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Long‐lasting increased pain sensitivity in rat following exposure to heroin for the first time

1998; Wiley; Volume: 10; Issue: 2 Linguagem: Inglês

10.1046/j.1460-9568.1998.00083.x

1460-9568

Jean‐Paul Laulin, A. Larcher, Evelyne Célèrier, Michel Le Moal, Guy Simonnet,

Neuroscience and Neuropharmacology Research

Abstract Acute dependence, defined as a precipitation of somatic signs by an antagonist, may occur after a single administration of an opiate drug. Because hyperalgesia is a consistent sign of the withdrawal syndrome, we tested the effectiveness of heroin, an opiate used by addicts, to induce pain facilitation even after a first exposure to the drug. In opiate‐naive rats, subcutaneous injection of heroin induced analgesia followed by allodynia, a decrease in pain threshold. This latter phenomenon was observed in the absence of noxious stimuli and lasted several days. An N ‐methyl‐ d ‐aspartate (NMDA) receptor antagonist, MK‐801 prevented such long‐lasting allodynia. These results suggest that allodynia is an early sign reflecting neural plasticity associated with the development of dependence.