Michael Foster, who introduced experimental physiology to Cambridge, used a frog sciatic nerve-muscle preparation in his practical classes. A very similar preparation was used to teach generations of medical, veterinary and natural science students over a period of around 140 years. However, obtaining frogs became increasingly difficult, and there was a desire to reduce the use of vertebrates in our classes. As a result, in 2014 we moved to the use of earthworms (Lumbricus terrestris) instead. We report here on the ‘Earthworm Action Potentials’ practical class which we have developed and refined over the last ten years, with a view to inspiring the development of similar introductory neurobiology classes in other physiology departments.

Worms, readily obtained from a fishing-bait supplier, are anaesthetized by immersion in a 15% ethanol solution for 7 minutes, and are then decapitated. Standard dressmakers’ pins are inserted at different positions along the length of the worm. Stimulating and recording electrodes attached to AD Instruments’ PowerLab system are connected to these pins and can be used to initiate action potentials in the worm’s median and lateral giant fibres. Because these are essentially single-fibre action potentials, the all-or-none law can be easily demonstrated. Experiments that students then perform within our three-hour class include measuring conduction velocity, refractory period, bidirectionality and effects of temperature. Following dissection to expose the nerve cord, students also investigate the effects of reducing sodium levels in the worm’s extracellular fluid. Unexpected findings from this class have led to final-year honours research projects using the same preparation, described separately in a cognate submission (Knight & Fraser).

A small minority of first-year students are uncomfortable with the use of worms in a practical class, and so we have developed an interactive, online tutorial for those who do not wish to participate. However, responses from students have generally been positive and the class has been welcomed by our neurobiology staff members, who see it as an excellent introduction to their field. This very simple preparation helps to meet many of the same learning objectives that were covered in the traditional frog sciatic nerve preparation, plus some new ones, but with minimal consumable cost and a much higher level of reliability.

[This submission forms one of a pair of submissions together with the abstract of Knight and Fraser. We are hoping that, if accepted, they could please be allocated adjacent slots within a teaching-focused podium session]