Interaction of histamine with adrenergic smooth-muscle neurotransmission. III. Significance of magnesium ions for the effects of histamine on contractions induced by endogenous noradrenaline.
The significance of Mg2+ for the effects of histamine on smooth-muscle contractions in response to electrostimulation with different frequency has been studied in organs with adrenergic neurotransmission (prostatic part of vas deferens and anococcygeal muscle of rats). Reduction of the concentration of Mg-ions below 1.05 mM usually markedly potentiates the electrostimulation-induced contractions, whereas high Mg2+-concentrations (above 1.05 mM) sharply reduce their magnitude. The changes in the concentration of the Mg-ions in the nutrient medium do not influence essentially the inhibitory effects of histamine on smooth-muscle contractions in response to electrostimulation. In the presence of lower concentrations muscle contractions in response to electrostimulation. In the presence of lower concentrations of Mg-ions, the potentiating effect of histamine on electrostimulation does not change substantially. The rise in Mg2+-concentration above 1.05 mM considerably increases the potentiating action of the low histamine concentrations on the electrostimulation-induced contractions. This effect was more pronounced in smooth-muscle preparations stimulated with a lower frequency. The data obtained suggest that histamine counteracts the contractile response to electrostimulation induced by high concentrations of Mg-ions. It may be assumed that Ca-ions also participate in the realization of this histamine effect.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation; D006632:Histamine / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009638:Norepinephrine / Q000502:physiology*; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects*
D011941:Receptors, Adrenergic; D006632:Histamine; D008274:Magnesium; D009638:Norepinephrine