PREOPTIC RELEASE OF AMINO-ACID NEUROTRANSMITTERS EVALUATED IN PERIPUBERTAL AND YOUNG-ADULT FEMALE RATS BY PUSH-PULL PERFUSION

In order to evaluate the participation of amino acid neurotransmitters (AANT) in pubertal development, we measured the preoptic release rates of glutamate (Glu), aspartate (Asp), homocysteic acid (HCA), gamma-aminobutyric acid (GABA), glycine (Gly), and taurine (Tau) in female rats aged 26, 35 and 42 days. Push-pull cannulae were implanted in the preoptic area (POA) after reinforcing the os calvarium by cementing a slightly curved 2-mm thick polyethylene plaque. Four days later, 120-min perfusion experiments (0-90 min: artificial CSF; 90-120 min: CSF containing 50 mM KCl) were performed. Amino acid concentrations were measured in 15-min fractions after derivatization with phenylisothiocyanate, using reverse-phase high-performance liquid chromatography and UV detection. Rats aged 42 days showed significantly (p < 0.01) higher preoptic Asp release rates, as compared to 26-day-old rats; Glu output increased significantly (p < 0.05) in animals aged 35 and 42 days, as compared to 26-day-old rats. No significant changes in HCA release were observed. Preoptic release rates of GABA, Gly and Tau were significantly higher in 26-day-old animals as compared to 35-day-old (GABA, p < 0.05) and 3 5- and 42-day-old rats (Gly, Tau, p < 0.0 1). Basal release of Asp, Glu, HCA, Tau and GABA, but not of Gly, was significantly stimulated (p < 0.05) by KCl in all age groups. It is suggested that in peripubertal female rats, increased preoptic Asp and Glu release rates and decreased GABA and Tau output might enhance luteinizing hormone-releasing hormone secretion. This effect could be one of the mechanisms leading to the first preovulatory LH surge.