Some properties of the sting of the New Zealand nettle,Urtica ferox

Abstract

Extracts of hair fluid from a New Zealand stinging nettle (Urtica ferox) were tested on isolated rectus abdominis preparations of the frog,Hyla aurea. The muscle reacted in such a way as to indicate the presence in the hair fluid of acetylcholine (ca. 0⋅3 to 0⋅9μg per hair). Apart from the acetylcholine-like contraction, the muscle was subjected to a rapid irregular twitching in the presence of hair extract. The twitching could be reversibly suppressed or prevented by increasing the calcium content of the Ringer solution, or by adding mag­nesium, cobalt, strontium or nickel to the solution. The acetylcholine-like effect was not dis­turbed by such treatment. It is postulated that twitching results from a disturbance in the calcium metabolism of the muscle and a search for a 'calcium-sensitive’ factor indicates that it is neither phosphate, oxalate, formate, sulphate, fluoride, phytate, nor a chelating sub­stance similar toEDTA, but that it may be one of the guanidine group of compounds.