Spino-spinal mechanisms in the chloralose anaesthetized cat.

1. In chloralose anaesthetized cats the events in the lumbosacral cord that follow stimulation of a forepaw or neck nerve have been examined.2. Four events take place in the lumbosacral cord after forepaw or neck muscle nerve stimulation. These are: (1) a brief period of generalized enhanced motoneurone excitability, (2) a prolonged and as yet unexplained enhancement of monosynaptic reflexes, (3) a period of presynaptic inhibition in muscle and skin afferent fibres, and (4) a prolonged inhibition of spino-bulbo-spinal reflexes.3. A variable and sometimes selective reduction of one or another descending effects follows the placing of small lesions in the anterior portion of the suprasylvian gyrus.