Central pathways of some autonomic reflex discharges

1. Electrical stimulation of spinal sensory nerves evoked discharges in inferior cardiac and renal nerves. In the anaesthetized cat both an early and a late response could be recorded in each nerve. 2. For any one afferent input the central delay of the late cardiac nerve response was significantly less than that of the late renal nerve response. The central delay of the early responses was similar for both nerves. In the spinal cat only the early response was present. 3. Cooling the floor of the 4th ventricle abolished the late responses in renal nerves, but left reflex volleys in white rami and intercostal nerves unchanged. 4. Stimulation in the brain stem evoked responses in both cardiac and renal nerves which had a shorter latency than the reflexes evoked in these nerves by stimulating dorsal roots. 5. The late responses could be abolished by lesions in the cervical spinal cord. 6. Such evidence led to the conclusion that there are two pathways for reflex discharge into inferior cardiac and renal nerves, one involving a supraspinal relay and the other confined to the spinal cord.