1. ¹Neurologic Clinic, Department of Medical and Surgical Specialties and Public Health, University of Perugia, Perugia, Italy
2. ²Department of Biomedical Sciences, Headache Study Center, Institute of Toxicology and Clinical Pharmacology, University of Modena and Reggio Emilia, Modena, Italy
3. ³IRCCS, Fondazione Santa Lucia, Rome, Italy

Correspondence: Dr P Sarchielli, Neurologic Clinic, Department of Medical and Surgical Specialties and Public Health, University of Perugia, Santa Maria della Misericordia Hospital, Sant'Andrea delle Fratte, 06156 Perugia, Italy, Tel: +39 075 578 3609; Fax: +39 075 578 3609; E-mails:neuro.pg@tiscalinet.it; headache@unipg.it

Received 13 June 2006; Revised 7 August 2006; Accepted 14 August 2006; Published online 22 November 2006.

Abstract

Based on experimental evidence of the antinociceptive action of endocannabinoids and their role in the modulation of trigeminovascular system activation, we hypothesized that the endocannabinoid system may be dysfunctional in chronic migraine (CM). We examined whether the concentrations of N-arachidonoylethanolamide (anandamide, AEA), palmitoylethanolamide (PEA), and 2-arachidonoylglycerol (2-AG) in the CSF of patients with CM and with probable CM and probable analgesic-overuse headache (PCM+PAOH) are altered compared with control subjects. The above endocannabinoids were measured by high-performance liquid chromatography (HPLC), and quantified by isotope dilution gas-chromatography/mass-spectrometry. Calcitonin gene-related peptide (CGRP) levels were also determined by RIA method and the end products of nitric oxide (NO), the nitrites, by HPLC. CSF concentrations of AEA were significantly lower and those of PEA slightly but significantly higher both in patients with CM and PCM+PAOH than in nonmigraineur controls (p<0.01 and p<0.02, respectively). A negative correlation was found between AEA and CGRP levels in CM and PCM+PAOH patients (r=0.59, p<0.01 and r=-0.65, p<0.007; respectively). A similar trend was observed between this endocannabinoid and nitrite levels. Reduced levels of AEA in the CSF of CM and PCM+PAOH patients may reflect an impairment of the endocannabinoid system in these patients, which may contribute to chronic head pain and seem to be related to increased CGRP and NO production. These findings support the potential role of the cannabinoid (CB)1 receptor as a possible therapeutic target in CM.