Inhibition of Prolactin Secretion by GABA in Female and Male Rats

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Abstract
The effect of GABA on prolactin [PRL] secretion from the pituitary under physiological conditions in lactating female rats and in normal male rats was investigated. PRL was measured by RIA [radioimmunoassay] in blood samples taken from lactating mothers by means of an intrajugular silastic catheter, 10-15 days after delivery. GABA in doses of 825 .mu.g, but not 150 .mu.g, microinjected into the 3rd ventricle partially suppressed the serum PRL rise due to suckling. Aminooxyacetic acid (AOAA), 30 mg/kg i.p., which has been reported to produce a sharp increase in GABA content in the CNS, significantly suppressed the PRL increment during the suckling period. In non-suckled mothers, GABA or AOAA was ineffective in altering serum prolactin. In normal male rats, GABA and AOAA were able to partially suppress prolactin release due to ether stress. Increments in GABA content in the brain after microinjection of exogenous GABA or following suppression of enzymatic inactivation of the endogenous amino acid were able to inhibit PRL release under physiological conditions.

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