Brain arcuate nucleus

Lesions of the lateral hypothalamic area (LHA) cause anorexia, whereas ablation of the paraventricular nucleus (PVN) cause a hyperphagic obesity syndrome. Consistent with these results, LHA neurons express the orexigenic neuropeptides MCH and orexin. PVN neurons produce several neuropeptides that are anorex-igenic when administered directly into the brain (CRH, TRH, oxytocin), in addition to their better known roles as endocrine regulators. LHA and PVN receive rich inputs from axons of NPY/AgRP and aMSH/CART-producing neurons in the arcuate nucleus. 

FIGURE 14-2 The histaminergic system of the rat brain. (A) Frontal sections through the posterior hypothalamus showing the location of histaminergic neurons. Arc, arcuate nucleus DM, dorsomedial nucleus LM, lateral mammillary nucleus MM, medial mammillary nucleus MR, mammillary recess PM, premammillary nucleus 3V, third ventricle VMH, ventromedial hypothalamic nucleus. (Modified with permission from reference [5].)... 

The leptin receptor is expressed primarily in regions of the brain known to regulate feeding behavior— neurons of the arcuate nucleus of the hypothalamus... 

The anorexigenic (appetite-suppressing) neurons in the arcuate nucleus produce a-melanocyte-stimulating hormone (a-MSH), formed from its polypeptide precursor pro-opiomelanocortin (POMC Fig. 23-6). Release of a-MSH causes the next neuron in the circuit to send the signal to the brain, Stop eating ... 

Fig. 1. Location of dopaminergic perikarya (Au-A15) are depicted schematically on frontal sections (B-F) through the diencephalon of the rat. Section A is a sagittal view of the rat brain depicting the rostrocaudal location of frontal sections B-F. Abbreviations AH, anterior hypothalamus ARC, arcuate nucleus BST, bed nucleus of the stria terminalis f, fornix ic, internal capsule inf, infundibulum me, median eminence mt, mamillothalamic tract OC, optic chiasm ot, optic tract PH, posterior hypothalamus PIT, pituitary gland PeV, periventricular nucleus PVN, paraventricular nucleus RCH, retrochiasmatic area SON, supraoptic nucleus VMN, ventromedial nucleus ZI, zona incerta.

Everitt BJ, Meister B, Hokfelt T, Melander T, Terenius L, Rokaeus A, Theodorsson-Norhein E, Dockray G, Edwardson J, Cuello AC, Elde R, Goldstein M, Flemmings H, Ouimet C, Walaas I, Greengard P, Valet W (1986) The hypothalamic arcuate nucleus-median eminence complex immunohistochemistry of transmitters, peptides and DARPP-32 with special reference to coexistence in dopamine neurons. Brain Res Rev 77 97-155. 

He J-R, Molnar J, Barraclough CA (1994) Evidence that amplification of norepinephrine-induced LH release by morphine is indirectly due to suppression of tuberoinfundibular dopamine secretion. Brain Res 652 1-8. Hentschel K, Cheung S, Moore KE, Lookingland KJ (1998) Pharmacological evidence that neurotensin mediates prolactin-induced activation of tuberoinfundibular dopamine neurons. Neuroendocrinology 65 71-76. Hentschel K, Will YM, McMahon CD, Moore KE, Lookingland KJ (1999) Prolactin induces Fos-related antigen expression in neurotensin (NT)-IR neurons and increases numbers of NT-IR neurons in the arcuate nucleus. Soc Neurosci Abstr 25 1185. 

Hentschel K, Moore KE, Lookingland KJ (2000) Effects of prolactin on expression of Fos-related antigens in tyrosine hydroxylase-immunoreactive neurons in subdivisions of the arcuate nucleus. Brain Res 557 110-118. Hesketh R (1995) The Oncogene Facts Book, pp. 105-160. Academic Press, New York. 

Ibata Y, Kawakami F, Okamura H, Obata-Tsuto HL, Morimoto N, Zimmerman EA (1985) Light and electron microscopic immunocytochemistry of P-endorphin/ P-LPH-like immunoreactive neurons in the arcuate nucleus and surrounding areas of the rat hypothalamus. Brain Res 34P.233-242. 

Krajnak K, Nunez AA (1996) Short-photoperiod exposure reduces L-aromatic-amino-acid decarboxylase immunostaining in the arcuate nucleus and median eminence of male Syrian hamsters. Brain Res 772 95-101. 

Lin J-Y, Pan Y-T (1993) Bombesin and neurotensin excite neurons in hypothalamic arcuate nucleus in brain slices an extracellular single-unit study. Brain Res Bull 50 177-180. 

Lookingland KJ, Gunnet JW, Moore KE (1987b) Electrical stimulation of the arcuate nucleus increases the metabolism of dopamine in terminals of tuberoinfundibular neurons in the median eminence. Brain Res 436 161-164. 

Fatty acids. Normal brain tissne does not take np or metabolise fatty acids (hence its dependence on glucose, or the switch to ketone body ntUisation). However, the arcnate nucleus converts fatty acids to long-chain fatty acyl-CoA intermediates. The exact mechanism of appetite control is unclear, bnt it is known that the long-chain fatty acyl-CoA intermediates formed in the arcuate nucleus dampen appetite and rednce food intake. 

Li JJ, Zhou X, Yu LC (2005a) Involvement of neuropeptide Y and Y1 receptor in antinodception in the arcuate nucleus of hypothalamus, an immunohistochemical and pharmacological study in intact rats and rats with inflammation. Pain 118 232-242 Li P, Tong C, Eisenach JC, Figueroa JP (1994b) NMDA causes release of nitric oxide from rat spinal cord in vitro. Brain Res 637 287-291... 

There are other aspects of barrier function that also change with development. The tanycytic barrier between the median eminence and the arcuate nucleus develops after birth in the rodent (Peruzzo et al 2000). This means the arcuate nucleus is very vulnerable to circulating neurotoxins during the neonatal period. For example, monosodium glutamate destroys the arcuate nucleus with resulting obesity when given intravenously to a neonate, but not an adult. The epithelial cells, which line the ventricles of the brain, have tight junctions even over non-CVO sites in neonates, but not adults. Thus, neonates have a CSF-brain barrier, which limits the diffusion of substances between brain tissue and CSF... 

Rethelyi M (1984) Diffusional barrier around the hypothalamic arcuate nucleus in the rat. Brain Res 307 355-358. 

The distribution of dopamine in the brain is very non-uniform. There is some in the limbic system, and a large proportion is found in the corpus striatum - a part of the extrapyramidal motor system which is concerned with the coordination of movement. Dopamine-containing nerves are found in three main pathways in the brain. The nigrostriatal pathway contains about 75% Of the dopamine in the brain, and the cell bodies lie in the substantia nigra and the nerves terminate in the corpus striatum. The second important pathway is the mesolimbic pathway, the cell bodies of which lie in the mid-brain and project to parts of the limbic system, particularly the nucleus accumbens. The third, the tubero-infundibular system, consists of short neurons that run from the arcuate nucleus of the hypothalamus to the median eminence and the pituitary gland, the secretions of which they regulate. 

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