CROSSED AND UNCROSSED SEGMENTAL SYNAPTIC EFFECTS ON OBLIQUUS-EXTERNUS-ABDOMINIS MOTONEURONS FROM CUTANEOUS AND CUTANEOUS-MUSCLE NERVE IN SPINAL CATS AND ALPHA-CHLORALOSE-ANESTHETIZED CATS

Segmental synaptic responses in the obliquus externus abdominis (OEA) for stimulation of the dorsal cutaneous and cutaneous-muscle (CD) nerv e and the ventral cutaneous and cutaneous-muscle (CV) nerve were inves tigated in 49 spinal cats and 28 cats under alpha-chloralose anesthesi a (chloralose cats) with an intracellular recording method. The result that there was no monosynaptic PSP in OEA motoneurons for stimulation of the CD or CV nerves (containing the cutaneous-muscle nerve) indica tes that the cutaneous muscle of the dorsal or ventral area does not c onnect monosynaptically to the OEA motoneuron. The OEA motoneurons in chloralose cats received few effects from descending pathways coming f rom the upper spinal cord and the brain. Almost all OEA neurons had po lysynaptic EPSP responses for stimulation of the ipsilateral or contra lateral CD or CV nerves at 5-10T stimulus intensity in spinal or chlor alose cats, which indicates that the OEA muscle can contract bilateral ly when strong impulses of superficial afferents from the left or righ t skin or cutaneous muscle enter in the spinal cord.