Influences of locus coeruleus lesions and reserpine treatment on opioid physical dependence in rats.
OBJECTIVE
To study the role of locus coeruleus (LC) noradrenergic neurons in the opioid dependence.


METHODS
Chemical lesion of LC was produced by 6-hydroxydopamine (4 micrograms in 1 microL). Reserpine (Res) was used to deplete central noradrenaline. Composite scores of naloxone (4 mg.kg-1, ip) precipitated abstinence syndromes were calculated and the magnitude of weight loss was determined in chronic morphine (Mor)- or dihydroetorphine (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 syndrome, made worse the loss of body weight in chronic Mor-, but not DHE-, treated rats. A single dose of Res (0.5 mg.kg-1) speeded up the development of physical dependence on Mor.


CONCLUSIONS
The LC noradrenergic neurons play a role in suppression of some withdrawal symptoms.
Miao
H
H
Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, Beijing, China.
Qin
B Y
BY
D000818:Animals; D001835:Body Weight; D005048:Etorphine / Q000031:analogs & derivatives*; D005260:Female; D008125:Locus Coeruleus / Q000503:physiopathology*; D008297:Male; D009021:Morphine Dependence / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology; D009293:Opioid-Related Disorders / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D012110:Reserpine; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*
D005048:Etorphine; D012110:Reserpine; C034765:18,19-dihydroetorphine