Beta-adrenergic agonists reduce spontaneous motor activity through either beta 1 or beta 2 receptors.
In mice, the clenbuterol-induced decrease in spontaneous motor activity was antagonized by IPS-339 (beta 2 antagonist) but not by betaxolol (beta 1 antagonist), whereas the isoproterenol-induced decrease in spontaneous motor activity was completely antagonized by betaxolol and only partially by IPS-339. It can be concluded that the clenbuterol-induced decrease in spontaneous motor activity is of the beta 2-type, whereas that induced by isoproterenol is essentially of the beta 1 type. In addition, chronic treatment with clenbuterol induced a tachyphylaxis to the effect of clenbuterol but not of isoproterenol. After chronic administration of tricyclic antidepressants (imipramine and desipramine) the number of cortical beta 1 adrenergic receptors decreased without impairing the clenbuterol-induced decrease in spontaneous motor activity. We conclude that beta 2 adrenergic receptors mediate the clenbuterol-induced decrease in spontaneous motor activity and the tachyphylaxis to this effect after chronic treatment.
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002976:Clenbuterol / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D007099:Imipramine / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000502:physiology
D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol; D007099:Imipramine; D003891:Desipramine; D002976:Clenbuterol