nerve function. To learn whether the maturation of postsynaptic cells are also affected b y the early dietary manipulation, dendritic morphology, neuronal and g lial densities and numbers were studied within the area of the nucleus of the solitary tract (NTS). Examination of dendritic morphologies in Golgi-Cox stained neurons revealed that cells with multipolar and fus iform somata in the rostral NTS exhibited longer dendrites following d ietary NaCl deprivation during development (deprived rats) than in con trols. These changes were generally maintained in rats initially depri ved of NaCl and then fed a NaCl-replete diet postweaning (''recovered' ' rats). In contrast, ovoid neurons were not affected by NaCl deprivat ion but had increases in the lengths of their dendrites following ''re covery.'' Along with dendritic alterations, the packing density of neu rons in the rostral NTS was greater in NaCl-deprived rats than in cont rols, but was similar to controls following ''recovery.'' Glial packin g density also increased following deprivation and remained high in '' recovered'' rats. These results indicate that activity-dependent event s as well as events not related to afferent activity (e.g., hormonal c hanges) may influence the morphological development of NTS neurons. In addition, significant interactions among primary afferent fibers, cen tral neurons, and glia may direct development within the central gusta tory system.