Figure 9.

Acute sequential hindbrain transections. (A) Histological parasagittal section (0.18 mm lateral) through hindbrain showing the mid-collicular line of transection (Neutral red stained section) and (B) annotated schematic (Paxinos and Watson, 2007) of the two acute brainstem transections during active filling and voiding. The initial transection dissociated the rostral tissues from the brainstem (e.g., hypothalamic nuclei) leaving the brainstem intact. Voiding remained unaffected by this intervention. The second transection (shown) effectively disrupted the rostral periaqueductal gray (PAG), and resulted in loss of coordinated voiding, although filling responses remained. DRn, dorsal raphe nucleus; IC, inferior colliculus, Pn, pontine nucleus; tz, trapezoid body, VMHDM, ventromedial hypothalamic nucleus dorsomedial.