Figure 3.
Comparative distribution and functions of brainstem respiratory neurons. A: Outline of respiratory compartments in the rat VRC. The shaded regions indicate an approximate division of the VRC into a rostral part contributing to rhythm and pattern generation (pink), while more caudal regions appear to contribute only to the pattern of respiratory activity (green). B: Relative distribution of expiratory and inspiratory neuron subtypes in the VRC. Data adapted from plots of propriobulbar neurons recorded in the rat by Ezure et al. (1988; E-Aug, E-Dec, I-Aug, I-Dec, I-Con) & by Sun et al. (1998; E-I and I-E) and normalized to the peak number of expiratory neurons in BötC. Note that the distribution maxima for particular neuron subtypes corresponds to particular VRC compartments, but that the sharp borders shown in the cartoon in A do not adequately represent the actual blending of different cell distributions along the rostral caudal length of the VRC. C. Effect on expiratory duration (Te) of the excitatory amino acid DL-homocysteic acid (DLH) micro-stimulation of the BötC, preBötC, and rVRG. Redrawn with permission after Monnier et al., 2003. Note, stimulation in preBötC caused tachypnea (shortened Te) while stimulation in either the BötC or the anterior part of rVRG produced bradypnea (lengthened Te). Chemical stimulation in posterior portions of the rVRG does not affect respiratory rate (Wang et al., 2002; Monnier et al., 2003).