Effect of minaprine on synaptic transmission in the neocortex of the rat in vivo

Abstract

The effects of minaprine and/or excitatory amino acid antagonists on transcallosal responses were examined in urethane-anesthetized rats. The transcallosal response was recorded from the surface of the anterior neocortex, following electrical stimulation of the contralateral corpus callosum. The transcallosal response consisted of a biphasic positive-negative waveform. Intravenously-administered minaprine increased the amplitude of the positive- and negative-waves, in a dose-dependent manner. Intracortical injection of ( ± )-2-amino-5-phosphonovalerate (APV) and gamma- d-glutamylglycine (DGG) reduced the amplitude of the negative-wave, with no effects on the amplitude of the positive-wave. l-Glutamate diethylester (GDEE) had no effect on the transcallosal response. The minaprine-induced increase in the amplitude of the negative-wave was completely antagonized by simultaneous intracortical injections of APV and DGG which, per se, did not affect that transcallosal response. In contrast, APV and DGG had no effect on the increase in the amplitude of the positive-wave induced by minaprine. The enhancing effect of minaprine on the transcallosal response remained unaltered in case of an intracortical injection of GDEE. These findings indicate that the negative-wave of the transcallosal response may be related to receptors for excitatory amino acids. The possibility that the pharmacological action of minaprine on synaptic transmission in the neocortex may be linked to the excitatory amino acid receptors warrants further attention.