Figure 1.

Representative chart tracings which show respiratory movements before and 10–12 min after microinjection of (a) resiniferatoxin (RTX, 75 pmol in 500 nl) or (c) olvanil (10 nmol) into the commissural nucleus of the solitary tract (cNTS) of urethane-anaesthetized, spontaneously breathing rats. The adjacent photomicrographs (b,d) display the location of the injection sites (arrows) in neutral red stained brain stem sections from these same animals. Note that despite similar placement of the probe in both experiments only RTX evoked respiratory slowing (see Figures 2 and 3 for mean data). Injection of RTX (75 pmol in 500 nl) outside the lateral border of the cNTS (e,f) had no effect on respiration suggesting that the observed responses were evoked from within the cNTS. XII, hypoglossal nucleus.