The effects of reserpine (catecholamine depletor) and LHRH analogues on gonadotropin secretion, spermiation and ovulation of common carp were investigated. Injections of reserpine alone at a dose of 1 or 7 mg/kg of body weight stimulated spermiation, and reserpine at a dose of 1 mg/kg of body weight in combination with (D-Arg6, Trp7, Leu8, Pro9, NEt)-LHRH (s-GnRH-A) or with (D-Ala6, Pro9)-LHRH ...

Experiments were conducted to identify neurons in the bovine brain that express the LHRH gene and to determine whether LHRH mRNA levels are influenced by the ovaries. Two groups of postpubertal heifers were utilized: heifers killed during the mid-luteal phase of the estrous cycle (LUTEAL, n = 5) and heifers killed 14-16 wk following ovariectomy (OVX, n = 5). In situ hybridization was performed ...

beta-Endorphin blocks release of luteinizing hormone (LH)-releasing hormone (LHRH) into the hypophyseal portal vessels by stimulating mu-opiate receptors, thereby inhibiting secretion of LH. LHRH release is controlled by release of nitric oxide from nitricoxidergic (NOergic) neurons in the basal tuberal hypothalamus. To determine whether beta-endorphin exerts its inhibitory action on this NOerg...

The therapeutic options for the treatment of androgea-independent prostatic cancers are rather limited; this Is mainly because our under standing of the local mechanisms involved In the control of androgen independent proliferation of the tumor is stlH very poor. The present experlmeats have been performed to verify whether luteinizing hormone releasing hormone (LHRH) agonists may possess a dir...

We have previously shown that chelated copper stimulates the release of luteinizing hormone-releasing hormone (LHRH) from isolated hypothalamic granules. In this study, we wished to ascertain if chelated copper acts on hypothalamic neurons to stimulate LHRH release and, if so, what is the ligand specificity of this interaction. An in vitro system of explants of the median eminence area (MEA) wa...

PGs of the E series are involved in the control of LHRH secretion. The present experiments were conducted to clarify whether PGI2 (prostacyclin) might be also involved in such a control, using multiple methodological approaches on immortalized LHRH-secreting neurons. A RT-PCR procedure to detect mouse PGI2 receptor (IP) messenger RNA was first applied, and the results obtained showed the presen...

Previous studies demonstrated the involvement of transforming growth factor-alpha (TGF alpha), a member of the epidermal growth factor (EGF) family, in the developmental regulation of hypothalamic LHRH release. Although both TGF alpha and EGF stimulate LHRH release, they do not appear to act directly on LHRH neurons, as no EGF/TGF alpha receptors are detected on these cells in vivo. Instead, th...

To understand the mechanism of pulsatile luteinizing hormone-releasing hormone (LHRH) release, we examined whether cultured LHRH neurons exhibit spontaneous intracellular Ca(2+) ([Ca(2+)](i)) signaling. The olfactory placode and the ventral migratory pathway of LHRH neurons from rhesus monkey embryos at embryonic ages 35-37 were dissected out and cultured on glass coverslips. Two to five weeks ...

The objective of this study was to try to depress serum testosterone (T) in bulls by prolonged treatment with a potent luteinizing hormone-releasing hormone (LHRH) agonist. Eight sexually mature bulls (325 to 475 kg) were assigned to treatment or control groups. Treatment consisted of 150 micrograms nafarelin acetate 6-D-2-naphthyl-alanine-LHRH (LHRH-A) injected im every 6 h for 15 d. Bovine se...

Apparently, no agonist has been found that is comparable in potency to the luteinizing hormone-releasing hormone (LHRH) for release of LH and follicle-stimulating hormone (FSH) without substitutions with unnatural or D forms of natural amino acids. Of 139 known "agonist analogs" of LHRH, two were active in the range of 65%. The four LHRHs known to occur in nature involve a total of six amino ac...