Changes in sensitivity of the isolated guinea-pig vas deferens induced by a lyophilized Phoradendron latifolium leaf infusion.

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.

Supersensitivity of the isolated guinea-pig vas deferens induced by a toxic fraction of scorpion venom (Tityus serrulatus).

Tityustoxin (TsTx), a toxic fraction of Tityus serrulatus venom, was studied on the isolated guinea-pig vas deferens. It increased significantly the maximal response of the preparation to both norepinephrine and acetylcholine and decreased the effective median dose of norepinephrine. The effect of TsTx on norepinephrine median dose was unchanged when atropinized or pharmacologically "denervated" preparations were used but was abolished when both procedures were associated.

Prejunctional supersensitization of adrenergic transmission of the isolated guinea pig vas deferens produced by an atoxic fraction from scorpion venom (Tityus serrulatus).

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.

Supersensitivity induced by the toxin of Brazilian scorpion venom (Tityus serrulatus Lutz e Mello).

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.

Effects of para-chlorophenylalanine and tryptophan on learning of a brightness discrimination in rats.

Both the learning of brightness discrimination, discrimination reversal and a simple oddity problem, and the pain-sensitivity to electric shock were studied in rats treated with 100 mg/kg of D, L-parachlorophenylalanine (PCPA), 100 mg/kg of D, L-tryptophan (TP) or 2.0 ml/kg of control solution (CS). At the end of the last behavioral session all animals were killed and the levels and rate of 5-hydroxytryptamine (5-HT) synthesis were measured.