Capsaicin effects on blinking

Abstract

-Blinking is a normal human phenomenom involving trigeminal and facial patways. To gain understanding on the neurobiology of blinking, five normal subjects were investigated before and after a pplication of transdermal capsaicin at the forehead for two weeks. No effects of topical capsaicin were detected in eye blink rates. However, when capsaicin was applied to a female subject with blepharospasm, s h e showed a dramatic restoration of her vision subsequent to blinking modification. Deactivation of abnormal A-to-C fibers cross talks at the trigeminal-facial pathways seems to be the most likely mechanism of such improvement.KEY WORDS: capsaicin, visuomotor integration, C-fibers, blinking, dystonia.Efectos de la capsaicina en el parpadeo RESUMEN -El parpadeo es un fenómeno normal en los humanos que involucra las vías trigéminas faciales. Con el fin de conocer un poco más la neurobiología de este fenómeno estudiamos cinco individuos norm ales antes y después de aplicar capsaicina trasdérmica en la frente de cada uno de ellos, por dos semanas. La frecuencia de parpadeo no se alteró con la aplicación de capsaicina tópica. Sin embargo, cuando la misma sustancia se aplicó a una paciente con blefaroespasmo hubo dramática restauración de su visión, la cual fue secundaria a la modificación de la actividad muscular palpebral. La desactivación del cruce patológi-co de información que pasa de las fibras A a las fibras C, pertenecientes a las vías trigémino-faciales, pare c e ser el mecanismo de acción relacionado con la aplicación de capsaicina, el que estaría directamente re l a c i o n ado con la recuperación clínica observada en la paciente con blefaroespasmo.

Capsaicin: A promising therapy - A critical reappraisal

“…Deactivation of abnormal A-to-C fibers crossed in the trigeminal -facial pathways thought to be the most likely mechanism of this improvement. [51] Capsaicin and burning mouth syndrome Burning mouth syndrome (BMS) could be considered as an expression of atypical facial pain. Systemic capsaicin is therapeutically effective for the shortterm treatment of BMS but gastrointestinal toxicity limits its large-scale, long-term use.…”

Evaluación neurofuncional del tallo cerebral. Parte I: Reflejo del parpadeo

“…Esto se debe a una pérdida de la inhibición de los nociceptores supraespinales, con activación concomitante de las fibras A, que origina una comunicación aberrante entre estos dos tipos de fibras. 75,76…”

The Capsaicin-Blink Reflex Linkage in Chronic Migraine Revisited

“…BMS also had a clear decrease of thresholds, with central hypersensitivity for R3 responses of the BR elicited even at stimulation levels considered low to activate C fibres (11). Lack of inhibition of C nociceptors with concomitant activation of A fibres leading to abnormal crosstalk at brainstem levels present in BMS and in some movement disorders associated with C fibre aberrant activity that is responsive to capsaicin application seems to be the most likely mechanism of capsaicin effects in CM as well as in other supraspinal pain disorders (11, 12).…”