Effects of hemivibrissotomy in the rat: time-dependent asymmetries in turning and biogenic amines induced by apomorphine

Abstract

Behavioral and neurochemical changes accompanying unilateral removal of vibrissae were investigated in the rat. Rats were tested either 4 hours or 10 days after hemivibrissotomy. A systemic injection of apomorphine (0.5 mg/kg) induced turning behavior towards the intact vibrissae side in rats tested 4 hours after hemivibrissotomy. Compared to these animals, apomorphine induced more turning towards the side of vibrissae removal and less turning towards the intact side in animals tested 10 days after vibrissae removal. This reversal is suggestive of time-dependent changes in dopamine receptor sensitivity. Analysis of biogenic amines (dopamine, norepinephrine, serotonin) in the hemispheres ipsi- and contralateral to the side of vibrissae removal revealed evidence for neurochemical changes in apomorphine- and amphetamine-treated rats. Lateralized and bilateral differences were found in the neostriatum, septum and ventral mesencephalon, which were dependent on the side and duration of hemivibrissotomy. These results are discussed with respect to the behavioral and neural analogy between hemivibrissotomy and unilateral 6-hydroxydopamine lesions of the nigrostrial system.