CCK(B) receptors in the periaqueductal grey are involved in electroacupuncture antinociception in the rat cold water tail-flick test.
Cholecystokinin octapeptide (CCK-8) (0.25-2.0 ng), the CCK(A) receptor antagonist L-364,718 (60-100 ng) or the CCK(B) receptor antagonist L-365,260 (0.3125-1.25 ng) was administered into the periaqueductal grey (PAG) of male SD rats. The antinociceptive effect induced by electroacupuncture (EA) stimulation of different frequencies was then measured by the cold water tail-flick (CWT) test. The results showed that (1) microinjection of CCK-8 into the PAG can significantly block the antinociceptive effect induced by all frequencies of EA stimulation. The effectiveness of the blockade was 100 > 2 Hz. In addition, CCK-8 blocks the antinociception seen following termination of the electrical stimulation at 100 Hz; (2) microinjection of L-365,260 (1.25 ng) into the PAG significantly increased the 100 Hz EA antinociceptive effect but not the 2 Hz EA antinociceptive effect and microinjection of L-364,718 into PAG did not affect either 2 or 100 Hz EA antinociception. These results demonstrate that CCK-8 in the PAG can antagonize the antinociceptive effect induced by EA stimulation, and the CCK effect is likely to be mediated by the CCK(B) receptor, but not the CCK(A) receptor.
Chen
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Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA. Chenyang@astro.ocis.temple.edu
Geller
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Adler
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D000818:Animals; D015671:Electroacupuncture; D007276:Injections, Intraventricular; D008297:Male; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology*; D010487:Periaqueductal Gray / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011949:Receptors, Cholecystokinin / Q000187:drug effects / Q000502:physiology*; D012844:Sincalide / Q000494:pharmacology
D011949:Receptors, Cholecystokinin; D012844:Sincalide