Histophysiology and innervation of the pituitary gland of the goldfish, Carassius auratus L.: a light and electron microscope investigation

Six secretory cell types (prolactin-, ACTH-, somatotropin- (STH-), TSH-, and two presumptive gonadotropin- (GTH-) secreting cells) were identified in light or electron microscope preparations of goldfish pars distalis. A further two cell types of unknown function were demonstrated in the pars intermedia. Cellular identification was based on the position of cells within the adenohypophysis and on the staining properties or morphological characteristics of the cytoplasmic granules.The prolactin-, ACTH-, and STH-secreting cells and the pars intermedia cells appeared to release granules into the basement membrane whereas granule release from TSH- and GTH-secreting cells was not found.Many of the adenohypophysial cell types were innervated directly or across a basement membrane by B-type neurohypophysial fibers. A-type neurosecretory fibers were associated with blood vessels and pituicytes within the neurohypophysis. The possible role(s) of the two types of pituicytes is discussed.