Projections from the arcuate/ventromedial region of the hypothalamus to the preoptic area and bed nucleus of stria terminalis in the brain of the ewe; lack of direct input to gonadotropin-releasing hormone neurons

Pompolo, Sueli; Rawson, John A; Clarke, Iain J.

doi:10.1016/s0006-8993(01)02372-1

Cited by 70 publications

(52 citation statements)

References 68 publications

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“…In rats, there are substantial projections of NPY neurones from the arcuate nucleus to the PVN [13]and from the brain stem to the PVN [17]. In sheep, the distribution of NPY neurones in the central nervous system is similar to that in rats [8], however, anterograde tracing studies do not indicate a major innervation from the dorsal part of the arcuate nucleus to the CRH-containing cells of the PVN [14]. Nevertheless, this does not preclude such a projection as NPY-immunoreactive cells that are located in the ventral part of the arcuate nucleus [15]may project to the PVN.…”

Section: Discussionmentioning

confidence: 99%

“…Anterograde tracing studies in sheep show that only very few neurones (of unidentified phenotype) project from the dorsal part of the arcuate nucleus to the PVN [14], but recent work has shown that there is also a population of NPY-immunoreactive neurones in the ventral part of the arcuate nucleus [15]. Furthermore, it has been shown in the rat that noradrenergic neurones in the brain stem often co-express NPY [16, 17].…”

Section: Introductionmentioning

confidence: 99%

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Noradrenaline, but Not Neuropeptide Y, Is Elevated in Cerebrospinal Fluid from the Third Cerebral Ventricle following Audiovisual Stress in Gonadectomised Rams and Ewes

Turner

Rivalland²,

Clarke³

et al. 2002

Neuroendocrinology

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There are sex differences in the activation of the hypothalamo-pituitary-adrenal axis in response to stress, but the source of these differences is unknown. The hypothalamo-pituitary-adrenal axis is regulated by corticotropin-releasing hormone and arginine-vasopressin neurones located in the paraventricular nucleus and these, in turn, are regulated by neural systems that include afferent noradrenergic and neuropeptide Y (NPY)-producing neural pathways. We tested the hypothesis that concentrations of noradrenaline and NPY will be elevated in cerebrospinal fluid (CSF) sampled from the third cerebral ventricle in response to stress, and these responses will differ in males and females. We collected concurrent samples of CSF (1 ml) from the third ventricle and blood (5 ml) from the jugular vein from gonadectomised rams (n = 7) and ewes (n = 5) at 10-min intervals for 3 h. This procedure was conducted on a day when no stress was imposed and on a day when audiovisual stress was imposed for 5 min after 1 h of sampling. Following the audiovisual stress, plasma concentrations of cortisol and CSF concentrations of noradrenaline were elevated (p < 0.05), but CSF concentrations of NPY did not change. Adrenaline was not detected in samples of CSF. The rise in plasma cortisol following the stress was greater (p < 0.05) in ewes than in rams, but there were no sex differences in the rise in noradrenaline. Basal concentrations of NPY in the CSF were higher (p < 0.05) in rams than in ewes. We conclude that the sex differences in the stress-induced activity of the hypothalamo-pituitary-adrenal axis in sheep are not likely to be due to differences in the level of noradrenergic and/or NPY input to the hypothalamus.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Noradrenaline, but Not Neuropeptide Y, Is Elevated in Cerebrospinal Fluid from the Third Cerebral Ventricle following Audiovisual Stress in Gonadectomised Rams and Ewes

Turner

Rivalland²,

Clarke³

et al. 2002

Neuroendocrinology

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“…Interestingly, in the rat, GH concentrations are reduced by NPY [15], while NPY increases GH in sheep [16]. Furthermore, sheep have fewer projections extending from the arcuate nucleus to the paraventricular nucleus as compared with the number of projections from the arcuate nucleus to the preoptic area and the bed nucleus of the stria terminalis, a pattern which differs from that found in the rodent [17]. These efferent projections from the arcuate nucleus contain NPY/AGRP and α-MSH/CART, peptides known to be critical in appetite regulation [18, 19, 20].…”

