No abstract

Kisspeptins are a family of small peptides that play a key role in the neuroendocrine regulation of the reproductive function through neural pathways that have not yet been completely identified. The present study aimed to investigate the distribution of kisspeptin neurone fibres in the female rat brain by comparing precisely the immunoreactive pattern obtained with two antibodies: one specifically directed against kisspeptin-52 (Kp-52), the longest isoform, and the other directed against kisspeptin-10 (Kp-10), whose sequence is common to all putative mature isoforms. With both antibodies, immunoreactive cell bodies were exclusively observed in the arcuate nucleus, and immunoreactive fibres were confined to the septo-preoptico-hypothalamic continuum of the brain. Fibres were observed in the preoptic area, the diagonal band of Broca, the septohypothalamic area, the anteroventral periventricular, suprachiasmatic, supraoptic, paraventricular and periventricular nuclei, the dorsal border of the ventromedian nucleus, the dorsomedial and arcuate nuclei, and the median eminence. In the latter structure, varicose fibres were mainly distributed in the internal layer and were detected to a lesser extent throughout the external layer, including around the deeper part of the infundibular recess. Most regions of immunoreactive cells and fibres matched perfectly for the two antibodies. However, fibres in the dorsolateral septum, anterior fornix, accumbens nucleus and the lateral bed nucleus of the stria terminalis were only recognised by antibody anti-Kp-10, suggesting that anti-Kp-10 may recognise a wider range of kisspeptin isoforms than anti-Kp-52 or cross-react with molecules other than kisspeptin in rat tissue. Overall, these results illustrate the variety of projection sites of kisspeptin neurones in the rat and suggest that these peptides play a role in different functions.

The present study describes the distribution and morphological characteristics of neurons and nerve fibers containing the catecholamine-synthesizing enzymes, tyrosine hydroxylase and dopamine-beta-hydroxylase, in the sheep brainstem and diencephalon on the basis of immunohistochemical procedures. Neurons and fibers were considered to be dopaminergic if they showed anti-tyrosine hydroxylase immunoreactivity, without corresponding anti-dopamine-beta-hydroxylase immunoreactivity. The structures labeled with both antisera were considered noradrenergic or adrenergic. The distribution of catecholaminergic neurons corresponds to that described by other authors with similar methods in the rat and in primates. The noradrenergic neurons belong to cell groups A1 to A7 and the dopaminergic neurons to cell groups A8 to A15. In almost all studied areas, the catecholaminergic innervation is similar to that observed in the other species. However, the central catecholaminergic systems of the sheep showed some specific characteristics: (1) groups A3 and A4, described in the rat, were not found, (2) group A14 contains fewer neurons than in the rat, (3) group A15 does not contain a dorsal but only a ventral portion, (4) there is a larger dispersion of neurons within each group, especially A6 and A7, than in rodents, and (5) there is a larger noradrenergic innervation of the catecholaminergic groups than in the other species.

No abstract

No abstract

The preoptic area contains most of the luteinizing hormone releasing hormone immunoreactive neurons and numerous monoaminergic afferents whose cell origins are unknown in sheep. Using tract tracing methods with a specific retrograde fluorescent tracer, fluorogold, we examined the cells of origin of afferents to the medial preoptic area in sheep. Among the retrogradely labeled neurons, immunohistochemistry for tyrosine hydroxylase, dopamine-beta-hydroxylase, phenylethanolamine N-methyltransferase, and serotonin was used to characterize catecholamine and serotonin fluorogold labeled neurons. Most of the afferents came from the ipsilateral side to the injection site. It was observed that the medial preoptic area received major inputs from the diagonal band of Broca, the lateral septum, the thalamic paraventricular nucleus, the lateral hypothalamus, the area dorsolateral to the third ventricle, the perimamillary area, the amygdala, and the ventral part of the hippocampus. Other numerous, scattered, retrogradely labeled neurons were observed in the ventral part of the preoptic area, the vascular organ of the lamina terminalis, the ventromedial part of the hypothalamus, the periventricular area, the area lateral to the interpeduncular nucleus, and the dorsal vagal complex. Noradrenergic afferents came from the complex of the locus coeruleus (A6/A7 groups) and from the ventro-lateral medulla (group A1). However, dopaminergic and adrenergic neuronal groups retrogradely labeled with fluorogold were not observed. Serotoninergic fluorogold labeled neurons belonged to the medial raphe nucleus (B8, B5) and to the serotoninergic group situated lateral to the interpeduncular nucleus (S4). In the light of these anatomical data we hypothesize that these afferents have a role in the regulation of several functions of the preoptic area, particularly those related to reproduction. Accordingly these afferents could be involved in the control of luteinizing hormone releasing hormone (LHRH) pulsatility or of preovulatory LHRH surge.

