Section of the Pituitry Stalk in the Rhesus Monkey

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Abstract
The effects of pituitary stalk section on anterior pituitary secretion were studied in 20 female rhesus monkeys. Vascular connections between the hypothalamus and the pituitary gland were permanently interrupted in all but 4 animals. Prolactin [PRL] levels rose rapidly and remained significantly elevated in all effectively stalk-sectioned animals for as long as the observation period (up to 3 yr). Only smaller and transient elevations of PRL were seen in the animals in which revascularization of the anterior pituitary gland had occurred. Growth hormone and cortisol were significantly decreased after stalk section, and were not released by insulin. Radioimmunoassayable luteinzing hormone (LH) levels decreased following surgery; by bioassay, LH became undetectable within 5 wk after stalk section, indicating that gonadotropin-releasing hormone is essential for the viability of the gonadotrope. Plasma PRL concentrations can be used to monitor completeness of pituitary gland isolation from direct hypothalamic influence. Stalk-sectioned monkeys provide goods models to study direct pituitary effects of various hormones or drugs.