The effect of NO on the slow component of the glutamate response depends on cGMP.

<p>(A) Application of the cGMP analog 8-Br-cGMP (1 mM) to the axonal endings of type 4 CBCs (A₁) reduced the duration of the slow component of the glutamate response (A₃). (A₄, A₅) While the charge transferred during the response was significantly reduced by 8-Br-cGMP, this cGMP analog did not affect the maximum amplitude of the glutamate response. (B) Addition of the sGC inhibitor ODQ (100 µM) to the internal solution of the recording pipette prevented the action of NO on the slow component of the glutamate response in type 4 CBCs (B₃). Note the previously recorded ON CBC to the left (B₂). (B₄, B₅) Neither the charge transferred during the glutamate response nor the maximum response amplitude were significantly affected by NOC-12 application in presence of ODQ. (C) Similar to ODQ, addition of the PKG inhibitor KT-5823 (1 µM) to the internal solution abolished any effect of NO on the slow component of the glutamate response (C₃, C₄). Note that dialysis of ODQ and KT-5823 had a shortening effect on the slow component of the glutamate response by itself. Image scale bars = 10 µm; ns = not significant.