Figure 2.

mGlu₃ activation blocks the long-term potentiation (LTP) enhancing effects of βARs. (a) Schematic of weak and strong theta burst stimulation (TBS) protocols. (b) Average time course of normalized field excitatory postsynaptic potential (fEPSP) slopes recorded from the SC-CA1 synapse in rat hippocampal slices. Strong TBS induced a larger potentiation of fEPSPs compared with weak TBS measured 50 min post stimulation. (c) Bath application of ISO (1 μM) enhances the effects of weak TBS. Black horizontal bar represents drug add. (d) When ISO and LY379268 (100 nM) are co-applied, the enhancing effects of ISO were antagonized relative to ISO-alone experiments. This blockade was reversed when slices were pretreated with the mGlu₃ NAM VU0469942 (30 μM). The gray horizontal bar represents the NAM drug addition and the black horizontal bar represents ISO±LY379268. (e) Summary data for experiments in (b–d). Bars represent mean±SEM. *p<0.05 vs control, 1 μM ISO+LY379268, and 30 μM VU0469942. (f and g) ISO does not enhance and ISO+LY379268 does not attenuate the effects of strong TBS. Insets for b–d and f are representative fEPSP traces for the various experimental conditions measured during baseline (1) and 50 min post stimulation (2). Calibration: 1 mV vertical and 1 ms horizontal for all traces.