Endocannabinoid and nitric oxide interaction mediates food intake in neonatal chicken

Endocannabinoids and opiates have regulatory role in some physiological functions in mammals but their interaction(s) have not been studied in avian. This survey is designed to investigate interaction of these systems on feeding behavior in neonatal chickens. In experiment 1, chicken intracerebroventricular (ICV) injected with saline, DAMGO (µ-opioid receptors agonist, 125 pmol), SR141716A (CB1 receptors antagonist, 6.25 µg) and SR141716A + DAMGO. In experiment 2, saline, DAMGO, AM630 (CB2 receptors antagonist, 1.25 µg) and DAMGO + AM630. Experiments 3–6 followed the procedure similar to experiments 1 and 2, except DPDPE (δ-opioid receptors agonist, 40 pmol) and U-50488H (κ-opioid receptors agonist, 30 nmol) instead of DAMGO were used. In experiment 7, saline, Naloxone (opioid receptors antagonist, 5 µg), 2-AG (CB1 receptors agonist, 2 µg), Naloxone + 2-AG were used. Experiment 8 was similar to experiment 7, except CB65 (CB2 receptors agonist, 1.25 µg) used instead of 2-AG. Cumulative food intake was recorded until 120 min post injection. Data provided that, ICV injection of DAMGO decreased food intake and its effect amplified by CB1 and CB2 receptors antagonist (P 0.05). Hyperphagia-induced by CB1 and CB2 receptors agonist amplified by naloxone (P < 0.001). Perhaps there is interaction between endocannabinoid and opioidergic systems on appetite regulation in chicken.

Feeding behavior is regulated via a complex network which interacts via diverse signals from central and peripheral tissues. Endocannabinoids modulate release of GABA in a variety of regions of the central nervous system. Endocannabinoids and GABAergic system have an important role in the central regulation of appetite. Thus, the present study examines the possible interaction of central canabinoidergic and GABAergic systems on food intake in 3-h food-deprived (FD3) neonatal layer-type chicks. The results of this study showed that intracerebroventricular (ICV) injection of 2-AG (2-Arachidonoylglycerol, selective CB1 receptors agonist, 2µg) significantly increased food intake and this effect of 2-AG was attenuated by Picrotoxin (GABAA antagonist, 0.5µg) (P 0.05). Also, hyperphagic effect of CB65 (CB2 receptors agonist, 1.25µg) was not affected by Picrotoxin or CGP54626 (p>0.05). Moreover, the food intake of chicks was significantly increased by ICV injection of GABAA agonist (Gaboxadol, 0.2 µg) and SR141716A (CB1 receptors antagonist, 6.25µg) significantly decreased Gaboxadol-induced hyperphagia (P 0.05). These data showed there might be an interaction between central cannabinoidergic and GABAergic systems via CB1 and GABAA receptors in control of food intake in neonatal layer chicks.

The endocannabinoids (ECBs) have diverse physiological functions including the regulation of food intake and metabolism. In mammals, ECBs regulate feeding primarily through the CB1 receptors within the brain whereas the CB2 receptors are primarily involved in the regulation of immune function by direct action on peripheral immune cells and central glia. The central effect of ECBs on feeding behavior has not been studied in non-mammalian species. Therefore, the present study investigated the effect of CB65, a selective CB2 receptors agonist, on food intake in the neonatal chicks. In addition, the effect of astressin, a CRF receptor antagonist, on CB65-induced food intake was also investigated. Intracerebroventricular injection of the CB65 (1.25μg) increased the food intake at 30- and 60-min post-injection significantly as compared to the control group. Pretreatment with a selective CB2 receptor antagonist, AM630, but not astressin, significantly attenuated the CB65-induced food intake. These results suggested that CB2 receptor agonists act on the brain to induce food intake.

