Taste reactivity alterations after IL-1β microinjection into the ventromedial hypothalamic nucleus of the rat

Abstract

The ventromedial hypothalamic nucleus (VMH) is a central site of action of interleukin-1β (IL-1β) induced feeding disturbances. This study was designed to elucidate taste-related perceptual and motivational processes potentially contributing to the anorexia and adipsia seen after bilateral IL-1β microinjection into the VMH. A saccharin conditioned taste aversion (CTA) paradigm was tested after the central IL-1β administration. To further investigate whether gustatory deficits are involved in development of the feeding alterations, IL-1β induced changes of taste responsiveness were also studied in taste reactivity tests. Administration of the cytokine into the VMH did not cause the development of CTA. During taste reactivity tests, however, IL-1β treated rats displayed significantly poorer ingestive reactions to pleasant taste stimuli than did animals of the control group. In addition, the aversive responses of IL-1β injected rats to pleasant tastes were significantly more robust than those of control animals. The cytokine treated animals also showed stronger aversion than ingestion to hedonically positive tastes. The present findings indicate that (1) anorexigenic and adipsogenic consequences of IL-1β microinjection into the VMH are not due to development of cytokine induced CTA; and (2) hedonic responsiveness to palatable tastes is processed by IL-1β mediated neural mechanisms in the VMH.