SPLTRAK Abstract Submission
Sodium Restriction Alters Behavioral and Cortical Responses to Intra-Oral Infusion of NaCl in Conscious Rats
Alisa M. Goldstein, Christopher A. Guerra, Michael S. King
Stetson University, DeLand, FL, United States

To determine the effect of restricting dietary NaCl on behavioral and neural responses to subsequent NaCl intake, taste reactivity (TR) behaviors and Fos-immunoreactive (Fos-IR) neurons in the gustatory cortex (GC) elicited by intra-oral infusion of 1M NaCl were counted. Nine adult male Wistar rats were used in this study; 4 were placed on a low NaCl diet (Envigo, 0.01% NaCl) for 3 weeks prior to testing while control rats (n=5) were maintained on a normal rodent diet (0.3% NaCl).  Following implantation of intra-oral cannulas and recovery from surgery, the typically ‘aversive’ 1M NaCl was infused (0.233ml/min for 5 min), TR behaviors were videotaped, and then rats were sacrificed and their brains processed for the Fos protein.  Fos-IR neurons in the medial and lateral granular (GI), dysgranular, and agranular insula were counted at 5 positions along the anterior-posterior axis of the GC.  NaCl-restricted rats performed over 4x more ingestive and 28x fewer aversive TR behaviors than control rats (p’s<0.001).  The clearest effects were on tongue protrusions (10x increase in restricted rats) and gapes (22x decrease in restricted rats).  Also, NaCl restriction significantly increased the number of Fos-IR neurons throughout the GC.  Overall, there were 3x more Fos-IR neurons in the GC of restricted than control rats (p<0.001). The biggest differences in the number of Fos-IR neurons were in the rostral and dorsal parts of the GC.  These data indicate that dietary restriction of NaCl changes a largely aversive response to 1M NaCl to an ingestive behavioral response, and increases the number of GC neurons that respond to NaCl, particularly in the rostral and dorsal regions of the GC.  Future studies will attempt to determine the role of GC subareas in the behavioral alterations caused by NaCl restriction.