Cannabidiol inhibits the hyperphagia induced by cannabinoid-1 or serotonin-1A receptor agonists

Background: Feeding behavior is regulated via a complex network which interacts through diverse signals from central and peripheral tissues. OBJECTIVES: The main purpose of the current study was to determine the role of central cannabinoidergic (CBergic) system on ghrelin-induced hypophagia in 3-h food deprived (FD3) neonatal chicken. METHODS: In experiment 1, chicks were ICV injected with control solution, ghrelin (0.6 nmol), SR141716A (selective CB1 receptors antagonist, 6.25 µg) and ghrelin + SR141716A. In experiment 2, chickens received ICV injection of (A) control solution, ghrelin (0.6 nmol), AM630 (selective CB2 receptors antagonist, 1.25 µg) and ghrelin + AM630. In experiment 3, chickens were ICV injected with control solution, 2-AG (selective CB1 receptors agonist, 2µg), GSK1614343 (selective ghrelin receptors antagonist, 6 nmol) and 2-AG + GSK1614343. In experiment 4, the birds received control solution, CB65 (selective CB2 receptors agonist, 6.25 µg), CB65 + GSK1614343. Then the cumulative food intake was measured until 120 min post injection. RESULTS: According to the results, ICV injection of the ghrelin, significantly decreased cumulative food intake (P<0.05). Co-injection of the ghrelin + SR141716A and/or ghrelin + AM630 significantly amplified ghrelin-induced hypophagia compared to control group (P<0.05). Hyperphagia observed by ICV injection of the 2-AG (2 µg) (P<0.05). Co-injection of the 2-AG + GSK1614343 increased food intake compared to control group (P<0.05). ICV injection of the CB65 (1.25 µg) significantly increased food intake (P<0.05). Also, co-injection of the CB65 + GSK1614343 significantly amplified cumulative food intake in FD3 neonatal layer-type chicken (P<0.05). CONCLUSIONS: These results suggested ghrelin-induced hypophagia mediates via CB1 and CB2 receptors in neonatal layer-type chicken

The present study aimed to identify the role of dopaminergic and cannabinoidergic systems in the ghrelin-induced hypophagia among meat-type chickens. In the first experiment, intracerebroventricular (ICV) injection was applied to birds with control solution, D1 receptor antagonist (5 nmol), ghrelin (6 nmol), and D1 receptor antagonist plus ghrelin. The second to sixth experiments were similar to the first one, with the difference that D2 receptor antagonist (5 nmol), D3 receptor antagonist (6.4 nmol), D4 receptor antagonist (6 nmol), the precursor of dopamine (125 nmol), and 6-hydroxy dopamine (150 nmol) instead of D1 antagonist were injected into the broiler chickens. In experiment 7, control solution and different levels of ghrelin antagonists (5, 10, and 20 nmol) were injected. In experiment 8, the chickens were ICV injected with control solution, ghrelin antagonist (10 nmol), dopamine (40 nmol), and ghrelin antagonist plus dopamine. In experiments 9 and 10, CB1 and CB2 receptors antagonist (6.25µg and 5µg) were co-injected with ghrelin (6 nmol), respectively, measuring the food intake for 120 min after the injection. It was observed that ghrelin ICV injection considerably reduced food intake, whereas ghrelin antagonist increased food intake, depending on the dose (P<0.05). In addition, ghrelin-induced hypophagia was significantly attenuated by D1 receptor antagonist and 6-hydroxy dopamine (P<0.05), while the dopamine precursor considerably elevated the ghrelin-induced food intake (P<0.05). The dopamine-induced feeding behavior was diminished by the co-administration of [D-Lys-3]-GHRP-6 (10 nmol)+dopamine (40 nmol) (P<0.05). In addition, CB1 receptor antagonists enhanced the ghrelin influence on food intake (P<0.05). The results implied that the hypophagic impact of ghrelin was probably mediated by D1 and CB1 receptors within neonatal broilers.

