Effects of central and peripheral administration of an acute-phase protein, α-1-acid-glycoprotein, on feed intake and rectal temperature in sheep.

In rodents, an acute-phase protein, α-1-acid-glycoprotein (AGP), was shown to provide a link between inflammation and suppression of feed intake by acting as a leptin receptor agonist. The objective of this study was to determine the effects of AGP on feed intake and rectal temperature in sheep. Ewes were ovariectomized, implanted with a cannula into a lateral ventricle of the brain, and kept indoors in individual pens. Feed intake and rectal temperature were determined for sheep in all experiments. In the first experiment, ewes (n = 4) received 1 of 4 treatments [0 (control), 0.012 (low), 0.06 (medium), or 0.30 (high) mg/kg BW AGP] into the lateral ventricle (ICV). All sheep received all treatments in a Latin square design balanced for carryover effects with 10 d between treatments. In the second experiment, ewes (n = 10) received 1 of 2 treatments (0 and 3 mg/kg BW of AGP) intravenously (IV) in a completely randomized design. In the third experiment, ewes (n = 19) received peripheral treatments (IV) of an antipyretic [0 (control) or 2.2 mg/kg BW flunixin meglumine (FLU)] 30 min before receiving central AGP [0 (control) or 0.3 mg/kg BW of AGP] in a completely randomized design. All data were analyzed using a mixed model analysis of variance and tested for effects of treatment, time, and the interaction of treatment and time. Cumulative 48-h feed intake after administration of treatments was also determined. In the first experiment, there was no effect of ICV treatment (P = 0.37) on feed intake rate or on cumulative feed intake (P = 0.31). There was an effect of ICV treatment (P = 0.002) on rectal temperatures, which were greater (P < 0.05) after the high dose of centrally administered AGP. In the second experiment, there was no effect of AGP administration IV on feed intake rate (P = 0.98), on cumulative feed intake (P = 0.41) or on rectal temperature (P = 0.71). In the third experiment, there was an effect of central AGP treatment (P < 0.0001) and an interaction of central AGP and time (P < 0.0001) on rectal temperature, whereas FLU had no effect (P = 0.93), demonstrating that AGP increased rectal temperatures regardless of antipyretic treatment. These results indicate that central AGP increases rectal temperature in sheep by pathways that do not involve prostaglandins. Further research is needed to determine whether AGP may be an important integrator of energy balance and inflammation.

Interaction of the dopaminergic and Nociceptin/Orphanin FQ on central feed intake regulation in chicken.

1. The aim of the current study was to determine the effects of the central dopaminergic system on N/OFQ-induced feed intake in 3-h feed-deprived neonatal broilers. 2. In experiment 1, chicken received intracerebroventricular (ICV) injections of a control solution, SCH 23 390 (D1 receptors antagonist, 5 nmol), N/OFQ (16 nmol) or their combination (SCH23 390 + N/OFQ). In experiment 2, a control solution, AMI-193 (D2 receptors antagonist, 5 nmol), N/OFQ (16 nmol) or their combination (AMI-193 + N/OFQ) were ICV injected into chickens. In experiment 3, birds received ICV injections of a control solution, NGB2904 (D3 receptors antagonist, 6.4 nmol), N/OFQ (16 nmol) and co-injection of NGB2904 + N/OFQ. In experiment 4, ICV injections of the control solution, L-741,742 (D4 receptors antagonist, 6 nmol), N/OFQ (16 nmol) or their combination (L-741,742 + N/OFQ) were applied to broilers. In experiment 5, birds were ICV injected with control solution, L-DOPA (dopamine precursor, 125 nmol), N/OFQ (16 nmol) and L-DOPA + N/OFQ. Cumulative feed intake was recorded until 120 min after injection. 3. According to the results, ICV injection of N/OFQ significantly increased feed intake (P < 0.05). Co-injection of N/OFQ and D1 receptor antagonist (SCH 23390) amplified hyperphagic effect of N/OFQ (P < 0.05). The N/OFQ-induced feed intake was increased by the D2 receptor antagonist (P < 0.05). The hyperphagic effect of N/PFQ was weakened by co-injection of L-DOPA + N/OFQ (P < 0.05). 4. These results suggested that an interaction exists between dopamine and N/OFQ via D1 and D2 receptors on central feed intake in neonatal broiler chickens.

