Effect of Gamma Aminobutyric Acid on 5-Hydroxytryptamine Release Related to Sexual Function / 대한비뇨기과학회지

ABSTRACT

5-hydroxytryptamine (5-HT) containing pathways exert a inhibitory or facilitate effect on copulation. The administration of gamma aminobutyric acid (GABA) receptor agonists to the central nervous system in rats inhibits male copulatory behavior, whereas the administration of antagonists facilitates corpulatory behavior. GABA may influence the erection through dopaminergic pathway. But few about the effect of GABA on serotoninergic neuron are known. Raphe nuclei give rise to the major serotonergic innervation to the hippocampal formation and the GABAergic interneurons are located at the hippocampal formation also. This study was performed to investigate the influence of GABA, inhibitory interneuron, on the 5-HT release from rat hippocampal slices to understand the connection of the serotonergic neurons to GABAergic interneurons. The hippocampus was obtained from the male rat brain and sliced to a 400 Im thickness. After 30 minutes preincubation in the normal buffer, the slices were incubated for 20 minutes in a buffer containing 0.1 microM [3H]5-HT for uptake, and washed. After administration of GABA, the release of [3H] 5-HT into the buffer was measured and the radioactivities in each buffer and the tissue were counted using liquid scintillation counter and the results were expressed as a percentage of the total activity. Spontaneous release of [3H] 5-HT from the rat hippocampal slices decreased rapidly during the first 40 minutes of incubation. Through the rapid release of [3H] 5-HT, a steady state of [3H] 5-HT release was obtained from the 50 minutes of incubation. The value of released [3H] 5-HT after 50 minutes was expressed as percent of the value at 50 minutes. After administration of GABA (10(-4)M), the values (mean +/- SE) of released (3H)5-HT were 97.3 +/- 3.8% at 60 minutes and 91.2 +/- 3.4% at 70 minutes. The values of control group were 96.6 +/- 1.9% at 60 minutes and 89.6 +/- 2.3% at 70 minutes. There were no changes in the release of (3H)5-HT after administration of GABA. These results suggest that there are few connections between GABA and serotoninergic neurons and GABA does not influence the release of 5-HT in rat hippocampus.