Comparison of antagonistic properties of substance P analogs, spantide I, II and III, on evoked tongue jerks in rats

Objective: To study and evaluate the effects of perfusion through cerebral ventricles with substance P (SP) and its analogs: spantide I, II and III on evoked tongue jerks (ETJ) in male rats.

Methods: During the perfusion, stimulation of the tooth pulp caused retractive movements of the stretched tongue, the amplitudes of which were recorded. The mean amplitudes of evoked tongue jerks (ETJ) recorded during each 10 min. period of perfusion with McIlwain-Rodnight's solution and solutions containing Peptides were compared.

Results: Perfusion of cerebral ventricles with SP caused a significant increase in the mean amplitude of evoked tongue jerks. Spantide I caused a complete respiratory arrest in all of the examined Animals, so its effect on the trigemino-hypoglossal reflex could not have been tested. Spantide II, in the first two minutes, induced a transient significant decrease in ETJ amplitude, followed by an increase in ETJ in the next 8 min. SP perfused after spantide II caused a further significant increase in ETJ, as compared with control. Perfusion of cerebral ventricles with spantide III caused a significant, dose-dependent decrease in ETJ. SP perfused after spantide III caused a smaller increase in ETJ than it was observed without spantide III.

Conclusion: Spantide III was found to be a strong antagonist of SP in trigemino-hypoglossal reflex.