Central injection of oxytocin reduces food intake and affects hypothalamic and adipose tissue gene expression in chickens.

Oxytocin (OT) is a well-characterized neurotransmitter that participates in a wide range of physiological processes including the inhibition of food intake. The avian ortholog, mesotocin (MT), differs from OT by a single amino acid. Little is known regarding the function of OT in regulating energy balance in birds; thus, this study was designed to determine the effects of central OT injection on food intake and adipose tissue physiology in chicks. At 4-d post-hatch, broiler chicks were fasted for 3 h and injected intracerebroventricularly with 0 (vehicle), 0.63, 2.5, 5.0, or 10 nmol OT. Oxytocin decreased food and water intake during the entire 180-min observation period. The reduction in water intake was likely not prandial because chicks that were food restricted after OT injection also drank less. There was increased c-Fos immunoreactivity in several appetite-associated hypothalamic nuclei in OT-injected chicks at 1 h, including the arcuate (ARC), dorsomedial nucleus (DMN), lateral hypothalamus (LH), paraventricular nucleus (PVN), and ventromedial hypothalamus (VMH). OT treatment was associated with reduced hypothalamic corticotropin-releasing factor (CRF) mRNA and increased cloacal temperature at 1 h post-injection. We then investigated appetite- and adipose tissue-associated effects of OT in chicks from lines that have undergone long-term selection for either low (LWS) or high (HWS) juvenile body weight. Central injection of OT decreased food intake in both lines with the magnitude of response greater in the HWS than LWS chicks. Adipose tissue abundance of fatty acid-binding protein 4, monoglyceride lipase (MGLL), MT, and perilipin-1 mRNA was greater in LWS than HWS chicks. Lipoprotein lipase, MGLL, and MT mRNAs increased in response to OT injection in LWS but not HWS chicks. In conclusion, central injection of OT induced anorexia, reduced water intake, increased body temperature, and was associated with activation of the ARC, DMN, LH, PVN, and VMH in the hypothalamus. The effects on appetite and body temperature may involve CRF signaling in the hypothalamus and lipolysis in the adipose tissue, respectively. There were differences in the appetite, and adipose tissue response to OT in body weight-selected lines of chicks supports that MT plays a role in energy balance regulation in chickens.

Interaction of neuropeptide Y receptors (NPY1, NPY2 and NPY5) with somatostatin on somatostatin-induced feeding behaviour in neonatal chicken.

1. The present study was conducted to investigate whether brain somatostatin increases feed intake in neonatal chickens. The mediating role of neuropeptide Y receptors on feed intake induced by somatostatin was investigated. 2. In this study, seven experiments were designed, each with four treatment groups (n = 44 in each experiment). In Experiment 1, chicks received control solution and 0.5, 1 and 2 nmol of somatostatin through intracerebroventricular (ICV) injection. In experiments 2, 3 and 4, chickens were ICV injected with control solution and 1.25, 2.5 and 5 µg of B5063 (NPY1 receptor antagonist), SF22 (NPY2 receptor antagonist) and SML0891 (NPY5 receptor antagonist), respectively. In experiment 5, 6 and 7 chickens received ICV injection of B5063, SF22, SML0891, with a co-injection of + somatostatin, control solution and somatostatin. The cumulative feed intake was measured until 120 min post injection. 3. Somatostatin significantly increased feed intake in FD3 chicks. Both B5063 and SML0891 dose-dependently decreased feed intake compared with the control group, while SF22 led to a dose-dependent increase in feed intake. In addition, the hyperphagic effect of somatostatin significantly decreased with co-injection of B560 plus somatostatin (p < 0.05), but SF22 and SML0891 had no effect on feed intake induced by somatostatin in chicks (p > 0.05). 4. Based on the results of this study, it is likely that somatostatin increased feed intake and NPY1 receptor acts as a mediator in hyperphagic effect of somatostatin in neonatal chicks.

Physiological responses to central and peripheral injection of polyinosinic-polycytidylic acid in chicks.

