Histamine H3 receptors contribute to drinking elicited by eating in rats

A role for endogenous histamine and its H3 receptor subtype for mediating drinking elicited by eating was examined in adult male Sprague-Dawley rats. The i.p. injection of the H3 agonist R-alpha-methylhistamine (Ramh, 2.5 mg/kg) shortened the latency to initiate drinking and increased 1-h water intake in nondeprived rats freely eating pellets and drinking water. The ICV injection (through a surgically implanted chronic cannula) of 10 micrograms Ramh increased water intake; this Ramh-induced drinking was abolished by previous ICV injection of the H3 antagonist thioperamide (Th, 60 micrograms). For rats drinking and eating after 24-h food deprivation, s.c. Th inhibited drinking behavior: for example, 10 mg/kg Th s.c. delayed the latency to initiate drinking and inhibited 1-h water intake without inhibition of food intake. In contrast, 60 micrograms Th ICV failed to inhibit food-related drinking in rats eating after food deprivation. For nondeprived rats eating a small cracker, 10 mg/kg Th s.c. delayed the latency to initiate drinking and abolished water intake without effect of eating, and 60 micrograms Th ICV had similar effects upon drinking elicited by ingestion of cracker. The IG infusion (through a surgically implanted gastric catheter) of 2 ml 600 or 900 mOsm/kg NaCl, a treatment that is subthreshold for increase in systemic plasma osmolality at the initiation of drinking, elicited drinking that was abolished by 10 mg/kg Th s.c. and attenuated by 60 micrograms Th ICV. The IG infusion of 2 ml 1800 mOsm/kg NaCl, a treatment that is above threshold for increase in systemic plasma osmolality, elicited drinking that was attenuated by 10 mg/kg s.c. or 60 micrograms Th ICV. These results demonstrate that peripheral and central H3 receptors for histamine have a role in drinking elicited by eating and the postprandial gastrointestinal osmotic consequences of eating. These findings extend the evidence demonstrating a histaminergic contribution to food-related drinking in rats.     

Instrumentation for medium-throughput two-dimensional capillary electrophoresis with laser-induced fluorescence detection

In two-dimensional capillary electrophoresis, a sample undergoes separation in the first dimension capillary by sieving electrophoresis. Fractions are periodically transferred across an interface into a second dimension capillary, where components are further resolved by micellar electrokinetic capillary electrophoresis. Previous instruments employed one pair of capillaries to analyze a single sample. We now report a multiplexed system that allows separation of five samples in parallel. Samples are injected into five first-dimension capillaries, fractions are transferred across an interface to 5 second-dimension capillaries, and analyte is detected by laser-induced fluorescence in a five-capillary sheath-flow cuvette. The instrument produces detection limits of 940 +/- 350 yoctomoles for 3-(2-furoyl)quinoline-2-carboxaldehyde labeled trypsin inhibitor in one-dimensional separation; detection limits degrade by a factor of 3.8 for two-dimensional separations. Two-dimensional capillary electrophoresis expression fingerprints were obtained from homogenates prepared from a lung cancer (A549) cell line, on the basis of capillary sieving electrophoresis (CSE) and micellar electrophoresis capillary chromatography (MECC). An average of 131 spots is resolved with signal-to-noise greater than 10. A Gaussian surface was fit to a set of 20 spots in each electropherogram. The mean spot width, expressed as standard deviation of the Gaussian function, was 2.3 +/- 0.7 transfers in the CSE dimension and 0.46 +/- 0.25 s in the MECC dimension. The standard deviation in spot position was 1.8 +/- 1.2 transfers in the CSE dimension and 0.88 +/- 0.55 s in the MECC dimension. Spot capacity was 300.     

Preabsorptive pregastric vagally mediated histaminergic component of drinking elicited by eating in the rat.

Preabsorptive stimulation by food was confined to the pregastric (oropharynx and esophagus) segment of the gastrointestinal tract by having 40 male Sprague-Dawley rats sham-feed liquid food which then drained out a gastric cannula. This procedure provided a paradigm for studying the effect of preabsorptive pregastric food-contingent stimulation on drinking behavior. Sham feeding elicited drinking that was (a) attenuated by complete bilateral subdiaphragmatic vagotomy (with hepatic branch intact), (b) attenuated by peripheral cholinergic blockade with atropine methyl nitrate (0.25 mg/kg, ip), and (c) abolished by combined antagonism of H? and H? histamine receptors with the use of ip dexbrompheniramine (1 mg/kg) and cimetidine (16 mg/kg). Results provide evidence for a preabsorptive pregastric vagally medicated histaminergic component of drinking elicited by eating in the rat. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A vagally mediated histaminergic component of food-related drinking in the rat.

Six experiments with 95 male albino Sprague-Dawley rats (1) demonstrated that exogenous histamine was a potent stimulus for drinking behavior that was dependent upon an intact abdominal vagus and (2) provided evidence for a histaminergic component of the stimulus for food-related drinking in the rat. Histamine elicited drinking in a dose-related manner typically within 5 min after sc injection in Ss. Threshold for increased drinking was 1.25 mg/kg, and 2.5 mg/kg elicited half of the maximal drinking response that followed 20 mg/kg. Bilateral subdiaphragmatic vagotomy, with the hepatic branch left intact, severely attenuated drinking in response to systemic histamine: Vagotomized Ss drank later and less than did normal Ss after doses of histamine between 1.25 and 40 mg/kg. This attenuation was attributed to the destruction of vagal afferent fibers because histamine-elicited drinking was not affected by blockade of vagal efferents with atropine methyl nitrate. Drugs antagonistic to peripheral H? histamine receptors specifically inhibited drinking in response to histamine: Cimetidine or metiamide injected ip delayed and decreased drinking after sc histamine and temporarily decreased drinking after hypovolemia produced by sc polyethylene glycol, but failed to inhibit drinking after water deprivation, cellular dehydration, or isoproterenol. Finally, cimetidine or metiamide inhibited drinking in temporal association with a meal of liquid or solid food without slowing the rate of eating or decreasing food intake. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abdominal vagotomy inhibits osmotically induced drinking in the rat.

