TRPV1 receptors expressed by human urothelial cells respond to capsaicin and thermal stimuli. Capsaicin evoked release of adenosine triphosphate suggests that human urothelial TRPV1 is involved in the afferent branch of the micturition reflex. Inflammatory mediators decrease the TRPV1 thermal threshold of activation to body temperature and increase its expression. This finding may be relevant for symptoms associated with cystitis.

Summary Objective Thirty percent of patients with epilepsy are refractory to medication. The majority of these patients have mesial temporal lobe epilepsy (MTLE). This prompts for new pharmacologic targets, like ATP‐mediated signaling pathways, since the extracellular levels of the nucleotide dramatically increase during in vitro epileptic seizures. In this study, we investigated whether sodium‐dependent high‐affinity γ‐aminobutyric acid (GABA) and glutamate uptake by isolated nerve terminals of the human neocortex could be modulated by ATP acting via slow‐desensitizing P2X7 receptor (P2X7R). Methods Modulation of [3H]GABA and [14C]glutamate uptake by ATP, through activation of P2X7R, was investigated in isolated nerve terminals of the neocortex of cadaveric controls and patients with drug‐resistant epilepsy (non‐MTLE or MTLE) submitted to surgery. Tissue density and distribution of P2X7R in the human neocortex was assessed by Western blot analysis and immunofluorescence confocal microscopy. Results The P2X7R agonist, 2′(3′)‐O‐(4‐benzoylbenzoyl)ATP (BzATP, 3–100 μm) decreased [3H]GABA and [14C]glutamate uptake by nerve terminals of the neocortex of controls and patients with epilepsy. The inhibitory effect of BzATP (100 μm) was prevented by the selective P2X7R antagonist, A‐438079 (3 μm). Down‐modulation of [14C]glutamate uptake by BzATP (100 μm) was roughly similar in controls and patients with epilepsy, but the P2X7R agonist inhibited more effectively [3H]GABA uptake in the epileptic tissue. Neocortical nerve terminals of patients with epilepsy express higher amounts of the P2X7R protein than control samples. Significance High‐frequency cortical activity during epileptic seizures releases huge amounts of ATP, which by acting on low‐affinity slowly desensitizing ionotropic P2X7R, leads to down‐modulation of neuronal GABA and glutamate uptake. Increased P2X7R expression in neocortical nerve terminals of patients with epilepsy may, under high‐frequency firing, endure GABA signaling and increase GABAergic rundown, thereby unbalancing glutamatergic neuroexcitation. This study highlights the relevance of the ATP‐sensitive P2X7R as an important negative modulator of GABA and glutamate transport and prompts for novel antiepileptic therapeutic targets.

Refractoriness to existing medications of up to 80 % of the patients with mesial temporal lobe epilepsy (MTLE) prompts for finding new antiepileptic drug targets. The adenosine A 2A receptor emerges as an interesting pharmacological target since its excitatory nature partially counteracts the dominant antiepileptic role of endogenous adenosine acting via inhibitory A 1 receptors. Gain of function of the excitatory A 2A receptor has been implicated in a significant number of brain pathologies commonly characterized by neuronal excitotoxicity. Here, we investigated changes in the expression and cellular localization of the A 2A receptor and of the adenosine-generating enzyme, ecto-5′-nucleotidase/ CD73, in the hippocampus of control individuals and MTLE human patients. Western blot analysis indicates that the A 2A receptor is more abundant in the hippocampus of MTLE patients compared to control individuals. Immunoreactivity against the A 2A receptor predominates in astrocytes staining positively for the glial fibrillary acidic protein (GFAP). No colocalization was observed between the A 2A receptor and neuronal cell markers, like synaptotagmin 1/2 (nerve terminals) and neurofilament 200 (axon fibers). Hippocampal astrogliosis observed in MTLE patients was accompanied by a proportionate increase in A 2A receptor and ecto-5′-nucleotidase/CD73 immunoreactivities. Given our data, we hypothesize that selective blockade of excessive activation of astrocytic A 2A receptors and/or inhibition of surplus adenosine formation by membrane-bound ecto-5′-nucleotidase/CD73 may reduce neuronal excitability, thus providing a novel therapeutic target for drug-refractory seizures in MTLE patients. • Ecto-5′-nucleotidase/CD73 localizes in close proximity with adenosine A 2A receptors in astrocytes of the human hippocampus. Keywords Mesial temporal lobe epilepsy (MTLE• Up-regulation of A 2A receptors and ecto-5′-nucleotidase/CD73 associates with astrogliosis of the hippocampus of MTLE patients.• Targeting astrocytic A 2A activation and/or adenosine formation via ecto-5′-nucleotidase/CD73 may control neuronal excitability.• Inhibitors of astrocytic A 2A receptors and ecto-5′-nucleotidase/CD73 may be a novel therapeutic strategy to control drug-refractory MTLE.

The functional properties of EPCs are associated with enhanced subacute permeability of BBB and improved clinical outcome after acute ischemic stroke.

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The model organism Neurospora crassa undergoes programmed cell death when exposed to staurosporine. Here, we show that staurosporine causes defined changes in cytosolic free Ca2+ ([Ca2+]c) dynamics and a distinct Ca2+ signature that involves Ca2+ influx from the external medium and internal Ca2+ stores. We investigated the molecular basis of this Ca2+ response by using [Ca2+]c measurements combined with pharmacological and genetic approaches. Phospholipase C was identified as a pivotal player during cell death, because modulation of the phospholipase C signaling pathway and deletion of PLC-2, which we show to be involved in hyphal development, results in an inability to trigger the characteristic staurosporine-induced Ca2+ signature. Using Δcch-1, Δfig-1 and Δyvc-1 mutants and a range of inhibitors, we show that extracellular Ca2+ entry does not occur through the hitherto described high- and low-affinity Ca2+ uptake systems, but through the opening of plasma membrane channels with properties resembling the transient receptor potential (TRP) family. Partial blockage of the response to staurosporine after inhibition of a putative inositol-1,4,5-trisphosphate (IP3) receptor suggests that Ca2+ release from internal stores following IP3 formation combines with the extracellular Ca2+ influx.

Hippocampus mossy fibre terminals activate CA3 pyramidal neurons via two distinct mechanisms, both quantal and glutamatergic: (i) rapid excitatory transmission in response to afferent action potentials and (ii) delayed and prolonged release following nicotinic receptor activation. These processes were analysed here using rat hippocampus mossy fibres synaptosomes. The relationships between synaptosome depolarisation and glutamate release were established in response to high‐KCl and gramicidin challenges. Half‐maximal release corresponded to a 52 mV depolarisation step. KCl‐induced release was accompanied by transient dissipation of the proton gradient across synaptic vesicle membrane. Nicotine elicited a substantial glutamate release from mossy fibre synaptosomes (EC50 3.14 μM; Vmax 12.01 ± 2.1 nmol glutamate/mg protein; Hill’s coefficient 0.99). However, nicotine‐induced glutamate release was not accompanied by any change in the membrane potential or in the vesicular proton gradient. The effects of acetylcholine (200 μM) were similar to those of nicotine (25 μM). Nicotinic α7 receptors were evidenced by immuno‐cytochemistry on the mossy fibre synaptosome plasma membrane. Therefore, the same terminals can release glutamate in response to two distinct stimuli: (i) rapid neurotransmission involving depolarisation‐induced activation of voltage‐gated Ca2+ channels and (ii) a slower nicotinic activation which does not involve depolarisation or dissipation of the vesicular proton gradient.

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