1. The purpose of the present study was to determine if intracerebroventricular (ICV) and intraperitoneal (IP) injection of polyinosinic-polycytidylic acid (poly I:C), a viral mimetic that binds to toll-like receptor-3 (TLR3), affects food intake, voluntary activity, cloacal temperature, plasma corticosterone (CORT) and glucose concentrations, and crop emptying rate in chicks (Gallus gallus). 2. Both ICV and IP injection of poly I:C significantly decreased food intake. 3. IP but not ICV injection of poly I:C significantly suppressed voluntary activity, whereas ICV injection decreased time spent sitting. Both ICV and IP injection of poly I:C significantly increased plasma CORT and glucose concentration. Neither ICV nor IP injection of poly I:C significantly affected cloacal temperature. 4. In addition, ICV injection of poly I:C significantly reduced crop emptying rate, whereas IP injection had no effect. 5. These results suggested that central TLR3 is related to anorexia, stress response and retardation of crop emptying while peripheral TLR3 is related to anorexia, change in behaviour and stress responses during viral infection in chicks.

Consequence of dopamine D2 receptor blockade on the hyperphagic effect induced by cannabinoid CB1 and CB2 receptors in layers.

1. Endocannabinoids (ECBs) and their receptors play a regulatory function on several physiological processes such as feed-intake behaviour, mainly in the brain. This study was carried out in order to investigate the effects of the dopaminergic D1 and D2 receptors on CB1/CB2 ECB receptor-induced hyperphagia in 3-h feed-deprived neonatal layer chickens. 2. A total of 8 experiments were designed to explore the interplay of these two modulatory systems on feed intake in neonatal chickens. In Experiment 1, chickens were intracerebroventricular (ICV) injected with control solution, l-DOPA (levo-dihydroxyphenylalanine as precursor of dopamine; 125 nmol), 2-AG (2-arachidonoylglycerol as CB1 receptor agonist; 2 µg) and co-administration of l-DOPA (125 nmol) plus 2-AG (2 µg). Experiments 2-4 were similar to Experiment 1 except birds were injected with either 6-OHDA (6-hydroxydopamine as dopamine synthesis inhibitor; 150 nmol), SCH23390 (D1 receptor antagonist; 5 nmol) and AMI-193 (D2 receptor antagonist; 5 nmol) instead of l-DOPA, respectively. Additionally, Experiments 5-8 followed the previous ones using the same dose of l-DOPA, 6-OHDA and dopamine antagonists except that birds were injected with CB65 (CB2 receptor agonist; 5 µg) instead of 2-AG. Coadministrations were at the same dose for each experiment. Cumulative feed intakes were measured until 120 min after each injection. 3. ICV administration of 6-OHDA and AMI-193 significantly attenuated 2-AG-induced hyperphagia. Interestingly, the hyperphagic effect of CB65 was significantly attenuated by administration of l-DOPA, whereas the administration of 6-OHDA and AMI-193 together amplified the hyperphagic effect of CB65. 4. It was concluded that cannabinoid-induced feeding behaviour is probably modulated by dopamine receptors in neonatal layer-type chickens. It seems that their interaction may be mediated by the D2-dopamine receptor.

Hypothalamic-pituitary GnRH/LH axis activity is affected by salsolinol in sheep during lactation: Effects of intracerebroventricular infusions of salsolinol and its antagonizing analogue.

