Effects of guanidinoacetic acid, gamma-guanidinobutyric acid and gamma-guanidinobutyryl-methylester on the mammalian cerebral cortex.

Abstract

The effects of guanidinoacetic acid, γ-guanidinobutyric acid and γ-guanidinobutyryl-methylester on the direct cortical response and the transcallosal response were investigated in the rabbit and cat.1. Guanidinoacetic acid suppressed the initial negative spike and augmented slightly the secondary negative wave of the direct cortical response in lower concentrations. In higher concentrations (0.5-1%), it abolished completely the initial negative spike. Disappearance of the initial negativity was accompanied by development of a surface positive wave.2. The effects of guanidinoacetic acid on the transcallosal response consisted of three; 1) suppression of the surface negative wave, 2) augmentation and prolongation of the surface positive wave, 3) development of a late slow negative wave. Sometimes, there occurred repetitive positive shifts in potential following this late slow negativity.3.γ-Guanidinobutyric acid augmented selectively the secondary negative wave, but did not affect directly the initial negative spike of the direct cortical response.4.γ-Guanidinobutyric acid augmented the surface negative component of the transcallosal response, leaving the surface-positive component unchanged.5. Methylesterification of γ-guanidinobutyric acid did not produce any change in the effects on cvoked potentials. Namely, γ-guanidinobutyryl-methylester augmented the secondary negative wave of the direct cortical response and the negative wave of the transcallosal response.6. Guanidinoacetic acid, γ-guanidinobutyric acid and γ-guanidinobutyryl-methylester corresponded neuropharmacologically to GABA, e-aminocaproic acid ande-aminocapronyl-methylester respectively.