Medullary afferent vagal axotomy disrupts NaCl-induced short-term taste aversion learning.

The effect of medullary afferent vagal axotomy on NaCl-induced short-term and long-term taste aversion learning (TAL) was examined to assess the relevance of the vagus nerve in drug-induced TAL. The results show that medullary afferent vagal axotomy disrupts NaCl-induced short-term (nondelayed) TAL, while having no effect on learning acquired with the same product in long-term (delayed) TAL protocols. Acquisition of learning in delayed discrimination tasks may be mediated by alternative mechanisms of nonvagal nature, e.g., the humoral system. The possibility that short-term and long-term TAL may be mediated by different neurobiological substrates is discussed.