Chemical and Histochemical Evaluation of the Distribution of Catecholamines in the Rabbit and Guinea Pig Hearts

Abstract

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.

The inotropic and chronotropic effects of catecholamines on the dog heart

“…Secondly the effect of noradrenaline in producing a greater inotropic effect for the same chronotropic effect than isoprenaline, before but not after cocaine, may be explained by the more rapid removal of noradrenaline by the uptake processes and thus a greater reduction in concentration at the site of action in the sinu-atrial node than in the muscle of the left ventricle. Angelakos, Fuxe & Torchiana (1963) have shown that the sinu-atrial nodes of the guinea-pig and rabbit hearts have a higher concentration of noradrenaline than the left ventricle and using a fluorescence histochemical technique have associated the higher concentration of noradrenaline in the sinu-atrial node with a denser adrenergic innervation. If it is assumed that the noradrenaline concentration in cardiac tissue reflects the density of adrenergic innervation, then the sinu-atrial node of the dog also possesses a denser adrenergic innervation than the left ventricle (Angelakos, 1965).…”

Selective Reserpine‐induced Supersensitivity of the Positive Inotropic and Chronotropic Responses to Isoprenaline and Salbutamol in Guinea‐pig Isolated Atria

“…This may be an alternative explanation for the preferential potentiation of the tension responses to isoprenaline by reserpine. If there were a greater receptor density in the right atrium than in the left atrium, which is possible in view of its denser innervation (Angelakos, Fuxe & Torchiana, 1963), then with each dose of isoprenaline a greater proportion might be occupied in the left atrium. Thus there are fewer spare receptors (Stephenson, 1956) and receptor proliferation might be expected to have a more marked effect upon the response size than in the right atrium where there may be more spare receptors and an increase in total receptor population would have proportionately less effect.…”

Involvement of uptake2 in the termination of activity of neurogenic noradrenaline in the rat isolated atrium.

“…The reason for this difference from the chronotropic responses is not clear. It could reflect a different spatial relationship of the terminal axons with conducting tissue on the one hand and with myocardial fibres on the other, or it might be related to the evidence (Angelakos, Fuxe & Torchiana, 1963) that sinoatrial tissue is associated with a far denser adrenergic nervous plexus than is atrial muscle.…”