Chronic and neuropathic pain is a significant problem affecting millions of people worldwide each year, with 1 in 5 individuals experiencing moderate to severe chronic or persistent pain. A number of different ion channels have been identified which play roles in pain transmission including NaV, TRP, P2X, NMDA and, more recently, HCN1 and HCN2 channels. We have used automated patch clamp instruments recording from 8 or 384 cells simultaneously to record NaV1.7, NaV1.8 and NaV1.9 in CHO cells. Current-voltage plots and pharmacology using protoxin II will be shown, as well as state-dependence of tetracaine. TRP channels are a family of cation channels with roles in many biological functions including pain perception and thermosensation. A number of selective TRPV1 antagonists were developed for the treatment of pain, however clinical studies discovered that there were undesirable side effects on core body temperature which has led to drug development targeting this ion channel to be largely halted. We recorded TRPV1 and TRPV3 activated by either ligand or heat. In this way, antagonists for ligand application of TRP channels could be identified which do not block the heat activated response. Ligand-gated ion channels involved in pain pathways include NMDA and P2X receptors. NMDA receptors have been implicated chronic and neuropathic pain. We have recorded NMDA receptor combinations NR1/NR2A and NR1/NR2B to investigate both positive modulation and negative modulation. P2X receptors, in particular P2X3 homomers or P2X2/3 heteromers, are thought to be involved in pain conditions such as allodynia and hyperalgesia. P2X2/3 and P2X3 receptors expressed in CHO or 1321N1 cells were activated by ATP and aß-methylene ATP in a concentration-dependent manner and blocked by suramin. HCN1 and 2 are primarily expressed in dorsal root ganglion neurons. The Na+/K+ inward current which flows due to activation of HCN channels, Ih, appears to have a role in mediating neuropathic pain. Indeed, in animal models some gain-of-function mutations or over-expression of HCN support this theory. We have measured HCN2 which was blocked by ivabradine and ZD-7288 in a concentration-dependent manner with an IC50 of 5.8 µM (n = 88) and 17.3 µM (n = 93), respectively. Human induced pluripotent stem cell-derived neurons (hiPSC-neurons) are an excellent model to study neuronal ion channels in a more native environment. Indeed, hiPSC-neurons may also be important models to study neurodegenerative diseases such as motor neuron disease, Alzheimer’s and Parkinson’s disease. We have used human glutamatergic-enriched cortical neurons derived from hiPSCs and NaV currents and ligand-gated currents mediated by GABAA, AMPA and nAChα7 receptors. Our results demonstrate that pain pathways can be successfully studied on automated patch clamp systems, facilitating the discovery of novel pain therapeutics.
Physiology 2019 (Aberdeen, UK) (2019) Proc Physiol Soc 43, C095
Oral Communications: Ion channels involved in pain pathways: An automated patch clamp study
A. R. Obergrussberger1, N. Becker1, M. Rapedius1, T. A. Goetze1, M. G. Rotordam1, N. Brinkwirth1, I. Rinke-Weiß1, S. Stölzle-Feix1, C. Haarmann1, M. George1, A. Brüggemann1, N. Fertig1
1. Nanion Technologies GmbH, Munich, Germany.
View other abstracts by:
Where applicable, experiments conform with Society ethical requirements.