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.