PAVLOVIAN CONDITIONING OF MORPHINE-INDUCED ALTERATIONS OF IMMUNE STATUS - EVIDENCE FOR PERIPHERAL BETA-ADRENERGIC-RECEPTOR INVOLVEMENT

The present studies examined the involvement of peripheral beta-adrene rgic receptor activity in the establishment and expression of conditio ned morphine-induced alterations of immune status. Previous work in ou r laboratory has shown that morphine's immunomodulatory effects can be come conditioned to environmental stimuli which predict drug administr ation. These immune alterations include conditioned changes in natural killer cell activity, interleukin-2 production, and mitogen-induced l ymphocyte proliferation. During the training phase of these experiment s, Lewis rats received two conditioning sessions during which a subcut aneous injection of 15 mg/kg morphine sulfate was paired with exposure to a distinctive environment. On the test day, rats were reexposed to the conditioned stimulus prior to sacrifice. Saline or nadolol (0.002 , 0.02, 0.2, or 2.0 mg/kg) was administered either prior to the traini ng sessions or prior to the test session. Administration of nadolol pr ior to training did not affect the development of conditioned alterati ons of immune status. Conversely, nadolol administration prior to test ing completely attenuated the expression of a subset of the conditione d morphine-induced changes in immune status. Taken together, these stu dies suggest that whereas peripheral beta-adrenergic receptor activity is not required for the establishment of conditioned morphine-induced alterations of immune status, it is involved in the expression of a s ubset of these conditioned immunomodulatory effects. (C) 1994 Academic Press, Inc.