Cortical response to somatosensory stimulation in medication overuse headache patients is influenced by angiotensin converting enzyme (ACE) I/D genetic polymorphism.
BACKGROUND
Medication overuse headache (MOH) is a disabling health problem. Convincing evidence attributes a pathophysiologic role to central sensitization. By recording somatosensory evoked potentials (SSEPs) in patients with MOH, we observed increased sensitization and deficient habituation to repetitive sensory stimuli consistent with drug overuse. The renin-angiotensin system in the brain seems to play a relevant role in neural plasticity and dependence behavior. We therefore sought differences in SSEP sensitization and habituation in patients with MOH who underwent angiotensin converting enzyme (ACE) I/D polymorphism analysis.


METHODS
We recorded median-nerve SSEPs (two blocks of 100 sweeps) in 43 patients with MOH. We measured N20-P25 amplitudes, and assessed sensitization using the first block amplitudes, and habituation using amplitude changes between the two sequential blocks. According to their genotype, subjects were divided into three groups: "D/D", "D/I" and "I/I" carriers.


RESULTS
The habituation slope of the two SSEP block amplitudes was significantly increased in the D/D subgroup (n = 16) with respect to that of the I/I subgroup (n = 6), with the D/I subgroup (n = 21) falling in between. In D/D carriers, the habituation slope correlated positively with the duration of the overuse headache, and the first SSEP block amplitudes, a measure of sensitization, increased in strict relationship with the type of overused medication in the MOH patients overall and in the D/D subgroup; this was not so in the D/I and I/I subgroups.


CONCLUSIONS
In patients with MOH, the homozygote D/D ACE polymorphism influences habituation and sensitization to repeated sensory stimuli in strict relationship with medication overuse. We suggest that angiotensin peptides influence neuronal mechanisms of plasticity by interacting with central monoaminergic synaptic transmission.
Don Carlo Gnocchi Onlus Foundation, Italy. cherub@inwind.it
Cherubino
C
Di Lorenzo
Gianluca
G
Coppola
Antonio
A
Currà
Gaetano
G
Grieco
Filippo M
FM
Santorelli
Chiara
C
Lepre
Elisa
E
Porretta
Esterina
E
Pascale
Francesco
F
Pierelli
D000328:Adult; D000700:Analgesics / Q000009:adverse effects; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D051271:Headache Disorders, Secondary / Q000235:genetics* / Q000503:physiopathology*; D006720:Homozygote; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D007703:Peptidyl-Dipeptidase A / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000502:physiology; D012084:Renin-Angiotensin System / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D019966:Substance-Related Disorders / Q000235:genetics
D000700:Analgesics; C488034:ACE protein, human; D007703:Peptidyl-Dipeptidase A