Gross mapping of α1-adrenoceptors that regulate behavioral activation in the mouse brain

Brain alpha(1)-adrenoceptors that participate in behavioral activation were mapped in the mouse brain by determining where microinjection of the alpha(1)-antagonist, terazosin, inhibited behavioral activity in a novel cage test. A total of 5 out of 23 tested regions were shown to be involved including the dorsal pons/locus coeruleus region (DP/LC), the dorsal raphe/periaqueductal gray area (DR/PAG), the vermis cerebellum (CER), the nucleus accumbens (ACC) and the medial preoptic area (MPOA). Injection in the 4th ventricle was also effective perhaps by acting on several of these regions simultaneously. A partial inhibition was obtained from the motor cortex. Coinjection of the alpha(1/2)-agonist, 6-fluoronorepinephrine (6FNE) but not the alpha(2)-agonist, dexmedetomidine (DMT) reversed the behavioral inhibition in all regions. It is hypothesized that brain motoric alpha(1)-receptors elicit behavioral activation by coordinately exciting several monoaminergic, motor and motivational systems. (C) 2003 Elsevier B.V. All rights reserved.