The current study was designed to evaluate the effects of central administration of L-arginine (The precursor of nitric oxide), N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, selective opioid receptor agonists and involvement of central nitrergic/opioidergic systems on feeding behavior in neonatal layer-type chicks. The results of this study showed that the intracerebroventricular (ICV) injection of L-arginine (400 and 800 nmol) significantly decreased food intake (P < 0.001) but the injection of 200 nmol L-arginine had no effect on cumulative food intake in FD3 chickens (P > 0.05). The ICV injection of L-NAME (200 and 400 nmol) increased food intake (P < 0.001) but 100 nmol of L-NAME had no significant effect (P > 0.05). On the other hand, the co-injection of 100 nmol L-NAME significantly attenuated the anorexigenic effect of 800 nmol L-arginine (P < 0.001). Moreover, the food intake of chicks was significantly decreased by ICV injection of DAMGO (μ-opioid receptor agonist, 125 pmol) (P < 0.001) while both DPDPE (δ-opioid receptor agonist, 40 pmol) and U-50488H (κ-opioid receptor agonist, 30 nmol) significantly stimulated food intake (P < 0.001). In addition, the hypophagic effect of DAMGO was significantly amplified by administration of L-arginine (P < 0.001) while the administration of L-NAME attenuated the hypophagic effect of DAMGO (P < 0.001). In contrast, co-injection of L-arginine or L-NAME with DPDPE had no effect on the hyperphagia induced by DPDPE as well as the hyperphagic effect of U-50488H on food intake was not affected by concurrent injection of L-arginine or L-NAME (P > 0.05). These results suggest that nitrergic and opioidergic systems have an important role on feeding behavior in the CNS of neonatal layer-type chicks and it seems that interaction between them is mediated by μ-opioid receptor.

Effects of Se-phenyl thiazolidine-4-carboselenoate on mechanical and thermal hyperalgesia in brachial plexus avulsion in mice: Mediation by cannabinoid CB1 and CB2 receptors

Central dopaminergic (DAergic) and adrenergic systems have a prominent role in appetite regulation; however, their interaction(s) have not been studied in neonatal layer chickens.Therefore, the current study aimed to determine the interaction of central DAergic and noradrenergic systems in food intake regulation in neonatal layer chickens. In the first experiment, chickens received the intracerebroventricular (ICV) injection of a control solution, prazosin (i.e., &amp;alpha;1 adrenergic receptor antagonist; 10 nmol), dopamine (DA; 40 nmol), and prazosin plus DA. The second to fifth experiments were similar to the first experiment except that the birds were injected with yohimbine (i.e., &amp;alpha;2 receptor antagonist; 13 nmol), metoprolol (i.e., &amp;beta;1 adrenergic receptor antagonist; 24 nmol), ICI 118,551 (i.e., &amp;beta;2 adrenergic receptor antagonist; 5 nmol), and SR59230R (i.e., &amp;beta;3 adrenergic receptor antagonist; 20 nmol) instead of prazosin. In the sixth experiment, the chickens received ICV injection with the control solution and noradrenaline (NA; 75, 150, and 300 nmol). In the seventh experiment, the birds were injected with the control solution, SCH23390 (i.e., D1 DAergic receptor antagonist; 5 nmol), NA (300 nmol), and SCH23390 plus NA In the eighth experiment, the control solution, AMI-193 (i.e., D2 DAergic receptor antagonist; 5 nmol), NA (300 nmol), and AMI-193 plus NA were injected. Then, cumulative food intake was recorded at 30, 60, and 120 min after the injection. According to the obtained results, the ICV injection of DA (40 nmol) significantly decreased food intake in comparison to that reported for the control group (p &amp;lt;0.05). The co-injection of yohimbine plus DA significantly amplified DA-induced hypophagia in the neonatal chickens (p &amp;lt;0.05). In addition, the co-administration of ICI 118,551 plus DA significantly inhibited the hypophagic effect of DA in the neonatal chickens (p &amp;lt;0.05). Furthermore, NA (75, 150, and 300 nmol) significantly reduced food intake in a dose-dependent manner (p &amp;lt;0.05). The co-injection of SCH23390 plus NA decreased the hypophagic effect of NA in the neonatal chickens, compared to that reported for the control group (p &amp;lt;0.05). The co-injection of AMI-193 plus NA diminished NA-induced hypophagia, compared to that reported for the control group (p &amp;lt;0.05). The aforementioned results suggested that there is an interconnection between central DAergic and noradrenergic systems through &amp;alpha;2/&amp;beta;2 adrenergic and D1/D2 DAergic receptors in food intake regulation in neonatal chicks.

