1. Spermine and philanthotoxin potentiate excitatory amino acid responses of Xenopus oocytes injected with rat and chick brain RNA.
- Author
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Brackley P, Goodnow R Jr, Nakanishi K, Sudan HL, and Usherwood PN
- Subjects
- Animals, Aspartic Acid analogs & derivatives, Aspartic Acid pharmacology, Chickens, Kainic Acid pharmacology, Male, Membrane Potentials drug effects, Microinjections, N-Methylaspartate, Oocytes drug effects, Oxadiazoles pharmacology, Poly A administration & dosage, Poly A genetics, Quisqualic Acid, RNA administration & dosage, RNA, Messenger, Rats, Rats, Inbred Strains, Xenopus, Amino Acids pharmacology, Bee Venoms pharmacology, Brain physiology, Neurotoxins pharmacology, Oocytes physiology, Polyamines, RNA genetics, Spermine physiology, Wasp Venoms pharmacology
- Abstract
The effects of spermine and a synthetic analogue (PhTX-343) of the polyamine amide toxin, delta-philanthotoxin, on the responses of Xenopus oocytes to application of amino acids were examined using voltage clamp. The oocytes were injected with either total rat brain RNA or chick cerebrum, poly(A+)RNA. The responses to N-methyl-D-aspartate and L-kainate were potentiated by low concentrations (10(-11)-10(-7) M) of PhTX-343 and by 10(-5)-10(-4) M spermine. There was variability between oocytes in terms of their responsiveness to these compounds and recovery from their effects was slow and often incomplete. Prolonged or repeated applications of PhTX-343 and spermine eventually resulted in inhibition. Higher concentrations of these compounds always inhibited the responses to acidic amino acids. Low concentrations of PhTX-343 and spermine also potentiated the responses to nicotine and gamma-aminobutyric acid. These results are discussed in terms of the postulated polyamine binding site on the N-methyl-D-aspartate receptor.
- Published
- 1990
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