Action of substance P on neurotico-hypertensive rats.

The action of an eledoisin-hexapeptide analogue (EH) upon learning and memorising processes of 48 male Wistar laboratory rats aged between 5 and 6 months was studied and is reported in this paper. The animals suffered from neurogenic hypertension which had been experimentally induced by applying emotional stress. A comparison between the action of EH (Lys-Phe-Ile-Gly-Leu-MetNH2) and that of Substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-MetNH2) on conditioned-reflex learning in the intact rat had been reported by the authors in one of their previous papers [7]. The following results were obtained with regard to EH and its action upon rats with neurogenic hypertension. The learning process was favoured, as it had been by 2 or 3 weeks of exercise. Defective learning and memorizing process as well as impaired behavioural patterns, interpreted as neurotic phenomena, were normalized by doses of 250 microgram/kg and 500 microgram/kg. Blood pressures were reduced, depending on dosage. The action of the EH analogue used on the central nervous system was stronger than that on blood pressure. Discontinuance of peptide application was followed by the phenomenon of "state-dependent learning". The results are likely to suggest possible involvement of such peptide sequences in the regulation of processes which are relevant to the whole. That effect is of particular interest, as Substance P is under discussion as a transmitter or modulator in mammals.