Central regulatory mechanisms for neurotransmitters of food intake vary among animals. Endocannabinoids have crucial role on central food intake regulation in mammals but its role has not been studied in layer-type chicken. Thus, in this study 6 experiments designed to evaluate effects of intracerebroventricular (ICV) administration of 2-AG (2-Arachidonoylglycerol, selective CB1 receptors agonist), SR141716A (selective CB1 receptors antagonist), JWH015 (selective CB2 receptors agonist), AM630 (selective CB2 receptors antagonist) on feeding behavior in 3 h food deprived neonatal layer-type chickens. In experiment 1, birds ICV injected with control solution and 2-AG (0.25, 0.5 and 1 μg). In experiment 2: control solution, SR141716A (6.25, 12.5 and 25 μg) were ICV injected to birds. In experiment 3 animals received: control solution, SR141716A (6.25 μg), 2-AG (1 μg) and co-injection of SR141716A+2-AG. In experiment 4, chickens received control solution and JWH015 (6.25, 12.5 and 25 μg). In experiment 5, control solution and AM630 (1.25, 2.5 and 5 μg) were injected. In experiment 6, the birds received control solution, AM630 (1.25 μg), JWH015 (25 μg) and co-administration of AM630+JWH015. Then, cumulative food intake was recorded until 120 min after injection. According to the results, 2-AG dose dependently increased cumulative food intake while SR141716A reduced appetite compared to control group (P < 0.05). Injection of 2-AG (1 μg) amplified food intake and its effect minimized by SR141716A (6.25 μg) (P < 0.05). Also, ICV injection of JWH015 (25 μg) dose dependently increased food intake and co-injection of JWH015+AM630 decreased JWH015-induced food intake (P < 0.05). These results suggest CB1 and CB2 receptors have an important role on ingestive behavior in FD3 neonatal layer-type chicken.

Endocannabinoids are critically involved in brain reward functions, mediated by activation of CB1 receptors, reflecting their high density in the brain. However, the recent discovery of CB2 receptors in the brain, particularly in the midbrain dopamine neurons, has challenged this view and inspired us to re-examine the roles of both CB1 and CB2 receptors in the effects of cannabis. In the present study, we used the electrical intracranial self-stimulation paradigm to evaluate the effects of various cannabinoid drugs on brain reward in laboratory rats and the roles of CB1 and CB2 receptors activation in brain reward function(s). Two mixed CB1 / CB2 receptor agonists, Δ9 -tetrahydrocannabinol (Δ9 -THC) and WIN55,212-2, produced biphasic effects-mild enhancement of brain-stimulation reward (BSR) at low doses but inhibition at higher doses. Pretreatment with a CB1 receptor antagonist (AM251) attenuated the low dose-enhanced BSR, while a CB2 receptor antagonist (AM630) attenuated high dose-inhibited BSR. To confirm these opposing effects, rats were treated with selective CB1 and CB2 receptor agonists. These compounds produced significant BSR enhancement and inhibition, respectively. CB1 receptor activation produced reinforcing effects, whereas CB2 receptor activation was aversive. The subjective effects of cannabis depend on the balance of these opposing effects. These findings not only explain previous conflicting results in animal models of addiction but also explain why cannabis can be either rewarding or aversive in humans, as expression of CB1 and CB2 receptors may differ in the brains of different subjects.

Effect of intracerebroventricular (ICV) injection of antimicrobial peptide expressed in the body-2 (LEAP-2) and its interaction with cannabinoid and ghrelin systems on food intake in broiler chickens.

