title: Thiopental potentiation of isolated rabbit pulmonary artery contractions with alpha receptor agonists.
abstract: The effects of thiopental sodium on the adrenergic neuroeffector junction were studied in isolated rabbit pulmonary arteries. Basal tension was not altered by thiopental (2 X 10(-5) and 10(-4) M) but was increased by high concentrations of thiopental (5 X 10(-4) M). Thiopental (10(-4) and 5 X 10(-4) M) potentiated contractions induced by transmural electrical stimulation. Contractile responses to exogenously applied low concentrations of norepinephrine (NE) were potentiated by thiopental (2 X 10(-5), 10(-4) and 5 X 10(-4) M), whereas those to high concentrations were not altered. In strips previously incubated in 1-[7,8-3H]-NE (10(-7) M), the release of [3H] induced by transmural stimulation (5 Hz) was not altered by thiopental (10(-4) and 5 X 10(-4) M). Potentiation by thiopental (10(-4) M) of the responses to transmural stimulation was not affected by prior application of cocaine or hydrocortisone. Contractions induced by alpha receptor agonists (phenylephrine and methoxamine) were potentiated by thiopental (10(-4) M), while those induced by acetylcholine were not altered. Contractile responses to potassium chloride were attenuated by thiopental (10(-4) M). Amobarbital sodium and pentobarbital sodium (10(-4) M, respectively) attenuated contractions induced by NE. It may be concluded that thiopental specifically increases the responsiveness of postsynaptic alpha receptors to NE.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000322:Adrenergic Agonists / Q000494:pharmacology*; D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004558:Electric Stimulation; D006854:Hydrocortisone / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride; D011651:Pulmonary Artery / Q000294:innervation / Q000502:physiology*; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013874:Thiopental / Q000494:pharmacology*
chemical_list: D000322:Adrenergic Agonists; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D011189:Potassium Chloride; D008729:Methoxamine; D003042:Cocaine; D013874:Thiopental; D000109:Acetylcholine; D006854:Hydrocortisone; D009638:Norepinephrine