Alpha(1)-adrenergic and alpha(2)-adrenergic balance in the dorsal pons and gross behavioral activity of mice in a novel environment.
BACKGROUND
Central alpha(1)- and alpha(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(1)-receptors may induce inactivity by leading to unopposed alpha(2) activity.


OBJECTIVE
The aim of this study was to test if central blockade of alpha(2)-receptor function restores behavioral activity in alpha(1)-receptor-blocked mice.


METHODS
Dose-response studies were undertaken on the effects of alpha(1)- and alpha(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(1)-receptors in the pons with the antagonist, terazosin, was reversed by either a low dose of an alpha(2)-antagonist, atipamezole, or a low dose of an alpha(2)-agonist, dexmedetomidine, but was exacerbated by a high dose of the alpha(2)-agonist.


CONCLUSIONS
The results support the hypothesis that blockade of alpha(1)-receptors in the dorsal pons of mice produces inactivity by causing unopposed activity of alpha(2)-receptors. This condition may be relevant to inactive states seen after stress or during depressive illness.
Stone
Eric A
EA
Department of Psychiatry, New York University School of Medicine, 550 First Ave., New York, NY, 10016, USA.
Lin
Yan
Y
Ahsan
Mohammad R
MR
Quartermain
David
D
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D020927:Dexmedetomidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004777:Environment; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects; D011149:Pons / Q000187:drug effects* / Q000378:metabolism; D011224:Prazosin / Q000031:analogs & derivatives / Q000494:pharmacology; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects*; D018341:Receptors, Adrenergic, alpha-2 / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D007093:Imidazoles; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; C050701:atipamezole; D020927:Dexmedetomidine; C041226:Terazosin; D011224:Prazosin