Section: Introductionmentioning

confidence: 99%

A Role for Agouti-Related Protein in Appetite Regulation in a Species with Continuous Nutrient Delivery

et al. 2004

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Knowledge of specific neurotransmitters as well as the pathways and mechanisms regulating appetite in ruminants that continually graze, such as sheep, is incomplete. Although fundamentally agouti-related protein (AGRP) has a similar function across species to increase food intake, the regulation of AGRP may vary across grazing and intermittent feeders. To investigate the role of orexigenic peptides in the regulation of feed intake, we first extracted messenger RNA from sheep that were fasted for 3 days, which was then used for PCR followed by cloning and sequencing to demonstrate the presence of hypothalamic AGRP expression. Ovine AGRP was closely related to the bovine, but contained sequence differences with human and mouse AGRP. Analysis of genomic DNA also revealed a similar gene structure to other published species. Secondly, using dual-labeled immunohistochemistry, we determined that there was both increased AGRP immunoreactivity and increased abundance of c-Fos immunoreactivity in AGRP neurons in the arcuate nucleus of fasted sheep. Because AGRP neurons are activated by fasting, we hypothesized that AGRP would stimulate feeding in this ruminant species. Sheep fed ad libitum were injected intracerebroventricularly with concentrations of AGRP at 0.2 and 2.0 nmol/kg. AGRP at 2.0 nmol/kg significantly increased food intake at 4, 6 and 12 h (p < 0.05). A 4th study was done to investigate the interactions of AGRP and neuropeptide Y (NPY) on food intake over a 24-hour period. Intracerebroventricular injections of either AGRP or NPY significantly increased cumulative food intake over saline controls. When AGRP and NPY were injected in combination, food intake was increased over saline controls; however, AGRP did not potentiate the effects of NPY. These results demonstrate that AGRP stimulates food intake in sheep and highlights the important differences between this species and rodent models.

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“…Furthermore, the proportion of GnRH neurons in close proximity to NPY fibers in the preoptic area and mediobasal hypothalamus is reduced in heifers with increased BW gain (Alves et al 2011). However, it remains to be determined whether these changes in NPY projections to GnRH neurons involve NPY cells from the ARC in heifers, because in the female sheep there is no significant direct input originating from the ARC to GnRH neurons located in the preoptic area (Pompolo et al 2001). Taken together, these observations indicate that increased hypothalamic NPY activity in juvenile heifers may play a role in restraining the pulsatile release of GnRH and LH necessary for final reproductive development.…”

Section: Discussionmentioning

confidence: 99%

Reciprocal changes in leptin and NPY during nutritional acceleration of puberty in heifers

Cardoso¹,

Alves²,

Prezotto³

et al. 2014

Journal of Endocrinology

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Feeding a high-concentrate diet to heifers during the juvenile period, resulting in increased body weight (BW) gain and adiposity, leads to early-onset puberty. In this study, we tested the hypothesis that the increase in GnRH/LH release during nutritional acceleration of puberty is accompanied by reciprocal changes in circulating leptin and central release of neuropeptide Y (NPY). The heifers were weaned at 3.5 months of age and fed to gain either 0.5 (Low-gain; LG) or 1.0 kg/day (High-gain; HG) for 30 weeks. A subgroup of heifers was fitted surgically with third ventricle guide cannulas and was subjected to intensive cerebrospinal fluid (CSF) and blood sampling at 8 and 9 months of age. Mean BW was greater in HG than in LG heifers at week 6 of the experiment and remained greater thereafter. Starting at 9 months of age, the percentage of pubertal HG heifers was greater than that of LG heifers, although a replicate effect was observed. During the 6-h period in which CSF and blood were collected simultaneously, all LH pulses coincided with or shortly followed a GnRH pulse. At 8 months of age, the frequency of LH pulses was greater in the HG than in the LG group. Beginning at 6 months of age, concentrations of leptin were greater in HG than in LG heifers. At 9 months of age, concentrations of NPY in the CSF were lesser in HG heifers. These observations indicate that increased BW gain during juvenile development accelerates puberty in heifers, coincident with reciprocal changes in circulating concentrations of leptin and hypothalamic NPY release.

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Projections from the arcuate/ventromedial region of the hypothalamus to the preoptic area and bed nucleus of stria terminalis in the brain of the ewe; lack of direct input to gonadotropin-releasing hormone neurons

Cited by 70 publications

References 68 publications

Noradrenaline, but Not Neuropeptide Y, Is Elevated in Cerebrospinal Fluid from the Third Cerebral Ventricle following Audiovisual Stress in Gonadectomised Rams and Ewes

Noradrenaline, but Not Neuropeptide Y, Is Elevated in Cerebrospinal Fluid from the Third Cerebral Ventricle following Audiovisual Stress in Gonadectomised Rams and Ewes

A Role for Agouti-Related Protein in Appetite Regulation in a Species with Continuous Nutrient Delivery

Reciprocal changes in leptin and NPY during nutritional acceleration of puberty in heifers

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