Pituitary response to auditory stress: effect of treatment with α-methyl-p-tyrosine. Usefulness of a factorial mixed design for statistical analysis

Eight adult male rats were chronically cannulated in the jugular vein and placed individually in a sound-attenuated cubicle. Four of the animals were also implanted with a permanent cannula in the right lateral ventricle of the brain. Each animal was submitted twice to auditory stress at a 24-h interval. Before each stress, the rats were pretreated with either saline or α-methyl-p-tyrosine (α-MT), the order of administration of the drug and its vehicle being alternated in the eight rats. The injections were made either intravenously or intraventricularly. Auditory stress significantly depressed plasma growth hormone (GH) levels irrespective of the type of pretreatment. Mean plasma GH levels were significantly lower after α-MT pretreatment. α-MT pretreated animals had higher mean plasma corticosterone (B) levels which remained unchanged during stress. Plasma follicle stimulating hormone (FSH) levels were not modified by stress nor by α-MT pretreatment. The intraventricular administration of α-MT at a dose ...