ATP is a known mediator of inflammatory and neuropathic pain. However, the mechanisms by which specific purinergic receptors contribute to chronic pain states are still poorly characterized. Here, we demonstrate that in response to peripheral nerve injury, P2X₄receptors (P2X₄R) are expressedde novoby activated microglia in the spinal cord. Usingin vitroandin vivomodels, we provide direct evidence that P2X₄R stimulation leads to the release of BDNF from activated microglia and, most likely phosphorylation of the NR1 subunit of NMDA receptors in dorsal horn neurons of the spinal cord. Consistent with these findings, P2X4-deficient mice lack mechanical hyperalgesia induced by peripheral nerve injury and display impaired BDNF signaling in the spinal cord. Furthermore, ATP stimulation is unable to stimulate BDNF release from P2X₄-deficient mice microglia in primary cultures. These results indicate that P2X₄R contribute to chronic pain through a central inflammatory pathway. P2X₄R might thus represent a potential therapeutic target to limit microglia-mediated inflammatory responses associated with brain injury and neurodegenerative disorders.

Cognitive deficits in schizophrenia severely compromise quality of life and are poorly controlled by current antipsychotics. While 5‐HT₆ receptor blockade holds special promise, molecular substrates underlying their control of cognition remain unclear. Using a proteomic strategy, we show that 5‐HT₆ receptors physically interact with several proteins of the mammalian target of rapamycin (mTOR) pathway, including mTOR. Further, 5‐HT₆ receptor activation increased mTOR signalling in rodent prefrontal cortex (PFC). Linking this signalling event to cognitive impairment, the mTOR inhibitor rapamycin prevented deficits in social cognition and novel object discrimination induced by 5‐HT₆ agonists. In two developmental models of schizophrenia, specifically neonatal phencyclidine treatment and post‐weaning isolation rearing, the activity of mTOR was enhanced in the PFC, and rapamycin, like 5‐HT₆ antagonists, reversed these cognitive deficits. These observations suggest that recruitment of mTOR by prefrontal 5‐HT₆ receptors contributes to the perturbed cognition in schizophrenia, offering new vistas for its therapeutic control.

P2X₄purinergic receptors are calcium-permeable, ATP-activated ion channels. In the CA1 area of the hippocampus, they are located at the subsynaptic membrane somewhat peripherally to AMPA receptors. The possible role of P2X₄receptors has been difficult to elucidate because of the lack of selective antagonists. Here we report the generation of a P2X₄receptor knock-out mouse and show that long-term potentiation (LTP) at Schaffer collateral synapses is reduced relative to that in wild-type mice. Ivermectin, which selectively potentiates currents at P2X₄, was found to increase LTP in wild-type mice but had no effect in P2X₄knock-out mice. We suggest that calcium entry through subsynaptic P2X₄receptors during high-frequency stimulation contributes to synaptic strengthening.

The nucleus accumbens (NAc) is an important cerebral area involved in reward and spatial memory (Pennartz et al., 1994), but little is known about synaptic plasticity in this region. Here, electron microscopy revealed that, in the NAc, metabotropic glutamate receptors 2/3 (mGlu2/3) immunostaining was essentially associated with axonal terminals and glial processes, whereas postsynaptic dendrites and neuronal cell bodies were unstained. Electrophysiological techniques in the NAc slice preparation demonstrated that activation of mGlu2/3 with synaptically released glutamate or specific exogenous agonist, such as LY354740 (200 nm, 10 min), induced long-term depression of excitatory synaptic transmission (mGlu2/3-LTD). Tetanic-LTD and pharmacological mGlu2/3-LTD occluded each other, suggesting common mechanisms. The mGlu2/3-LTD did not require synaptic activity but depended on the cAMP–protein kinase A cascade. Selective inhibition of P/Q-type Ca²⁺channels with ω-agatoxin-IVA occluded the expression of mGlu2/3-LTD, and, conversely, the inhibitory effects of ω-agatoxin-IVA were abolished during mGlu2/3-LTD. Thus, mGlu2/3 play an important role in the control of use-dependent synaptic plasticity at prelimbic cortex–NAc synapses: their activation causes a form of LTD mediated by the long-lasting reduction of P/Q-type Ca²⁺channels contribution to transmitter release.

It has been suggested that the auxiliary subunits of high voltage-activated (HVA) calcium channels modulate T-type, low voltage-activated (LVA) calcium channels. Such a regulation has yet to be documented, especially because there has been no biochemical characterization of T-channels. To monitor total protein levels and plasma membrane expression of T-channels in living cells, external epitopes (hemagglutinin, FLAG) were introduced into human recombinant Ca(V)3 channels that were also N-terminally fused to green fluorescent protein. Utilizing Western blot techniques, fluorescence flow cytometry, immunofluorescence, luminometry, and electrophysiology, we describe here that beta(1b) and alpha(2)-delta(1) subunits enhance the level of Ca(V)3 proteins as well as their plasma membrane expression in various expression systems. We also report that, in both Xenopus oocytes and mammalian cells, the alpha(2)-delta(1) subunits increase by at least and beta(1b) 2-fold the current density of Ca(V)3 channels with no change in the electrophysiological properties. Altogether, these data indicate that HVA auxiliary subunits modulate Ca(V)3 channel surface expression, suggesting that the membrane targeting of HVA and LVA alpha(1) subunits is regulated dynamically through the expression of a common set of regulatory subunits.