The effect of bradykinin on denervated tongue.

1. The contractile response of the chronically denervated tongue of the cat to chorda stimulation, and to close arterial injections of bradykinin, acetylcholine (ACh) and other drugs was examined.2. Bradykinin in doses of 50 ng-20 mug injected close arterially always produced a contractile response of the denervated tongue. Sodium nitrite (1 mg i.a.) and isoprenaline (3-200 ng i.a.) also produced contracture; histamine (40-100 ng i.a.) evoked an increase in tension in only 2 out of 5 experiments.3. Tubocurarine in doses of 0.25-1 mg injected intra-arterially, produced a large and long-lasting contracture of the denervated tongue. When the contracture was over, the effect of bradykinin was reduced to about half; the effects of ACh and chordo-lingual nerve stimulation were markedly reduced (over 80%), and those of sodium nitrite and isoprenaline were transiently abolished. Gallamine only slightly reduced the effect of bradykinin.4. Close intra-arterial injection of physostigmine (100 mug) potentiated the effect of ACh and chordo-lingual nerve stimulation, but did not increase the response to bradykinin.5. Cocaine (1 mg/kg i.v.) deeply depressed the response to bradykinin, and moderately reduced the responses to ACh (41%) and to chorda stimulation (66%).6. In 2 out of 7 experiments, close arterial injections of bradykinin (100-500 ng) to the denervated tibialis anterior muscle of the cat, produced a contractile response. Bradykinin in small doses (200-250 ng) injected immediately before ACh potentiated its effect. On the other hand, the effect of ACh was depressed when given immediately after a big dose of bradykinin (10-15 mug).7. The possible mechanism of action of bradykinin and other substances on denervated muscle is discussed.