Noradrenergic and behavioural effects of naloxone injected in the locus coeruleus of morphine-dependent rats and their control by clonidine
✍ Scribed by E. Esposito; A. Kruszewska; G. Ossowska; R. Samanin
- Publisher
- Springer
- Year
- 1987
- Tongue
- English
- Weight
- 453 KB
- Volume
- 93
- Category
- Article
- ISSN
- 0033-3158
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✦ Synopsis
Naloxone HCl (10 micrograms/0.5 ml) was injected in the locus coeruleus (LC) of morphine-dependent rats and the behavioural manifestations of morphine withdrawal and the cortical levels of 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4) were measured 30 min later. Naloxone precipitated a withdrawal syndrome and raised cortical MHPG-SO4 in animals made dependent by ascending doses of morphine for 11 days. An injection of clonidine intraperitoneally (200 micrograms/kg) or in the LC (5 micrograms/0.5 microliter) blocked most aspects of the withdrawal syndrome except jumping and had no effect on the naloxone-induced rise in cortical MHPG-SO4. The findings confirm the hypothesis that the LC is one of the sites where naloxone and clonidine, respectively, precipitate and reduce the narcotic withdrawal syndrome but argue against a role of noradrenergic neurons originating in the LC and innervating the cortex in the ability of clonidine to suppress some aspects of withdrawal syndrome precipitated by naloxone in morphine-dependent animals.