Contralateral projections of barosensitive neurons of the nucleus tractus solitarii.

Axonal projections of single barosensitive neurons of the nucleus tractus solitarii (NTS) which fired in synchrony with heartbeat, were studied in Nembutal-anesthetized, paralyzed, and artificially ventilated cats. The majority of them were orthodromically activated by electrical stimulation of the ipsilateral cervical vagal nerve. Antidromic mapping by electrical stimulation of the medulla could identify the axonal projections in 14 of the 25 barosensitive NTS neurons examined. Their stem axons crossed the midline to the contralateral side and ascended rostrally. The contralateral axons of some neurons issued collaterals in the rostral ventrolateral medulla (RVLM) medial to and ventromedial to the facial nucleus. The contralateral axons of the other neurons ascended toward the pons without any sign of issuing collaterals within the medulla.