following intracerebroventricular injection , xylazine , naphazoline and methoxamine , but not phenylephrine , produced similar effects.3 the sedation caused by intraperitoneal injection of clonidine was antagonized by intracerebroventricularly injected phentolamine , yohimbine , piperoxan and tolazoline but not by labetalol , thymoxamine or prazosin.4 the relative potencies of the agonists in causing sedation and of the antagonists in inhibiting the sedative effect of clonidine clearly demonstrated that the central alpha-adrenoceptors mediating clonidine-induced sedation are the same as the peripheral presynaptic alpha ( 2 ) -adrenoceptors.5 all the alpha-adrenoceptor agonists caused hypothermia after intracerebroventricular injection , but their order of potency was different from that in producing sedation .
C0034784
alpha-adrenoceptors
C0001639
alpha ( 2