الفهرس 
Acknowledgement
Psychotropic drugs and cortical excitabilityOnly 14 pages are availabe for public view
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Abstract
Trans-cranial magnetic stimulation (TMS) is a safe and painless technique for evoking activity in neurons in the human brain through the intact scalp and skull(1). On one hand, TMS is used to explore inhibitory and excitatory interactions within motor cortical regions in several neuropsychiatric disorders(6). On the other hand TMS is a noninvasive test that allows assessment of different pharmacological effects on cortico-spinal excitability in humans(7).When the magnetic energy is typically delivered as a series of pulses. This manner the technique is called as repetitive TMS (rTMS). Its therapeutic effect is believed to occur by causing changes in cortical metabolism and blood flow(20) or by influencing brain-derived neurotrophic factors (BDNF)(21) Different TMS protocols can be used to study different components of cortical excitability and provide insight in to the regulation of different neurotransmitter systems(8). Recent TMS studies strongly support the view that TMS can contribute to a better understanding of the complex neurobiological basis of psychotropic agents as in (11),(12),(13),(390),(15),(16). The aim of the present study: measurement the effect of psychotropic drugs on cortical excitability using trans-cranial magnetic stimulation (TMS). Subjects and methods: Forty three patients participated in the study. The patients were selected consecutively from those attended the Psychiatry unit at the department of Psychiatry and Neurology, Assiut University Hospital, Assiut, Egypt. They were diagnosed as having MDD based on based on DSM-Ⅴ criteria. The age matched control group consists of twenty healthy volunteers. They had no history of psychiatric disorders. All patients were assessed with the followingNeurophysiological assessment Psychological assessmentThe neurophysiological assessment For patients as well as the normal volunteers; cortical excitability was studied by measurement of the resting and active motor threshold, cortical silent period, and trans-callosal inhibition. Cortical excitability parameters were studied in patients two times “pre-treatment and post-treatment” The psychological assessment: Mini-Mental State Examination (MMSE). Beck Depression Inventory Scale (BDI). There was significant higher RMT and AMT in MDD patients compared with control group, while CSP and TCI were significantly decreased in MDD patients. There was significant increase of excitability of motor cortex after sertraline intake, while quetiapine is associated with significant increase in CSP and olanzapine is associated with increase in both CSP and TCI. The study suggests hypoexcitability of the motor cortex (increased RMT and AMT) coupled with inhibitory deficits (decreased CSP and TCI durations) in patients with MDD. Also, TMS as an investigational tool might be useful to distinguish between different psychotropic drugs. Sertraline associated with increased excitability of motor cortex. Quetiapine and olanzapine associated with potentiation of GABAB inhibitory neurotransmission. Olanzapine is associated with an increase in TCI. Recommendations 1- For the future research in this field we suggest to increase the sample of patients to allow better analysis of their data and to have more reliable results. Future studies are needed to test cortical excitability in both hemispheres as important consideration in light of supposed hemispheric laterality differences in MDD. Assessment of cortical excitability after repeated drug administration “chronic drug use” is recommended to investigate the effect of long term use. Further studies are needed to test whether more reliable and specific effects can be obtained with different TMS stimulation protocols.