[The effect of substance P on the swimming behavior of rats under stressing and nonstressing conditions].

Experiments of acute and chronic stressing were investigated in rats. The behavioural features were analyzed. The acute stressing situation involves a swimming test from which rats can escape by entering a little platform. Repeated experiments every 10 min cause an exponential decreased reaction response. 250 micrograms/kg substance P i.p. accelerate the learning reactions. Chronic stress situation was managed by immobilization of several hours daily in a period of 11 d. Neurotic behavioural features were observed after application of 250 micrograms/kg substance P i.p., such as twitch of ears and head, "wet dog" shakes and increased grooming. In open field there were decreased locomotor and exploratory reactions after injection of 250 micrograms/kg substance P i.p. In an added acute stress exposition behavioural characteristics were improved after these doses of the peptide, such as unsuccessful trial to jump out, latency to liberate and period of no moving. The results were discussed in relation to the function of substance P as a regulatory peptide.