Fig. 3.
Inhibitory effect of dynorphin on mossy fiber synaptic transmission is not dependent on N- or P-type Ca2+channels. Normalized field potentials are plotted against time.A, In control conditions, the reduction of mossy fiber responses (n = 9) by 500 nm dynorphin was of similar magnitude to the reduction obtained by dynorphin after ω-CgTx (n = 7) blockade of synaptic transmission (B). C, In the presence of ω-Aga IVA (n = 6) or CdCl2 (n = 6), the effects of dynorphin on mossy fiber responses were also similar. D, Two separate pathways were monitored, and LTP was induced on one of the pathways. After the responses had stabilized (30–60 min), dynorphin was applied. The inhibition by dynorphin of the LTP-expressing pathway (filled circles) is greater than for the control pathway (open circles). These experiments indicate that the inhibitory effects of dynorphin on mossy fiber synaptic transmission is not dependent on N- or P-type Ca2+ channels, but it is influenced by LTP.