Does LHRH meet the criteria for a hypothalamic releasing factor?

Hormonal responses in gambling versus alcohol abuse: A review of human studies

The endocrine system plays an essential role in communication between various organs of the body to maintain homeostasis. Both substance use disorders (SUDs) and non-substance abuse disrupt this system and lead to hormonal dysregulations. Here, we focus on the comparison between the function of the endocrine system in gambling disorders and alcohol addiction to understand the commonalities and differences in their neurobiological and psychological underpinnings. We review human research to compare findings on gambling addiction and alcohol dependence pertaining to the dynamic interplay between testosterone and cortisol. Understanding and classifying similarities in hormonal responses between behavioural addiction and SUDs may facilitate development of treatments and therapeutic interventions across different types of addictive disorders, while describing differences may shed light on therapeutic interventions for specific disorders. Although research on gambling addiction is in its infancy, such evaluation may still have a positive effect for addiction research, thereby stimulating discovery of "crossover" pharmacotherapies with benefits for both SUDs and nonsubstance addictions.

Pituitary portal plasma levels of oxytocin during the estrous cycle, lactation, and hyperprolactinemia

The median eminence receives fibers from both parvocellular and magnocellular OT neurons in the hypothalamus. The OT neuronal terminal in the median eminence is secretory and is the major source of the neuropeptide in the blood of pituitary portal vessels. The OT secretion into pituitary portal plasma increases by ovarian steroids, PRL, and the suckling stimulus. The OT secretion into the blood of pituitary portal vessels changes in parallel with the altered secretion of PRL from the pituitary. Because of correlative association between pituitary portal plasma OT and systemic plasma PRL and much abundant evidence for a direct stimulatory action of OT on PRL release, we propose that the pituitary portal vascular system serves as the window for the central OT neurotransmission to the pituitary lactotropes.

Dopaminergic inhibition of glycoprotein hormone alpha-subunit in normal subjects

The pituitary glycoprotein hormones thyrotropin (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) consist of two noncovalently linked subunits, alpha and beta. In addition to producing intact hormone, the pituitary releases free alpha-subunit, which is stimulated by gonadotropin-releasing hormone (GnRH) and thyrotropin-releasing hormone (TRH). However, little is known about the dopaminergic regulation of free alpha-subunit in vivo. The effect of dopamine (DA), metoclopramide (MTC), and the specific DA D-1 receptor agonist, fenoldopam, on circulating alpha-subunit levels was studied in normal men and women. Normal women received 4-hour infusions of either glucose (n = 6) or DA at rates of 0.04 (n = 6), 0.4 (n = 6), and 4.0 micrograms/kg.min (n = 6). After 3 hours, 10 mg MTC was administered intravenously (IV). The high dose of DA significantly lowered alpha-subunit levels (P less than .05). No response to MTC was observed in any of the groups. Six women received glucose or DA infusion (4.0 micrograms/kg.min) for 18 hours. DA significantly reduced basal alpha-subunit levels compared with control infusion (P less than .05). MTC administration after 17 hours induced a significant increase in alpha-subunit levels on the day of DA infusion compared with control (P less than .05). In a third study, nine normal males received fenoldopam (0.5 microgram/kg.min) or placebo infusions for 4 hours. Fenoldopam did not affect basal alpha-subunit levels, but the alpha-subunit response to a GnRH/TRH bolus was significantly increased during fenoldopam compared with control (P less than .05). The results suggest that alpha-subunit release may be modulated by the dopaminergic system in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic inhibition of hypothalamic-pituitary-ovarian axis and body weight gain by brain-directed delivery of estradiol-17 beta in female rats

The effect of preferential delivery of estradiol (E2) into the brain on both the hypothalamic-pituitary-ovarian axis and weight gain was studied in female rats. When E2 was coupled to a lipoidal dihydropyridine-pyridinium carrier, the resulting carrier E2 complex (CE), upon a single intravenous administration to cycling female rats, caused a dose-dependent inhibition of ovulation which lasted 3 times longer than with uncoupled E2. The dose of CE that delayed ovulation for 4 days was one twentieth the amount of E2 needed to produce the same effect. Studies in ovariectomized (OVEX) rats indicated that the prolonged ovulation-blocking action of CE appeared to be related to a sustained storage and release of E2 in the brain, which in turn suppressed the release of hypothalamic luteinizing hormone-releasing hormone (LHRH) and pituitary luteinizing hormone (LH). Upon single intravenous administration in pubertal female rats, CE caused a dose-dependent reduction of body weight gain for a minimum period of 28 days. The inhibitory action of CE on body weight gain was more potent and longer lasting than that of E2 in pubertal rats. When administered in OVEX rats, CE produced a loss of body weight that lasted significantly longer than that produced by uncoupled E2 in these rats. These results suggest that the biological action of E2 can be potentiated by this novel chemical delivery system.

Immunocytochemistry of luteinizing hormone-releasing hormone during spontaneous and thyroxine-induced metamorphosis of bullfrogs

Double-bridge peroxidase-antiperoxidase immunocytochemistry was used to compare the developmental appearance of immunoreactive LH-RH (ir-LH-RH) in brains of bullfrog (Rana catesbeiana) tadpoles during either spontaneous or thyroxine-induced metamorphosis. During spontaneous metamorphosis, ir-LH-RH was localized in fibers of the external layer of the median eminence (ME) of stage XIII-XXV animals, while immunoreactive perikarya and other immunostained brain structures were absent. The extent and intensity of ME immunostaining increased concomitantly with measured ME morphological development. Tadpoles induced with thyroxine to metamorphic stages XIX-XXI exhibited ME structural development and neurohypophysial neurosecretory staining similar to spontaneously metamorphosed individuals of equal stages. However, comparable ME ir-LH-RH immunostaining and gonadal size were both less developed in thyroxine-treated animals, although increased relative to non-metamorphic vehicle-injected controls. These results indicate that the hypothalamic LH-RH system changes concurrently with ME structural development during spontaneous metamorphosis. Reduced ME ir-LH-RH staining and gonadal size in thyroxine-treated animals suggest that during prometamorphosis, factors other than thyroxine alone may coordinate the normal maturation of the hypothalamo-pituitary-gonadal axis of the bullfrog.