The intrinsic cardiac ganglion neurons were studied with immunohistochemical PAP technique for localization of calcitonin gene-related peptide (CGRP) in this paper. The result showed that there are many CGRP immunoreactive nerve fibers and a few CGRP immunoreactive neurons within the atrial wall. This fact suggest that CGRP immunoreactive fibere in the heart originate not only from extrinsic cardiac ganglia, but also from intrinsic cardiac ganglia. It is well known that CGRP is closely related to sensory function, and therefore, these CGRP immunoreactive neurons probably be sensory in nature. This result provide some new morphological evidences for identifing the intrinsic cardiac reflex pathway.

Ten to twenty ?l of 20-50% horseradish peroxidase (HRP) in normal saline solution was injected into the myocardium of the anterior wall of left and right ventricles in 11 rabbits. The areas containing sino-atria as well as atrio-ventricular nodes and the dorsal wall of the atria were removed separately. Frozen or cryostate sections of these tissues 25-40?m thick, were incubated according to the HRP (tetramethylbenzidine "TMB" method)-AChE combined method. The blue granules produced by the HRP with TMB were observed in the perikarya of a few AChE intensely positive ganglion cells which were located in the epicardium of the dorsal wall of the atria. This indicated the processes of the HRP-AChE double labeled cells distributed to the myocardium of the anterior wall of the ventriculum. It is generally believed that the nerve cells of strong AChE activity can be referred as cholinergic neurons. For this reason, the present study may give further identification to assert the parasympathetic innervation of the ventricular myocardium. The parasympathetic postganglionic neurons innervated the anterior wall of left and right ventriculi are situated primarily in the epicardium of the posterior wall of the atria.

We Injecte(?) 12-16 ?l 20—40% HRP in normal sanne into the myocardium orthe anterior wall of the left ventricle in six rats and 10 ?l choleragenoid-horsera-dish peroxidase conjugate(CB-HRP)in three rats.The Th1-3 DRG and the nodoseganglia of both side were removed.The sections of these ganglia were proceeded bythe TMB chromogentic reaction for HRP and immunohistochemical reaction(the firstantibody is the substance P antiserum).There are three types of labeled cells——theHRP labeled cells.Sp-IR cells,and HRP-Sp-IR double labeled cells were observedin the Th1-3 DRG and nodose ganglia of both side.The parts of Sp-IR nerve fib-ers in the heart wall originate from the DRG and nodose ganglia and these neuronsprojecting the HRP-Sp-IR nerve fiber contained substanse P.Their functions may berelated to the pain(nociceptive)sensation of the heart.This study may also be aevidence of the main function of the cardiac sympathetic afferent fiber is the con-duction of the pain sensation.A few of HRP-Sp-IR double labeled cells in thenodose ganglion observed suggest that the cardiac parasympathetic afferent fibermay participate in conduction of the pain sensation.This question requires furtherstudy.