Intracerebroventricular administration of octopamine stimulates food intake of chicks through alpha(2)-adrenoceptor

β2 adrenergic receptors and leptin interplay to decrease food intake in chicken

1. The present study was designed to examine the effects of intracerebroventricular (ICV) injection of different α and [Formula: see text] adrenergic receptor antagonists on leptin-induced hypophagia in broiler chickens.2. The study consisted of six experiments. In all experiments, chickens were deprived of feed for 3 h prior to the ICV injections and thereafter were returned immediately to the individual cages and cumulative feed intake, based on the percentage of body weight, was measured at 30, 60 and 120 min post-injection.3. In experiment 1, leptin (2.5, 5 or 10 µg) were injected in birds. In experiment 2, groups received either control solution, prazosin (10 nmol), leptin (10 µg) or a co-injection of prazosin (10 nmol) and leptin (10 µg). The other experiments were conducted as experiment 2, but instead of prazosine (10 nmol), yohimbine (13 nmol) was used in experiment 3, metoprolol (24 nmol) in experiment 4, ICI 118,551 (5 nmol) in experiment 5 and SR 59230R (5 nmol) in experiment 6 were injected either in a group or in combination with leptin (10 µg).4. The results of this study revealed a dose-dependent hypophagic effect of leptin and, in experiment 5, ICV co-injection of ICI118, 551 (5 nmol) and leptin (10 µg) significantly attenuated this effect (P˂0.5). These results suggest that the hypophagic effect of leptin is probably mediated by β2 adrenergic receptors in chickens.

Analysis of Some Biogenic Amines by Micellar Liquid Chromatography

Micellar liquid chromatography (MLC) with the use of high performance liquid chromatography (HPLC) was used to determine some physicochemical parameters of six biogenic amines: adrenaline, dopamine, octopamine, histamine, 2-phenylethylamine, and tyramine. In this paper, an influence of surfactant’s concentration and pH of the micellar mobile phase on the retention of the tested substances was examined. To determine the influence of surfactant’s concentration on the retention of the tested amines, buffered solutions (at pH 7.4) of ionic surfactant—sodium dodecyl sulfate SDS (at different concentrations) with acetonitrile as an organic modifier (0.8/0.2 v/v) were used as the micellar mobile phases. To determine the influence of pH of the micellar mobile phase on the retention, mobile phases contained buffered solutions (at different pH values) of sodium dodecyl sulfate SDS (at 0.1 M) with acetonitrile (0.8/0.2 v/v). The inverse of value of retention factor () versus concentration of micelles () relationships were examined. Other physicochemical parameters of solutes such as an association constant analyte—micelle ()—and partition coefficient of analyte between stationary phase and water (hydrophobicity descriptor) () were determined by the use of Foley’s equation.

Clonidine, octopaminergic receptor agonist, reduces protein feeding in the blow fly, Phormia regina (Meigen)

Results in this study are consistent with those of Murdock and his colleagues who clearly demonstrated that clonidine, an agonist of octopaminergic receptors in some insects, significantly increases sucrose feeding. Their studies, however, did not examine the effect of clonidine on protein feeding. Injection of a 20 microg/microl/fly dose of clonidine significantly reduces protein feeding in both sexes of Phormia regina, instead of stimulating feeding as is observed with carbohydrate feeding. The manner in which the flies are fed prior to starvation and the method of testing influences the amounts of diet consumed. It is proposed that the biogenic amines influence the state of hunger (i.e., protein versus carbohydrates) while other chemicals and neural mechanisms (i.e., such as sulfakinins and stretch receptors, respectively) affect satiety.

Influence of 5-HT1A agonist on the feeding behavior of Coturnix japonica (Galliformes: Aves)

In this study, we investigate the effect of serotonin receptor 5-HT1A stimulation on the feeding behavior of quails (Coturnix japonica). The administration of 5-HT1A agonist, 8-OH-DPAT (0.05 to 5.0 mg/Kg) dose-dependently inhibited the food intake in normally fed quails. Greater inhibition was attained with 5.0 mg/kg (0.93 ± 0.21 g vs. 5.83 ± 0.25 g, P < 0.05, 2 h after food offer). A comparable response was obtained from previously fasted quails. At end of 2 h, a higher dose of 8-OH-DPAT induced more intense hypophagy (1.59 ± 0.41 g vs. 6.85 ± 1.04 g, P < 0.0001). Previous treatment with the antagonist 5-HT1A/beta-adrenergic, propranolol, failed to block the inhibitory action of 8-OH-DPAT, but instead, intensified it (controls, 5.22 ± 1.09 g; 8-OH-DPAT, 1.41 ± 0.19 g; propranolol + 8-OH-DPAT, 0.44 ± 0.25 g, P < 0.01, for all comparisons). The administration of an isolated higher dose of propranolol induced a hypophagic action (controls, 4.5 ± 0.8 g vs. propranolol, 2.0 ± 0.2 g, P < 0.01). Current outcomes suggest a possible role of 5-HT1A receptor on the feeding behavior of quails, as opposed to mammals. On the other hand, the intensified hypophagy induced by previous administration of propranolol raises the hypothesis of a beta-adrenergic excitatory mechanism that controls the feeding behavior of quails.

Moderate weight-lowering effect of octopamine treatment in obese Zucker rats

Octopamine is proposed as a substitution product of synephrine by diverse drug industries that advertise new weight-lowering products or medicinal plants enriched in this biogenic amine. We have already reported that octopamine is able to activate in vitro lipolysis in rat adipocytes via beta3-adrenergic receptor activation, while it activates glucose uptake in human fat cells via its oxidation by amine oxidases. In this work, we tested whether a chronic challenge with octopamine could exert anti-obesity effects. A treatment consisting in daily i.p. administration of octopamine (81 micromol/kg) was compared on a four-week period with calorie restriction in the genetically obese Zucker rat. Octopamine treatment resulted in a 19% decrease in body weight gain, when compared to the 177 g gained by controls during the same period. The decrease in body weight gain was detectable only after three weeks of treatment and was apparently not due to a pronounced and sustainable anorectic effect of octopamine since: 1) cumulated food consumption was only reduced by 10%; 2) the experimental 18% reduction of food intake provoked a rapid decrease in body weight gain, significant in less than two weeks. The lipolytic responses to isoprenaline or octopamine and the stimulation of glucose transport by insulin or by the amine oxidase substrate tyramine were unmodified by the treatments. Noteworthy, the elevated plasma insulin of obese rats was lowered by octopamine. This study shows that octopamine can reduce body weight gain in obese rats, without apparent adverse effects, but with less efficacy than beta3-AR agonists.