Histological and histochemical study of the effect of levodopa on the neuro - endocrine cells of suprarenal medulla in adult male rabbit

ABSTRACT

Parkinsonism is the disease of nigrostriatal dopamine deficiency. The symptoms of the disease are due to central dopamine depletion. L-Dopa, is the most effective therapeutic agent presently available for treatment of parkinsonism. It is extensively decarboxylated in liver to dopamine [can't cross the blood brain barrier]. Only small amount reach the brain as L-DOPA through the blood brain barrier. Most of the peripheral effects are due to its pharmacologically active metabolite dopamine. However, the mechanism of these effects is still unknown. This work was performed to study the effect of L-DOPA as antiparkinsonian drug on the neuro-endocrine cells of the suprarenal gland. The study included four equal groups of adult male rabbits [10 in each]. The animals of the first two groups were given distilled water and served as controls. The animals of the last 2 groups were received 35mg/kg body weight/day of L-DOPA orally for two and six months respectively. Paraffin sections were prepared and stained with Hx and E, Pascaul's stain, Singh modification of Masson Hamperl and chromaffin reaction for adrenaline, noradrenalin and dopamine. The results showed apparent crowdness and packing of the medullary cells exerted by the trophic action of the drug and its metabolites. There was also sinusoidal dilatation produced by direct action of the drug and its metabolite dopamine. With different stains; the neuro-endocrine cells progressively enlarged in size, apparently increased in number with increased intensity of their cytoplasmic granules. This explains their ability to uptake and decarboxylate amine precursors into amines. Their apparent increase in number and hormonal secretion may explain the causes of cardiac arrhythmia affecting the patients receiving this drug