The aim of the study was to test the hypothesis that salsolinol, a derivative of dopamine, is involved in the regulation of hypothalamic-pituitary gonadotropic (GnRH/LH) axis activity in lactating sheep. In the first experiment performed on sheep during the fifth week of lactation, a structural analogue of salsolinol (1-MeDIQ) was infused into the third brain ventricle (IIIv) to antagonize its action within the central nervous system (CNS). A push-pull perfusion of the infundibular nucleus/median eminence was performed simultaneously, and blood samples were collected from the jugular vein. In the second experiment, sheep received infusions of salsolinol into the IIIv, 48 hours after the weaning of their 8-week-old lambs. Blood samples were collected during the experimental periods, and the anterior pituitary (AP) tissue was dissected immediately after the end of the experiment. Perfusate GnRH concentration (experiment 1), plasma LH concentration (experiments 1 and 2), and relative LHß mRNA levels in the AP tissue (experiment 2) were assayed. Blocking of salsolinol action in the CNS of lactating sheep caused a significant (P < 0.001) decrease in the perfusate GnRH concentrations in comparison with controls. Treatment with 1-MEDIQ also significantly decreased (P < 0.001) the LH concentration in the blood plasma. In turn, salsolinol infused 48 hours after lamb weaning significantly (P < 0.001) increased plasma LH concentration, reflected in the significant (P < 0.05) increase in the amplitude of LH pulses in the treated sheep as compared to the control animals. There was no significant difference in the relative levels of LHß-subunit mRNA in the AP between control and salsolinol-infused sheep. The results lead to a conclusion that salsolinol affects the secretory activity of the GnRH/LH axis in sheep during lactation. Whether salsolinol infused into the IIIv evokes this stimulatory effect by itself or by modulation of other regulatory systems needs to be clarified.

Differential gene expression pattern in hypothalamus of chickens during fasting-induced metabolic reprogramming: functions of glucose and lipid metabolism in the feed intake of chickens.

Fasting-induced hypothalamic metabolic reprogramming is involved in regulating energy homeostasis and appetite in mammals, but this phenomenon remains unclear in poultry. In this study, the expression patterns of a panel of genes related to neuropeptides, glucose, and lipid metabolism enzymes in the hypothalamus of chickens during fasting and refeeding were characterized by microarray analysis and quantitative PCR. Results showed that 48 h of fasting upregulated (P < 0.05) the mRNA expressions of orexigenic neuropeptide Y and agouti-related protein but downregulated (P < 0.05) that of anorexigenic neuropeptide pro-opiomelanocortin; growth hormone-releasing hormone; islet amyloid polypeptide; thyroid-stimulating hormone, ß; and glycoprotein hormones, α polypeptide. After 48 h of fasting, the mRNA expression of fatty acid ß-oxidation [peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyltransferase 1A, and forkhead box O1], energy sensor protein [sirtuin 1 (SIRT1) and forkhead box O1], and glycolysis inhibitor (pyruvate dehydrogenase kinase, isozyme 4) were enhanced, but that of fatty acid synthesis and transport associated genes (acetyl-CoA carboxylase α, fatty acid synthase, apolipoprotein A-I, endothelial lipase, and fatty acid binding protein 7) were suppressed. Liver and muscle also demonstrated similar expression patterns of genes related to glucose and lipid metabolism with hypothalamus, except for that of acetyl-CoA carboxylase α, acyl-CoA synthetase long-chain family member 4, and apolipoprotein A-I. The results of intracerebroventricular (ICV) injection experiments confirmed that α-lipoic acid (ALA, pyruvate dehydrogenase kinase, isozyme 4 inhibitor, 0.10 µmol) and NADH (SIRT1 inhibitor, 0.80 µmol) significantly suppressed the appetite of chickens, whereas 2-deoxy-d-glucose (glycolytic inhibitor, 0.12 to 1.20 µmol) and NAD(+) (SIRT1 activator, 0.08 to 0.80 µmol) increased feed intake in chickens. The orexigenic effect of NAD(+) was also blocked by cotreatment with NADH. However, ICV injection of either GW7647 (PPARα agonist) or GW6471 (PPARα antagonist) showed no effects on feed intake. Results suggested that hypothalamic glycolysis (inhibited by ALA and promoted by 2-deoxy-d-glucose) and SIRT1 (inhibited by NADH and promoted by NAD(+)), not PPARα, were probably involved in feed intake regulation in chickens.

Intracerebroventricular injection of ghrelin produces hypophagia through central serotonergic mechanisms in chicken.

