Brain areas essential or non-essential for emesis

This study was undertaken to better delineate those brain regions that are either essential or non-essential for vomiting. Fictive vomiting, identified by a characteristic pattern of respiratory nerve discharge, was induced by a combination of emetic drugs and electrical stimulation of abdominal vagal afferents in decerebrate, paralyzed cats. Regions non-essential for coordinating vomiting included the entire cerebellum, structures rostral to the medullary retrofacial nucleus, and spinal cord. Fictive coughing was also elicited following cerebellar removal but was not studied after other procedures. The respiratory-related components of fictive vomiting were abolished by large lesions or kainic acid injections in the lateral medulla at the level of the retrofacial nucleus, where respiratory pre-motor and motor neurons are known to exist. Electrical stimulation of this region of the brainstem failed to evoke vomiting. The results of the present study are consistent with our previous electrical stimulation [Brain Res., 270 (1983) 154-158] and c-fos [J. Neurosci., 14 (1994) 871-888] studies and the hypothesis that emesis is coordinated not by a unique, well-defined 'vomiting center' but rather by a distributed control system located in the medulla between the levels of the obex and the retrofacial nucleus.