Basal forebrain facilitation of reflex swallowing in the cat

In adult cats anaesthetized with urethane, electrical and chemical stimulation of the basal forebrain facilitated reflex swallowing elicited by electrical stimulation of the superior laryngeal nerve. A systematic stereotaxic mapping study using electrical stimulation revealed that the facilitatory sites were distributed along the course of the ansa peduncularis, specifically its rostral forebrain and hypothalamic components associated with the anterior amygdalar area, substantia innominata, lateral preoptic area, anterior hypothalamus and nucleus accumbens. By means of acute discrete radiofrequency lesions, the descending pathways mediating facilitatory influences from the nucleus accumbens and the amygdala to the brain stem were found to traverse the lateral hypothalamus. Ventral tegmental facilitatory sites in the midbrain are likely to be associated with these descending pathways; however, there is evidence for independent participation of this region of the brain in the control of swallowing. Chemical stimulation by means of microinjections of dopamine and apomorphine into the amygdala and nucleus accumbens also enhanced reflex swallowing. It is concluded that the results of this investigation implicate the basal forebrain as a site of integration of viscero-olfacto-gustatory information needed for the enactment of ingestive behaviour.