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Cholecystokinin-8 (CCK-8) has no effect on heart rate in rats lacking CCK-A receptors
M Kurosawa1, S Iijima, A Funakoshi
1Basic Medical Research Center, International University Health and Welfare, Otawara, Tochigi 324-8501, Japan. mieko-ku@iuhw.ac.jp
Abstract:
Heart rate responses to i.v. administration of cholecystokinin-8 (CCK-8) were investigated in Otsuka Long-Evans Tokushima Fatty (OLETF) rats lacking CCK-A receptors and control Long-Evans Tokushima Otsuka (LETO) rats. The heart rate decreased after i.v. administration of 3 nmol.kg(-)(1) of CCK-8 in LETO rats, but not in OLETF rats. Bradycardia in the LETO rats disappeared after treatment with MK-329, but not after treatment with L-365,260. The expression of CCK-A receptor precursor mRNA was found exclusively in the atrium in LETO rats. These results suggest that CCK-8 decreases heart rate via CCK-A receptors located in the atrium of the rats.