Effect of somatostatin and its antagonist on morphine analgesia in mice

AIM: To study the effects of somatostatin (SST) and its antagonist cyclo-(7 -aminoheptanoyl-Phe-D-Trp-Lys-Thr [Bzl]) (SSA) on morphine-induced analgesi a. METHODS: The pain assays were the hot plate and the tail flick test. RES ULTS: SST or SSA per se administered intracerebrally at the doses of 0.1 an d 1 mg/mouse did not change the pain threshold of mice both in the hot plat e and in the tail flick test. However, at the higher dose (10 mg/mouse), SS T and SSA decreased the pain threshold in the tail flick test only. SST and SSA administered at the dose of 0.1 mg/mouse did not change morphine-induc ed analgesia. By contrast, SST and SSA at the doses of 1 and 10 mg/mouse re duced morphine analgesia effects both in the hot plate as well as in the ta il flick test. CONCLUSION: Our results indicate that SSA as well as SST may be useful in studying pain mechanisms.