Differential regional distribution and release of two forms of gonadotropin-releasing hormone in the chicken brain.
The functional significance of two molecular forms of gonadotropin-releasing hormone (GnRH) in the chicken brain was investigated. The differential distribution of [Gln8]GnRH (chicken GnRH-I, cGnRH-I) and [His5,Trp7,Tyr8]GnRH (chicken GnRH-II, cGnRH-II) was determined using high performance liquid chromatography and radioimmunoassay with region-specific antisera. Potassium-stimulated release of immunoreactive cGnRH-I and cGnRH-II from brain regions was assessed in tissue incubations. cGnRH-I and cGnRH-II varied independently in different brain areas. The concentration of cGnRH-I was highest in the median eminence of the hypothalamus, and a small quantity was also detected in the midbrain and cerebrum. cGnRH-II was more widely distributed throughout the brain, with highest concentrations in areas of the hypothalamus outside the median eminence and in the medulla. Potassium stimulated the release of cGnRH-I from the median eminence 4-fold, while cGnRH-II release was not detectable. Neither cGnRH-I nor cGnRH-II was released from the medulla. These data suggest: 1) cGnRH-I is the prime regulator of gonadotropin release from the pituitary, and 2) cGnRH-II may have a neurotransmitter or neuromodulator role in areas of the brain outside the median eminence.
Department of Chemical Pathology, University of Cape Town Medical School, South Africa.
I A
IA
Katz
R P
RP
Millar
J A
JA
King
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002645:Chickens / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives
D007987:Gonadotropin-Releasing Hormone; C037700:LHRH, Gln(8)-; C047717:LHRH, His(5)-Trp(7)-Tyr(8)-; D011761:Pyrrolidonecarboxylic Acid