INFLUENCES OF LOCUS-COERULEUS LESIONS AND RESERPINE TREATMENT ON OPIOID PHYSICAL-DEPENDENCE IN RATS

AIM: To study the role of locus coeruleus (LC) noradrenergic neurons i n the opioid dependence. METHODS: Chemical lesion of LC was produced b y 6-hydroxydopamine (4 mu g in 1 mu L). Reserpine (Res) was used to de plete central noradrenaline. Composite scores of naloxone (4 mg . kg(- 1), ip) precipitated abstinence syndromes were calculated and the magn itude of weight loss was determined in chronic morphine (Mor)- or dihy droetorphine (DHE)-treated rats. RESULTS: Lesions of LC made Mor, but not DHE, abstinence syndrome more serious. Multiple doses of Res (0.5 mg . kg(-1). d(-1) x 3 d) increased scores of Mor and DHE abstinence s yndrome, made worse the loss of body weight in chronic Mor-, but not D HE-, treated rats. A single dose of Res (0.5 mg . kg(-1)) speeded up t he development of physical dependence on Mor. CONCLUSION: The LC norad renergic neurons play a role in suppression of some withdrawal symptom s.