Fig. 4.

KAR activation does not depress transmission via indirect interneuronal activation. A, A summary of experiments shows that the normal effect of DA (mean ± SEM shown as solid horizontal line ± dotted horizontal lines) on fEPSPs is unaffected by both a cocktail of antagonists for GABA_B receptors (SCH 50911, 20 μm) and adenosine receptors (DPCPX, 10 μm) and a cocktail of antagonists for muscarinic receptors (atropine, 10 μm), NO synthase [N-nitro-l-arginine (l-NNA), 100 μm], dopamine receptors (sulpiride, 100 nm), and serotonin receptors (NAN-190, 50 μm). B, Spontaneous IPSCs are recorded at 0 mV. After addition of 200 nm DA, a large increase in sIPSC frequency is observed. In a solution containing high divalent concentrations (8 mm Ca and 17 mm Mg), the DA-induced increase in sIPSC frequency is absent in a different cell. C, The depressant action of DA on fEPSPs is unaffected by the solution with high divalents. D, The normal effect of DA on fEPSPs (filled circles) is unaffected by the solution with high divalents (open circles).