Brain stem innervation of the caudal neurosecretory system.

The innervation of the caudal neurosecretory system of Poecilia sphenops (black molly) was studied by use of the retrograde horseradish peroxidase (HRP) method. The structure of the caudal neurosecretory system in this species was well suited for application of HRP procedures. Acrylamide/HRP gel implants were placed in the nucleus of the caudal neurosecretory system. Two neuronal groups which contained HRP filled cells were found in the brains tem. Bilateral projections originate from the dorsal tegmentum of the midbrain and the reticular nucleus of the medulla.