Figure 7.

Hyperexcitation Blocks dIN Pacemaker Properties

(A) The responses of a dIN to three consecutive applications of NMDA at different microiontophoresis currents (gray bars). The right hand trial results in repetitive firing followed by seizure-like depolarization.

(B) A dIN’s response to microperfusion of 100 μM NMDA in TTX (gray bar). Injecting hyperpolarizing current (−70 pA) into the dIN reveals reliable oscillations, which quickly change to seizure-like depolarization at the current withdrawal. The boxed area (a) is expanded below. The dotted line indicates the resting membrane potential level.