Abstract
The hippocampal network presents various types of oscillatory activities subserving diverse physiological functions including learning and memory. An intrinsic synchronous bursting of the interneurons appearing during early postnatal period in a form of giant depolarizing potentials (GDPs) is proposed to be involved in the maturation of the interneuronal networks (Ben-Ari et al., 2004), however, the molecular mechanism of its generation remains poorly understood. In juvenile rats and mice, extracellular ATP excites inhibitory interneurons and increase pyramidal IPSCs through activation of interneuronal P2Y1 receptors in the CA3 (Kawamura et al., J Neurosci 49 2004). Here we examined whether ATP-mediated signaling in the interneurons affects the GDPs. The spontaneous GDP activities were recorded from CA3 pyramidal neurons in the coronal hippocampal slice of the rats (P4-8). MRS2179, a specific antagonist to P2Y1 receptors abolished GDP and significantly reduced its frequency in a reversible manner. PPADS (a non-selective P2 receptor antagonist), but not TNP-ATP (a blocker of P2X receptors) and U-73122 (an inhibitor of phospholipase C), also significantly reduced the GDP frequency. 2meSADP, a selective P2Y1 receptor agonist, first increased GDP frequency, which was followed by a reduction. These results point to a possible involvement of ATP release and activation of interneuronal P2Y1 receptors underly the generation of intrinsic oscillatory activities in the rat hippocampus. [Jpn J Physiol 55 Suppl:S141 (2005)]
