Decreased locomotor and investigatory exploration after denervation of catecholamine terminal fields in the forebrain of rats

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Examined exploratory behaviors in 7 experiments with male Sprague-Dawley rats after bilateral microinjections of 6-hydroxydopamine (6-OHDA) into 2 hypothalamic sites that produced different patterns of denervation of forebrain catecholamine (CA) terminal fields. After anterolateral injections, Ss locomoted and reared less in a novel open field, responded abnormally to changes in degree of novelty of the open field, and investigated a novel object less. These are seen as deficits in exploratory behavior because they were not secondary to the inhibition of open-field behavior by hyperemotionality, general motor disability, or failure to detect novel spaces or objects. Anterolateral injections produced loss of CA fibers, determined histochemically, in neocortical, hippocampal, anterolateral hypothalamic, mesolimbic, mesocortical, and anteromedioventral striatal terminal fields and loss of dopaminergic perikarya in the A10 and anteromedial A9 cell groups. No deficits in exploratory behaviors occurred, however, after bilateral anteromedial 6-OHDA injections that denervated neocortical, hippocampal, and anteromedial hypothalamic CA terminal fields. A critical forebrain CA innervation for exploratory responses to novel stimuli may be within areas that were denervated by anterolateral but not by anteromedial hypothalamic 6-OHDA injections. These areas are mesolimbic, mesocortical, anteromedioventral, and anterolateral hypothalamic terminal fields. (54 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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