[Age-related aspects of the reaction of isolated strips of rat rectum and colon to carbacholine, atropine and pentamine].

Experiments in vitro were made to record isotonic contractions of isolated strips of the rectum and colon of rats distributed into 4 age groups. It was shown that in one-week-old rats, the rectal and colonic strips reacted to carbacholine (1 x 10(-10--1 x 10(-5) M) to a far less extent than those in adult rats. In the course of postnatal development the reaction of the colonic strips to carbacholine reached the adult rat level more rapidly. Pretreatment of the colonic strips from one- and two-week-old rats with pentamine solutions (2 x 10(-5)--1 x 10(-4) M) led to the increased carbacholine response rather than to its lowering which was the case in the adult animals. Pretreatment of the strips in question with atropine solutions (1 x 10(-14)--1 x 10(-6) M) decreased the response to the cholinomimetic to a more significant extent than in the adult animals. High concentrations of the cholinomimetic did induce a considerable percentage of contractions.