The effect of suxamethonium on the response to stretch of Golgi tendon organs in the cat.

1. The effects of intra-arterial infusion of suxamethonium (succinylcholine, SCh) on the response to stretch of Golgi tendon organs in the soleus muscle of the cat have been studied. 2. SCh infusion produced a gradual facilitation of the discharge of tendon organs with low thresholds to passive muscle stretch, but had no detectable effect on tendon organs with high thresholds to stretch. 3. The time course of excitation and recovery of low-threshold tendon organs after SCh infusion was much longer than that of muscle spindle primary and secondary sensory endings. 4. Control experiments showed that there was no change in the passive tension of the soleus muscle during SCh infusion, thus excluding the possibility that the excitation of the low-threshold tendon organs is caused by an increase in passive muscle tension. 5. These findings complement recent observations that SCh can excite receptors other than those in muscle spindles, and indicate that SCh activation on its own may not be a sufficient criterion on the basis of which to identify muscle spindle afferent axons.