Fig. 7.

Effects of blockade of N-methyl-d-aspartate (NMDA) receptors in the medullary lateral tegmental field (LTF) on left inferior cardiac sympathetic nerve activity (SNA) of a spontaneously breathing, urethane-anesthetized cat. A and B: traces (top to bottom) show arterial pulse (AP), intratracheal pressure (ITP, as an index of respiration), SNA (preamplifier band pass = 30–3,000 Hz, 50-µV vertical calibration), and integrated SNA (cumulative integration) before (control) and after bilateral microinjection of d-2-amino-5-phosphonopentanoate (D-AP5). C: traces show autospectra (AS) of SNA and coherence functions relating SNA to the AP and ITP before (black line) and after (gray-shaded area) bilateral microinjection of D-AP5 into the LTF. Spectra are based on 35 20-s windows with 50% overlap and frequency resolution of 0.05 Hz per bin. They are shown on the same power scale before and after blockade of NMDA receptors. For spectral analysis, the sympathetic nerve recording was passed through a 50/60-Hz noise eliminator and further processed with a moving averager (50-ms time constant). A Digidata 1322A digitizer (Axon Instruments, Union City, CA) was used to acquire data.