Objective    To investigate the effect of exogenous orexinA on the pyramid neurons and interneurons in the prefrontal cortex prelimbic (PL) area.     Methods    The pyramid neurons and interneurons in PL area of Kunming mice were selected from prefrontal cortex slices by infrared visual patch clamp technique. The morphology and electrophysiological features of the pyramid neurons and interneurons were observed. The effect of exogenous orexinA at a concentration of 400 nmol/L on these cells was studied using the whole cell configuration.     Results    The pyramid neurons were large

pyramidal in cell body with clear apical dendrites extending vertically and several basal dendrites radiating. The interneurons were comparatively smaller and had several processes from cell body. In current clamp mode

all 54 pyramid neurons having been recorded showed frequency adaption

and the 15 recorded interneurons discharged rapidly and had no frequency adaption. While in voltage clamp mode

36 pyramid neurons were regarded as Ih(+) pyramid neurons for recorded hyperpolariztion-activated cation current

and the left 18 and 15 interneurons were Ih(-). Exogenous orexinA had a total reaction rate of 51.9% on 54 recorded pyramid neurons under current clamp

and a rate of 66.7% on 36 Ih(+) pyramid neurons and of 22.2% on the Ih(-) pyramid neurons under voltage clamp. All 15 recorded interneurons had no reaction to exogenous orexinA under either mode.     Conclusion    OrexinA plays excitatory effect on pyramid neurons in the prefrontal cortex PL area

and this effect is much more noticeable in pyramid neurons with Ih currents.