Increasing concentrations of acetyl hexapeptide-3 (Argireline) decreases EPSP amplitudes and slightly increases paired-pulse facilitation in the crayfish neuromuscular junction

Abstract

Many commonly used chemicals in cosmetic treatments are highly toxic. As a result, bio-safe synthetic alternatives to toxic cosmetic treatments, especially those concerning anti-wrinkle activity, are currently under investigation. It is thus crucial that the efficacy of these synthetic alternatives be ascertained. The synthetic hexapeptide Argireline (acetyl hexapeptide-3) is advertised to act as a safer alternative to commonly used cosmetic toxins and provide an effective mechanism for anti-wrinkle activity. This mechanism is the inhibition of Ca²⁺-dependent exocytosis, specifically the inhibition of SNARE proteins (Blanes-Mira et al. 2002). Since Argireline is claimed to mimic commonly used neurotoxins, we wanted to investigate if increasing the concentration of this chemical produces an inhibitory effect on EPSP amplitudes and synaptic plasticity in the neuromuscular junction of crayfish. To test this, we used the method of intracellular recording to measure the EPSPs of the crayfish muscle fibers upon paired-pulse stimulation of a crayfish nerve. Our results show that the EPSP amplitudes decreased as the concentration of Argireline increased in crayfish saline. Contrary to our expected results for synaptic plasticity, our data show no form of synaptic depression. In fact, our results show a slight, yet mostly negligible, increase in facilitation as the concentration of Argireline increased. Our study ultimately attempts to establish the efficacy of Argireline as a synthetic hexapeptide in the crayfish neuromuscular junction and our results suggest that Argireline does in fact conclusively decrease EPSP amplitudes although also slightly increasing synaptic facilitation.