MODULATION OF VOMITING BY THE MEDULLARY MIDLINE

Studies were conducted to investigate the possible role of the brainst em midline region as a source of facilitatory input for the vomiting p rocess. Experiments were conducted using the 'fictive vomiting' model in decerebrate, paralysed cats. Dysfunction of the medullary midline r egion produced by localized injections of the neurotoxin kainic acid a bolished or greatly attenuated fictive vomiting. In addition, some res piratory-related midline neurons were found to fire in synchrony with cc-active phrenic and abdominal nerve discharge during fictive vomitin g. These experiments demonstrate the importance of the medullary midli ne for the normal occurrence of the vomiting process. An explanation f or the post-lesion elimination of vomiting is that the lesions remove an important source of facilitatory input to spinal respiratory motone urons and/or to the brainstem circuitry that mediates vomiting.