Topographic relationship of neurotensin-containing axon terminals with cardiac and noncardiac principal ganglion cells in the stellate ganglia of the cat

Abstract

The pattern of association between neurotensin (NT)-immunoreactive (NTIR) preganglionic nerve terminals and cardiac and noncardiac neurons in the stellate ganglion of the cat is analyzed, based on the finding of an excitatory modulation effect of exogenous NT on cardiac functions. For this purpose, NT-containing terminals were labeled by immunohistochemistry, and ganglion cells were detected by retrograde labeling of cardiac and vertebral nerves to identify cardiac and noncardiac neurons. To determine a possible regional localization of NTIR terminals and ganglion cells, the ganglia were divided into four areas: caudal, dorsomedial, cranial, and ventromedial, related to the two major afferent nerves (thoracic white rami 3 [T3WR] and 2 [T2WR]) and the two efferent nerves (vertebral and cardiac). NTIR terminals were widespread in the complete ganglion tissue; they covered practically all the regions explored, although two clusters of high concentration of NTIR terminals were detected in the cranial and caudal areas. By retrograde labeling it was found that cardiac cells were arranged around the exit of the cardiac nerve and that the vertebral neurons were extended from the exit of the vertebral nerve to the entrance of T3WR. The finding of association of NTIR terminals with cardiac neurons may account for the cardioregulatory effect of NT; however, since the presence of NTIR terminals close to the noncardiac neurons is notorious, other regulatory functions of NT must be considered.