EFFECTS OF GASTRIN-RELEASING PEPTIDE (GRP) ON THE MECHANICAL-ACTIVITYOF THE HUMAN ILEOCECAL REGION IN-VITRO

Mechanical activity was recorded in muscle preparations isolated from the human ileocaecal region. Gastrin-releasing peptide (GRP, 10(-9) 10 (-7) mol L-1) produced two types of response in the different muscle l ayers. Longitudinally cut strips showed a concentration-dependent incr ease in the rhythmic activity, whereas the circularly orientated layer s generally reacted with a small decrease in tone. These effects could not be influenced by blockade of adrenergic or cholinergic receptors or nerve blockade with tetrodotoxin (TTX). Application of pentagastrin did not mimic the action of GRP. These findings suggest a direct acti on of GRP on smooth muscle via distinct receptors which have already b een demonstrated to exist in human gastrointestinal tract. The opposit e effects on circular and longitudinal strips might indicate a modulat ory role of GRP in the control of ileocolonic transit.