et al.. Pulsatile cerebrospinal fluid and plasma ghrelin in relation to growth hormone secretion and food intake in the sheep.. Journal of Neuroendocrinology, Wiley, 2008, 20 (10), pp.1138-46. 10.1111/j.1365-2826.2008 Pulsatile CSF and plasma ghrelin in relation with GH secretion and food intake in the sheep.Grouselle Dominique, * Chaillou Elodie, *Caraty Alain, Bluet-Pajot Marie-Therese, Zizzari Philippe, *Tillet Yves, Epelbaum Jacques. Key words : plasma, CSF, pulsatile patterns. AddressesElodie Chaillou and Dominique Grouselle contributed equally to this work.The definitive version is available at www.blackwell-synergy.com ABSTRACTAs in other species, exogenous administration of ghrelin, an endogenous ligand for the GH secretagogue receptors can stimulates feeding behaviour and GH secretion in the sheep. However the importance of endogenous ghrelin for these two functions as well as its central or peripheral origin remained to be established. In this study, CSF ghrelin concentrations were measured in five anoestrous ewes and found to be more than 1000-fold lower than circulating plasma levels, in keeping with the even lower concentration in hypothalamic as compared to abomasum tissue extracts. CSF and plasma ghrelin levels were measured every 10 minutes over a 6 hours sampling period in 5 unanesthetised ovariectomised-estradiol implanted ewes. Mean CSF ghrelin concentrations were 1400-fold lower than circulating plasma levels. Cluster analysis indicated that CSF ghrelin levels were markedly pulsatile with a greater number of peaks than plasma ghrelin. Pulsatility parameters were closer for GH and CSF ghrelin than between GH and plasma ghrelin. Plasma ghrelin and GH levels were significantly correlated in three out of five ewes but CSF ghrelin and GH in one ewe only. Half of the CSF ghrelin episodes were preceded by a ghrelin peak in plasma with a 22 min delay. Cross-correlations between plasma GH and plasma or CSF ghrelin did not reach significance but a trend towards cross-correlation was observed from 20 to 0 min between plasma and CSF ghrelin. At 09h00, when food was returned to ewes, voluntary food intake did not elicit a consistent change in plasma or CSF ghrelin levels. In contrast, a peripheral ghrelin injection (1 mg, i.v.) immediately stimulated food intake, feeding behaviour, and GH secretion. These effects were concomitant with a more than ten-fold increase in plasma ghrelin levels while CSF ghrelin values only doubled 40 to 50 minutes after the injection. This suggests that peripherally-injected ghrelin crosses the blood brain barrier but only in low amount 2/29 and with relatively slow kinetics when compared to its effects on GH release and food intake. Taken together, these results support the notion that, in the ovariectomised-oestradiol implanted sheep model, peripheral ghrelin injection rapidly induces GH secretion, food intake and feeding behaviour, probably by acting on GHS-R1 receptors located in brain regions in which the blood brain barrier is not complete such as, for instance, the arcu...

No abstract