Pentagastrin in the circulation acts directly on the brain to depress motility of the stomach in sheep.

The mechanism whereby pentagastrin inhibits the frequency of contractions of the reticulo-rumen in conscious sheep was studied by comparing the effects of a range of doses given by continuous infusion into the jugular vein and the carotid artery. The intracarotid infusions at rates of 1 and 2 micrograms/kg per h were more effective than the jugular infusions (P less than 0.05). This is the first report that pentagastrin administered intravenously acts directly on the brain to alter the motility of a portion of the digestive tract. This agrees with the fact that in sheep and other ruminants, the gastric centres in the medulla dictate the frequency of cyclical motility in the reticulum.