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. Author manuscript; available in PMC: 2015 Feb 1.
Published in final edited form as: Neuropharmacology. 2013 Oct 21;77:10.1016/j.neuropharm.2013.10.005. doi: 10.1016/j.neuropharm.2013.10.005

Figure 2. Dynorphin activates kappa receptors to decrease IPSPs at a presynaptic site.

Figure 2

A. Concentration-response curve (logistic fit) of the dynorphin effect. Dynorphin decreased IPSPs by a maximum of 23%, with an apparent EC50 of 0.50 μM (dashed line) and a near maximum effect at 1 μM. U69 also depicted (open squares) for comparison: near-maximum effect was obtained at 0.5 μM. B. Upper panel: IPSP recordings obtained with the PPF paradigm. Dynorphin (1 μM) diminished P1 with little effect on P2, increasing the paired-pulse ratio (P2/P1). RMP was −76. Arrows indicate stimulation artifact. Lower left: recordings from upper panel superimposed and normalized to P1 to magnify the increase of PPF. For equivalent P1 amplitudes, P2 (identified with numbers) was larger in the presence of dynorphin. Lower right: bar graph average depicting the PPF change relative to control condition: dynorphin (1 μM) and U69 (1 μM) increased PPF by 28% and 26% respectively.