Colpaert F C, Niemegeers C J, Janssen P A, Van Ree J M
Eur J Pharmacol. 1978 Jan 1;47(1):115-9. doi: 10.1016/0014-2999(78)90381-3.
The narcotic cueing activity of sufentanil, fentanyl, morphine and met-enkephalin was studied upon their injection into the lateral brain ventricle of the rat. Comparative studies on the analgesic activity of the three narcotics support a close correlation between the narcotic cueing and the analgesic activity of narcotic drugs.