Neuropeptide Y in the forebrain of the adult male cichlid fish Oreochromis mossambicus: Distribution, effects of castration and testosterone replacement

Abstract

We studied the organization of the neuropeptide Y (NPY)-immunoreactive system in the forebrain of adult male cichlid fish Oreochromis mossambicus and its response to castration and testosterone replacement by using morphometric methods. Immunoreactivity for NPY was widely distributed in the forebrain, and the pattern generally resembled that in other teleosts. Whereas immunoreactivity was conspicuous in the ganglia of nervus terminalis (NT; or nucleus olfactoretinalis), a weak reaction was detected in some granule cells in the olfactory bulb and in the cells of area ventralis telencephali pars lateralis (Vl). Moderately to intensely immunoreactive cells were distinctly seen in the nucleus entopeduncularis (NE), nucleus preopticus (NPO), nucleus lateralis tuberis (NLT), paraventricular organ (PVO), and midbrain tegmentum (MT). NPY fibers were widely distributed in the forebrain. Castration for 10/15 days resulted in a drastic loss of immunoreactivity in the cells of NE (P<0.001) and a significant decrease (P<0.01) in their cell nuclear size. However, cell nuclei of the NT neurons showed a significant increase in size. A highly significant reduction in the NPY-immunoreactive fiber density (P<0.001) was observed in several areas of the forebrain. Although testosterone replacement reversed these changes, fibers in some areas showed supranormal responses. Immunoreactive cells in Vl, NPO, NLT, PVO, and MT and fiber density in some other areas did not respond to castration. We suggest that the NPY-immunoreactive elements that respond to castration and testosterone replacement may serve as the substrate for processing the positive feedback action of the steroid hormone.

Reproduction phase‐related variations in neuropeptide Y immunoreactivity in the olfactory system, forebrain, and pituitary of the female catfish, Clarias batrachus (Linn.)

“…The gonads were dissected out, weighed, fixed in Bouin's fixative, and processed for histological staining. Whereas the animals of group 2 were used as sham controls and treated with peanut oil, the animals in group 3 received a single intramuscular injection of the combination of testosterone propionate, testosterone phenyl propionate, and testosterone isocaproate in oil base at a dose of 10 g/g body weight, as previously reported (Sakharkar et al, 2005). Fifteen days after the treatments, the fish were anesthetized and perfused transcardially with PBS (25 ml), followed by equivalent amount of Zamboni's fixative.…”

“…Pretreatment with testosterone and estradiol resulted in massive augmentation in NPY mRNA levels in the telencephalon/ POA of goldfish (Peng et al, 1994). In tilapia, although GnRH neurons in the hypothalamic nucleus lateralis tuberis (NLT) do not contain steroid receptors , testosterone has been shown to up-regulate the NPY content in the neurons of the NE (Sakharkar et al, 2005). NPY has been suggested to mediate positive sex steroid effects on GnRH (Trudeau, 1997) and to influence the GnRH-LH cell axis (Peng et al, 1993(Peng et al, , 1994.…”

“…Some useful information on effects of gonadectomy and/or sex steroid replacement on NPY in the brain of adult, as well as immature teleosts, is also available (Peng et al, 1994;Sakharkar et al, 2005;Doyon et al, 2006). Juvenile C. batrachus may serve as a suitable model with which to examine the NPY-expressing brain loci that are sensitive to gonadal steroids in the internal milieu.…”

“…These studies underscore a strong possibility that the NPY neuronal system might be involved in receiving and processing of the sex steroid-borne information and regulation of reproduction. The neuroanatomical organization of NPY is well established in the brain of teleosts (Pickavance et al, 1992;Subhedar et al, 1996;Gaikwad et al, 2004;Sakharkar et al, 2005) as well as nonteleostean actinopterygian fish (Chiba, 1997), but limited information is available on the involvement of various NPY-containing elements in the regulation of reproduction. The aim of the present study was to investigate the reproduction phase-related changes in the NPYcontaining neuroanatomical substrates in the forebrain and pituitary and to establish its correlation with the LH cells-ovary axis of the teleost Clarias batrachus.…”

Importance of Cocaine- and Amphetamine-Regulated Transcript Peptide in the Central Nucleus of Amygdala in Anxiogenic Responses Induced by Ethanol Withdrawal

“…The images ( Â 480) were analyzed using Leitz-LaborLux S microscope, CCD video camera system (JVC, Japan) and Leica-Qwin Standard software (version 3). The method has already been standardized in our laboratory (Sakharkar et al, 2005).…”