Pharmacological nature of newer imidazoli(di)nes on rat anococcygeus muscle.
The Pharmacological nature of newer imidazoli(di)nes (clonidine analogs) on rat anococcygeus muscle (RA) was investigated. Clonidine analogs produced dose-dependent (1 X 10(-3) to 1 X 10(-5) M) contractions on RA. The relative affinity (pD2) values were in the rank order of ST 375 greater than ST 567 greater than ST 608 greater than CLO greater than ST 600 greater than ST 363 greater than noradrenaline (NA) greater than ST 91 greater than ST 93. The intrinsic activity (alpha E) values of ST 93, ST 91, ST 600 and clonidine were comparable to alpha E of NA while the other analogs showed lower values. The responses of the clonidine analogs and NA on RA were antagonised in the presence of phentolamine and prazosin but were unaffected by yohimbine. Propranolol, atropine, cyproheptidine, mepyramine and metiamide had no effect on the responses. Reserpine pretreatment did not inhibit the responses of clonidine analogs on RA. The data suggests that newer clonidine analogs exhibited differences for their receptor occupation and receptor activation. The excitatory effects of newer clonidine analogs on RA are mediated through the stimulation of postsynaptic alpha (alpha 1) adrenoceptors.
Veeranjaneyulu
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Department of Pharmacology, L.M. College of Pharmacy, Gujarat University, Ahmedabad, India.
Mehta
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Dave
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D000818:Animals; D003000:Clonidine / Q000031:analogs & derivatives / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D015016:Yohimbine / Q000494:pharmacology
D007093:Imidazoles; D015016:Yohimbine; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin