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To find whether effects of adrenergic and cholinergic agents on cerebral artery were dependent on maturity, we examined responses of isolated cerebral artery strips harvested from premature, term newborn and adult baboons. Although cerebral arteries from many species are only mildly sensitive to norepinephrine, we found the perinatal cerebral arteries to be quite responsive to the amine. Cerebral arteries from premature and newborn baboons were significantly (P less than 0.001) more sensitive to norepinephrine than were arteries from adults; medium effective concentration (EC50) for norepinephrine were 3 X 10(-8), 6 X 10(-8) and 32 X 10(-8)M for prematures, newborns and adults, respectively. Arteries showed a similar age-dependence in the sensitivity of the response to phenylephrine, an alpha 1-adrenoceptor agonist. EC50 values for KC1 did not differ among groups, nor did the maximum response to norepinephrine. Arteries from premature and newborn baboons showed marked contractile response to acetylcholine (maximum tensions 5.9 +/- 0.6 and 6.4 +/- 0.8 g/mm2, respectively), whereas arteries from adult baboons showed little response (0.6 +/- 0.1 g/mm2). Arteries from premature and newborn animals showed a more marked relaxation response to isoproterenol than did arteries from adult animals; the degree of relaxation from an induced contraction was 63% (premature), 72% (newborn) and 10% (adult). There was no age-dependence in the relaxation response to sodium nitrite. We conclude that the events coupling alpha 1, beta or muscarinic receptor activation with cerebral arterial contraction or relaxation are more effective in perinatal than in adult baboons.

Helically cut strips of thoracic aorta and main pulmonary artery from rabbits of varying age were examined for their ability to relax with cumulative doses of isoproterenol (ISO) and sodium nitrite (NaNO2) in the presence of appropriate blocker(s) in isolated tissue baths. The baths contained Kreb's solution maintained at 37°C and oxygenated with 95% O2  5% CO2. The vessels were preconstricted with 3 × 10−6M 5-hydroxytryptamine (5HT) which produced approximately 95–100% of maximal contraction to the drug. The relaxation induced by ISO or NaNO2 was expressed as a percent of contraction produced by this dose of 5HT. The magnitudes of percent relaxation produced by 1 × 10−3M NaNO2 were the same for all age groups, but those produced by ISO were significantly less in the 1–2 day and 7–10 day groups than in the 1 month and 4–5 month groups in both the aorta and pulmonary artery (p < 0.01). These findings indicate that the beta-adrenergic receptor function in the aorta and pulmonary artery of the newborn rabbit is not fully developed but it matures with age.