The pharmacology of beta-endorphin binding sites in the caudal dorsomedial medulla

The purpose of this study is to characterize the binding properties of an endogenous opioid, p-endorphin, in the caudal dorsomedial medulla (CDMM). The CDMM contains an important cardioregulatory region, called the nucleus of solitary tract (nTS). The nTS is richh innervated w ith P-endorphin producing neurons (Joseph et al., 1983) and possesses p-opioid receptors (Xia and Haddad, 1991). There is conflicting evidence indicating there is also a population of 5-opioid receptors in this area (Dashwood et al., 1988; Xia and Haddad. 1991). Further evidence suggests that pendorphin also binds to a nonopioid receptor in the CNS (Houghten et al.. 1984). Therefore, the cardioregulatory actions of p-endorphin may be mediated by a number of receptor subtypes in the nTS. To date, there has been no pharmacological binding profile for p-endorphin binding sites in the nTS. The purpose of this study is to identify the receptor(s) to which P-endorphin binds to in the nTS. This P-endorphin binding profile may then provide an important link between P-endorphin's observed cardiovascular effects and a specific receptor subtype mediating these actions. The long term implications of this pharmacological profile may help provide important therapeutic applications toward the treatment of analgesia without the deleterious cardiovascular side effects commonly associated with opioids and may provide an alternative treatment to clinical hypertension.