Spinal cord location of the motoneurons innervating the tail muscles of the cat.

The localisation of the motoneuronal pool of the individual tail muscles of the cat was studied by using intramuscular injections of horseradish peroxidase (HRP) to retrogradely label motoneurons innervating tail muscles. The motoneurons innervating muscles located on the medial side, extensor caudae medialis (ECM) and flexor caudae brevis (FCB), were placed in the mediodorsal area of the ventral horn, while those of extensor caudae lateralis (ECL) and flexor caudae longus (FCL) muscles were located in the ventral part of the ventral horn in S2 and 3 segments. The distribution of these motoneurons was shifted to the lateral side in coccygeal segments, but the motoneurons of lateral muscles (ECL, FCL) were located lateral to those of medial muscles (ECM, FCB). The motoneurons of abductor caudae externus (ACE), abductor caudae internus (ACI) and iliocaudalis and levator ani (IC) were distributed in the intermediate area of the ventral horn. The minimum and maximum diameters of motoneurons innervating the tail muscles were measured and shown in histograms. The histograms were unimodal and the motoneurons of ECM, ECL, FCL and FCB were bigger than those of ACE and ACI.