Effects of anesthetic agents on the adrenocortical system of female baboons

Invasive surgical procedures are often used to study the reproductive and adrenocortical endocrine systems in primates. Anesthetic agents must, therefore, be used that have the least confounding effects on these systems. The present study was designed to characterize various adrenocortical endocrine responses of female baboons (Papio anubis), each treated for 120 minutes with an infusion of ketamine HCl (6 mg/min) in 5% dextrose in water (0.40 ml/min), a combination of ketamine and acetylpromazine (0.6 mg acetylpromazine and 6 mg ketamine HCl/min) in 5% dextrose in water, or inhalation of vaporized halothane (1.0% halothane, N₂O 25%, 1 liter/min; O₂ 75%, 3 liters/min). Blood samples were collected throughout the treatment period, and serum was assayed for prolactin (PRL), dehydroepiandrosterone (DHA), dehydroepiandrosterone sulfate (DHAS), and cortisol (F). No significant elevations in DHA, F, or PRL concentrations were found following infusion of ketamine alone. Only serum DHAS concentrations were significantly altered after long-term exposure to ketamine. Acetylpromazine increased PRL concentrations tenfold to levels significantly greater than those in ketamine- and halothane-treated animals but had no effect on serum DHA, DHAS, or F. Treatment with halothane had no effect on serum PRL, DHA, or DHAS but did suppress F (>40%) concentrations over time. These data indicate that ketamine is best suited for the collection of biological samples when deep analgesia is not required but that halothane is preferable in the latter situation.