Abstract

Agonists for the -opioid receptor are powerful analgesics and are highly addictive; however, the contribution of the - and -opioid and opioid receptor-like receptors to motivational states is less clear. Agonists at each receptor modulate neurons in a circuit that selectively controls nociceptive transmission. This circuit can operate in both pain-inhibiting and pain-facilitating states, and the action of opioids contributes to and is determined by the state of the circuit. There is growing evidence that the state of the circuit is determined by aversive and appetitive motivational states, and that this contributes to adaptive behavioural choice.

Author affiliations

1. Box 0453, University of California, 513 Parnassus Avenue, San Francisco, California 94143, USA.
   Email: hlf@itsa.ucsf.edu

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