Age-dependent alterations in the response of isolated rat aortas to thiobarbiturates

Responses to thiamylal and thiopental were compared in helical strips of rat thoracic aortas of different ages (5-6, 10-12 and 20-22 weeks old), precontracted partially with phenylephrine or prostaglandin F(2alpha) (PGF(2alpha)). Thiamylal and thiopental, in concentrations of 3 x 10(-5) to 10(-4) M, produced a dose-dependent relaxation in aortas at 5-6 weeks of age, no significant change of tension in those at 10-12 weeks of age, and a marked constriction in those at 20-22 weeks of age. These thiobarbiturates, in a high concentration of 10(-3) M, produced a profound relaxation in aortas at any age studied. It is concluded that the responses to thiobarbiturates of thoracic aorta precontracted with phenylephrine or PGF(2alpha) alter with age.