Effects of synthetic peptides on giant neurons identified in the ganglia of an African giant snail ( Achatina fulica Férussac)—II

Abstract

1. 1. Thirteen synthetic biologically-active peptides, which were classified into the peptides proposed as neurotransmitters in mammals and invertebrates and neurol venom peptides, were investigated for their effects on the following six identifiable giant neurons of an African giant snail ( Achatina fulica Férussac): RAPN (right anterior pallial neuron), INN (intestinal nerve neuron), RPeNLN (right pedal nerve large neuron), LPeNLN (left pedal nerve large neuron), d-LPeLN (dorsal-left pedal large neuron) and d-LPeCN (dorsal-left pedal constantly firing neuron). 2. 2. Oxytocin and proctolin at 10 −4M excited the RAPN membrane potential, whereas FMRFamide at the same concentration inhibited the same neuron. FMRFamide at 10 −4M markedly inhibited the d-LPeLN membrane potential, sometimes produced inhibition of RPeNLN and LPeNLN, showed varied effects (excitatory or inhibitory) on INN, and had no effect on d-LPeCN. The other peptides examined had almost no effect on any of the neurons tested.