In the present study, we investigated the ability of a recently introduced non‐xanthine A2A receptor antagonist, ZM241385 (4‐(2‐[7‐amino‐2‐(2‐furyl{1,2,4}‐triazolo{2,3‐a{1,3,5}triazin‐5‐yl‐aminoethyl)phenol) to displace binding of the prototypical A2A adenosine receptor agonist [3H]CGS21680 (2‐[4‐(2‐p‐carboxyethyl)phenylamino]‐5′‐N‐ethylcarboxamidoadenosine) and to modify the facilitatory responses caused by the A2A selective agonists, CGS21680 and HENECA (2‐hexynl‐5′‐N‐ethylcarboxamidoadenosine) in rat hippocampal preparations. ZM241385 was nearly equipotent to displace [3H]CGS21680 (30 nM) binding to hippocampal (Ki of 0.52 nM) and to striatal membranes (Ki of 0.35 nM), whereas HENECA was a more potent displacer of [3H]CGS21680 binding to striatal (Ki of 4.5 nM) than to hippocampal membranes (Ki of 19 nM). HENECA (3–30 nM) was equipotent with CGS21680 to facilitate veratridine‐evoked [3H]acetylcholine release from superfused hippocampal synaptosomes and ZM241385 (20 nM) inhibited the facilitatory effects of both HENECA (30 nM) and CGS21680 (30 nM); this antagonism was mimicked by CSC (250 nM). In contrast, CGS21680 (10–30 nM) was more potent than HENECA (10–30 nM) to facilitate synaptic transmission in Schaffer fibres/CA1 pyramid synapses of hippocampal slices and the facilitatory effect of CGS21680 (10 nM) was blocked by ZM241385 (20 nM) whereas CSC (250 nM) caused a 40% attenuation of this CGS21680‐induced facilitation. These results indicate that ZM241385 is the first A2A antagonist with equal potency to displace [3H]CGS21680 binding to striatal and limbic regions, and with general efficiency to antagonize HENECA‐ or CGS21680‐mediated facilitatory responses in the hippocampus.

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The effect of guanine nucleotide-binding protein (G protein) modifiers on the binding of the adenosine A2A receptor agonist 2-[4-(2-p-carboxyethyl[3H])phenyl-amino]-5'-N-ethylcarboxamidoadenosine ([3H]CGS 21680) and of the adenosine A1 receptor agonist [3H]R-phenylisopropyladenosine ([3H]R-PIA) to rat cortical and striatal membranes was studied. Guanosine 5'-(beta,gamma-imido)triphosphate (1-300 microM), which uncouples all G proteins, more effectively inhibited [3H]CGS 21680 (30 nM) binding in the cortex than [3H]R-PIA (2 nM) binding to cortical or striatal membranes or [3H]CGS 21680 (30 nM) binding in the striatum. N-Ethylmaleimide (1-300 microM) or pertussis toxin (1-100 microg/ml), which uncouple G(i)/G(o) protein-coupled receptors, more effectively inhibited [3H]R-PIA binding to cortical or striatal membranes and [3H]CGS 21680 binding in the cortex than [3H]CGS 21680 binding in the striatum. Cholera toxin (2.5-250 microg/ml), which uncouples G(S) protein-coupled receptors, more effectively inhibited [3H]CGS 21680 binding in the striatum than [3H]CGS 21680 binding in the cortex and less effectively inhibited [3H]R-PIA binding to cortical or striatal membranes. Treatment of solubilised cortical membranes with pertussis toxin (50 microg/ml) decreased [3H]CGS 21680 (30-100 nM) binding which almost fully recovered after reconstitution with G(i)/G(o) proteins. The K(i) for displacement of [2-3H]-(4{2-[7-amino-2-(2-furyl)(1,2,4)triazolo(2,3-a)(1,3,5)triazin+ ++-5-ylamino]ethyl}phenol) ([3H]ZM 241385, 1nM) by CGS 21680 was 110 nM (95%CI: 98-122 nM) in non-treated, 230 (167-292) nM in pertussis toxin (25 microg/ml)-treated and 222 (150-295) nM in cholera toxin (50 microg/ml)-treated cortical membranes; in contrast, the K(i) for displacement of [3H]-5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo(4,3-e)-1,2,4-triazol o(1,5-c)pyrimidine ([3H]SCH 58261, 1 nM) by CGS 21680 was 74 (57-91) nM in non-treated, 71 (44-100) nM in pertussis toxin-treated and 147 (100-193) nM in cholera toxin-treated cortical membranes. Finally, CGS 21680 displaced monophasically the binding of the A1 antagonist, [3H]8-cyclopentyl-1,3-dipropylxanthine (2 nM), and the A1 agonist, [3H]R-PIA (2 nM), in 2 or 10 mM Mg(2+)-medium, either at 25 degrees C or 37 degrees C, in cortical or striatal membranes. These results indicate that CGS 21680 does not bind to A1 receptors and that limbic CGS 21680 binding sites differ from striatal-like A2A receptors since they couple to G(i)/G(o) proteins, as well as to G(s) proteins.

