Caudal to the diencephalon, substantial retrograde labeling was found in the PAG [...]. Remarkably, in the PAG, we noted that the distribution pattern of retrogradely labeled cells changed along its rostrocaudal axis (Fig. 3N–P). Thus, at the level of the nucleus of Darkschewitsch, most of the retrograde labeling was distributed in the dorsomedial PAG (Fig. 3N). Proceeding caudally, at the level of the oculomotor and trochlear nuclei, a distinct cluster of marked neurons was found in the dorsolateral PAG, whereas other parts of the PAG contained relatively sparse numbers of marked neurons (Fig. 3O). In contrast, at caudal levels of the PAG, retrogradely labeled neurons were distributed more evenly throughout the lateral, ventrolateral, dorsomedial, and dorsolateral parts of the PAG (Fig. 3P). Collator note: level 39, Swanson Atlas, 1998. |