Cardiovascular and respiratory responses to electrical stimulation of the midbrain in the rat

In descending through the midbrains of rats with stimulation electrodes, we have observed some remarkable reversals of pressor and depressor autonomic effects as the electrode was moved from one locus to another. Autonomic effects of stimulating in the midbrain areas that we studied are of special interest because stimulations in some of these midbrain loci have pain-relieving effects (Hosobuchi et al., 1977, 1979; Mayer et al., 1971; Soper, 1976). Our observations of cardiac arrest are of particular concern because of the use that is being made of midbrain electrical stimulation to relieve pain in human patients.