Investigation of the Different Types of Opioid Receptor Involved in Electroconvulsive Shock-induced Antinociception and Catalepsy in the Rat

Abstract

Abstract The effects of novel opioid antagonists on the behavioural syndrome induced by electroconvulsive shock (ECS) in rats have been examined and compared with those of the established agent naloxone. A single ECS produced catalepsy and significantly increased tail immersion response times during the 15 min following the seizure. These responses were inhibited by a low dose of naloxone (1 mg kg−1, i.p.) and also by RX8008M (16-methylcyprenorphine; 1 mg kg−1, i.p.) which blocks μ- and δ- but not κ-opioid receptor function. In comparison, the antinociception and catalepsy induced by ECS was not attenuated by the selective δ-receptor antagonist naltrindole (1 mg kg−1, i.p.). These results suggest that ECS-induced antinociception and catalepsy may be mediated by endogenous opioids acting at μ-opioid receptors and are consistent with biochemical studies showing the release of β-endorphin in both animals and man following this procedure.