Excitation of Intradental Sensory Units by Pharmacological Agents

Recordings were made from intradental sensory nerves in the tooth of the cat. Local application of bradykinin and histamine failed to induce impulse activity, even when applied to the exposed pulp, whereas 5‐hydroxytryptamine produced bursts of impulses with short latency, lasting a few seconds. Application of compound 48/80 induced an increase in impulse activity after a delay of some minutes and this activity persisted for about 2 h irrespective of whether the agent was removed or not. The impulse frequency decreased promptly when the temperature was raised and recovered when the temperature was lowered again. Pre‐treatment with polyphloretin phosphate (PPP) inhibited the excitatory action of compound 48/80. The threshold of excitation to cold stimulation was lowered after introduction of compound 48/80. Since the principal action of compound 48/80 is to release endogenous substances from mast cells the present findings may indicate that the increase in impulse activity is secondary to a release of biogenic substances. However, at present a direct action of compound 48/80 can not be excluded.