Leptin stimulates growth hormone secretion via a direct pituitary effect combined with a decreased somatostatin tone in a median eminence-pituitary perifusion study.

The aim of this study was to examine the effect of recombinant human leptin on growth hormone (GH) secretion in perifused anterior pituitary slices from adult pigs. Anterior pituitary slices from sows were perifused and treated with recombinant human leptin (10 nM) and GH-releasing hormone (GHRH; 1 nM). In some experiments, pituitary slices were coincubated with stalk median eminence (SME).

Long-term effects on bone of postnatal immunization against GHRH in female and male rats.

The effects of neonatal passive immunization against GHRH on bone was examined in male and female rats. Pups were treated subcutaneously with GHRH-antiserum (GHRH-Ab) from day 1 to day 10 of age. Bone mineral content (BMC) and bone mineral density (BMD) were evaluated at monthly intervals until 7 months.

Differential GH-releasing hormone regulation of GHRH receptor mRNA expression in the rat pituitary.

To understand the capacity of growth hormone-releasing hormone (GHRH) to regulate expression of the GHRH receptor, we studied the effects of GHRH on GHRH receptor mRNA expression in immature and adult rats by use of pituitary cell culture and immunoneutralization approaches. Pituitary cell cultures from neonatal (2-day-old) and adult (70-day-old) rats were treated with GHRH for 4, 24, or 72 h. The effect of GHRH on GHRH receptor mRNA expression depended on the duration of GHRH exposure in both age groups; short-term (4 h) GHRH treatment significantly reduced GHRH receptor mRNA expression (P < 0.

The effects of a continuous infusion of hexarelin on pulsatile growth hormone release, growth axis and galanin gene expression and on the response of the growth axis to growth hormone-releasing hormone.

The effect of a 6 hour continuous infusion of Hexarelin (100 micrograms/hour) on GH peak frequency, amplitude and duration, GH trough concentrations, the interval between successive peaks and the pituitary responsiveness to GHRH, as well as GH axis and galanin mRNA contents, were examined in conscious adult male rats. Plasma GH concentrations peaked within 15 minutes after the initiation of Hexarelin infusion, but returned to baseline levels by 60 minutes. No significant differences between Hexarelin and saline infused rats were noted for any of the parameters of pulsatile GH release analyzed.

Acute and chronic galanin administration decreases hypothalamic galanin synthesis in both male and female adult rats: evidence for a long-loop galanin autofeedback.

The secretion of growth hormone (GH) in both male and female rats is controlled by two main neuropeptides, GH-releasing hormone (GHRH), which is stimulatory, and somatostatin, which is inhibitory. Recently, it has been shown that galanin (GAL) also stimulates GH secretion, although the underlying mechanism is still unknown. It was the aim of this study to begin to elucidate if and how GAL regulates its own production at the hypothalamic and pituitary level.