title: Vagotomy facilitates extinction of conditioned taste aversions in rats.
abstract: Results from three experiments indicate that severing the subdiaphragmatic vagus in rats increased the rate of extinction of learned taste aversions. In Experiment 1, although vagotomized rats acquired a saccharin aversion equivalent to that of controls when the illness-inducing agent was the blood-borne toxin apomorphine, vagotomized rats tended to consume more saccharin than controls during repeated extinction tests. In Experiment 2, vagotomy disrupted retention and increased extinction of a preoperatively acquired saccharin aversion. Disruptions were found when the taste aversion was induced by copper sulfate, a local gastric irritant (Experiment 2A), or apomorphine, a systemic toxin (Experiment 2B); in each experiment vagotomized rats consumed more saccharin than controls on the first retention test and extinguished the prior to surgery. Experiment 3 demonstrated that vagotomy did not affect retention or extinction of a shock-induced conditioned emotional response (lick to suppression) to noise. It is concluded that integrity of the vagus is not necessary for acquisition of a learned taste aversion when a blood-borne toxin is used as the ill-inducing agent. However, the vagus apparently mediates an integral portion of the conditioned response following taste-illness acquisition regardless of whether the illness agent is a local gastric irritant or a systemic toxin.
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology; D003214:Conditioning, Classical / Q000502:physiology*; D005108:Extinction, Psychological / Q000502:physiology*; D008297:Male; D051381:Rats; D013649:Taste / Q000502:physiology*; D014629:Vagotomy, Proximal Gastric; D014630:Vagus Nerve / Q000502:physiology*