Venospastic activity of somatostatin in vivo in man: naloxone reversible tachyphylaxis.

When the dorsal hand vein (DHV) is locally injected with somatostatin (SS) it spasms visibly. These spasms can be measured using the computerized venospasm technique. Acute, complete long-lasting tolerance (tachyphylaxis) develops following 2-4 injections of somatostatin. A revival of sensitivity to SS is induced in the fatigued vein by the local injection of naloxone. This suggests that endogenous opioids could participate partially or totally in SS tachyphylaxis. The analgesic effect displayed by somatostatin on the dramatic pain of the cluster attack is quantitatively similar to that of ergotamine; the therapeutic mechanism of both drugs has until now remained undefined.