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Aims: To characterise the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of single ascending doses of oxathridine, a first‐in‐class histamine‐3 receptor partialagonist, in healthy male volunteers. Methods: A randomised, double‐blind, placebo‐controlled study including the NeuroCart, consisting of a battery of drug sensitive neurophysiological tests, was performed. Oxathridine was administered orally as an aqueous solution. After dosing, safety and NeuroCart tests (adaptive tracking [AT], body sway [BS], saccadic peak velocity [SPV], smooth pursuit [SP] eye movements, VAS according to Bond and Lader, VAS according to Bowdle [VAS B&L, Bowdle], pharmaco‐electroencephalogram [pEEG], Sustained Attention to Response Task [SART]) were performed at set times. Results: Forty volunteers completed the study. Given doses were: 0.5, 2.5, 5, 0.25 and 1.5 mg. At 5 mg, unacceptable and unanticipated adverse events (AEs) of (orthostatic) hypotension and pseudo‐hallucinations were reported. Statistically significant effects ([CI]; p‐value) of 2.5 mg and 5 mg oxathridine were observed on AT ([−8.28, −1.60]; p = 0.0048), ([−8.10, −1.51]; p = 0.00530), BS ([0.6, 80.2]; p = 0.0455), ([5.9, 93.1]; p = 0.0205) and SPV ([−59.0, −15.9]; p = 0.0011), ([−43.9, −1.09]; p = 0.0399), respectively. Oxathridine 5 mg significantly increased all three VAS Bowdle subscale scores; VAS external ([0.183, 0.476]; p = <.0001), VAS internal ([0.127, 0.370]; p = 0.0001) and VAS feeling high ([0.263, 0.887]; p = 0.0006). Conclusion: NeuroCart tests indicated central nervous system (CNS) depressant effects. Oxathridine also unexpectedly caused pseudohallucinations. Although this led to the decision to stop further development of oxathridine, these observations suggest that the H3R system could be an interesting new target for the development of novel antipsychotics. [ABSTRACT FROM AUTHOR]

Anandamide (N-arachidonoyl-ethanolamine) was recently identified as a brain arachidonate derivative that binds to and activates cannabinoid receptors, yet the mechanisms underlying formation, release and inactivation of this putative messenger molecule are still unclear. Here we report that anandamide is produced in and released from cultured brain neurons in a calcium ion-dependent manner when the neurons are stimulated with membrane-depolarizing agents. Anandamide formation occurs through phosphodiesterase-mediated cleavage of a novel phospholipid precursor, N-arachidonoyl-phosphatidylethanolamine. A similar mechanism also governs the formation of a family of anandamide congeners, whose possible roles in neuronal signalling remain unknown. Our results and those of others indicate therefore that multiple biochemical pathways may participate in anandamide formation in brain tissue. The life span of extracellular anandamide is limited by a rapid and selective process of cellular uptake, which is accompanied by hydrolytic degradation to ethanolamine and arachidonate. Our results thus strongly support the proposed role of anandamide as an endogenous neuronal messenger.

Understanding the actions of the neurotransmitter dopamine in the brain is important in view of its roles in neuropsychiatric illnesses. Dopamine D1 receptors, which stimulate both adenylyl cyclase and phospholipase C, and D2 receptors, which inhibit them, can nevertheless act synergistically to produce many electrophysiological and behavioral responses. Because this functional synergism can occur at the level of single neurons, another, as yet unidentified, signalling pathway activated by dopamine has been hypothesized. We report here that in Chinese hamster ovary (CHO) cells transfected with the D2 receptor complementary DNA, D2 agonists potently enhanced arachidonic acid release, provided that such release has been initiated by stimulating constitutive purinergic receptors or by increasing intracellular Ca2+. In CHO cells expressed D1 receptors, D1 agonists exert no such effect. When D1 and D2 receptors are coexpressed, however, activation of both subtypes results in a marked synergistic potentiation of arachidonic acid release. The numerous actions of arachidonic acid and its metabolites in neuronal signal transduction suggest that facilitation of its release may be implicated in dopaminergic responses, such as feedback inhibition mediated by D2 autoreceptors, and may constitute a molecular basis for D1/D2 receptor synergism.

Aims: Anaphylaxis guidelines recommend intramuscular adrenaline, commonly 300 μg administered using an auto‐injector device. However, overweight/obese patients may require a higher adrenaline dose for adequate cardiovascular (CV) response. This study evaluated the pharmacokinetics (PK) and pharmacodynamic (PD) CV profiles after a single 500 μg adrenaline injection via Anapen auto‐injector in healthy normal weight males and otherwise healthy, overweight or obese females. Methods: In this exploratory open‐label, single‐centre study, 54 healthy volunteers aged 18‐50 years received a single 500 μg adrenaline injection (Anapen auto‐injector) in the thigh (antero‐lateral middle third [18 males] or antero‐inferior third [36 females]). Assessments included depot depth (ultrasonography), plasma adrenaline levels (liquid chromatography‐tandem mass spectrometry) and heart rate (HR; ECG Holter monitor). Results: Ultrasonography showed that 82.4% of normal weight males received intramuscular injections; all overweight and obese females received subcutaneous injections. Anapen injection produced rapid increases in circulating adrenaline levels and significant increases in systolic blood pressure (SBP) and HR. Second peak plasma adrenaline concentrations (Cmax2) were reduced, and time to Cmax2 increased in overweight and obese females compared with males with normal body mass index; area under the curve (0–240 min) (AUC(0‐240)) was increased in overweight and obese females. Obese females had reduced maximal SBP values compared with normal weight males or overweight females; overweight and obese females had markedly different HR time courses compared with normal weight males. Conclusion: A 500 μg adrenaline injection via Anapen produced rapid PK/PD changes in normal weight, overweight and obese subjects, irrespective of intramuscular or subcutaneous injection, and was well tolerated. [ABSTRACT FROM AUTHOR]

G protein-coupled receptors (GPCRs) are allosteric proteins that adopt inactive (R) and active ([R.sup.*]) conformations in equilibrium. [R.sup.*] is promoted by agonists or occurs spontaneously, leading to constitutive activity of the receptor. Conversely, inverse agonists promote R and decrease constitutive activity. The existence of another pharmacological entity, referred to as 'protean' agonists (after Proteus, the Greek god who could change shape), was assumed on theoretical grounds. It was predicted from the existence of constitutive activity that a same ligand of this class could act either as an agonist or an inverse agonist at the same GPCR. Here, we show that proxyfan, a high-affinity histamine [H.sub.3]-receptor ligand, acts as a protean agonist at recombinant [H.sub.3] receptors expressed in the same Chinese hamster ovary cells. In support of the physiological relevance of the process, we show that proxyfan also behaves as a protean agonist at native [H.sub.3] receptors known to display constitutive activity. On neurochemical and behavioral responses in rodents and cats, proxyfan displays a spectrum of activity ranging from full agonism to full inverse agonism. Thus, protean agonism demonstrates the existence of ligand-directed active states L[R.sup.*] different from, and competing with, constitutively active states [R.sup.*] of GPCRs, and defines a pharmacological entity with important therapeutic implications.

Author(s): Olivier Guillin [1]; Jorge Diaz [2]; Patrick Carroll [3]; Nathalie Griffon [1]; Jean-Charles Schwartz [1, 2]; Pierre Sokoloff (corresponding author) [1] Brain-derived neurotrophic factor (BDNF), like other neurotrophins, is [...]