5-HT4 receptors modulate LTD.

<p>A1: LFS induces LTD under control conditions. A2: Activation of 5-HT4-receptors significantly facilitates LTD. A3/4: Blockade of 5-HT4-receptors through RS 39604 or GR 113808 prevented LTD. B: Summary of changes in synaptic strength illustrated in A1-4. The antagonist GR 13808 is not included in the ANOVA. C: Averaged time courses of normalized EPSP responses during LFS. Control: white circles, RS 67333: black circles, RS 39604: gray circles, GR 113808: dark gray squares. D1: The PKA inhibitor H 89 prevented LTD under control conditions. D2: H 89 prevented LTD even in the presence of the 5-HT4 receptor agonist RS 67333. E: A 5-HT4 receptor agonist failed to modulate NMDA receptor mediated EPSPs during 30 minutes wash-in. Scale bars: 2 mV and 20 ms (A,D), 1 mV and 20 ms (E).