A A~~~~~4~~~, E. T., K. FUXE and hf. L. TORCHIANA, Chemical and histochemical evaluation o f the distribution o f catecholamines in the rabbit and guinea pig hearts. Acta physiol. scand. 1963. 59. 184-192. -Chemical determinations of noradrenaline (NA), adrenaline (.4), and dopamine (DA) were made in the right and left atria and ventricles (RA, LA RV. LV) of rabbit and guinea pig hearts. The concentration of these amines was also studied in the sino-auricular (SA) node of the rabbit. Some of these tissues were also examined for the distribution of catecholamines using a histochemical fluorescence technique. NA was the predominant catecholamine present in atria and ventricles. It was more concentrated in the RA than LA and in the RV than in the LV of the rabbit and guinea pig. In the latter KA was distinctly higher in the atria than in the ventricles. By contrast A was more concentrated in ventricles than in atria of both species and accounted for about 5-10 per cent of the total catecholamine content. DA was found predominantely in the atria, more in RA than in LA. High concentrations of DA were found in the SA node region. Histochemical studies on rabbit tissues showed that the catecholamines were found within nerve structures. A high density offluorescent fibers and fiber bundless was found in the SA node region. An excellent correlation between the histochemical and chemical findings was obtained when both NA and DA were considered.

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