Results of a study with 35 male Sprague-Dawley rats show that after complete bilateral transection of the abdominal vagus (Vgx-C9), with the hepatic branch left intact, Ss drank later and less than normal after cellular dehydration induced by hypertonic saline. When access to water was delayed for 1 hr after cellular dehydration, Vgx-C Ss initiated drinking quickly with normal latency, but (a) a gastric water preload was a more effective stimulus for drinking suppression in Vgx-C than in normal Ss; (b) gastric emptying of a water or phenol red solution preload was more rapid in Vgx-C than in normal Ss; and (c) when gastric emptying dysfunction in Vgx-C Ss was removed by having Ss sham drink, Vgx-C and normal Ss sham drank equivalent amounts of water. Thus, disordered preabsorptive satiety caused by abnormally rapid gastric emptying of water was a factor in the decreased drinking of Vgx-C rats after cellular dehydration. Disordered satiety for ingested water could not, however, account for the abnormal latency to initiate drinking after cellular dehydration in Vgx-C rats. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integrated membrane filters for minimizing hydrodynamic flow and filtering in microfluidic devices

Microfluidic devices have gained significant scientific interest due to the potential to develop portable, inexpensive analytical tools capable of quick analyses with low sample consumption. These qualities make microfluidic devices attractive for point-of-use measurements where traditional techniques have limited functionality. Many samples of interest in biological and environmental analysis, however, contain insoluble particles that can block microchannels, and manual filtration prior to analysis is not desirable for point-of-use applications. Similarly, some situations involve limited control of the sample volume, potentially causing unwanted hydrodynamic flow due to differential fluid heads. Here, we present the successful inclusion of track-etched polycarbonate membrane filters into the reservoirs of poly(dimethylsiloxane) capillary electrophoresis microchips. The membranes were shown to filter insoluble particles with selectivity based on the membrane pore diameter. Electrophoretic separations with membrane-containing microchips were performed on cations, anions, and amino acids and monitored using conductivity and fluorescence detection. The dependence of peak areas on head pressure in gated injection was shown to be reduced by up to 92%. Results indicate that separation performance is not hindered by the addition of membranes. Incorporating membranes into the reservoirs of microfluidic devices will allow for improved analysis of complex solutions and samples with poorly controlled volume.     

Physiology of drinking elicited by eating.

Notes that much of normal drinking occurs around mealtime and that little is known about the physiological mechanisms involved, despite the identification of neurological substrates and physiological mechanisms for drinking in response to homeostatic deficit. The present author discusses the course of ingested food along the gastrointestinal tract, where food elicits a neuroendocrine cascade of events with the potential for mobilizing drinking. This perspective helps to identify histamine, and perhaps insulin and serotonin, as serving vagally mediated mechanisms that can elicit drinking around mealtime to preclude homeostatic imbalance. The experimental study of how normal drinking behavior ensures homeostasis by precluding homeostatic imbalance has the advantage of promising to enrich, rather than to damage, the status of homeostasis as a guiding principle for understanding the neurobiology of behavior. The concept would be enriched because it would become clear that cognitive functions such as learning, remembering, and planning one's behavior at times guarantee homeostasis and therefore prevent the necessity of a rapid behavioral response to repair the physiological emergency of a homeostatic deficit. (3? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms for enhanced feeding in the cold in rats.

The effect of environmental cold upon feeding, food-motivated behavior, and gastric clearance of food was studied in 36 female Sherman rats in 4 experiments. Ss ate liquid diet in either a 5 or 22Deg. C ambient temperature (T-sub(a)) following (a) 24-hr food deprivation at T)a) of either 5 or 22Deg. C or (b) 0- or 48-hr food deprivation at T-sub(a) 22Deg. C. Ss ate more at 5 than at 22Deg. C regardless of the ambient temperature during deprivation. Ss increased feeding in the cold by increasing meal frequency but not meal size. Cold (5Deg. C) also enhanced the urge to eat. Ss barpressed for food more often in the cold on a VI 30-sec schedule when gastric clearance of food was prevented by a pyloric noose and when food cleared from the stomach normally. Quinine adulteration of food suppressed food intake only in the 22Deg. C. Cold (5Deg. C) enhanced gastric clearance of liquid food within 20 min of ingestion. Results support the view that the peripheral sensation of cold is an adequate stimulus for feeding and that cold T-sub(a) can stimulate feeding directly by increasing the urge to eat and indirectly, secondary to increased gastric clearance. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial forebrain bundle lesions: Specific loss of feeding to decreased glucose utilization in rats.

Found that bilateral destruction of the medial forebrain bundle in female Sherman rats eliminated feeding to decreased intracellular glucose utilization (glucoprivation). The deficit was specific. Feeding was enhanced by dietary dilution and reduced by dietary concentration. More was eaten in the cold and less in the heat. The Ss were not differentially sensitive to quinine adulteration. They returned to normal body weight following regimens of gavage or of restricted feeding. Moreover, they did not differ from normal Ss in drinking to various thirst stimuli. It is suggested that the glucoprivic mechanism makes but a minor contribution to the initiation of spontaneous feeding. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)