It has been stated that central injection of ghrelin is acting as an anorexigenic peptide in chicken. Ghrelin activity was studied through some neuronal pathways. The present study was designed in 4 experiments to examine the hypophagic response of ghrelin through the central serotonergic system in chicken. The guide cannula was surgically implanted in the right lateral ventricle of the chickens. In experiment 1, intacerebroventricular injection with PCPA (1.5 mg) performed followed by ghrelin (0.6 nmol). In experiments 2, 3 and 4 prior to ghrelin injection, chickens received fluoxetine (10 µg), 8-OH-DPAT (15.25 nmol), SB242084 (1.5 µg) respectively via guide cannula intacerebroventricularly. Cumulative food intake was determined at 3 h post injection. The results of this study showed that flouxetine pretreatment significantly amplified ghrelin hypophagia in chicken (p < 0.05). The hypophagic effect of ghrelin was attenuated by pretreatment with PCPA and SB242084 (p < 0.05) but 8-OH-DPAT had no effect. These results suggest that hypophagic effect of ghrelin probably is mediated by serotonergic mechanisms via 5-HT(2C) receptor.

The effect of melanocortin (Mc3 and Mc4) antagonists on serotonin-induced food and water intake of broiler cockerels.

The current study was designed to examine the effects of intracerebroventricular injections of SHU9119 [a nonselective melanocortin receptor (McR) antagonist] and MCL0020 (a selective McR antagonist) on the serotonin-induced eating and drinking responses of broiler cockerels deprived of food for 24 h (FD24). For Experiment 1, the chickens were intracerebroventricularly injected with 2.5, 5, and 10 µg serotonin. In Experiment 2, the chickens received 2 nmol SHU9119 before being injected with 10 µg serotonin. For Experiment 3, the chickens were given 10 µg serotonin after receiving 2 nmol MCL0020, and the level of food and water intake was determined 3 h post-injection. Results of this study showed that serotonin decreased food intake but increased water intake among the FD24 broiler cockerels and that these effects occurred in a dose-dependent manner. The inhibitory effect of serotonin on food intake was significantly attenuated by pretreatment with SHU9119 and MCL0020. However, the stimulatory effect of serotonin on water intake was not altered by this pretreatment. These results suggest that serotonin hypophagia and hyperdipsia were mediated by different mechanisms in the central nervous system, and that serotonin required downstream activation of McRs to promote hypophagia but not hyperdipsia in the FD24 chickens.

Central injection of exogenous IL-1ß in the control activities of hypothalamic-pituitary-gonadal axis in anestrous ewes.

This study was performed to determine the effect of intracerebroventricular (icv) injection of interleukin (IL)-1ß on the gene expression, translation and release of gonadotropin-releasing hormone (GnRH) and the GnRH receptor (GnRHR) gene expression in the hypothalamus of anestrous ewes. In the anterior pituitary gland (AP), the expression of genes encoding: GnRHR, ß subunits of luteinizing hormone (LH) and folliculotropic hormone (FSH) was determined as well as the effect of IL-1ß on pituitary gonadotropins release. The relative mRNA level was determined by real-time PCR, GnRH concentration in the cerebrospinal fluid (CSF) was assayed by ELISA and the plasma concentration of LH and FSH were determined by radioimmunoassay. Our results showed that icv injection of IL-1ß (10 or 50 µg/animal) decreased the GnRH mRNA level in the pre-optic area (POA) (35% and 40% respectively; p ≤ 0.01) and median eminence (ME) (75% and 70% respectively; p ≤ 0.01) and GnRHR gene expression in ME (55% and 50% respectively; p ≤ 0.01). A significant decrease in GnRHR mRNA level in the AP in the group treated with the 50 µg (60%; p ≤ 0.01) but not with the 10 µg dose was observed. The centrally administrated IL-1ß lowered also GnRH concentration in the CSF (60%; p ≤ 0.01) and reduced the intensity of GnRH translation in the POA (p ≤ 0.01). It was not found any effect of icv IL-1ß injection upon the release of LH and FSH. However, the central injection of IL-1ß strongly decreased the LHß mRNA level (41% and 50%; p ≤ 0.01; respectively) and FSHß mRNA in the case of the 50 µg dose (49%; p ≤ 0.01) in the pituitary of anestrous ewes. These results demonstrate that the central IL-1ß is an important modulator of the GnRH biosynthesis and release during immune/inflammatory challenge.

