Letters to the Editor

Abstract

Extract

Sir:- Ryegrass stagers continues to attract attention in agricultural research not only because the disorder poses management problems in affected animals but also because its aetiolqy has been subject to much speculation. A putative aetiological role for tremorgenic mycotoxins in ryegrass stqgers was first reported in New Zealand⁽¹⁾ partly on the basis of experimental evidence that small doses of penitrem A. given per os, could elicit a tremor and incoordination syndrome similar to ryegrass staggers. Subsequent studies on the mode of action of tremorgenic mycotoxins included the observation of differences in the release of neurotransmitter amino acids, notably glutamic acid. aspartic and y-aminobutyric acid, from isolated nerve endings (synaptosomes) prepared from the cerebral cortex or spinal cord of rats given tremorgens.⁽⁵⁾ Similar neurochemical changes, particularly with respect to olutamict acid, were observed in sheep synaptosomes prepared either from cerebral cortex or corpus striatum of animals very severely responding to intravenous administration of penitrem A. Unstimulated release of glutamic acid from synaptosomes was so large that no further release occurred following treatment with veratrine. However, animals showing only moderate tremor did not differ fron controls.⁽⁵⁾⁽⁷⁾