Effects of synthetic peptides on giant neurones identified in the ganglia of an African giant snail ( Achatina fulica Ferussac)

Abstract

1. 1. The effects of 13 synthetic biologically active peptides were investigated on the five identifiable giant neurones of an African giant snail (Achatina fulica Férussac), PON (periodically oscillating neurone), TAN (tonically autoactive neurone), d-RPLN (dorsal-right parietal large neurone), VIN (visceral intermittently firing neurone) and d-LCDN (dorsal-left cerebral distinct neurone). 2. 2. The peptides examined were: (1) peptides proposed as neurotransmitters in mammals: metenkephalin, substance P, neurotensin, LH-RH, [Gln 8]-LH-RH, oxytocin and Arg-vasopressin; (2) peptides proposed as neurotransmitters in invertebrates: proctolin and FMRF-amide; and (3) natural venom peptides: bombesin, ranatensin C, vespakinin X and vespakinin M. 3. 3. Of the peptides examined, oxytocin markedly excited PON [minimum effective concentration (MEC): 3 × 10 −7 M], d-RPLN (MEC: 10 −5 M) and VIN (MEC: 10 −6 M). On the other hand, Arg-vasopressin was only slightly excitatory at the concentration of the screening tests (10 −4M) on PON, and was ineffective on d-RPLN and VIN. 4. 4. FMRF-amide markedly inhibited TAN (MEC: 10 −6 M) and d-LCDN (MEC: 3 × 10 −5 M). 5. 5. The other peptides examined were found to be ineffective on the five neurones tested.