Neuromuscular effects of toxins isolated from southern prickly ash (Zanthoxylum clava-herculis) bark
Bowen, J.M.; Cole, R.J.; Bedell, D.; Schabdach, D.
American Journal of Veterinary Research 57(8): 1239-1244
1996
ISSN/ISBN: 0002-9645 PMID: 8836382 Document Number: 467751
The nature and mechanisms of neuromuscular effects of toxic principles in bark of Southern Prickly Ash tree that might contribute to its clinical toxicity in cattle were investigated. Extracts were prepared from bark samples, using 2 extraction methods. Contractile responses, resting potentials, miniature end-plate potentials (MEPP), and end-plate potentials of rat phrenic nerve-hemidiaphragm preparations were recorded. Blood pressure and contractile responses of the cranial tibial muscle to nerve stimulation were recorded in an anaesthetized dog. Topical anaesthetic activity in rabbits was determined by evaluation of the corneal reflex. One extract (XS) usually stimulated muscle contractile response, whereas the other (XI) inhibited this response when evoked by nerve stimulation, but not when evoked by direct muscle stimulation. XI had a hypotensive effect, but lacked topical anaesthetic activity and effect on resting potentials. This extract also reduced amplitude of MEPP and end-plate potentials, but did not affect their time course or the frequency of MEPP. XS was not active in presence of neuromuscular blocking agent tubocurarine. It is concluded that active principles in Southern Prickly Ash extracts appear to exert their action on neuromuscular transmission probably through blockade of post-junctional, end-plate receptors (XI) or enhanced release of neurotransmitter (XS).