The distribution of lamprey GnRH-III in brains of adult sea lampreys (Petromyzon marinus).
In the sea lamprey, Petromyzon marinus, two forms of GnRH, lamprey GnRH-I and -III, have been demonstrated to be neurohormones regulating the pituitary-gonadal axis. The objective of the present study was to determine the distribution of lamprey GnRH-III in the brains of adult sea lampreys and to compare it to the distribution of lamprey GnRH-I. For this purpose, two kinds of immunostaining were employed: one was a single immunostaining by one of two GnRH antibodies using two successive sections; the other was double immunostaining of a single section. A dense accumulation of neuronal cells immunoreactive (ir) to antisera against either lamprey GnRH-I or -III was found in the arc-shaped preoptico-anterior hypothalamic area. Additional smaller numbers of irGnRH cells were found in the periventricular zone of the posterior hypothalamus. In the above-mentioned locations, the distribution of both irGnRH-I and -III cells was intermixed and very similar, but the cells exhibiting GnRH-III immunoreactivity were distinctly different from those exhibiting GnRH-I immunoreactivity. The relative numbers of irGnRH-III cells were larger than those of irGnRH-I cells in the preoptico-anterior hypothalamic area, and more than 90% of GnRH cells in the posterior hypothalamus were irGnRH-III cells. Both irGnRH-I and -III cells projected their fibers primarily into the neurohypophysis. The relative densities of the accumulated irGnRH-III fibers were similar to those of irGnRH-I fibers in the anterior neurohypophysis but higher than those of irGnRH-I fibers in the posterior neurohypophysis. The present study provides further immunocytochemical data to the already compelling physiological evidence that indicates that both lamprey GnRH-I and -III act through the hypothalamic-pituitary-gonadal axis to modulate reproductive processes in the sea lamprey.
Nozaki
M
M
Sado Marine Biological Station, Niigata University, Tassha, Aikawa, Sado Niigata, 952-2135, Japan.
Ominato
K
K
Gorbman
A
A
Sower
S A
SA
D000818:Animals; D001921:Brain / Q000166:cytology; D001923:Brain Chemistry / Q000502:physiology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007150:Immunohistochemistry; D007798:Lampreys / Q000378:metabolism*; D007814:Larva; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism
D020033:Protein Isoforms; D007987:Gonadotropin-Releasing Hormone