alpha sub(1)-Adrenergic and alpha sub(2)-adrenergic balance in the dorsal pons and gross behavioral activity of mice in a novel environment

• Published in: Psychopharmacology 2005-11, Vol.183 (1), p.127-132
• Main Authors: Stone, Eric A, Lin, Yan, Ahsan, Mohammad R, Quartermain, David
• Format: Article
• Language: English
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-005-0171-8

Rationale: Central alpha sub(1)- and alpha sub(2)-adrenoceptors in a number of different brain regions are known to have opposing actions on gross behavioral activity, with the former stimulating and the latter inhibiting activity. Therefore, blockade of alpha sub(1)-receptors may induce inactivity by leading to unopposed alpha sub(2) activity. Objective: The aim of this study was to test if central blockade of alpha sub(2)-receptor function restores behavioral activity in alpha sub(1)-receptor-blocked mice. Methods: Dose-response studies were undertaken on the effects of alpha sub(1)- and alpha sub(2)-agonists and antagonists microinjected into the dorsal pons on gross behavioral activity in a novel cage test. Results: The behavioral inactivity resulting from blockade of alpha sub(1)-receptors in the pons with the antagonist, terazosin, was reversed by either a low dose of an alpha sub(2)-antagonist, atipamezole, or a low dose of an alpha sub(2)-agonist, dexmedetomidine, but was exacerbated by a high dose of the alpha sub(2)-agonist. Conclusion: The results support the hypothesis that blockade of alpha sub(1)-receptors in the dorsal pons of mice produces inactivity by causing unopposed activity of alpha sub(2)-receptors. This condition may be relevant to inactive states seen after stress or during depressive illness.