TY - JOUR T1 - 5-Hydroxytryptamine<sub>2</sub> Receptor Facilitates GABAergic Neurotransmission in Rat Hippocampus JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 805 LP - 812 VL - 285 IS - 2 AU - Roh-Yu Shen AU - Rodrigo Andrade Y1 - 1998/05/01 UR - http://jpet.aspetjournals.org/content/285/2/805.abstract N2 - 5-Hydroxytryptamine (5-HT; serotonin) administration enhances GABAergic synaptic activity recorded in pyramidal neurons of the CA1 region of hippocampus. Previous studies have attributed this effect to the activation of HT-53 receptors located on GABAergic interneurons. During unrelated experiments, we noticed that under our recording conditions, 5-HT can still increase GABAergic synaptic activity after the complete blockade of 5-HT3 receptors. This indicated the involvement of an additional 5-HT receptor subtype. Therefore, we reinvestigated the effects of 5-HT on GABAergic synaptic activity recorded in pyramidal cells of the CA1 region. The ability of 5-HT to increase GABAergic synaptic activity in the presence of 5-HT3 receptor blockade was mimicked by the selective 5-HT2 agonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane and blocked by the selective 5-HT2 antagonist ketanserin. This indicated that the additional 5-HT receptor belongs to 5-HT2 receptor family. 5-HT2 receptor activation resulted in an increase in the frequency of spontaneous inhibitory postsynaptic currents as well as a shift in their amplitude distribution toward larger sizes. These effects were absent in the presence of tetrodotoxin. We interpret these results to indicate that 5-HT2 receptors activate GABAergic interneurons in the slice, leading to an increase in GABAergic synaptic activity onto pyramidal cells of the CA1 region. The American Society for Pharmacology and Experimental Therapeutics ER -