Cannabinoids mediate analgesia largely via peripheral type 1 cannabinoid receptors in nociceptors.
Although endocannabinoids constitute one of the first lines of defense against pain, the anatomical locus and the precise receptor mechanisms underlying cannabinergic modulation of pain are uncertain. Clinical exploitation of the system is severely hindered by the cognitive deficits, memory impairment, motor disturbances and psychotropic effects resulting from the central actions of cannabinoids. We deleted the type 1 cannabinoid receptor (CB1) specifically in nociceptive neurons localized in the peripheral nervous system of mice, preserving its expression in the CNS, and analyzed these genetically modified mice in preclinical models of inflammatory and neuropathic pain. The nociceptor-specific loss of CB1 substantially reduced the analgesia produced by local and systemic, but not intrathecal, delivery of cannabinoids. We conclude that the contribution of CB1-type receptors expressed on the peripheral terminals of nociceptors to cannabinoid-induced analgesia is paramount, which should enable the development of peripherally acting CB1 analgesic agonists without any central side effects.
Agarwal
Nitin
N
Institute for Pharmacology, University of Heidelberg, Im Neuenheimer Feld, Heidelberg, 69120 Germany.
Pacher
Pal
P
Tegeder
Irmgard
I
Amaya
Fumimasa
F
Constantin
Cristina E
CE
Brenner
Gary J
GJ
Rubino
Tiziana
T
Michalski
Christoph W
CW
Marsicano
Giovanni
G
Monory
Krisztina
K
Mackie
Ken
K
Marian
Claudiu
C
Batkai
Sandor
S
Parolaro
Daniela
D
Fischer
Michael J
MJ
Reeh
Peter
P
Kunos
George
G
Kress
Michaela
M
Lutz
Beat
B
Woolf
Clifford J
CJ
Kuner
Rohini
R
D000483:Alleles; D000698:Analgesia; D000818:Animals; D063385:Cannabinoid Receptor Modulators / Q000502:physiology; D002186:Cannabinoids / Q000494:pharmacology*; D002490:Central Nervous System / Q000187:drug effects; D017931:DNA Primers; D004594:Electrophysiology; D005727:Ganglia, Spinal / Q000166:cytology / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D036421:Nerve Fibers, Unmyelinated / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects*; D017933:Peripheral Nervous System / Q000187:drug effects*; D010523:Peripheral Nervous System Diseases / Q000473:pathology; D043884:Receptor, Cannabinoid, CB1 / Q000187:drug effects* / Q000235:genetics
D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids; D017931:DNA Primers; D043884:Receptor, Cannabinoid, CB1