Central control of sympathetic cardioacceleration in medulla oblongata of the cat

Abstract

Under chloralose, as well as under pentobarbital anesthesia, stimulation of the dorsal medulla elicited after decerebration a cardioacceleration comparable to that before decerebration. Similar increases in the heart rate were also obtained after additional ablation of the remaining midbrain and portion of the pons. In addition, it is possible in these decerebrate animals to elicit cardioaccelerator reflexes by occluding the common carotid arteries or by stimulating the central end of the sciatic nerve. Our findings are contrary to those reported by Peiss (J. Physiol., London 151: 225, 1960) and do not support his contention that the dorsal medulla constitutes only an afferent cardioaccelerator pathway to the hypothalamus. Our results support the concept that an important integrative mechanism for cardioacceleration, as well as for vasomotor reaction, resides in the dorsal medulla, and that higher neural structures such as the hypothalamus serve a regulatory function.