Polysynaptic pathways from hindlimb cutaneous afferent nerves to tail muscle motoneurons in unanesthetized and spinalized cats.

Postsynaptic potentials (PSPs) were recorded in 57 extensor caudae lateralis (ECL) motoneurons and 82 flexor caudae longus (FCL) motoneurons of 36 decerebrated and spinalized (L1-2) adult cats, upon electrical stimulation of hindlimb cutaneous nerves, such as the sural nerve, superior peroneus nerve, and plantar section of the tibial nerve. With low threshold stimulation (1.2-5.0 T), excitatory PSPs (EPSP, EPSP/IPSP) predominated in ECL and FCL motoneurons. In a few ECL and FCL motoneurons, however, inhibitory PSPs were observed. Increasing the stimulus intensity from 1.2 T to 5.0 T led to an increase in amplitude of the PSPs. The central latencies of the PSPs were distributed over a wide range and minimal latencies of PSPs corresponded to 3.5 and 3.8 ms in ECL and FCL motoneurons, respectively. The measurement of central latencies reveals the oligo- and polysynaptic neural pathways from hindlimb cutaneous nerves to tail muscle motoneurons.