Abstract
In vivo and in vitro rates of intestinal rhythmic contractions were measured in the same rats varying in age from very young to the senescent. Two rat strains, three small intestine locations, and six ages were compared. Contraction rates determined in vivo and in vitro were similar. Rhythmic contractions at all ages were fastest in the duodenum, slower in the jejunum, and slowest in the ileum. Contractions at 10 days of age were significantly slower than' at all other ages; otherwise no systematic age-associated difference in contractions was demonstrated in either strain. Several factors were suggested as possibly influencing the developmental aspects of contraction rate and, therefore, their potential involvement in the early post natal period was suggested. It appears that old age does not influence the rate at which rhythmic contractions occur in the small intestine of the rat, and very possibly, these results are applicable to other species including humans.