Hypothalamus

About: Hypothalamus is a research topic. Over the lifetime, 22301 publications have been published within this topic receiving 1085925 citations.

Oxytocin, motherhood and bonding

Abstract: Release of the peptide hormone oxytocin in the brain has been shown to influence both maternal, sexual and social bonding behaviours although there are a number of species differences. This review summarizes findings on the distributions of oxytocin and oxytocin receptors in the brain, together with factors governing their expression, release of the peptide in the brain and its behavioural actions. A model of how oxytocin may act to alter maternal and socio-sexual behaviours is proposed which initially involves activation of oxytocin neurones in a single brain site, the paraventricular nucleus of the hypothalamus (PVN), following vaginal and cervical stimulation. This causes a co-ordinated release of the peptide in the PVN and its terminal projection regions for up to 1 h and this promotes different behavioural components, primarily through modulation of classical transmitter systems.

Increased neuropeptide-Y messenger ribonucleic acid (mRNA) and decreased neurotensin mRNA in the hypothalamus of the obese (ob/ob) mouse

Abstract: The obese hyperglycaemic ob/ob mouse exhibits hyperphagia and other abnormalities of hypothalamic function. We measured hypothalamic concentrations of four peptides implicated in the control of appetite and energy expenditure, neuropeptide-Y (NPY), neurotensin, galanin, and somatostatin, by RIA and their respective mRNAs using semiquantitative Northern blotting. Using lean (+/+) mice as controls, we found unchanged concentrations of NPY, galanin, and somatostatin and a 25% reduction in neurotensin (P < 0.01). Neurotensin mRNA was similarly decreased (by 30%; P < 0.02), while NPY mRNA was increased 3-fold (P < 0.01). Centrally administered neurotensin decreases food intake, whereas NPY potently stimulates food intake. An increase in NPY gene expression together with reductions in neurotensin concentration and mRNA in the hypothalamus may be implicated in the development of hyperphagia and other neuroendocrine abnormalities seen in the ob/ob mouse.

Hypothalamic growth hormone secretagogue receptor regulates growth hormone secretion, feeding, and adiposity

Abstract: Growth hormone secretagogues (GHSs) stimulate GH secretion and food intake. GHS receptor (GHS-R) mRNA has been identified mainly in the arcuate nucleus (Arc) and ventromedial nucleus of the hypothalamus and in the pituitary. Ghrelin, an endogenous ligand for GHS-R, has recently been purified from rat stomach. Although ghrelin is also expressed in the hypothalamus, the physiological significance of the ghrelin/GHS-R system is still unknown. We have created transgenic (Tg) rats expressing an antisense GHS-R mRNA under the control of the promoter for tyrosine hydroxylase (TH), thus selectively attenuating GHS-R protein expression in the Arc. Tg rats had lower body weight and less adipose tissue than did control rats. Daily food intake was reduced, and the stimulatory effect of GHS treatment on feeding was abolished in Tg rats. GH secretion and plasma insulin-like growth factor-I levels were reduced in female Tg rats. These results suggest that GHS-R in the Arc is involved in the regulation of GH secretion, food intake, and adiposity.

Responses of hypothalamic and pituitary mRNA to physical and psychological stress in the rat

Abstract: In-situ hybridization histochemistry was used to measure corticotrophin-releasing factor mRNA and proenkephalin A mRNA in the paraventricular nucleus (PVN), and pro-opiomelanocortin (POMC) mRNA in the anterior pituitary of the rat. Levels of message were determined at 1, 2, 4 and 8 h after exposure to a variety of physical and psychological stresses. Corticotrophin-releasing factor mRNA in the PVN and POMC mRNA in the anterior pituitary increased in response to i.p. hypertonic saline, restraint and swim stress but not to cold stress. Proenkephalin A mRNA was raised only in response to the physical stress of i.p. injection of hypertonic saline. These results suggest that different afferent pathways and hypothalamic neurotransmitters may be involved in mediating the hypothalamic response to different physical and psychological stresses.

Ventral lateral geniculate nucleus efferents to the rat suprachiasmatic nucleus exhibit avian pancreatic polypeptide-like immunoreactivity.

Abstract: The distribution of avian pancreatic polypeptide-like (APP) immunoreactivity was investigated in the suprachiasmatic nucleus (SCN) of the rat hypothalamus with immunohistochemical methods. Specificity of the antisera was established by the absence of all immunoreactive staining in tissue incubated in antisera which had been preabsorbed with the pure APP antigen. In addition, the antisera exhibited no significant cross reactivity with vasoactive intestinal polypeptide, vasopressin, somatostatin, or secretin. Within the rat SCN, APP immunoreactivity is restricted to varicose axons in the ventral and lateral aspects of the nucleus; the dorsomedial component of the nucleus is totally devoid of immunoreactivity and immunoreactive perikarya are not present in any portion of the SCN. The immunoreactive axons in the ventrolateral portion of the nucleus form an extensive plexus which is distributed in a pattern closely corresponding to the distribution of retinal and ventral lateral geniculate (vLGN) efferents to the SCN. No immunoreactive perikarya are observed in the retina following immunoperoxidase staining for APP and neither unilateral nor bilateral enucleation causes an observable alteration in the pattern of APP axon distribution within the SCN, thus indicating that the fiber plexus is not of retinal origin. In contrast, APP immunoreactive neurons are present in the same area of the vLGN in which retrogradely filled neurons have been demonstrated following iontophoretic injection of HRP into the SCN. Bilateral electrolytic lesions of the vLGN result in a total loss of immunoreactive axons in both SCN. Unilateral vLGN lesions cause a loss of approximately 60 to 75% of the immunoreactive fibers in the ipsilateral SCN with a lesser contralateral loss. These observations provide further information on the organization of afferents to the rat SCN and demonstrate that the vLGN projection is chemically distinct from other SCN afferents.