Inhibition of Ascaris Muscle by γ-Aminobutyric Acid: a Possible New Assay Method

Abstract

Ascaris lumbricoides, a round worm commonly found in the intestine of pig, has been used as an isolated muscle preparation for the investigation of anthelminthic potency¹. We are now making a wider assessment of Ascaris as a pharmacological tool. Responses were recorded from a length of dorsal muscle, cut from the anterior region of the worm, mounted in an organ bath containing modified Tyrode's solution at 37° C (refs. 2 and 3). In our experiments the most striking pharmacological effects have been seen with γ-aminobutyric acid (GABA), which produced a rapid reversible inhibition of Ascaris muscle, reflected as a relaxation of the preparation, in concentrations as low as 0.5 µg/ml. The time required for full development of relaxation at this concentration is 3–4 min. In contrast, the common anthelminthic agent piperazine produces a much slower relaxation (more than 10–15 min) at concentrations of the order of 50 µg/ml. Similar relative concentrations of GABA and piperazine have been shown to depress spike potentials in Ascaris muscle^4,5.