Endogenous opiates and stress. Behavioral activation elicited in the rat and effects of naltrexone, diprenorphine and morphine.
Acute exposure to intense (95dB) white noise may selectively increase the open field behavior of rats. Previous studies have indicated that this effect was mediated in part by endogenous opioid neuropeptides. Three experiments were carried out to characterize further and more specifically the stress-activation syndrome, on behavioral and pharmacological grounds. The time course within which blockade of opiates by naltrexone was effective behaviorally was examined. A second experiment examined the issue of cross-tolerance with opiates, by using dependent subjects, while a final experiment examined involvement of enkephalins, by assessing the effects of the drug diprenorphine upon stressed-behavior. Blockade with naltrexone was achieved with a small dose of the drug, and had a behavioral effect restricted to the initial 6 min of a 12-min test. Morphine-dependent rats proved not to be tolerant behaviorally to the activating effect of noise. Finally, diprenorphine did not mimic the effects of naltrexone. It produced no clear changes in the measures at any dose tested.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004174:Diprenorphine / Q000494:pharmacology*; D004723:Endorphins / Q000502:physiology*; D006801:Humans; D008297:Male; D009019:Morphinans / Q000494:pharmacology*; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000031:analogs & derivatives*; D009271:Naltrexone / Q000494:pharmacology*; D009622:Noise / Q000009:adverse effects; D051381:Rats; D011919:Rats, Inbred Strains; D011955:Receptors, Drug / Q000187:drug effects; D013315:Stress, Psychological / Q000523:psychology*; D013997:Time Factors
D004723:Endorphins; D009019:Morphinans; D011955:Receptors, Drug; D004174:Diprenorphine; D009270:Naloxone; D009271:Naltrexone; D009020:Morphine