D-1-CLASS DOPAMINE-RECEPTOR INVOLVEMENT IN THE BEHAVIORAL RECOVERY FROM PREFRONTAL CORTICAL INJURY

Following unilateral aspiration of the left medial agranular cortex (A Gm) region of prefrontal cortex, rats demonstrate contralateral neglec t, characterized by a failure to orient to visual, tactile and auditor y stimuli presented on the contralateral body side. While dopamine (DA ) has been implicated in cortical neglect and its recovery, this study specifically examined D-1-class DA receptors for their involvement in spontaneous recovery from neglect caused by AGm ablation. In the firs t experiment, left AGm-ablated rats demonstrated severe neglect of con tralateral stimuli of each modality which spontaneously recovered over a period of several weeks. Recovered rats were given 7.0 mu g/kg (s.c .) of the D-1-selective antagonist SCH 23390. SCH 23390 reinstated sev ere neglect of contralateral stimuli, yet had no effect on orientation to ipsilateral stimuli. The same dose had no effect on the orientatio n behavior of controls. In a second experiment, D, receptor characteri stics were quantified via binding of [H-3]SCH 23390 to tissue homogena tes of the caudate-putamen of recovered AGm-ablated rats. Numbers and affinities of striatal D, receptors of rats with unilateral AGm ablati ons did not differ between hemispheres or from values obtained from le sioned controls. Considered together, these findings indicate that rec overy from neglect produced by cortical injury is associated with an i ncreased dependence on D-1 class receptor-mediated events, and that th is increased dependence is unlikely to be mediated through changes in D-1-class receptor numbers or affinities within caudate-putamen.