Gustatory functions, sodium appetite, and conditioned taste aversion survive excitotoxic lesions of the thalamic taste area.

Abstract

Rats with bilateral, electrophysiologically guided, ibotenic acid lesions of the gustatory thalamus (THLX) were tested for their ability to perform a variety of taste-guided behaviors. First, in daily 30-min sessions, the rats were given repeated 10-s access periods to a range of concentrations of sucrose, NaCl, or QHCl, plus water. Both the control and the THLX rats exhibited similar concentration-response functions, regardless of hydrational state. Next, on 3 trials, the rats were given 15 min access to 0.3 M l-alanine and then injected with LiCl (0.15 M, 1.33 ml/100 g body weight ip). All rats learned a taste aversion following 1 pairing with LiCl. Finally, on 3 separate occasions, the rats were injected with furosemide, and Na(+)-appetite was evaluated 24 hr later. All rats expressed an equivalent sodium appetite after the first furosemide injection, but only the control rats increased intake of 0.51 M NaCl with repeated sodium depletions. These observations reinforce prior data implying that an intact gustatory thalamus is not necessary for the expression of some taste-guided behaviors.