RESUMEN
The central nervous system [CNS] is the primary target system which is affected by cyanide toxicity. Repeated exposure to potassium cyanide causes loss of tyrosine-hydroxylase-containing neurons and locomotor dysfunction. Cyanide intoxication causes progressive degeneration of the CNS similar to neuropathology associated with Parkinson's disease and cell death in certain brain areas. The purpose of this study is to demonstrate the effect of potassium cyanide which is considered as an example of one of the three derivatives of cigarette smoking: nicotine, carbon monoxide and hydrogen cyanide. Our investigation involved 25 male albino rats. Ten of them were assigned as the control group and the remaining were injected with potassium cyanide [0.02 mg/kgm body weight every day] intraperitoneally over 4 weeks. Parts of the motor cortex of each animal were freshly cut for demonstration of acid phosphatase enzyme activity. Another part was immediately processed for routine histological examination. The last part was prepared for electron microscopic examination. Light microscopic examination of the motor cortex of cyanide treated rats revealed marked degenerative changes involving the majority of their cells. Many cells were shrunken, having irregular outline, containing many cytoplasmic vacuoles and pyknotic nuclei. Cresyl violet stained sections showed chromatolysis [in the form of marked reduction of staining of Nissl substance] in the majority of cortical neurons. Transmission electron micrographs revealed both neuronal and axonal degenerative changes in cyanide treated rats. Pyramidal cells showed irregular shape, many cytoplasmic vacuoles, corrugated cell membrane, degenerated mitochondria and condensed nuclei. In addition, the nerve fibers showed, beading appearance and irregularity of the myelin layers. Thus our results might draw more attention to the harmful effects of smoking as well as might explain fine tremors affecting head and fingers of old aged heavy smokers, concerning the cerebral cortical neuronal affection especially pyramidal cells following cyanide exposure