“…Some information is presently available to support a role for this opioid in the modulation of the interactive effect of noxious and hypertensive stimuli on the respon siveness of NRGC neurons. First, the endogenous opioids, including the enkephalins, are intimately related to the central regulation of nociception [4,16,29,30,38] and circulation [1,27,28,30,31,36], Second, results from our laboratory and others have further shown that the NRGC is actively involved in the antinociceptive [8,17,22,33] and cardiovascular suppressive [19,37] ac tions of morphine and the enkephalins. Third, opioid receptors [2] and enkephalinergic fiber terminals [18,32,35] have been identified in the medullary reticular forma tion, including the NRGC.…”