The effect of melanocortin (Mc3 and Mc4) antagonists on serotonin-induced food and water intake of broiler cockerels

The current study was designed to examine the effects of intracerebroventricular injections of SHU9119 [a nonselective melanocortin receptor (McR) antagonist] and MCL0020 (a selective McR antagonist) on the serotonin-induced eating and drinking responses of broiler cockerels deprived of food for 24 h (FD24). For Experiment 1, the chickens were intracerebroventricularly injected with 2.5, 5, and 10 microg serotonin. In Experiment 2, the chickens received 2 nmol SHU9119 before being injected with 10 microg serotonin. For Experiment 3, the chickens were given 10 microg serotonin after receiving 2 nmol MCL0020, and the level of food and water intake was determined 3 h post-injection. Results of this study showed that serotonin decreased food intake but increased water intake among the FD24 broiler cockerels and that these effects occurred in a dose-dependent manner. The inhibitory effect of serotonin on food intake was significantly attenuated by pretreatment with SHU9119 and MCL0020. However, the stimulatory effect of serotonin on water intake was not altered by this pretreatment. These results suggest that serotonin hypophagia and hyperdipsia were mediated by different mechanisms in the central nervous system, and that serotonin required downstream activation of McRs to promote hypophagia but not hyperdipsia in the FD24 chickens.

Delivery of therapeutic agents through intracerebroventricular (ICV) and intravenous (IV) injection in mice.

Despite the protective role that blood brain barrier plays in shielding the brain, it limits the access to the central nervous system (CNS) which most often results in failure of potential therapeutics designed for neurodegenerative disorders. Neurodegenerative diseases such as Spinal Muscular Atrophy (SMA), in which the lower motor neurons are affected, can benefit greatly from introducing the therapeutic agents into the CNS. The purpose of this video is to demonstrate two different injection paradigms to deliver therapeutic materials into neonatal mice soon after birth. One of these methods is injecting directly into cerebral lateral ventricles (Intracerebroventricular) which results in delivery of materials into the CNS through the cerebrospinal fluid. The second method is a temporal vein injection (intravenous) that can introduce different therapeutics into the circulatory system, leading to systemic delivery including the CNS. Widespread transduction of the CNS is achievable if an appropriate viral vector and viral serotype is utilized. Visualization and utilization of the temporal vein for injection is feasible up to postnatal day 6. However, if the delivered material is intended to reach the CNS, these injections should take place while the blood brain barrier is more permeable due to its immature status, preferably prior to postnatal day 2. The fully developed blood brain barrier greatly limits the effectiveness of intravenous delivery. Both delivery systems are simple and effective once the surgical aptitude is achieved. They do not require any extensive surgical devices and can be performed by a single person. However, these techniques are not without challenges. The small size of postnatal day 2 pups and the subsequent small target areas can make the injections difficult to perform and initially challenging to replicate.

Central role of the melanocortin-4 receptors in appetite regulation after endotoxin.

Melanocortin-4 receptors (MC4R) are key factors in the depression of appetite during disease. This study was designed to determine the role of agouti-related protein (AgRP) in the effect of endotoxin (lipopolysaccharide, LPS) on appetite. Sheep received an intracerebroventricular injection of either saline or AgRP (0.5 nmol/kg of BW) 1 h before intravenous injection of either saline or LPS (0.6 microg/kg of BW) at time 0 and again at 4 h. Agouti-related protein prevented the reduction in feed intake due to LPS (P < 0.05). In a second experiment, AgRP gene expression was unaffected at 3 h and increased (P < 0.01) at 6 h after LPS. Immunohistochemical evidence indicated that there was an increase in the percentage of AgRP neurons with c-Fos immunoreactive nuclei 6 h after sheep were injected with LPS (P < 0.04) and a corresponding decrease in a-melanocyte-stimulating hormone neurons coexpressing c-Fos (P < 0.001). In situ hybridization provided evidence for an increase in AgRP gene expression and a decrease in proopiomelanocortin gene expression 6 h after LPS (P < 0.05). In a final experiment, physiological elevation of orexigenic agents by short-term fasting kept feed intake at the same level as controls, in spite of the presence of LPS, similar to the effects of AgRP in Exp. 1. The AgRP inhibition of the MC4R prevents appetite inhibition in response to LPS and well after LPS inhibition of feed intake, both AgRP and a-melanocyte-stimulating hormone may change in a pattern that favors appetite increases. These studies support the notion of the MC4R as a critical component of the mechanism for appetite suppression due to endotoxin.

