Cannabidiol modulates serotonergic transmission and reverses both allodynia and anxiety-like behavior in a model of neuropathic pain

Pain. 2019 Jan;160(1):136-150. doi: 10.1097/j.pain.0000000000001386.

Abstract

Clinical studies indicate that cannabidiol (CBD), the primary nonaddictive component of cannabis that interacts with the serotonin (5-HT)1A receptor, may possess analgesic and anxiolytic effects. However, its effects on 5-HT neuronal activity, as well as its impact on models of neuropathic pain are unknown. First, using in vivo single-unit extracellular recordings in rats, we demonstrated that acute intravenous (i.v.) increasing doses of CBD (0.1-1.0 mg/kg) decreased the firing rate of 5-HT neurons in the dorsal raphe nucleus, which was prevented by administration of the 5-HT1A antagonist WAY 100635 (0.3 mg/kg, i.v.) and the TRPV1 antagonist capsazepine (1 mg/kg, i.v.) but not by the CB1 receptor antagonist AM 251 (1 mg/kg, i.v.). Repeated treatment with CBD (5 mg/kg/day, subcutaneously [s.c.], for 7 days) increased 5-HT firing through desensitization of 5-HT1A receptors. Rats subjected to the spared nerve injury model for 24 days showed decreased 5-HT firing activity, mechanical allodynia, and increased anxiety-like behavior in the elevated plus maze test, open-field test, and novelty-suppressed feeding test. Seven days of treatment with CBD reduced mechanical allodynia, decreased anxiety-like behavior, and normalized 5-HT activity. Antiallodynic effects of CBD were fully prevented by capsazepine (10 mg/kg/day, s.c., for 7 days) and partially prevented by WAY 100635 (2 mg/kg/day, s.c., for 7 days), whereas the anxiolytic effect was blocked only by WAY. Overall, repeated treatment with low-dose CBD induces analgesia predominantly through TRPV1 activation, reduces anxiety through 5-HT1A receptor activation, and rescues impaired 5-HT neurotransmission under neuropathic pain conditions.

MeSH terms

  • Action Potentials / drug effects
  • Animals
  • Anxiety / drug therapy*
  • Anxiety / etiology*
  • Cannabidiol / therapeutic use*
  • Capsaicin / analogs & derivatives
  • Capsaicin / pharmacology
  • Disease Models, Animal
  • Exploratory Behavior / drug effects
  • Feeding Behavior / drug effects
  • Ganglia, Spinal / cytology
  • Hyperalgesia / drug therapy*
  • Hyperalgesia / etiology*
  • Hyperalgesia / therapy
  • Lysergic Acid Diethylamide / pharmacology
  • Male
  • Maze Learning / drug effects
  • Neuralgia / complications*
  • Neuralgia / pathology
  • Piperazines / therapeutic use
  • Piperidines / pharmacology
  • Pyrazoles / pharmacology
  • Pyridines / therapeutic use
  • Rats
  • Rats, Wistar
  • Serotonin / metabolism*
  • Serotonin Antagonists / pharmacology
  • Swimming

Substances

  • Piperazines
  • Piperidines
  • Pyrazoles
  • Pyridines
  • Serotonin Antagonists
  • Cannabidiol
  • Serotonin
  • AM 251
  • N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide
  • Lysergic Acid Diethylamide
  • capsazepine
  • Capsaicin