ALTHOUGH an injection of local anaesthetic is supposed to reduce pain, many people find the jab itself agonising. Now, researchers from the clinical shock study group at the Western Infirmary, Glasgow, have found through a controlled study of 25 volunteers that warming the anaesthetic drug lignocaine to 37C significantly cuts down the pain. Among the suggestions that the doctors put forward in the British Medical Journal to explain why warming works is that cold solutions may simply stimulate the pain receptors more or, alternatively, warmed receptors are blocked faster.