SummaryLevels of blood coagulation factors, cholesterol and triglyceride were measured in human plasma. Prothrombin was significantly elevated in type Ha hyperlipidaemia; prothrombin and factors VII, IX and X in type lib; and prothrombin and factors VII and IX in type V. Multiple regression analysis showed significant correlation between the levels of these plasma lipids and the vitamin K-dependent clotting factors (prothrombin, factors VII, IX and X). Higher cholesterol levels were associated with higher levels of prothrombin and factor X while higher triglyceride levels were associated with higher levels of these as well as factors VII and IX. Prothrombin showed a significant cholesterol-triglyceride interaction in that higher cholesterol levels were associated with higher prothrombin levels at all levels of triglyceride, with the most marked effects in subjects with higher triglyceride levels. Higher prothrombin levels were noted in subjects with high or moderately elevated (but not low) cholesterol levels. Ultracentrifugation of plasma in a density of 1.21 showed activity for prothrombin and factors VII and X only in the lipoprotein-free subnatant fraction. Thus, a true increase in clotting factor protein was probably present. The significance of the correlation between levels of vitamin K-dependent clotting factors and plasma lipids remains to be determined.

Unsaturated free fatty acids and adenosine operate two neuromodulatory systems with opposite effects on neuronal function. Here, we tested if fatty acids controlled inhibitory adenosine A 1 receptors. Arachidonate (AA, 10 mm) decreased the B max of an A 1 receptor agonist, (R) 3 H]PIA (from 1.20 to 0.57 nm) binding to brain membranes of young adult rats (2 months old), these effects being mimicked by other cis but not trans unsaturated or saturated fatty acids. AA (10 mm) increased the potency of the A 1 receptor agonist, 2-chloroadenosine to inhibit hippocampal synaptic transmission in young adult rats (EC 50 decreased from 337 to 237 nm), which may constitute a safety feedback mechanism to control AA-induced neurotoxicity. Upon aging, there were increased free fatty acid levels and a concomitant decreased density of A 1 receptors. This was more marked in hippocampal nerve terminals of aged rats (24 months old) and may be the determinant factor contributing to the lower potency of 2-choloroadenosine in aged rats (EC 50 955 nm), in spite of the decreased K d of PIA binding upon aging. The effects of AA on A 1 receptor binding were attenuated upon aging, AA being devoid of effects in aged rats. Accordingly, AA (10 mm) failed to modify the potency of 2-choloroadenosine in aged rats (EC 50 997 nm). However, albumin, which quenches free fatty acids, increased A 1 receptor density by 65% and 2-chloroadenosine potency (EC 50 703 nm) in aged rats, suggesting that the increased fatty acids levels in aged rats may contribute to the decreased potency of A 1 receptor agonists in aged rats. Also, the observed saturation of the control by AA of A 1 receptors may contribute to the decreased adaptability of neuromodulation to different firing conditions in aged rats.-Keywords: adenosine; A 1 receptors; arachidonic acid; hippocampus; synaptic transmission.Adenosine is a neuromodulator, mainly inhibiting synaptic transmission through activation of adenosine A 1 receptors in nerve terminals, as well as a neuroprotective signal generated upon metabolic imbalance and acting as a transcellular messenger to decrease neuronal metabolism mostly through activation of nonsynaptic A 1 receptors (reviewed in [1]). These inhibitory A 1 receptors tonically inhibit synaptic transmission and synaptic plasticity phenomena [2] and control physiological processes such as learning and memory [3] as well as pathological processes such as epilepsy [4] or neuronal cell death [5]. The functioning of this neuromodulatory/neuroprotective system is controlled by the formation of extracellular adenosine but is also fine-tuned by regulation of A 1 receptor efficiency through direct receptor phosphorylation [6,7] and also indirectly through modification of the membrane structure or lipid environment of the receptor [8±10].Another trans-cellular neuromodulatory system, operated by unsaturated free fatty acids, namely by arachidonic acid (AA), also controls physiological processes such as synaptic plasticity [11] as well as pathological processes such as epil...

