Brief application of AF2 produces long lasting potentiation of nAChR responses in Ascaris suum

Resistance of parasitic nematodes to the cholinergic anthelmintic levamisole is associated with a reduction in the proportion of time that acetylcholine receptor ion-channels are in the open state decreasing the response of nematode parasites to the drug. Here we examine electrophysiological and contractile responses to acetylcholine and the cholinergic agonist, levamisole, in Ascaris suum muscle looking for a pharmacological approach that may be developed to increase the response to cholinergic agonists. We found that short application of the FMRFamide, AF2, produced modulation (long lasting potentiation) of the peak membrane potential response to acetylcholine but not to levamisole. Since levamisole preferentially activates L-type acetylcholine receptors, we also tested the effect of nicotine (selective activator of N-type acetylcholine receptors) and bephenium (selective activator of B-type acetylcholine receptors) and found again no effect of AF2 on peak membrane potential responses. We then tested atropine on the AF2 potentiation of acetylcholine and found it to inhibit the peak potentiation suggesting that AF2 receptors interact with muscarinic receptors to produce the potentiation of acetylcholine. We saw similar atropine sensitive potentiation of acetylcholine responses in our muscle contraction experiments. The potentiation of the acetylcholine responses shows that nematode acetylcholine receptors are capable of a level of plasticity. A model involving calcium release from the sarcoplasmic reticulum, CaM Kinase, calcineurin, muscarinic receptors and AF2 receptors is proposed to explain our observations. These observations are important because they point to a pharmacological approach that may be developed to counter resistance to cholinergic anthelmintics

Stochastic systems simulation optimization

10.1007/s11460-011-0168-5Frontiers of Electrical and Electronic Engineering in China63468-48

Using an engineered glutamate-gated chloride channel to silence sensory neurons and treat neuropathic pain at the source

Peripheral neuropathic pain arises as a consequence of injury to sensory neurons; the development of ectopic activity in these neurons is thought to be critical for the induction and maintenance of such pain. Local anaesthetics and anti-epileptic drugs can suppress hyper-excitability however these drugs are complicated by unwanted effects on motor, CNS and cardiac function and alternative more selective treatments to suppress hyper-excitability are therefore required. Here we show that a glutamate-gated chloride channel (GluCl) modified to be activated by low doses of Ivermectin (but not glutamate) is highly effective in silencing sensory neurons and reversing neuropathic pain related hypersensitivity. Activation of GluCl expressed in either rodent or human iPSC-derived sensory neurons in vitro potently inhibited their response to both electrical and algogenic stimuli. We have shown that silencing is achieved both at nerve terminals and the soma and is independent of membrane hyperpolarisation and instead likely mediated by lowering of the membrane resistance. Using intrathecal adeno-associated virus serotype-9 based delivery, GluCl was successfully targeted to mouse sensory neurons in vivo, resulting in high level and long lasting expression of GluCl selectively in sensory neurons. This enabled reproducible and reversible modulation of thermal and mechanical pain thresholds in vivo; analgesia was observed for three days after a single systemic dose of Ivermectin. We did not observe any motor or proprioceptive deficits and noted no reduction in cutaneous afferent innervation or up-regulation of the injury marker ATF-3 following prolonged GluCl expression. Established mechanical and cold pain related hypersensitivity generated by the spared nerve injury model of neuropathic pain was reversed by Ivermectin treatment. The efficacy of Ivermectin in ameliorating behavioural hypersensitivity was mirrored at the cellular level by a cessation of ectopic activity in sensory neurons. These findings demonstrate the importance of aberrant afferent input in the maintenance of neuropathic pain and the potential for targeted chemogenetic silencing as a new treatment modality in neuropathic pain