Abstract
Synaptic plasticity such as long-term potentiation (LTP) or long-term depression (LTD) is the cellular mechanism underlying learning and memory. In sensory cortices, cortical plasticity has also an important role in the development of neural circuits. However, the differential roles and mechanisms for various types of LTP and LTD are not clear. In the present study, we investigated supragranular LTP and two types of supragranular LTD in the slices obtained from the rat auditory cortex, and compared their properties. Frontal cortical slices (400 μm thick) were prepared from male Wistar rats (4-6 weeks old). Supragranular field potentials elicited by the stimulation applied to layer IV-V were recorded through a metal electrode. Trans-synaptic components sensitive to glutamate receptor antagonists exhibited marked LTP after tetanic stimulation (100 Hz for 1 s) applied to layer IV-VI. The same field potential components exhibited LTD after low-frequency stimulation (1 Hz for 900 s) applied to layer VI. LTD of supragranular field potentials were also induced by tetanic stimulation (100 Hz for 1 s) applied to supragranular layers near the recording site. Induction of LTP and the two types of LTD was completely abolished in the presence of 50 μM APV, an NMDA receptor antagonist, indicating that the induction of these three types of supragranular plasticity is dependent on NMDA receptors. [Jpn J Physiol 55 Suppl:S151 (2005)]
