Study for the isolation of neuroactive peptides from the ganglia of Achatina fulica Ferussac.

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Supported partly by the Monbusho Grant, achatin-I (Gly-D-Phe-L-Ala-L-Asp)having a D-phenylalanine residue. which excited neurones of an African giant snail (Achatina fulica Ferussac). was isolated from Achatina ganglia. Its pharmacological characteristics were studied in detail. Although another peptide was isolated. its structure is not yet determined. The results obtained are described below.(1990)1. The amino acid sequence of achatin-I was recognized easily as Gly-PheAla-Asp, but synthetic Gly-L-Phe-L-Ala-L-Asp had no effect. Synthetic Gly-DPhe-L-Ala-L-Asp showed marked excitatory effects on the Achatina neurones, and its instrumental analyses were completely identical to those of the native achatin-I.2. ED_<50> for the achatin-I excitation of an Achatina neurone, PON. was 2.0 x 10_<-6> M (95 % confidence limit = 1.4 - 2.6 x 10_<-6> M). With this, this peptide could be proposed as an excitatory neurotransmitter of the neurone.3. Among eight stereoisomers of the peptide, only achatin … More -I showed marked effects, indicating the stereospecificity of the effects.(1991)4. Among more than twenty synthetic derivatives of achatin-I. cinly achatin-I showed the marked effects. The amino group in N-terminal of achatin-I and the two carboxylic groups in C-terminal were indispensable to show the effects. The distances between the three groups in the molecule were also essential.5. None of the blockers to the conventional neurotransmitters showed modulatory effects on the achatin-I excitation of the Achatina neurones.6. Another neuroactive (neuroinhibitory) peptide, found in the Achatina ganglia, was probably APGWamide, but further experiments are needed to decide it. The ganglia of a fresh-water snail (Pila luzonica) collected in Davao were too small for our purpose.(1990 and 1991)7. Takeuchi visited University of Santo Tomas (UST) (Manila) and Davao Medical School Foundation. Yamamoto, Deura, Mori, Mano and Seki visited UST. They discussed the collaboration and gave their lectures. Kanapi, Dayao. Torrala and Rivera visited Gifu University, Fujita Health University (Toyoake) and Suntory Institute for Bioorganic Research (Osaka). Some gave their lectures there. Less