1 @entity5128 ( @entity1041 ) 0.125 mM to 20 mM potentiates the response of the anococcygeus muscle to field stimulation of the motor adrenergic nerves without affecting the response to @entity1063 suggesting a pre-synaptic origin of potentiation. The potentiation is greatest at low, submaximal, frequencies (2 Hz) of stimulation and only slight at the higher frequency of 20 Hz. This difference is due to the restraint imposed on the demonstration of potentiation by maximal or near maximal motor responses since reduction of the mechanical response at 20 Hz by either @entity5521 (post-synaptic block) or @entity2997 (pre-synaptic block) resulted in a great increase in potentiation of the response at this frequency. 2 @entity1041 in concentrations up to 1 mM similarly potentites the response to inhibitory nerve stimulation and again the greatest effect is at low frequencies. Higher concentrations (5-20 mM) progressively depress the inhibitory response. It is suggested that @entity1041 may specifically antagonize the post-synaptic action of the inhibitory transmitter and that at higher concentrations of @entity1041 this effect dominates the pre-synaptic action in increasing transmitter release. 3 @entity1041 has no effect on the motor response to @entity6114 . 4 @entity1041 (5-20 mM) causes a maintained rise in muscle tone. Part of this is abolished by @entity5521 but part is resistant. A similar muscle stimulant action of @entity1041 is observed in muscles from @entity35 previously treated with @entity2955 in which indirect sympathomimetic drugs and field stimulation could no longer produce a motor response. These results suggest that part of the motor effect of @entity1041 is due to an increased spontaneous release of @entity1063 and part to a direct action on the muscle. 5 @entity1041 0.125 mM to 20 mM antagonize the stimulant action of @entity5402 . Dose-response curves show a parallel shift to the right with no change in the maximum response suggesting a competitive @entity3897 -like action. Such an effect has previously been reported in amphibian tissue but not so far as we can determine in @entity1 preparations. 6 The possible mode of action of @entity1041 is discussed.

The action of @entity5128 on the response of the XXXX anococcygeus muscle to motor and inhibitory nerve stimulation and to some drugs.

@entity2997 :: ('MESH:D006145', 'Chemical') :: ['guanethidine'] @entity1 :: ('9606', 'Species') :: ['mammalian'] @entity1041 :: ('MESH:D013662', 'Chemical') :: ['TEA'] @entity5128 :: ('MESH:D019789', 'Chemical') :: ['Tetraethylammonium chloride'] @entity5521 :: ('MESH:D010646', 'Chemical') :: ['phentolamine'] @entity2955 :: ('MESH:D016627', 'Chemical') :: ['6-hydroxydopamine'] @entity3897 :: ('MESH:D001285', 'Chemical') :: ['atropine'] @entity35 :: ('10116', 'Species') :: ['rats'] @entity1063 :: ('MESH:D009638', 'Chemical') :: ['noradrenaline'] @entity5402 :: ('MESH:D002217', 'Chemical') :: ['carbachol'] @entity6114 :: ('MESH:D014439', 'Chemical') :: ['tyramine']
@entity35 :: (10116,Species) :: ['rat']
