Lateral parabrachial lesions impair taste aversion learning induced by blood-borne visceral stimuli

The lateral parabrachial area (LPB), main relay from the area postrema (AP) , plays a role in processing visceral information and is thus of potential importance in taste aversion learning (TAL). This study used a lesion appro ach to address whether LPB functional relevance depends upon the features o f toxins that serves as visceral stimuli in TAL. In addition, we explored w hether LPB involvement in TAL is restricted to those toxic events detected by the AP or whether it has a more general role. Results showed that LPB-le sioned animals were disrupted in acquiring a TAL induced by blood-borne AP- dependent aversive stimuli (intraperitoneal methylscopolamine) and by AP-in dependent stimulus (intraperitoneal ethanol), but still, clearly developed strong aversions when intragastric hypertonic sodium chloride, a vagally pr ocessed aversive stimulus, served as the aversive stimulus. These findings suggest that the LPB plays a critical role in TAL induced by blood-borne to xins, such as methylscopolamine or ethanol, but is not necessary for vagall y mediated stimulus, such as sodium chloride. The present results are discu ssed in the context of the hypothesis holding separable and independent neu ral systems underlying TAL. (C) 2001 Elsevier Science Inc. All rights reser ved.