ABSTRACT
Histamine H(3)-receptors act as heteroreceptors on many neurons. The effects of H(3)-ligands (an agonist, R-alpha-methylhistamine and an antagonist, thioperamide) on levodopa-induced turning behavior in a rat model of Parkinson's disease were quite similar to those seen with alpha(2)-adrenoceptor ligands (dexmedetomidine and atipamezole). R-alpha-methylhistamine clearly reduced contralateral turning behavior but the increase of turning behavior after thioperamide was less clear. The lack of effect of H(3)-ligands, in contrast to alpha(2)-ligands, on the amphetamine-induced ipsilateral turning behavior points to different roles or neuronal distribution of these two presynaptic receptors. We propose that in this lesion model, H(3)-receptors modify those pathways participating striatal outflow.
