Formation of GABAergic Neural Networks in the Bötzinger Complex in Rats in the Early Postnatal Period in Normal Conditions and with Prenatal Deficiency of Endogenous Serotonin

Abstract

The dynamics of the distribution of GABAergic neurons and neurons expressing different types of GABA receptors (GABA-Aα1 and GABA-B1) in the Botzinger complex during the early postnatal period (the period of functional maturation of the receptor system in mammals) were studied in normal conditions and after prenatal reductions in serotonin content in Wistar rats. Brains from rat pups of two groups were studied on days 5, 9, and 20 after birth: controls (n = 9), born to intact females, and experimental (n = 13), born to mothers treated with parachlorophenylalanine during pregnancy to decrease endogenous serotonin content. GABA-synthesizing neurons and neurons expressing GABA-Aα1 and GABA-B1 receptors were detected immunocytochemically. Maturation of the inhibitory GABAergic network in the Botzinger complex occurred during the early postnatal period (by day 9). GABA production occurred simultaneously with GABA-Aα1 and GABA-B1 expression, though their maturation differed. GABA-Aα1 receptors formed earlier (by day 9) and coincided in time with GABA expression. Maturation of GABA-B1 receptors occurred later – only by week 3. Prenatal serotonin deficit led to a delay in the expression of GABA and GABA-Aα1 receptors in neurons of this nucleus and produced impairment to the formation of a network of terminals and synapses containing GABA and GABA-Aα1 and GABA-B1 receptors.