Abstract 276 Poster Session II, Sunday, 5/2 (poster 62)

Cerebral hypoxia-ischemia (HI) is responsible for dystonic movements in 10% of premature neonates and this suggest the involvement of the dopaminergic system. Previous studies of young rats have shown bilateral reduction of dopaminergic D2 receptors in the rat striatum 14 days after HI induced at 7 days of age, even in macroscopically intact brains1. The aim of this study was the analysis of variations in expression of D2 receptors ARNm in non-atrophic brains following HI.

Methods: HI was induced in thirty 7-day-old rats according the Rice model the left carotid artery was ligated, followed by ischemia with 8% O2 for 2 hours. Rats were sacrificed at the age of 21 days. D2 receptors were studied by in situ hybridization 15µm frontal slices of the striatum were incubated with a combination of 3 oligonucleotide probes labeled with 35S. Labeling was revealed by autoradiography after washing.

Results: The table summarizes the results as percentages of variation in relation to controls (30 animals) and to the contralateral hemisphere

Right HI/Right control 99.94% Left HI/Left control 96.82%

Left control/Right control 99.66% Left HI/Right HI 96.55%

These results demonstrate the absence of significant variation in D2 receptor ARNm in the 7-day-old rat striatum after HI. Preliminary results after shorter periods (24 and 48 hours after HI) demonstrated a significant reduction in the expression of ARNm on the lesioned side.

Comments: These results confirm those of Filoux for macroscopically intact brains and suggest a different mechanism for the decrease in D2 receptors, i.e. neuronal death with compensatory gliosis or prolonged change in the function of D2 receptors.