CEREBRAL TRAUMA-INDUCED CHANGES IN CORPUS STRIATAL DOPAMINE-RECEPTOR SUBTYPES

A device designed specifically for mild to severe concussions was used to produce quantitative experimental blunt brain injury in male Wista r rats. We have examined the effects of varying magnitudes of cerebral trauma on the maximal binding capacity (B-max) of D1 and D2 dopamine (DA) receptors. The B-max for each receptor subtype was obtained from Scatchard analyses of [H-3]-SCH 23390 and [H-3]Spiperone binding to st riatal membrane. Anesthetized rats were injured-one, two, or three tim es-once every 24 h, with either a 68- or 268-g rubber-headed reflex ha mmer accelerated from a predetermined distance. Uninjured nonanestheti zed (NA) and anesthetized (A) rats served as controls. No significant difference in receptor density was observed between NA and A rats for each receptor subtype. Immediately (0 h) following injury from the 68- g hammer weight, the density of D1 receptors decreased (50%), then inc reased (30%) above control levels by 24 h. The same pattern was observ ed with the 268-g hammer weight. Analysis of variance (ANOVA) showed t hat there was no overall effect of number of injuries or treatment on the density of D1 and D2 receptor subtypes. However, there was an inte raction of both variables on the DI, but not D2, receptor subtype. Par tial ANOVA for receptor densities after rats were injured either one, two, or three times showed that receptor density was altered only afte r the rats were injured one time. These results suggest that striatal DA D1 receptors are downregulated and then upregulated following isola ted injury to the cerebral cortex.