Octopamine Release from an Identified Neurone in the Locust

1. The release of octopamine from the extensor-tibiae muscle preparation of the locust in response to high K saline and DUMETi stimulation has been demonstrated. This release has been measured using a radioenzyme assay for octopamine. 2. Both forms of stimulated release have been shown to be calcium sensitive. 3. Three potential problems of studying the release of transmitters from neuromuscular preparations using radiolabelled compounds have been identified, (a) The cellular location of the labelled compounds is unknown, (b) The site of the high K induced release is unknown, (c) The contraction of the muscle could cause nonspecific release of radioactivity from the muscle.