both catecholamines reduced the membrane resistance.3 noradrenaline ( 5 x 10 ( -6 ) m ) or isoprenaline ( 5 x 10 ( -7 ) m ) reduced the resting tension , raised the mechanical threshold required to produce the contraction and suppressed the amplitude of phasic contractions evoked by electrical depolarization of the membrane.4 the action potential evoked by an outward current pulse in the presence of tetraethylammonium ( tea ) was not affected by 5 x 10 ( -6 ) m isoprenaline , while the mechanical response was markedly suppressed.5 the excitatory junction potential ( e.j.p . ) evoked by electrical field stimulation was blocked by atropine .
C0007412
catecholamines
C0028351
noradrenaline