Effect of intracerebroventricular administration of substance P and its hexapeptide fragment on the estrus cycle in female rats.

The purpose of the reported experiments was the study of the effects of intracerebroventricular (i.c.v.) administration of substance P (SP 1--11) and its hexapeptide C-terminal fragments SP 6--11 and (pGlu6)SP6--11 on the length of the estrus cycle. In the animals with a regular sequence of estrus aliquots of 250 pmol of the three peptides: SP 1--11, SP 6--11 and (pGlu6)SP 6--11 on the carier dextrane were infused into the left lateral cerebral ventricle through a chronically implanted cannula. For control, dextran solution in 0.9% NaCl was infused in a similar way. I.c.v. infusion of dextran in 0.9% NaCl, SP 1--11 and (pGlu6)SP 6--11 caused no significant changes in the length of the estrus cycle during which the infusion was done. Infusion of SP 6--11 prolonged the diestrus phase in most animals. This observation indicates that SP 6--11 exerted an effect on the hypothalamic mechanism controlling the secretion of gonadotropins by the hypophysis.