A series of cyclic, conformationally restricted analogs of somatostatin have been prepared and tested for their ability to inhibit the binding of [3H]naloxone and [D-Ala2, D-Leu5][3H]enkephalin to rat brain membranes. The most potent analog, D-Phe[Cys-Tyr-D-Trp-Lys-Thr-Pen]-Thr-NH2 where Pen is penicillamine in [D-Phe5,[Cys6, Tyr7, D-Trp8, Pen11]]somatostatin-(5-12)-octapeptide amide, exhibited high affinity for μ-opiate receptors (IC50 value of [3H]naloxone = 3.5 nM), being 7800 times more potent than somatostatin. The cyclic octapeptide also displayed high μ-opiate receptor selectivity with an IC50 ([D-Ala2-, D-Leu5]enkephalin)/IC50 (naloxone) ratio of 271. The high affinity and selectivity of the somatostatin analog for μ-opiate receptors may be of use in examining the physiological role(s) of the μ-opiate receptor.
|Original language||English (US)|
|Number of pages||4|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - 1985|
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