Abnormal innervation of the cat soleus muscle

The soleus-nerve muscle preparation has been extensively employed as a standard preparation for physiological and pharmacological studies on mammalian muscle contractile properties (for example Feng & Li, 1941; Brown & Matthews, 1960). This preparation has also been used in the investigation of motor nerve terminal responses (Riker, Roberts, Standaert & Fujimori, 1957; Bowman, Goldberg & Raper, 1969; Riker & Okamoto, 1969), and recently microelectrode analysis of neuromuscular transmission (Hoekman, Dretchen & Standaert, 1974). The present report is of significance in the surgical preparation of this widely used nerve-muscle system. Further, while evidence of altered physiological or pharmacological responses is lacking, that does not preclude the possibility that the sub-population of cats with this unusual innervation of the soleus muscle may also exhibit aberrant functional responses. During the past 12 years our laboratories have regularly employed mongrel cats to prepare in situ soleus nerve-muscle preparations (Riker et al., 1957) for pharmacological investigations. Of the more than 2400 animals used for this preparation, 15 (about 0,6 %) exhibited abnormal innervation of the soleus muscle; II of these observations were made on single-leg preparations in different cats, and 2 were made on double-leg preparations (Okamoto & Riker, 1969; Lowndes, Baker & Riker, 1974) in 2 cats. In these 2 animals the abnormal innervation was present bilateralIy. In normal cats (Crouch, 1969) the soleus nerve arises from the tibial portion of the sciatic nerve. The sciatic nerve arises from the lumbosacral cord, passes dorsocaudalIy out the pelvic cavity through the great sciatic notch and runs between the muscles of the upper hind limb where it gives off branches to the biceps femoris, semimembranosus and semitendinosus muscles. The