RT Journal Article
SR Electronic
T1 Enhanced Long-Term Potentiation-Like Plasticity of the Trigeminal Blink Reflex Circuit in Blepharospasm
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 716
OP 721
DO 10.1523/JNEUROSCI.3948-05.2006
VO 26
IS 2
A1 Angelo Quartarone
A1 Antonino Sant'Angelo
A1 Fortunato Battaglia
A1 Sergio Bagnato
A1 Vincenzo Rizzo
A1 Francesca Morgante
A1 John C. Rothwell
A1 Hartwig R. Siebner
A1 Paolo Girlanda
YR 2006
UL http://www.jneurosci.org/content/26/2/716.abstract
AB Benign essential blepharospasm (BEB) is a focal cranial dystonia affecting eye closure. Here, we tested the hypothesis that BEB is associated with abnormal plasticity of the neuronal circuits mediating reflex blinks. In patients with BEB and healthy age-matched controls, we used the conditioning protocol introduced by Mao and Evinger (2001) to induce long-term potentiation (LTP)-like plasticity in trigeminal wide dynamic range neurons of the blink reflex circuit. High-frequency trains of electrical stimuli were repeatedly given over the right supraorbital nerve (SO) and timed to coincide with the R2 response elicited by a preceding SO stimulus. High-frequency stimulation (HFS) resulted in a long-lasting and input-specific potentiation of the R2 response in both groups, yet the facilitation of the R2 response was markedly increased in patients relative to controls. Botulinum toxin (BTX) injections in both orbicularis oculi muscles normalized the previously enhanced LTP-like plasticity of the R2 response. The increased responsiveness to HFS provides first-time evidence that LTP-like plasticity is increased in the trigeminal reflex circuit of patients affected by BEB. The results also show that the enhanced modifiability is not fixed in BEB, because BTX injections can transiently restore normal LTP-like plasticity. We propose that an abnormal corneal input induced by excessive blinking exacerbates increased LTP-like plasticity in BEB. BTX treatment removes the latter and restores plasticity toward normal values. Our results support the concept that maladaptive reorganization contributes to the pathophysiology of focal dystonias.