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. Author manuscript; available in PMC: 2012 Sep 8.
Published in final edited form as: Neuroscience. 2011 Jun 12;190:207–227. doi: 10.1016/j.neuroscience.2011.06.005

Fig. 8. Widespread labeling is evident in the caudal NTS after injections into a region containing the anterior part of the rostral VRG (arVRG) and the caudal ventrolateral nucleus of the medulla (CVL).

Fig. 8

FG was injected into the right arVRG (case 9139) at the site of respiratory unit activity (not shown) while a second electrode was used to record population respiratory activity in the left rVRG. Prior to injecting FG, injection of 3 nl of a 5 mM DLH solution (inset) in the right arVRG evoked a slowing of respiratory rate and decreases in heart rate and arterial pressure. In this instance, the central respiratory rhythm is represented by inspiratory unit activity recorded in the rVRG contralateral to the DLH and FG injections.

Sections A–C progress from caudal to rostral with A ~ 500 μm caudal and C ~ 200 μm rostral to obex. Substantial retrograde labeling was evident throughout the caudal NTS, especially the commissural (SolC) and caudal part of the medial (SolM) nuclei. However, labeling in the ventrolateral NTS (SolVL) was relatively light particularly compared with FG injections more caudally in the posterior part of the rVRG (compare C with Fig. 9B). In the contralateral NTS, a significant number of retrogradely labeled neurons were evident in the dorsolateral nucleus (SolDL in C).

Retrograde labeling is depicted as a pseudo-colored image composed of a monochrome darkfield image placed in the red channel of a blank RGB image, which was combined with inverted brightfield images of the DAB immunolabeled FG neurons. The inverted brightfield image was placed in a layer superficial to the darkfield image and combined with the latter using the lighten” command in Photoshop CS3®. The retrograde labeled neurons in the inverted images appear white on a dark background and therefore replace the (red) darkfield image where they occur. The resulting composite image provides white neurons against a red darkfield image. The FG injection site (D) is a pseudocolored image consisting of a low magnification darkfield image placed in the red channel of a blank RGB image. A grayscale inverted brightfield image of the same section was placed in both the green and blue channels. The FG injection consequently appears cyan against a red darkfield background image.