ABSTRACT
Opioid peptides (/Ï-endorphin, enkephalins and dynorphin) and their receptors are present in all brain areas associated with cardiovascular regulation (Goodman et al., 1980; Mansour et al., 1988). Most notable are hypothalamic nuclei such as the preoptic nucleus, paraventricular nucleus, lateral hypothalamic nucleus, the central nucleus of amygdala and hippocampus. In the pons and medulla oblongata, opioid-rich areas include the parabrachial, dorsal tegmental, vestibular and raphe nuclei, the nucleus reticularis paragigantocellularis and spinal cord dorsal gray. Particular high densities of opioid receptors are present in the caudal part of the nucleus tractus solitarii (Mansour et al., 1988; Hawkins et al., 1988).
