6 the results show ( a ) that prazosin has no effect on presynaptic alpha-adrenoceptor located on cholinergic nerve endings in the guinea-pig ileum and ( b ) that prazosin , phentolamine and phenoxybenzamine act on the same subgroup of postsynaptic alpha-adrenoceptors on the smooth muscle of the guniea-pig ileum .
C0034784
alpha-adrenoceptor
C0034783
adrenoceptors