Dietary sodium chloride experience influences the development of salt taste mechanisms in rat: An anatomical and neurophysiological analysis

Experience is known to influence the development of sensory systems. Exposure to a low sodium diet during perinatal development produces a long-term decrease in NaCl consumption in adult rats. Exposure to a high sodium diet during perinatal development produces a long-term increase in NaCl consumption in adult rats. The chorda tympani nerve is the primary afferent pathway for the salt taste modality. The objective of these experiments was to determine the effect of low or high dietary sodium exposure during development on the neurophysiology and central innervation of the afferent CT nerve.; Whole CT nerve electrophysiological recordings revealed that both the dietary manipulations (0.1% dietary sodium versus 3.0% dietary sodium ) and the duration of the dietary exposure period (manipulated sodium exposure until day 30 followed by a standard diet versus continuous manipulated sodium exposure) produced differential effects on the neurophysiological response properties to NaCl. When a perinatal exposure period to the dietary sodium manipulations was followed by a standard diet on day 30, the 0.1% sodium diet did not affect the CT responsiveness to sodium; however, similar exposure to the 3.0% sodium diet increased the amiloride-sensitive component of the CT sodium response. When exposure to 0.1% sodium was maintained until testing, the amiloride-sensitive transduction mechanism did not develop in a proper functional manner. When exposure to 3.0% sodium was maintained until testing, the components of the CT sodium response were proportionally altered such that the amiloride-sensitive component of the afferent neural signal was significantly decreased.; Labeling of the CT nerve with DiI allowed characterization of the central terminal field in the NST. Exposure from conception until adulthood to a 0.1% NaCl diet was sufficient for normal development of the CT terminal field. Exposure from conception until adulthood to a 6.0% NaCl diet produced an enlargement of the CT terminal field in the NST. The enlargement of the terminal field was specific to the dorsal most region of the CT innervation.; The combined results of these experiments demonstrated that moderate manipulations of dietary sodium exposure during development alter the anatomy and neurophysiology of the peripheral gustatory system in adult rats.