Reflex organization of cat masticatory muscles.

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Abstract
In the cat anesthetized with pentobarbital, reflex organization of the mastication was studied. Afferent activity from nerves in the mouth area induces a polysynaptic reflex in the digastric nerve and 2 phases of inhibition in masseter motoneurons tested with masseteric monosynaptic reflex responses. In the intracellular recordings, inferior dental nerve stimulation induced an EPSP [excitatory postsynaptic potential] with a central delay of 1.7 msec in digastric motoneurons. In masseter and synergist motoneurons a complex IPSP [inhibitory postsynaptic potential] was induced with a central delay of 1.6 msec, early-phase lasting about 15 msec and late-phase enduring for as long as 100 msec. Two phases of the IPSP were different in reactions to chloride injection, in the degree of membrane conductance changes and in sensitivities to strychnine. Digastric motoneurons were not inhibited from the masseter afferents and masseter motoneurons were not responsive to digastric nerve stimulation. Thus, reflex organization of the mastication is not like that of hind-limb muscles.