Treatment with 6-hydroxydopamine in planaria (Dugesia gonocephala s.l.): morphological and behavioral study

Morpho-functional and behavioral effects of exposure to 6-hydroxydopamine ( OHDA)-HCl (24 mu g/ml per day for 24 h and 7 days) were studied in planaria s (Dugesia gonocephala s.l.). Exposure to 6-OHDA-HCl for 24 h produced hypo kinesia of the specimens. These behavioral changes were more pronounced, le ading to complete immobility, after 7 days of exposure to the neurotoxin. M oreover, specimens exposed to 6-OHDA-HCl for 24 h and 7 days failed to show any behavioral response to nomifensine, thus furnishing evidence of the da mage of presynaptic dopamine terminals. Exposure to 6-HDA-HCl for 24 h sign ificantly reduced cathecolamine content in neuropil region, as demonstrated by histochemistry, and electron-dense presynaptic vesicles, as observed on electron microscopy examination. All these alterations were significantly more pronounced and were accompanied by swelling and strong increase of ele ctron-density in cytoplasm of numerous neurons after exposure to the neurot oxin for 7 days. This appears to be the first demonstration of the neurotox ic effects of 6-OHDA-HCl in flatworms. (C) 1999 Elsevier Science Inc. All r ights reserved.