Modulation of Catecholamine Release in the Central Nervous System by Multiple Opioid Receptors

Exogenous and endogenous opioids elicit a number of their effects in the organism by modulating the release of transmitters in the peripheral and central nervous system (CNS). This is due to the activation of receptors located at either axon terminals (presynaptic receptors) or at cell somata and/or dendrites (somatodendritic receptors). Indirect effects via neighboring neurons are also possible. In recent years, it has become apparent that opioids are able to inhibit the action potential-induced secretion ofnorepinephrine (NE) and dopamine (DA) in the CNS (Starke 1977; Westfall 1977; Henderson et al. 1979; Vizi 1979; Langer 1981; Szekely and Ronai 1982a,b; Jackisch et al. 1988; Illes 1989). This chapter will review research concerning this topic and focus specifically upon the idea of multiple opioid receptor types in modulating catecholamine release.