Department of Comparative Anatomy, Institute of Biology, S ´ wie¸tokrzyski University, Kielce, Poland A Comparative Study on Cardiac Ganglia in Midday Gerbil, Egyptian Spiny Mouse, Chinchilla Laniger and Pigeon T. Kuder*, E. Nowak, A. Szczurkowski and J. Kuchinka Address of authors: Department of Comparative Anatomy, Institute of Biology, S ´ wie ˛ tokrzyski University, 25-406 Kielce, 15 S ´ wie ˛ tokrzyska St, Poland; *Corresponding author: e-mail: tkuder@pu.kielce.pl With 4 figures Received Feburary 2002; accepted for publication July 2002 Summary Using the thiocholine method and histological techniques, the topography and morphology of cardiac ganglia in midday gerbil, Egyptian spiny mouse, chinchilla laniger and pigeon were studied. The results demonstrated that cardiac ganglia in all investigated species are embedded in epicardial fat. They formed plexo-ganglionic structures. Each of them composed of many ganglia (from seven up to 36) different in size and shape, and interconnected by fascicles of nerve fibres. Comparative analysis showed that the density of neural network and cell aggregations was different in individual species. The richest plexo-ganglionic structure was in pigeon. It was organized in three plexo-ganglia with an average of 30 ganglia. The largest one was located along the anterior interventricular sulcus. The cardiac ganglia of investigated mammals were localized mainly on the epicardium of atria; in Egyptian spiny mouse and chinchilla laniger on the ventral surface of right atrium, but in midday gerbil on the dorsal surface of left atrium. Moreover, in midday gerbil and Egyptian spiny mouse the little plexo- ganglionic structure on the ventricle were noticed. Addition- ally, in midday gerbil the single nerve cells might be observed between cardiac muscle of atria. It can be said that, the strongly developed cardiac plexus in pigeon is probably con- nected with his behaviour and functional properties of the heart. The arrangement of neurones in cardiac ganglia of all examined mammals was uniform over the whole surface of the sections, while in the pigeon, neurones were located mainly in the peripheral part of the ganglion. Introduction The cardiac ganglia have been examined and described in many species of amphibians, reptiles, birds and mammals. The research were concerned with their morphology, topography, cytoarchitectonics, ultrastructure and also physiology of car- diac neurones. The results of these researches revealed that the cardiac ganglia were found in a number of specific cardiac regions (Michell, 1956; Bojsen-Moller and Traum-Jensen, 1971; Randall et al., 1986; Baluk and Gabella, 1987; Hancock et al., 1987; Armour and Hopkins, 1990; Furukava et al., 1990; Pauza et al., 1997, 1999, 2000, 2002; Kuder and Tekieli, 1999, 2000; Pauziene et al., 2000). They formed a system of ganglionated plexuses of diverse size, shape and density. The highest density of epicardiac ganglia was found on the surfaces of the left and right atria. Moreover, the ganglia were located on both surfaces of cardiac ventricle. The classical view regarding cardiac ganglia is that they contain parasympathetic efferent post-ganglionic neurones (Bojsen-Moller and Traum-Jensen, 1971; Ellison and Hibbs, 1976; Baluk and Gabella, 1987; Hancok et al., 1987; Michell, 1956). On the other hand, the presence of a few adrenergic neurones in the cardiac ganglia was identified by Armour and Hopkins, (1990) and Yuan et al. (1994). Some authors demon- stratedmorphologicaldifferentiationofneuronesinthecardiac plexuses and they thought, that the function of the neurones may also be different (Edwards et al., 1995; Pauza et al., 1997). Nevertheless,thereisnothoroughstudyofthecardiacganglia in chinchilla laniger, Egyptian spiny mouse, midday gerbil and pigeon – except the congress abstracts (Kuder et al., 2000a,b; 2001). The present examinations concerning the topography, morphology and cytoarchitectonics in Egyptian spiny mouse, chinchilla laniger, midday gerbil and pigeon has been underta- ken to complete data and carry out the comparative analysis. Materials and Methods Eight adult Egyptian spiny mice (Acomys cahirynus), five chinchilla lanigers (Chinchilla laniger), seven midday gerbils (Meriones meridianus) and eight pigeons (Columba liva) of either sex have been used in the study. The animals were deeply anaesthetized with ether and intraperitoneal injection of Nembutal (20–40mg/kg). Then the hearts were taken out. Histochemical study Partofheartswerefixedin10%formalinandthentreatedbya whole-mount technique using the histochemical method of Koelle and Friedenwald (1949) modified by Gienc (1976, 1977) for use in macromorphological specimens. Histological study Other hearts were fixed in 4% neutral formalin, then embed- ded in paraffin and then cut on a microtome into 5–8 lm sections. The hearts were sectioned from the base of the heart. The sections were stained with haematoxylin and eosin and Nissl’s method. Results Midday gerbil Histochemical investigations revealed the presence of delicate plexo-ganglionic structures in the fatty tissue of gerbil’s U. S. Copyright Clearance Center Code Statement: 0340–2096/2003/3203–0134$15.00/0 www.blackwell.de/synergy Anat. Histol. Embryol. 32, 134–140 (2003) Ó 2003 Blackwell Verlag, Berlin ISSN 0340–2096