Dual effect of [D-Pen(2), D-Pen(5)]enkephalin on ion transport in guinea pig colon

Effects of the delta-opioid receptor ligand, [D-Pen(2), D-Pen(5)]enkephalin (DPDPE) on basal and endothelin-1-induced ion secretion in guinea pig colo n were investigated. Muscle-stripped segments of guinea pig colon were moun ted in Ussing flux chambers and changes in the short-circuit current (I-sc) were monitored continuously. DPDPE significantly reduced baseline I-sc at a low dose, 1 nM; however DPDPE increased I-sc at 10 and 100 mu M. Endothel in-1 stimulated ion secretion that was unaltered in tissues pretreated with DPDPE. In guinea pig colon, delta-opioid receptor activation evoked both a proabsorptive and prosecretory response. (C) 2000 Elsevier Science B.V. Al l rights reserved.