The effect of intracerebroventricular infusions of ghrelin and/or short fasting on the gene expression and immunoreactivity of somatostatin in the hypothalamic neurons and on pituitary growth hormone in prepubertal female lambs. Morphological arguments

The effect of intracerebroventricular infusions of ghrelin on the secretory activity of the GnRH/LH system in peripubertal ewes

“…The origin of the ghrelin used and its infused dose were based on the results of Iqbal et al (2006), who showed that in increasing plasma GH concentration in ovariectomised sheep, human ghrelin was more potent that ovine ghrelin synthesized by Osaka Peptide Institute. This observation was confirmed in our laboratory using intact prepubertal lambs (Polkowska et al, 2011). Immediately after the last infusion, the sheep were weighed and then slaughtered by decapitation under pentobarbital anaesthesia with an i.v.…”

“…However, it must be emphasized that the experimental factors chosen in this experiment, i.e. 72 h fasting and applied ghrelin (100 µg · day -1 ) were entirely sufficient to induce the response of somatotropic axis secretory activity under the same experimental design (Polkowska et al, 2011).…”

Influence of season and nutritional status on the direct effects of leptin, orexin-A and ghrelin on luteinizing hormone and growth hormone secretion in the ovine pituitary explant model

“…It has been proposed that ghrelin suppresses the activity of somatostatin, which leads to increased GH synthesis in ewe lambs on a negative energy balance [13]. In humans, a synergistic action of GHRH and ghrelin on GH secretion has been observed after intravenous administration of both hormones [40].…”

“…Reduction in the pulsatile secretion of LH because of nutritional restrictions can be reversed by leptin administration in sheep and cattle [10,11] and by orexin-A in female rats [12]. Leptin and ghrelin regulate GH secretion in both the negative and the positive energy balance states in sheep [10,13]. The expression of leptin receptors has been found not only in the hypothalamic nuclei responsible for the regulation of feed intake, including the mediobasal hypothalamus area and median eminence, but also in the anterior pituitary of the ewe [14,15].…”

The effect of intracerebroventricular infusions of ghrelin or short fasting on the gene expression and immunoreactivity of neuropeptide Y in the hypothalamic neurons in prepubertal female lambs: A morphofunctional study

“…Ghrelin has been shown to stimulate GH release when administered into the CNS in rats (Date et al, 2000b;Wren et al, 2000) and sheep (Iqbal et al, 2006;Polkowska et al, 2011), suggesting direct effects on the CNS. In addition to its GH releasing action it has been shown that ghrelin is involved in regulation of peripheral energy homeostasis (Inui, 2001).…”