Neuronal expression of c-Fos protein in the brain after intraperitoneal injection of leptin in Wistar rats

Leptin has been recognized to be an important neuroendocrine signal in the regulation of food intake and energy balance. We aimed to survey central neurons that might be activated after peripheral administration of leptin, by examining the distribution of neurons expressing c-Fos protein. Leptin dissolved at a dose of 500 μg/kg in physiological saline was intraperitoneally injected in Wistar rats. One and a half hours after the injection, rats were transcardially perfused with saline and fixed with fixatives. The brain was removed and sectioned at 40 μm in thickness. Every fourth section was treated with anti-c-Fos antiserum, and c-Fos protein was immunohistochemically stained using the avidin-biotin complex method. Control rats were injected with saline solution, and brain sections were processed similarly as described above. It was found that leptin injected intraperitoneally induced the neuronal expression of c-Fos protein in several nuclei throughout the brain. In the central nucleus amygdala, ventromedial nucleus of hypothalamus, periaqueductal gray matter, lateral parabrachial nucleus, and the solitary tract nucleus, numbers of neurons expressing c-Fos protein were much more in the test experiments than those in the control experiments. Intraperitoneally injected leptin was found to stimulate central neurons that may play some roles in the regulation of such as a food intake

Effects of peripheral administration of rat urotensinII on circulation, and on distribution of c-Fos immunoreactive neurons in the brain

The purpose of this study was to examine the effects of intravenous injection of urotensinII on the systemic blood pressure and heart rate, and to examine whether the intraperitoneal administration of urotensinII evoked the stimulation of central neurons. Urotensin, originally isolated fish neuro-endocrine systems, is a peptide which consists of 12 amino acids. Lately human urotensinII was identified to be consisted from 11 amino acids. Receptors of urotensin have been found to highly distribute in the mammalian cadrdiovascular systems. It has been reported that urotensin evoked contraction of thoracic artery, while the dilatation of blood vessels was alternatively induced. In this study, we examined the effects of peripheral injection of rat urotensinII consisted of 14 amino acids on the circulation and on the activity of neurons in the brain. It was found that intravenous injection of rat urotensinII elicited dose-dependently decrease in blood pressure, and increase or decrease in heart rate. To examine whether an intraperitoneal injection of rat urotensinII induced an excitation of central neurons, we used immunohistochemical method to study the expression of c-Fos protein in neurons of the rat brain after intraperitoneal injection of rat urotensinII (test experiment). In the control experiment rat was intraperitoneally injected saline solution without rat urotensinII. It was found that intraperitoneal injection of rat urotensinII induced expression of c-Fos protein in several nuclei in the brain. These results suggested that rat urotensinII might exhibit physiological functions via central neuronal pathway as well as peripheral direct pathways

Urocortin1-induced anorexia is regulated by activation of the serotonin 2C receptor in the brain

AbstractThis study was conducted to determine the mechanisms by which serotonin (5-hydroxytryptamine, 5-HT) receptors are involved in the suppression of food intake in a rat stress model and to observe the degree of activation in the areas of the brain involved in feeding. In the stress model, male Sprague–Dawley rats (8 weeks old) were given intracerebroventricular injections of urocortin (UCN) 1. To determine the role of the 5-HT2c receptor (5-HT2cR) in the decreased food intake in UCN1-treated rats, specific 5-HT2cR or 5-HT2b receptor (5-HT2bR) antagonists were administered. Food intake was markedly reduced in UCN1-injected rats compared with phosphate buffered saline treated control rats. Intraperitoneal administration of a 5-HT2cR antagonist, but not a 5-HT2bR antagonist, significantly inhibited the decreased food intake. To assess the involvement of neural activation, we tracked the expression of c-fos mRNA as a neuronal activation marker. Expression of the c-fos mRNA in the arcuate nucleus, ventromedial hypothalamic nucleus (VMH) and rostral ventrolateral medulla (RVLM) in UNC1-injected rats showed significantly higher expression than in the PBS-injected rats. Increased c-fos mRNA was also observed in the paraventricular nucleus (PVN), the nucleus of the solitary tract (NTS), and the amygdala (AMG) after injection of UCN1. Increased 5-HT2cR protein expression was also observed in several areas. However, increased coexpression of 5-HT2cR and c-fos was observed in the PVN, VMH, NTS, RVLM and AMG. Whereas, pro-opiomelanocortin mRNA expression was not changed. In an UNC1-induced stress model, 5-HT2cR expression and activation was found in brain areas involved in feeding control

Peripheral α2-β1 adrenergic interactions mediate the ghrelin response to brain urocortin 1 in rats

SummaryThe autonomic nervous system (ANS) conveys neuronal input from the brain to the stomach. We investigated mechanisms through which urocortin 1 (UCN1) injected intracerebroventricularly (ICV, 300pmol/rat) inhibits circulating ghrelin in rats. This was achieved by assessing (1) the induction of c-fos gene expression as a marker of neuronal activation in specific hypothalamic and caudal brainstem regulating ANS; (2) the influence of vagotomy and pharmacological blockade of central and peripheral α- and β-adrenergic receptor (AR) on ICV UCN1-induced reduction of plasma ghrelin levels (determined by ELISA); and (3) the relevance of this pathway in the feeding response to a fast in rats. UCN1 increased c-fos mRNA expression in key brain sites influencing sympathetic activity namely the hypothalamic paraventricular and ventromedial nuclei, locus coeruleus, nucleus of the solitary tract, and rostral ventrolateral medulla, by 16-, 29-, 6-, 37-, and 13-fold, respectively. In contrast, the dorsal motor nucleus of the vagus had little c-fos mRNA expression and ICV UCN1 induced a similar reduction in acylated ghrelin in the sham-operated (31%) and vagotomized (41%) rats. An intraperitoneal (IP) injection of either a non-selective α- or selective α2-AR antagonist reduced, while a selective α2-AR agonist enhanced ICV UCN1-induced suppression of plasma acylated ghrelin levels. In addition, IP injection of a non-selective β- or selective β1-AR agonist blocked, and selective β1-AR antagonist augmented, the ghrelin response to ICV UCN1. The IP injections of a selective α1- or non-selective β or β2-AR antagonists, or any of the pretreatments given ICV had no effect. ICV UCN1 reduced the 2-h food intake in response to a fast by 80%, and this effect was partially prevented by a selective α2-AR antagonist. These data suggest that ICV UCN1 reduces plasma ghrelin mainly through the brain sympathetic component of the ANS and peripheral AR specifically α2-AR activation and inactivation of β1-AR. The α2-AR pathway contributes to the associated reduction in food intake