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

• Published in: The European journal of neuroscience Vol. 10; no. 2; pp. 782 - 785
• Main Authors: Laulin, Jean-Paul, Larcher, Agnès, Célèrier, Evelyne, Moal, Michel Le, Simonnet, Guy
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science, Ltd 01.02.1998
• Subjects: allodynia; Animals; dependence; Dizocilpine Maleate - pharmacology; Excitatory Amino Acid Antagonists - pharmacology; heroin; Heroin - pharmacology; Male; Narcotics - pharmacology; nmda antagonists; opponent processes; Pain - psychology; Pain Measurement - drug effects; Pain Threshold - drug effects; rat; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate - antagonists & inhibitors; Vocalization, Animal - drug effects
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1046/j.1460-9568.1998.00083.x

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.