Thiopental potentiation of isolated rabbit pulmonary artery contractions with alpha receptor agonists.
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.
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*
D000322:Adrenergic Agonists; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D011189:Potassium Chloride; D008729:Methoxamine; D003042:Cocaine; D013874:Thiopental; D000109:Acetylcholine; D006854:Hydrocortisone; D009638:Norepinephrine