The dorsal raphe nucleus: a re-evaluation of its proposed role in opiate analgesia systems

Previous studies have concluded that (a) electrical stimulation in the periaqueductal gray/dorsal raphe nucleus (PAG/DRN) region specifically produces either non-opiate or opiate forms of antinociception dependent upon the dorsoventral level of stimulation and (b) the 'opiate' form of stim...

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Published inBrain research Vol. 447; no. 2; p. 246
Main Authors Klatt, D S, Guinan, M J, Culhane, E S, Carstens, E, Watkins, L R
Format Journal Article
LanguageEnglish
Published Netherlands 03.05.1988
Subjects
Analgesia
Animals
Electric Stimulation
Endorphins - physiology
Male
Pain - physiopathology
Periaqueductal Gray - physiology
Raphe Nuclei - physiology
Rats
Rats, Inbred Strains
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Summary:Previous studies have concluded that (a) electrical stimulation in the periaqueductal gray/dorsal raphe nucleus (PAG/DRN) region specifically produces either non-opiate or opiate forms of antinociception dependent upon the dorsoventral level of stimulation and (b) the 'opiate' form of stimulation-produced analgesia (SPA) arising from the ventral PAG/DRN region shows cross-tolerance with opiate forms of footshock analgesia, implying common neural substrates. This latter conclusion in turn implies that SPA elicited from the ventral PAG/DRN region would be expected to be antagonized by scopolamine, since this muscarinic cholinergic antagonist blocks opiate footshock analgesia. The present study demonstrates instead that neither 10 mg/kg naloxone nor 10 mg/kg scopolamine had any effect on SPA elicited from sites histologically verified to lie within the presumptive 'opiate' ventral PAG/DRN region. These data bring into question both the site specificity of opiate SPA and the common mediation of ventral PAG/DRN SPA and opiate forms of footshock analgesia.
ISSN:0006-8993
DOI:10.1016/0006-8993(88)91126-2