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Reactive gliosis, leading to the formation of glial scar, is the response of astrocytes to CNS injury. It is an ubiquitous reaction observed in a large number of pathological conditions, such as mechanical and chemical lesions, as well as degenerative processes (Fulcrand and Privat, 1977; Eng and De Armond, 1982). This reaction is twofold, being characterized by an astrocyte multiplication (hyperplasia) as well as an hypertrophy of the perikarya and processes (Hain et al., 1960; Nathaniel and Nathaniel, 1981). The main intracellular event is an increase of the number of gliafilaments, paralleled by a raise in GFAP immunoreactivity.

The time course changes in levels of mRNA encoding glutamic acid decarboxylase (GAD) and proenkephalin (PPE) was analyzed in the rat striatum following unilateral lesion of substantia nigra with 6-hydroxydopamine. The levels of both GAD and PPE mRNAs increased after the dopaminergic deafferentation, reaching concomitantly a maximal twofold increase on day 25. Thereafter, the mRNA levels declined; at 4 months, the amount of PPE mRNA remained slightly elevated whereas GAD mRNA had returned to the control value, suggesting the action of a compensatory mechanism. We also observed a rise of glial fibrillary acidic protein mRNA level which reflects a reactive astrocytosis. In contrast, alpha-tubulin mRNA level remained unchanged, indicating that no significant synaptogenesis occurs in this experimental situation. No obvious modification in mRNA levels was detected in the striatum contralateral to the lesion. These results highlight the role of the modulation of gene expression in adaptive processes to dopamine deficiency in striatal efferent pathways. Its relevance to the pathophysiology of Parkinson's disease is discussed.

Sweet clover leaves accumulate o-coumaric acid glucoside in the vacuole of the mesophyll cells. Protoplasts isolated from these cells are able to synthesize o-coumaric acid glucoside from exogeneous [14C]phenylalanine. Using this simplified system, kinetic analyses have shown that the glucoside is synthesized in the cytoplasm and thereafter transferred into the vacuole. No further degradation of the glucoside occurs in the isolated protoplasts after this transfer. Under our conditions, the vacuolar pH is reduced by light/dark transition and by inhibitors of photosynthesis. These treatments also depressed synthesis and transport of o-coumaric acid glucoside. The data support a relationship between the functioning of photosynthesis and pH cytoplasm/vacuole-dependent transport of o-coumaric acid glucoside into the vacuole. However as o-[ 14 C ] coumaric acid glucoside is taken up by isolated vacuoles without any energy requirement, no final conclusions can be drawn as to the coupling of o-coumaric acid glucoside transport with the acidification process. In intact plant or isolated protoplasts o-coumaric acid glucoside is synthesized as the trans isomer but accumulated in the vacuole in the cis form. When loaded with trans o-[ 14 C ] coumaric acid glucoside, reconstituted tonoplastic vesicles released this compound during molecular sieving on a Sepharose 4B column. In contrast, the labelled cis form was completely retained inside the vesicular lumen in a parallel experiment. These results suggest a selective permeability of the tonoplast to the two isomers which could be involved, in vivo, in the trapping of the glucoside inside the vacuole and its irreversible accumulation.