Changes of Pattern Reversal Evoked Potentials in Estrogen Replacement Therapy

Abstract

As a result of regression in the ovarian functions, estrogen level in the circulation drops down to 1/50 of its value in the normal reproductive cycle. The excitatory estrogen increases the sensitivity of the central nervous system to cathecholamines by changing the opening frequency of voltage related L type calcium channels and potentialising the effect of glutamate; in addition it inhibits the formation of y-amino butyric acid (GABA) bye the inhibition of glutamate decarboxylase enzyme. It is argused that estrogen increases the transmission in the optic pathways and that estrogen is responsible for the shorter latency values and higher amplitudes of visual evoked potentials in women. Inspired from this knowledge, after neuroophthalmologic examination, we recorded the monoocular pattern reversal visual evoked potentials (PRVEP) of both eyes of 30 post-menopausal women before and after replacement therapy with Tibolon. We found a statistically decrease in the mean PRVEP latencies and a statistically significant increase in mean amplitudes after replacement treatment (p<0.001). We attributed the changes in PRVEP values after replacment treatment to the action of Tibolon that acted as natural sex streoid which speeded the visual transmission time via the wide spread receptors in the central nervous system. It is concluded that PRVEP is an effective and objective electrophysiologic assesment method in evaluating the effiency of hormone replacement therapy in postmenopausal women.