Mentor: Stacia Sower, Ph.D. - Professor of Biochemistry
Effects of Mammalian NPY on GnRH -I and GnRH-III Concentrations in Static Culture of Hypothalamic Tissue of Adult Lampreys
The peptide methionine tyrosine (PMY), isolated first from the intestine (Conlon et. al, 1991) and then from the brain of the sea lamprey (Conlon et al., 1994), is a member of the neuropeptide Y (NPY) family. It is believed to play a physiological role in reproduction in lampreys by inhibiting the release of estradiol during the lampreys' sexually immature parasitic phase. Whether this inhibitory action, which diminishes during final maturation before ovulation, takes place at the level of the hypothalamus or at the level of the gonads is not known.
The main objective of this study was to determine if PMY exerted its inhibitory effects at the level of the hypothalamus by affecting the release of gonadotropin-releasing hormone (GnRH). GnRH is a major hypothalamic regulatory peptide which acts on the pituitary to stimulate the release of gonadotropins. At present, there is no lamprey PMY available, therefore, NPY, which is structurally similar to PMY, was used in this experiment.
To determine the effects of NPY on the release of GnRH from the hypothalamus, twelve hypothalamii were collected from landlocked female sea lampreys and were placed in static culture wells. Hypothalamii in triplicate were incubated for four hours in one of the following media; buffer solution, 10, 100 or 1000 ng of NPY/ml of media. The incubation media and the hypothalamii were collected and extracted. HPLC was used to purify the collected samples, and radioimmunoassays were done to quantify GnRH in each sample.
Determining the role of NPY in the sea lampreys will further our understanding of reproduction in lampreys. This will give us insight into the interrelationship of the hypothalamus and the pituitary-gonadal axis.