Cannabinoid 1 receptors are expressed in nociceptive primary sensory neurons.
Expression of cannabinoid 1 (CB1) and vanilloid 1 (VR1) receptor proteins was studied in adult, cultured rat dorsal root ganglion neurons. Immunostaining of CB1 receptors alone produced labelling in 57+/-2% of the cultured dorsal root ganglion neurons (n=3 cultures). The area of the labelled cells was between 200 and 800 microm(2) with an average of 527+/-68 microm(2). VR1 immunolabelling revealed immunopositivity in 42+/-6% of the total population of dorsal root ganglion neurons. Cells showing VR1-like immunopositivity had an area between 200 and 600 microm(2). The mean area of the VR1-like immunopositive neurons was 376+/-61 microm(2). Double immunostaining with antisera raised against the CB1 and VR1 receptor proteins, showed a high degree of co-expression between CB1 and VR1 receptors. An average of 82+/-3% of the CB1-like immunopositive cells also showed VR1-like immunoreactivity (n=3 cultures) while 98+/-2% of the VR1-like immunolabelled neurons showed CB1 receptor-like immunostaining (n=3 cultures). Our data suggests that nociceptive primary sensory neurons co-express CB1 and VR1 receptors to a very high degree. We propose that this may provide an anatomical basis for a powerful combination of VR1 mediated excitation and CB1-mediated inhibition of nociceptive responses at central and peripheral terminals of nociceptive primary afferents.
Ahluwalia
J
J
Department of Anaesthetics, Imperial College Medical School, Chelsea and Westminster Hospital, 369 Fulham Road, SW10 9NH, London, UK.
Urban
L
L
Capogna
M
M
Bevan
S
S
Nagy
I
I
D000818:Animals; D002186:Cannabinoids / Q000378:metabolism*; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism; D018613:Microscopy, Confocal; D009475:Neurons, Afferent / Q000378:metabolism*; D009619:Nociceptors / Q000378:metabolism*; D051381:Rats; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000378:metabolism*
D002186:Cannabinoids; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug