Two chemically and immunologically distinct forms of luteinizing hormone-releasing hormone are differentially expressed in frog neural tissues

Substance P inhibits the M-current in bullfrog sympathetic neurones

Substance P (SP, 2.5-10 microM) was applied by rapid bath perfusion to bullfrog lumbar sympathetic neurones in vitro, voltage-clamped through a single micro-electrode. In unclamped cells, SP produced a depolarization accompanied by an increase in apparent input resistance. Under voltage-clamp a voltage-dependent inward current was induced by SP, during which the time-dependent relaxations induced by square voltage commands were inhibited. It is concluded that SP inhibits the M-current (IM), a species of voltage-dependent K+-current, and that IM-inhibition was the primary cause of the inward current and membrane depolarization in the cells tested.

Characterization of a teleost gonadotropin-releasing hormone

A peptide that is recognized by certain antibodies raised against mammalian gonadotropin-releasing hormone has been purified from extracts of salmon brains by gel filtration and high-performance liquid chromatography. The primary structure of this 10-residue peptide is less than Glu-His-Trp-Ser-Tyr-Gly-Trp-Leu-Pro-Gly-NH2. This represents a difference of two amino acids between salmon and mammalian gonadotropin-releasing hormone and demonstrates that most of the molecule has been conserved during evolution. The synthetic form of salmon gonadotropin-releasing hormone is less potent than is mammalian gonadotropin-releasing hormone on mammalian cells and is biologically active in salmon.

Yeast mating pheromone activates mammalian gonadotrophs: evolutionary conservation of a reproductive hormone?

alpha-Factor, a tridecapeptide mating pheromone of yeast (Saccharomyces cerevisiae), has extensive sequence homology with the hypothalamic decapeptide gonadotropin-releasing hormone (GnRH). Both synthetic and natural preparations of alpha-mating factor were found to bind specifically to rat pituitary GnRH receptors and to stimulate the release of luteinizing hormone from cultured gonadotrophs. The ability of the yeast pheromone to reproduce the biological actions of GnRH in the mammalian pituitary gland indicates that the structural and functional properties of GnRH-related peptides may have been highly conserved during evolution.

Presence and distribution of radioimmunoassayable LHRH in the European eel, Anguilla anguilla

Eel brain contains a factor which exhibited a complete cross-reaction in a radioimmunoassay (RIA) for mammalian luteinizing hormone-releasing hormone (LHRH) and which exhibited a behavior similar to that of synthetic mammalian LHRH on Sephadex G-25. Eel brains contained 920 +/- 135 pg of this LHRH-like immunoreactive factor (IR-LHRH); 75% of immunoreactivity was present in the di- and mes-encephalon, 21% in the telencephalon and 4% in the hind-brain. Thus, IR-LHRH in eel brain exhibited a much wider distribution than in mammalian brain. Pituitary also contained a large amount of IR-LHRH (304 +/- 69 pg) at a concentration even higher than in median hypothalamic lobe; this result is probably related to the fact that, in teleost, median eminence is included into the pituitary. An immunoreactive substance was also present in the blood. In conclusion, the lack of sexual development and the low gonadotropic function in the eel, are apparently not related to an absence of LHRH.