Influence of rostral neural structures on the vasomotor functions of the medulla oblongata

Chinese J. Physiol 31(2): 79-93, 1988. In cats, the resting systemic arterial blood pressure (SAP) which rises on electrical stimulation of the dorsal medulla (DM), ventrolateral medulla (VLM) and paramedian reticular nucleus (PRN) under anesthesia with 2% halothane in oxygen were compared with those 30 min after termination of the inhalation (with application of lidocaine on the surgical wound and i.v. gallamine 2 mg/kg). The resting SAP under halothane were significantly lowered and functions of the DM and VLM much depressed. The depressor response of PRN stimulation was converted to the pressor one after deprivation of halothane anesthesia. In animals under little anesthetic influence, midcollicular decerebration significantly lowered the resting SAP, but both DM and VLM pressor responses were not significantly changed. In addition, the decerebration significantly diminished the peak pressor effects on PRN stimulation. Findings suggest that rostral neuro-structures do exert tonic influence (both excitatory and inhibitory) on medulla vasomotor functions. This is quite different from the classical concept, first proposed by Dittmar and Owsjannikown (1870s) and still considered nowadays as truthful, that the neural structures rostral to the caudal one third of pons was not critical in maintaining the resting SAP.