Initial characterization of the effects of Aloe vera at a crayfish neuromuscular junction

This study examines the effects of Aloe vera on neurotransmission processes in a well-established invertebrate neuromuscular junction preparation. We studied concentration-response relationships of an Aloe vera extract on excitatory junctional potentials (EJPs) at the opener muscle of the dactyl in the first and second walking limbs of crayfish (Procambarus clarkii and simulans). We observed concentration-dependent depolarizations of the muscle fibre membrane resting potential, depression of EJP amplitudes and an increase in latency to onset of the EJP following electrical stimulation of the isolated excitatory axon in the meropodite. These effects occurred with Aloe concentrations within the 1%-10% (wt-vol) range. Effects of lower concentrations, ranging to a minimum of 0.01% were equivocal. The effects of Aloe were at least partially, and in a majority of cases totally, reversible. EJPs reduced by Aloe could be restored by increasing the nerve stimulation amplitude. This, along with the latency increase, suggests a depression of action potential generation and conduction. The results provide a preliminary characterization of the effects of Aloe vera on the neurotransmission process and suggest that these effects may at least partially account for Aloe's analgesic and antiinflammatory effects. This study shows that the crayfish NMJ preparation should be useful for further elucidating the location(s) and mechanism(s) of action of Aloe on the nervous system.