Distribution, structure and projections of the frog intracardiac neurons.

Histochemistry for acetylcholinesterase was used to determine the distribution of intracardiac neurons in the frog Rana temporaria. Seventy-nine intracardiac neurons from 13 frogs were labelled iontophoretically by the intracellular markers Alexa Fluor 568 and Lucifer Yellow CH to determine their structure and projections. Total neuronal number per frog heart was (Mean ± SE) 1374 ± 56. Largest collections of neurons were found in the interatrial septum (46%), atrioventricular junction (25%) and venal sinus (12%). Among the intracellularly labelled neurons, we found the cells of unipolar (71%), multipolar (20%) and bipolar (9%) types. Multiple processes originated from the neuron soma, hillock and proximal axon. These processes projected onto adjacent neuron somata and cardiac muscle fibers within the interatrial septum. Average total length of the processes from proximal axon was 348 ± 50 µm. Average total length of processes from soma and hillock was less, 118 ± 27 µm and 109 ± 24 µm, respectively. The somata of 59% of neurons had bubble- or flake-shaped extensions. Most neurons from the major nerves in the interatrial septum sent their axons towards the ventricle. In contrast, most neurons from the ventral part of the interatrial septum sent their axons towards the atria. Our findings contradict to a view that the frog intracardiac ganglia contain only non-dendritic neurons of the unipolar type. We conclude that the frog intracardiac neurons are structurally complex and diverse. This diversity may account for the complicated integrative functions of the frog intrinsic cardiac ganglia.

[Distribution of the epicardiac neural ganglia in human fetuses of different age]. / Epikardiniu nerviniu mazgu pasiskirstymas skirtingo amziaus zmogaus vaisiuje.

OBJECTIVE: The epicardiac neural ganglia of the adult human heart are distributed in the seven neural ganglionated subplexuses. The aim of the present investigation was to determine the distribution of the epicardiac ganglia in human fetuses of different age, because intrinsic cardiac nervous system of the human fetus has not been enough investigated so far. MATERIAL AND METHODS: In the present study seventeen human fetus hearts were investigated, in which epicardiac neural ganglionated plexus was visualized by histochemical method for acetylcholinesterase. RESULTS: Analysis of the total hearts preparations showed that: (1) the epicardiac neural ganglionated plexus of the fetus at fifteen weeks of gestation has already differentiated into seven ganglionated subplexuses, structure of which is typical for the adult human heart; (2) the epicardiac plexus of fetuses at 15-40 weeks of gestation contains on average 865+/-40 epicardiac ganglia, that may widely range in number from 644 to 1193; (3) the largest number of the neural ganglia is concentrated on the posterior surface of both atria, where up to 76% of all ganglia maybe located; (4) the difference between the number of epicardiac ganglia in the human fetuses at the early (15-25 weeks) and late (26-40 weeks) stages of fetogenesis is not statistically significant (p>0.05). In conclusion, both the distribution and the number of the epicardiac ganglia of fetuses ranging from 15 to 40 weeks of gestation are not age-dependent but varied substantially from heart to heart.