Intracerebroventricular melanin-concentrating hormone stimulates food intake in sheep.

Melanin-concentrating hormone (MCH) stimulates feeding when injected intracerebroventricularly (ICV) in rats. At present it is not clear whether the function of MCH is similar in ruminants, which are species with a continuous delivery of nutrients. Therefore the current investigation sought to determine the role of MCH in sheep. In the first experiment, six, castrate male sheep were satiated and received one of four treatments [saline, 0.1, or 1.0 nmol/kg MCH, and NPY (0.1 nmol/kg)] injected ICV over 30s, then infused ICV for 6 h ( approximately 500 microl/h). Food intake was measured for 2 h before and at 2, 4, 6, 8, 12 and 24 h. In this experiment, feed intake was increased (P

Effect of prolactin infused into the third ventricle on LH secretion in follicular-phase and ovariectomized ewes.

This study tested a hypothesis that an acute enhancement of prolactin concentration within the central nervous system (CNS) would affect the LH secretion in ewes, depending on the level of endogenous estrogens in the organism. A 3-h long intracerebroventricular (icv.) infusion of ovine prolactin was made in late follicular-phase ewes, experiment 1, and in ovariectomized (OVX) ewes (experiment 2). No significant differences were found in mean LH concentrations and LH peak number before, during and after prolactin administration (50 microg/100 microl/h) in intact cyclic ewes. No diurnal rhythm in LH was detected in prolactin-infused ewes. From the two doses of prolactin used in OVX ewes (25 and 50 microg/100 microl/h) only the lower dose suppressed significantly the mean plasma LH concentration after the infusion, compared to those noted before (P < 0.01) and during (P < 0.001) prolactin treatment. Prolactin had no effect on LH pulse frequency in OVX ewes, however, a tendency to decrease in LH peak number was observed after administration of a lower dose. Plasma prolactin levels decreased significantly (P < 0.01 and P < 0.001) after the icv. infusion in all groups, indicating a high degree of effectiveness for exogenous prolactin at the level of the CNS.

Effect of melatonin on daily LH secretion in intact and ovariectomized ewes during the breeding season.

This study was conducted to find out whether daily LH secretion in ewes may be modulated by melatonin during the breeding season, when the secretion of both hormones is raised. Patterns of plasma LH were determined in luteal-phase ewes infused intracerebroventricularly (icv.) with Ringer-Locke solution (control) and with melatonin (100 microg/100 microl/h). Response in LH secretion to melatonin was also defined in ovariectomized (OVX) ewes without and after estradiol treatment (OVX+E2). Basal LH concentrations by themselves did not differ significantly before, during and after both control and melatonin infusions in intact, luteal-phase ewes. However, single significant (P<0.05) increases in LH concentration were noted during the early dark phase in the control and 1h after start of infusion in melatonin treated ewes. In both OVX and OVX+E2 ewes, melatonin decreased significantly (P<0.01, P<0.05, respectively) mean plasma LH concentrations as compared to the levels noted before the infusions. In OVX+E2 ewes, a single significant (P<0.05) increase in LH occurred 1h after start of melatonin treatment, similarly as in luteal-phase ewes. No significant differences in the frequencies of LH pulses before, during and after melatonin infusion were found in all treatments groups. In conclusion, melatonin may exert a modulatory effect on daily LH secretion in ewes during the breeding season, stimulating the release of this gonadotropin in the presence of estradiol feedback and inhibiting it during steroid deprivation. Thus, estradiol seems to be positively linked with the action of melatonin on reproductive activity in ewes.

Brain interleukin-1 is involved in blood interleukin-6 response to immobilization stress in rats.

