RESUMO
The effect of a lyophilized mistletoe infusion (LMI) was studied on isolated guinea-pig vas deferens. LMI caused a contraction which was partially blocked by phentolamine but not by atropine. LMI caused a shift to the left of the norepinephrine concentration-effect curve (CEC), an effect which appeared to be blocked by atropine and was absent in animals previously treated with reserpine and alpha-methyl-para-tyrosine. The increase of the norepinephrine maximal response induced by LMI was not blocked by atropine or pharmacological denervation. LMI caused a shift to the right of the acetylcholine CEC and had no effect on the acetylcholine maximal response. These results suggest that the effects seem to be due mainly to the presence of potassium ion in the LMI; however, the participation of muscarinic agonist(s) of reduced intrinsic activity or some tyramine-like substance could not be ruled out.
Assuntos
Erva-de-Passarinho , Extratos Vegetais/farmacologia , Plantas Medicinais , Ducto Deferente/efeitos dos fármacos , Acetilcolina/fisiologia , Animais , Atropina/farmacologia , Sistema Nervoso Autônomo/efeitos dos fármacos , Relação Dose-Resposta a Droga , Liofilização , Cobaias , Masculino , Contração Muscular/efeitos dos fármacos , Norepinefrina/fisiologia , Fentolamina/farmacologia , Potássio/análise , Espectrofotometria , Ducto Deferente/inervaçãoRESUMO
The effects of four atoxic fractions prepared from Tityus serrulatus venom on the response of isolated guinea pig vas deferens to norepinephrine (NE) and acetylcholine (Ach) were studied. The fractions, prepared by gel filtration on Sephadex G-50, did not contain Tityustoxin (TsTX) and were used in the concentration range 20-40 micrograms/ml tissue bath. Fraction III decreased the ED50 of NE 7.1-fold (P less than 0.01) and of Ach 17.8-fold (P less than 0.01) but did not significantly modify the maximal response (MR) to either agonist. The other fractions had much less pronounced effects, if any, on the ED50 and/or MR of either Ach or NE. The effect of Fraction III on responsiveness to NE was not demonstrable on vas deferens of pharmacologically "denervated" animals (pretreated with reserpine and alpha-methyl-p-tyrosine) but was demonstrable in tissue from normal animals tested in the presence of atropine. The effect of Fraction III on responsiveness to Ach was abolished by the presence of phentolamine in the tissue bath. These data indicate that Fraction III induces a prejunctional type of supersensitivity by acting mainly on adrenergic transmission and suggest that it may be a useful tool for the investigation of the mechanism of action of drugs that act on nerve terminals.
Assuntos
Acetilcolina/farmacologia , Norepinefrina/farmacologia , Venenos de Escorpião/farmacologia , Ducto Deferente/efeitos dos fármacos , Animais , Cromatografia em Gel , Relação Dose-Resposta a Droga , Cobaias , Masculino , Receptores de Neurotransmissores/efeitos dos fármacosAssuntos
Masculino , Animais , Acetilcolina , Norepinefrina , Venenos de Escorpião , Ducto DeferenteRESUMO
The purified toxin of the Brazilian scorpion venom (TsTX) enhances the pharmacological actions of directly and indirectly acting substances on several preparations. The enhancing action of TsTX is more pronounced for the indirectly acting drugs, which is highly suggestive of a prejunctional site of action. Secondarily, TsTX does also produce an unspecific increase of sensitivity at the level of the pharmacological receptor itself. The mechanism by which these changes are brought about remains to be determined.