Evidence from animal studies suggests that endogenous nitric oxide and dopamine (DA) have a regulatory role in the rewarding system, but their interaction(s) have not been studied in avian species. In this study, 4 experiments were performed to determine the effects of central administration of L-arginine (nitric oxide precursor; 200 nmol), NG-nitro-L-arginine methyl ester (L-NAME, a nitric oxide synthase inhibitor; 100 nmol), amphetamine (an indirect DA agonist; 125 pmol) and DA (40 pmol) on feeding behavior in neonatal layer-type chickens (each experiment included 4 groups, n=12 birds in each group). Prior to the initiation of the treatments, birds were fasted for 3 hours (FD3). In experiment 1, chickens received intracerebroventricular (ICV) injection of saline, L-NAME (100 nmol), amphetamine (125 pmol), and combination of L-NAME + amphetamine. In experiment 2, chickens received the ICV injection of saline, L-arginine (200 nmol), amphetamine (125 pmol) and their combination. In experiment 3, chickens received ICV injection of saline, L-arginine (200 nmol), DA (40 pmol) and L-arginine + DA. In experiment 4, chickens received ICV injection of saline, L-NAME (100 nmol), DA (40 pmol) and L-NAME + DA. Thereafter, the cumulative food intake (on the basis of metabolic body weight) was recorded until 2-h post injection. The results showed that ICV injection of amphetamine or DA significantly decreased food intake (P&lt;0.05). Also, co-administration of L-NAME + amphetamine attenuated the hypophagic effect of amphetamine (P&lt;0.05), while combined administration of L-NAME and DA had no effect on DA-induced hypophagia. Additionally, the hypophagic effect of amphetamine was significantly amplified by L-arginine (P&lt;0.05), but the combination of L-arginine and DA did not alter feeding behavior which was induced by DA. These results suggest an interaction between DAergic and nitrergic systems via a presynaptic mechanism on food intake regulation in layer-type chicken.

This review gives a brief overview of the expression patterns, molecular pharmacology and physiological role of the cannabinoid 2 receptor (CB2) in pain. Particular emphasis is given to the therapeutic utility of CB2 receptor agonists. Through studies utilizing selective CB2 receptor agonists, non-selective cannabinoid agonists in conjunction with selective CB1 and CB2 receptor antagonists, or CB2 receptor knockout mice, it is now clear that this receptor plays a critical role in nociception. To this end, CB2 receptors have been shown to modulate acute pain, chronic inflammatory pain, post-surgical pain, cancer pain and pain associated with nerve injury. Here we review these studies and the compounds that were utilized. We hypothesize the mechanism of action by which the CB2 receptor could be involved in these processes. Finally we summarize the most recent novel chemical scaffolds that are being investigated towards advancing selective CB2 receptor agonists into the clinic. Many new pharmacological agents have been identified by high throughput screening and small molecule lead discovery and optimization in the past 10 years. It is anticipated that at least some of these agents may ultimately constitute effective new pain therapeutics that lack the side effects associated with traditional cannabinoid ligands.

Nowadays inquiry of possible interplay between different neurotransmitters in brain function is one of the major fields of interest for researchers. In the current study, we aimed to survey interaction between glutamatergic and nitrergic systems on food intake in layers. In this regards, total of 308 one-day-old female layer-type chicks divided to 28 groups of 11 individuals in 7 defined experiments. All chickens were kept 3 h food deprived and used for intracerebroventricular (ICV) injection in the 5 day olds. In experiments 1–5, treatment groups received ICV injection of 10 µl control solution, l-arginine (precursor of NO synthesis; 800 nmol). In addition, birds administrated by different antagonists of glutamatergic receptors including MK-801 (NMDA receptor antagonist; 15 nmol), CNQX (AMPA/kainate receptor antagonist; 390 nmol), AIDA (mGLUR1 glutamate receptor antagonist; 2 nmol), LY341495 (mGLUR2 glutamate receptor antagonist; 150 nmol), UBP1112 (mGLUR3 glutamate receptor antagonist; 2 nmol) besides combination of mentioned antagonists of glutamatergic receptors + l-arginine (800 nmol). In the experiment 6, groups injected by control solution, glutamate (300 nmol), l-NAME (100 nmol) besides combination of both drugs. In the experiment 7, birds were ICV injected by control solution, glutamate (75 nmol), l-arginine (200 nmol) and combination of glutamate + l-arginine. Then cumulative food intake measured as following a known amount of a diet was given to the animals after 30, 60 and 120 min post injection. Based on the results, administration of MK-801 (15 nmol) significantly attenuated hypophagic effect induced by l-arginine (800 nmol) in neonatal chicks (P 0.05). Furthermore, co-administration of sub-effective doses of glutamate with l-arginine made significant hypophagic effect in comparison with control group and any of treatment group, which received sole glutamate or only l-arginine (P < 0.05). As a conclusion, it seems central glutamatergic system is modulating hypophagic effect induced by nitrergic system through NMDA receptor in neonatal layer chicks. Apparently, l-arginine and glutamate neurotransmitters showed synergistic effect on regulating food intake in layers.