Dopaminergic Suppression of Synaptic Transmission in the Lateral Entorhinal Cortex
Figure 6
Dopamine
hyperpolarizes membrane potential and reduces the input resistance of layer II
fan cells. (a) Membrane potential was shifted to more hyperpolarized
potentials by dopamine (*,). (b) Dopamine also reduced both peak and
steady-state input resistance (*,). (c) Voltage responses to applied current steps
before (c1) and after (c2) bath application of 50 M
dopamine in a representative cell. Action potentials are truncated. Circles in (c1) indicate the latencies at which peak and
steady-state input resistance were measured. Inset traces in (c2) compare the initial voltage deflection to
a −200 pA current
step before and after application of dopamine. Arrows indicate voltage responses before and after dopamine that were
similar in amplitude and which allow comparison of the magnitude of the inward
rectification. Note also the reduced input resistance
across the entire range of hyperpolarizing current pulses. (d) Current-voltage plots show peak and
steady-state responses to current steps of increasing size. Arrows indicate points at which a comparable
degree of inward rectification was observed during hyperpolarization to similar
voltages before and after dopamine application.