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The effect of commercial beverages on satiety and short‐term food intake (FI) has received little investigation in girls. The purpose of this study was to determine the effect of commonly consumed sugars‐containing beverages on FI regulation in normal weight (NW) (n=12; 15–85th BMI percentile) and overweight (OW)/obese (OB) girls (n=11; >;85th BMI percentile). On 4 separate mornings and in random order, girls (n=23) received 350 ml of either a fruit drink, carbonated cola, 1% chocolate milk or a water control 2 h after a standardized breakfast of milk, cereal, and orange juice. FI (mean kcal ± SEM) from an ad libitum pizza meal was measured 60 min later. Only 1% chocolate milk decreased FI (746 ± 64) compared with the water control (935 ± 64; P<0.001) in NW girls, but none of the beverages decreased FI in OW/OB girls. In the pooled sample (n=23), FI was decreased by carbonated cola and 1% chocolate milk compared with the water control, but the fruit drink failed to result in a statistically significant decrease in FI. Caloric compensation scores for the fruit drink, cola, and 1% chocolate milk were 76%, 80%, and 86% in NW, and 45%, 74%, and 59% in OW/OB girls, respectively. Prospective food consumption (P<0.05) and desire‐to‐eat (P<0.05) scores, when corrected for the energy content of the beverages, were lowest after 1% chocolate milk compared to both cola and fruit drink, and cola, respectively. In conclusion, the effect of sugars‐containing beverages on short‐term FI in girls was dependent on the interaction between macronutrient composition and body weight status.

We previously reported decreased food intake (FI) after a glucose drink and 30 min of video game playing (VGP) in normal weight boys, but the effect on FI in boys with increased adiposity is unknown. Therefore, we examined the effect of 30 min of pre‐meal VGP on subjective appetite, emotions and FI in overweight/obese (>85th BMI percentile) boys after a glucose drink. On four mornings, in random order and one‐week apart, boys (n = 22; age = 11.9 ± 0.3 y) consumed equally sweetened drinks (250 mL) of sucralose (0 kcal) or 50 g (200 kcal) glucose, with or without 30 min of subsequent VGP, 2 h after a standardized breakfast. Immediately after all test conditions FI (mean ± SEM kcal) from an ad libitum pizza meal was measured. Subjective appetite was measured at baseline (0 min), 20, 35, and 65 min (post‐meal). While glucose (p < 0.01) decreased FI (∆ = ‐103 ± 48 kcal) compared with the sucralose control, cumulative FI (drink kcal + meal kcal) was higher (p < 0.01). Fullness (p < 0.05) was lower, and subjective aggressiveness (p < 0.01), excitement (p < 0.01), upset (p = 0.05), and frustration (p < 0.05) higher after VGP; however, subjective emotions did not correlate with FI. In conclusion, the stronger effect of glucose compared with VGP on FI is indicative of the primary role of physiologic factors in the short‐term regulation of FI in overweight/obese boys. Grant Funding Source: Supported by The Danone Institute of Canada, Grant‐in‐aid program