Mianserin blocks alpha 2 adrenoceptors in submucous neurones of the guinea-pig caecum.
Intracellular recordings were made from submucous plexus neurones of the guinea-pig caecum in vitro. The peak amplitude of the adrenergic inhibitory postsynaptic potential (IPSP) was depressed by mianserin in a dose-dependent manner (300 nM-100 microM). This was due to a direct blockade of postsynaptic alpha 2 adrenoceptors. The nicotinic excitatory postsynaptic potential (EPSP) and the non-cholinergic EPSP were not affected by mianserin (100 microM). The presynaptic inhibition of the release of acetylcholine, mediated by presynaptic alpha 2 receptors, was also blocked by mianserin (30 microM). The results suggest that mianserin antagonizes both pre- and post-synaptic alpha 2 adrenoceptors in enteric plexus neurones.
D000317:Adrenergic alpha-Antagonists; D000818:Animals; D002432:Cecum / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D008803:Mianserin / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000037:antagonists & inhibitors; D011978:Receptors, Nicotinic / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects
D000317:Adrenergic alpha-Antagonists; D007473:Ion Channels; D011978:Receptors, Nicotinic; D008803:Mianserin; D009638:Norepinephrine; D004837:Epinephrine