Figure 2.

NMDA increases NO production in postnatal hippocampal neurons. A, Simultaneously obtained measures (every 20 s) of changes in [Ca²⁺]_i (fura-2) and NO (DAF-FM) in response to NMDA (bar). The slope of DAF-FM fluorescence begins to increase coincident with the upstroke of the [Ca²⁺]_i rise. The boxes around the DAF-FM traces identify the regions used to calculate DAF-FM slopes at baseline and during the initial response to NMDA. B, Calculation of DAF-FM slopes. Data comprising the DAF-FM traces within the boxes in A are presented, and lines produced by linear regression of each trace are superimposed on each trace. Beside each line is presented the calculated DAF-FM slope and the correlation coefficient (r²) of each regression. Because of crowding, the calculated slope and r² for the middle baseline trace has been omitted. C, NMDA-induced increases in DAF-FM slope are prevented by NOS inhibition with l-NAME and increased with MnTBAP, a superoxide dismutase mimetic. Mean ± SEM DAF-FM slopes at baseline and during the initial 4 min of NMDA stimulation obtained by linear regression in untreated neurons and neurons in which NO production has been blocked (l-NAME) or increased (MnTBAP). MnTBAP, by removing O₂^., prevents NO consumption by decreasing peroxynitrite formation, increasing NO availability. Statistical comparisons are made within treatments, comparing the DAF-FM slope during NMDA with that slope during baseline. ^*p < 0.05; ^†p < 0.01. A.U., Arbitrary units.