Distribution of compound potentials recorded from the surface of isolated stellate ganglia following stimulation of postganglionic branches, in rats and cats.

The experiments were performed on 9 cat and 18 rat isolated stellate ganglia. Rats and cats were anesthetized with alpha-glucochloralose or urethane, respectively. The ganglia, isolated with their branches, were transferred to a recording chamber and constantly superfused with artificial extracellular fluid bubbled with 95% O2 and 5% CO2. Branches of the ganglion were one by one placed in suction electrodes and stimulated. Antidromic evoked potentials were systematically recorded from numerous points on the ganglion surface. The area under the curve of the negative wave of each recorded potential was considered proportional to the number of neurons located in the vicinity of the recording electrode, projecting to the stimulated nerve. We have found that: (1) cardiac sympathetic neurons are located in the lower, caudal half of the ganglia; (2) vertebral sympathetic neurons occupy the cranial, upper half of the ganglia; (3) neurons with axons in the ansae are positioned near the point of exit of the respective ansa from the ganglion; (4) localization of neurons projecting to the same branches is very similar on both sides--right and left; (5) this localization is also similar in rats compared to cats.