ABSTRACT
This chapter reviews the information regarding connections of nucleus tractus solitarius (NTS) with other medullary areas controlling cardiovascular function and the possible role of excitatory amino acids, acetylcholine, and substance P as transmitters in this region. Functional identification of the sites eliciting responses similar to those produced by the stimulation of the carotid body was accomplished by microinjections of l-glutamate. The NTS sites eliciting responses similar to cardiopulmonary receptor stimulation were identified by microinjections of l-glutamate into an area located 0.5 mm rostral, 0.5 mm lateral, and 0.5 mm deep on either side with reference to the calamus scriptorius. Bilateral microinjections of muscimol into this NTS site blocked the responses to subsequent stimulation of cardiopulmonary receptors by phenylbiguanide. The possible role of vasopressin release during NTS stimulation was excluded because decrease in cerebral blood flow persisted even after intravenous administration of a vasopressin antagonist.
