Figure 3. The effects of bombesin receptor subtype 1 (BB1), 2 (BB2) and 3 (BB3) antagonists on gastrin-releasing peptide (GRP)-, [D-Tyr6,Apa-4Cl11,Phe13,Nle14]bombesin-(6-14) (DTACPN-BN)-, and bombesin-induced contractions of the porcine LES sling and clasp muscle strips.
The BB2 antagonist, [D-Phe6,des-Met14]BN(6-14) ethylamide (DPDM-BN EA) (1 μM), had a significant inhibitory effect on LES sling (A) and clasp (B) muscle strip contractions that were induced by GRP. The EC50 differences between the samples treated with GRP alone and with GRP plus DPDM-BN EA were significant (p < 0.05). The BB3 antagonist, Bantag-1 (1 μM), significantly inhibited the DTACPN-BN-induced LES sling (C) and clasp (D) muscle strip contractions (p < 0.05). *Represents significant differences compared with the DTACPN-BN alone (p < 0.05). Only DPDM-BN EA (1 μM) plus Bantag-1 (1 μM) had a significant inhibitory effect on LES sling (E) and clasp (F) muscle strip contractions that were induced by bombesin. The EC50 difference between the levels of bombesin alone and the levels of bombesin plus DPDM-BN EA combining with Bantag-1 was significant (p < 0.05).