Influence of cerebral ventricles perfusion with hexapeptide derivatives of substance P on evoked tongue Jerks in rats

The effects of perfusion through cerebral ventricles with two hexapeptides, C-terminal derivatives of substance P, on evoked tongue jerks (ETJ), were studied on male rats. During perfusion, stimulation of the infraorbital nerve caused retractive movements (ETJ) of the stretched tongue, the amplitudes of which were recorded. The mean amplitudes of ETJ recorded during each 10 min period of perfusion with McIlwain-Rodnight's solution and solution containing hexapeptides were compared.The biologically most active C-terminal hexapeptide derivative of substance P (pyro-Glu⁶)SP_6–11, perfused through cerebral ventricles in a concentration of 5 nmol/ml increased the ETJ. This effect was dose-dependent. A 10 times higher concentration in the perfusion fluid of the less biologically active hexapeptide SP_6–11 was not effective.The possibility that substance P, and its active fragments present in the fluid in cerebral ventricles, could modulate the reflex centers in the medulla is discussed.