All the experiments were performed on rabbits.
1. When γ-aminobutyric acid was injected intravenously, it caused a fall of blood pressure and some changes in respiration.
The thresholdal dose of γ-aminobutyric acid affecting blood pressure was less than 70 γ/kg. of body weight.
The effect of γ-aminobutyric acid on blood pressure increased linearly with the logarithm of its concentration. But, in very high concentrations, its effect decreased.
The optimal dose was 8-12 mg/kg. of body weight.
2.β-alanine and δ-aminovaleric acid also caused fall of blood pressure. But, their thresholdal doses were much larger than those of γ-aminobutyric acid.
ε-aminocaproic acid had only a slight effect and α-amino acids no effect on blood pressure.
Glutamate always caused a rise of blood pressure.
3. It was concluded that the depressive action of γ-aminobutyric acid on blood pressure is due to an optimal distance between the amino group and carboxylic group.