RESUMO
Recently, the skin is considered as one of the most respectable routes of drug introduction into the body. It forms a safe way in by passing organs suffering from chronic serious illness that interferes with drug metabolism. Overcoming of the skin barrier to facilitate easy and safe drug penetration is the target of many researchers working in this field. Application of ultrasound waves to the skin has made a revolution in penetration of many drugs across its barrier. The present study investigated the structural changes in the rat skin after ultrasound exposure by using light and scanning electron microscopes. Fifteen young albino rats were used in this study. Five of them were managed as control, while the other ten were classified as two experimental groups, five rats each. Animals of the first experimental group were exposed to ultrasound waves at a frequency of 48 KHz and intensity 0.5w/cm[2] for 5 minutes, While those of the other experimental group were exposed to the same dose for 10 minuets. The skin surface was examined by light and scanning electron microscopes comparing the findings with the skin samples of control rats. Variable degrees of skin damage included fractures of hair shafts, shedding of stratum corneum, destruction of stratum lucidum and partial separation of stratum granulosum, spinosum and basale. Also, the damage reached the papillary layer of the dermis that was removed leaving the reticular layer bared and produced wide clefts in particular areas and large carter like openings in other sites of the skin surface. The removal of the straum corneum together with the other epidermal changes and the formation of the wide clefts and crater openings could spot lights on the hidden structural changes of the skin and might explain the mechanism of transdermal drug penetration with ultrasound exposure