Pharmacological evidence that effects of vasotocin on brain maturation are mediated by GABA mechanisms.

Active sleep, brain weight as well as total lipids and galactolipids were assayed in 8-day-old rat pups, after daily administration (between 2 and 8 days of postnatal age) of saline, arginine vasotocin (AVT) (10(-7) mg), picrotoxin (5 x 10(-5) mg), valproic acid (10(-5) and 10(-6) mg) or of AVT + picrotoxin and AVT + valproic acid. AVT increases active sleep and decreases the weight, total lipids and the galactolipids of the brain. Although picrotoxin alone was without any apparent effects on maturational parameters, when administered together with AVT, it completely prevented AVT from producing its effects. Valproic acid had AVT-like effects when administered in a higher dose (10(-5) mg), but was without any apparent effects when administered in the lower dose (10(-6) mg). However, both doses intensely potentiated the effects of AVT. Since both drugs specifically interfere with the GABAergic neurotransmission, it is concluded that AVT retards the accumulation of brain lipids by activating a GABAergic pathway.