Intracardiac ganglia of the frog heart
The histochemistry for acetylcholinesterase was used to quantify the distribution of the intrinsic neurons in the hearts of 12 frogs Rana temporaria. Sixty-six intracardiac neurons from 12 frogs were injected ionophoretically by the intracellular mark- S142 Joint Meeting of Anatomical Societies, 19-22 May 2011, Bursa, Turkey Anatomy 2011; 5 Suppl ers Lucifer Yellow and AlexaFluor 586 to determine the neuronal morphology and projections. Total neuronal number per frog heart varied from 1060 to 1637 and was 1374 +/- 56 (Mean +/- SE), on average. About 46% of the neurons were located in the interatrial septum, 25% in the atrioventricular orifice, 12% on the sinus venosus, and 9% on the superior caval veins. Only 2% of the neurons were located on the external surface of atria, while 6% on the ventricles. The extracardiac nerves entered the frog heart by the superior caval veins. The dorsal and ventral septal nerves extended to the atrioventricular orifice and branched into the ventricle. Among the intracellularly labeled neurons, 67% were unipolar, 9% bipolar, 9% multipolar and 4% pseudounipolar. The frog ventricle received the axons of the neurons situated along the large nerve trunks. In contrast, frog atria received axons of the neurons situated further apart from the large nerve trunks in the septum. The axon hillocks of most of the neurons contained numerous thin subsidiary processes projecting onto adjacent neuronal somata and cardiac muscle fibers within septum. Vast majority of the intracardiac neurons were classified as Golgi I type neurons with long prominent axons. A few Golgi II type neurons lacking the prominent axons, the presumptive interneurons, were also found. Results of the present study demonstrate the wide morphological diversity of the frog intracardiac neurons.