Kappa isoreceptors: neuroendocrine and neurochemical evidence

It has become clear, in the area of opiate research, that there are multiple opioid receptors and endogenous ligands. The functional roles of these opioid systems are being established as these concepts evolve and as our analytical capabilities become more sophisticated and thorough. When complete dose-response studies are performed and a number of antagonists are examined, a clearer definition of isoreceptor populations may also occur. Such appears to be the case with kappa agonists, which may in fact comprise two groups of compounds (table 1). This separation into two groups has also been observed in the dog cerebral artery (table 1) (Altura et al. 1984). Taken together, these data are sufficient to propose the testable hypothesis that there are kappa isoreceptor populations in the brain that probably subserve a vast array of discrete and different regulatory functions.