Article date: October 1978
By: SONIA ARBILLA, S.Z. LANGER in Volume 64, Issue 2, pages 259-264
The α‐adrenoceptor blocking agent, tolazoline, and the O‐methylated metabolite of adrenaline, metanephrine, produced a concentration‐dependent increase of tension in the smooth muscle of the cat isolated nictitating membrane. These effects were considered to be due to the activation of postsynaptic α‐adrenoceptors.
The responses to nerve stimulation of this muscle were neither potentiated nor blocked by tolazoline (0.1 to 10 μm) or metanephrine (1 to 10 μm).
3H‐transmitter overflow evoked by electrical stimulation was not modified by tolazoline or metanephrine in concentrations in which these drugs stimulated the postsynaptic α‐adrenoceptors.
Since tolazoline and metanephrine failed to activate the presynaptic α‐adrenoceptors of the cat nictitating membrane under experimental conditions in which they stimulated the postsynaptic α‐adrenoceptors, these results further support the view that the presynaptic (a2) adrenoceptors differ from the postsynaptic (a1) adrenoceptors.
The α‐adrenoceptor blocking agent, tolazoline, and the O‐methylated metabolite of adrenaline, metanephrine, produced a concentration‐dependent increase of tension in the smooth muscle of the cat isolated nictitating membrane. These effects were considered to be due to the activation of postsynaptic α‐adrenoceptors.
The responses to nerve stimulation of this muscle were neither potentiated nor blocked by tolazoline (0.1 to 10 μm) or metanephrine (1 to 10 μm).
3H‐transmitter overflow evoked by electrical stimulation was not modified by tolazoline or metanephrine in concentrations in which these drugs stimulated the postsynaptic α‐adrenoceptors.
Since tolazoline and metanephrine failed to activate the presynaptic α‐adrenoceptors of the cat nictitating membrane under experimental conditions in which they stimulated the postsynaptic α‐adrenoceptors, these results further support the view that the presynaptic (a2) adrenoceptors differ from the postsynaptic (a1) adrenoceptors.
DOI: 10.1111/j.1476-5381.1978.tb17298.x
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