Interleukin (IL)-6, a cytokine for host defense responses to infection and inflammation, is known to be induced by non-invasive physical or psychological stress, too. To test possible involvement of brain IL-1 in the stress-induced IL-6 production, IL-1 mRNA expression in the hypothalamus, in parallel with blood IL-6 level, was examined in rats subjected to restriction of their movement (immobilization stress). When rats were immobilized, the hypothalamic IL-1 beta mRNA level was increased in 1 hr, followed by progressive rises in the serum IL-6 level. The immobilization-induced rise in serum IL-6 was mimicked by intracerebroventricular (icv) administration of IL-1 beta under normal conditions, whereas it was attenuated by icv injection of an IL-1 receptor antagonist. These results indicate that IL-1 in the hypothalamus plays a pivotal mediating role in the stress-induced peripheral IL-6 production.

Effect of intracerebroventricular orexin-B on food intake in sheep.

Orexin is a hypothalamic neuropeptide that regulates feeding behavior in rats. Orexin-B has recently been cloned in pigs and was shown to stimulate food intake after intramuscular injection. This study was designed to determine whether intracerebroventricular (ICV) and intravenous injections of orexin could regulate appetite in sheep. Suffolk wethers were moved to indoor facilities, adapted to diets for 6 wk, and trained to stand in stanchions for 3 to 6 h each day for 2 wk before indwelling ICV cannulas were installed. These sheep were provided water and they consumed feed ad libitum. On the day before an experiment, each sheep was cannulated in a jugular vein. On the day of an experiment, sheep were placed in stanchions and allowed to stand for 1 h before use. Sheep were then monitored over a 2-h control period before i.v. injection with saline or porcine orexin-B (3 micrograms/kg BW) or ICV injection with artificial cerebrospinal fluid (CSF), orexin (0.03, 0.3, or 3 micrograms/kg BW) or in a second experiment with either orexin B (0.03, 0.3, 3 micrograms/kg BW), neuropeptide-Y (NPY; 0.3 microgram/kg BW), or orexin plus NPY. Food intake was monitored for consecutive 2-h periods. The i.v. injections of orexin did not affect food intake or metabolite or hormone concentrations. In ICV sheep, orexin increased food intake at 2 (P < 0.04) and at 4 h (P < 0.02). Food intake was greatest with the 0.3 microgram/kg BW dosage of orexin (P < 0.05). In the first 2 h after injection, orexin had an effect similar to that of NPY (0.23 kg for orexin and 0.2 kg for NPY). The combination of NPY and orexin had a greater effect on food intake (to 0.34 kg) than did either orexin (P < 0.05) or NPY (P < 0.008) alone. Differences were not apparent in the subsequent 2-h interval. No differences were noted in free fatty acid, glucose, growth hormone, luteinizing hormone, or insulin concentrations following orexin injection. There was an effect of ICV orexin treatment on plasma cortisol concentrations (P < 0.002). Cortisol was increased by orexin at the 0- to 2-h (P < 0.008) and in the 2- to 4-h (P < 0.009) intervals after orexin injection. These data indicate that central administration of orexin stimulates feed intake in sheep.

Neuropeptide Y has a stimulatory action on feeding behavior in goldfish (Carassius auratus).

The purpose of the present study was to elucidate the possible role of neuropeptide Y (NPY) in the feeding regulation in fish. We examined the effects of intracerebroventricular (i.c.v.) or intraperitoneal (i.p.) neuropeptide Y administration on food intake in satiated goldfish, at different time intervals postinjection (0-2, 2-8 and 0-8 h). Food intake was significantly increased by i.c.v. administered neuropeptide Y (1 microg) at 2 h postinjection, while no significant differences in food intake were observed after i.p. treatment. The neuropeptide Y receptor antagonist, neuropeptide Y-(27-36), totally counteracted the stimulatory action of neuropeptide Y on feeding. The possible involvement of neuropeptide Y in the eating behavior evoked by food deprivation has been investigated. Food deprivation by either 24 or 72 h significantly increased feeding, and the neuropeptide Y receptor antagonist attenuated such feeding stimulation. From our findings, we suggest, first, that neuropeptide Y is involved in feeding central regulation in goldfish, acting via specific neuropeptide Y receptors, and second, that hypothalamic neuropeptide Y would be released in response to food deprivation, contributing to generate the consequent eating behavior stimulation in Carassius auratus.