THE AREA POSTREMA IS INVOLVED IN PARAQUAT-INDUCED CONDITIONED AVERSION BEHAVIOR AND NEUROENDOCRINE ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS

Paraquat is a herbicide capable of eliciting conditioned taste aversio n (CTA), a behavioral response characteristic of toxicosis. The area p ostrema (AP) is a hindbrain circumventricular organ previously shown t o be important in mediating signs of paraquat-induced toxicity, namely CTA and weight loss. The relationship between neural substrates for p araquat-induced CTA and activation of the hypothalamic-pituitary-adren al (HPA) axis was investigated in Sprague-Dawley rats with lesions cen tered on the AP (APX) and sham-operated (SHM) rats administered paraqu at (25 mu mol/kg) or saline (1 ml/kg). Injection of paraquat at a dose sufficient to condition taste aversion, but produce no other signs of overt toxicity, significantly increased plasma corticosterone concent rations in SHM rats up to 4 h after administration. Paraquat-induced a ctivation of the HPA axis was significantly attenuated in AP-lesioned rats as compared to sham-operated controls. These findings suggest the area postrema is a common neural substrate for the behavioral and neu roendocrine responses to paraquat.