Mapping study of Achatina giant neurons sensitive to molluscan peptides

Abstract

1. Mapping studies of the Achatina identifiable neuron types sensitive to the following 6 molluscan peptides were examined under current-clamp. 2. These were Ser- Mytilus inhibitory peptide (Ser-MIP), catch-relaxing peptide (CARP), oxytocin, small cardioactive peptide b (SCP b ), α-bag cell peptide (α-BCP) and egg-laying hormone (ELH). 3. These peptides at 10 −3 M (3 × 10 −4 M for ELH), with 0.5% Fast Green, were applied locally to the neuron to be tested by pneumatic pressure ejection (2 kg/cm 2 and 400 msec in duration). 4. Ser-MIP showed the inhibitory (hyperpolarizing) effects on the majority of neuron types tested. 5. CARP also produced inhibition of the 3 neuron types out of 16 types tested. 6. Oxytocin had an excitatory effect on two neuron types. 7. SCP b showed excitatory effects on 4 neuron types: the membrane conductance of 1 neuron type, d-RPeAN, measured under voltage-clamp was reduced by the peptide. 8. α-BCP showed no effect. 9. ELH produced slight inhibition of the 2 neuron types.