Complex responses activated by ibotenate in postnatal rat hippocampal neurons.

The actions of the excitatory amino acid ibotenate were investigated in postnatal rat hippocampal neurons. In neurons voltage clamped at negative membrane potentials using low-chloride internal solutions, ibotenate responses consist of an inward cationic current and two outward currents. The inward current is inhibited by 2-amino-5-phosphonovalerate (APV), a selective N-methyl-D-aspartate (NMDA) antagonist. The two outward currents consist of a picrotoxin and bicuculline-sensitive chloride current and a slowly developing calcium activated potassium current. The bicuculline sensitive current appears to be the product of contamination of ibotenate samples with the gamma-aminobutyric acid (GABA) agonist muscimol and not the result of a direct action of ibotenate.