Arterially perfused, decerebrate preparations of the insectivore, Suncus murinus were made to determine whether the
emetic reflex could be activated in such a preparation using a range of stimuli shown to be
emetic in conscious or anaesthetised Suncus. Efferent phrenic and vagus nerve activities and electromyograms (EMGs) from the temporalis, abdominal oesophagus and trapezius muscles were recorded, as well as longitudinal shortening of the oesophagus and dorso-ventral movements of the thorax. The preparations swallowed spontaneously every 0.6 to 6.5 min. The duration of a swallow was 3.1 +/- 0.3 s (recorded as the time taken for the oesophagus to shorten and recover to its resting position) and the oesophagus shortened by 3.5 +/- 0.4 mm during a swallow. The
emetic reflex was activated by electrical stimulation (30 Hz, 10-20 V, 0.2 ms pulse width, for 30 s) of abdominal vagal afferents (latency < 30 s) or by arterial perfusion with either 40 nM of the
capsaicin analogue
resiniferatoxin (latency 1.7 +/- 0.6 min), 6 microM
nicotine (latency 1.6 +/- 0.1 min) or 1 microM of the
phosphodiesterase IV inhibitor CP-80,633 (latency 8.9 +/- 3.9 min). These
emetic stimuli produced somatic and visceral movements in Suncus preparations indicative of activation of the
emetic reflex. There were pronounced contractions of the thorax that occurred simultaneously with oesophageal shortening and mouth opening, separated by thorax expansion and a burst of phrenic nerve activity. During
emetic-like episodes, oesophageal shortenings were only 0.84 +/- 0.1 s in duration, faster than the duration of shortening observed during swallowing (cf. swallowing, 3.1 +/- 0.3 s; P < 0.0001). The shortening of the oesophagus during
emetic-like episodes was 6.2 +/- 0.4 mm, which was greater than the shortening seen during swallowing (cf. swallowing, 3.5 +/- 0.4 mm; P < 0.0001). We conclude that the
emetic reflex can be activated in our Suncus preparations and that this non-sentient small adult animal model can now be used to study the neurophysiology and pharmacology of swallowing and
emesis.