Chronic exposure of sensory neurones to increased levels of nerve growth factor modulates CB1/TRPV1 receptor crosstalk

• Published in: British journal of pharmacology 2007-10, Vol.152 (3), p.404-413
• Main Authors: Evans, R M, Scott, R H, Ross, R A
• Format: Article
• Language: English
• Subjects: anandamide; Animals; Animals, Newborn; Arachidonic Acids - pharmacology; Biological and medical sciences; Calcium - metabolism; Calcium Channels - drug effects; Calcium Channels - metabolism; cannabinoid; Cannabinoid Receptor Modulators - pharmacology; CB1; Cells, Cultured; Chronic Disease; Dose-Response Relationship, Drug; DRG; Electrophysiology; Endocannabinoids; Fura-2; Ganglia, Spinal - cytology; Ganglia, Spinal - drug effects; Ganglia, Spinal - metabolism; Medical sciences; nerve growth factor; Nerve Growth Factor - administration & dosage; Nerve Growth Factor - pharmacology; NGF; pain; Pain - drug therapy; Pain - physiopathology; Patch-Clamp Techniques; Pharmacology. Drug treatments; Polyunsaturated Alkamides - pharmacology; Rats; Receptor, Cannabinoid, CB1 - drug effects; Receptor, Cannabinoid, CB1 - metabolism; Research Papers; Signal Transduction - drug effects; TRPV Cation Channels - drug effects; TRPV Cation Channels - metabolism; TRPV1
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0707411

Background: Anandamide (AEA) activates both cannabinoid CB1 and TRPV1 receptors, which are expressed on cultured dorsal root ganglion neurones. Increased levels of nerve growth factor (NGF) are associated with chronic pain states. Experimental approach: The aim of this study was to compare of the effects of AEA on CB1 receptor signalling and TRPV1‐CB1 crosstalk in low and high concentrations of NGF, using voltage‐clamp electrophysiology and Fura‐2 calcium imaging. Key results: Chronic exposure to high NGF (200 ng ml−1) as compared to low NGF (20 ng ml−1) increases the proportion of neurones that exhibit an inward current in response to AEA (1 μM), from 7 to 29%. In contrast, inhibition of voltage‐gated calcium currents by AEA is not significantly different in low NGF (33±9%, compared to high NGF 28±6%). Crosstalk between CB and TRPV1 receptors is modulated by exposure to high NGF. In low NGF, exposure to the CB1 receptor antagonist, SR141716A, (100 nM) increases the percentage of neurones in which AEA elicits an increase in [Ca2+]i, from 10 to 23%. In high NGF, the antagonist does not alter the percentage of responders (33 to 30%). In low NGF, exposure to the CB receptor agonist, WIN55 (1 μM) reduces capsaicin‐mediated increases in [Ca2+]i to 28±8% of control as compared to an enhancement to 172±26% of control observed in high NGF. Conclusions and implications: We conclude that cannabinoid‐mediated modulation of TRPV1 receptor activation is altered after exposure to high NGF. British Journal of Pharmacology (2007) 152, 404–413; doi:10.1038/sj.bjp.0707411; published online 13 August 2007