Identification and pharmacological characteristics of giant neurones situated in the buccal ganglia of an African giant snail ( Achatina fulica Férussac)

Abstract

1. The following four giant neurones were identified on the dorsal surface of the left buccal ganglion of an African giant snail ( Achatina fulica Ferussac): d-LBAN (dorsal-left buccal anterior neurone), d-LBMN (dorsal-left buccal medial neurone), d-LBCN (dorsal-left buccal central neurone) and d-LBPN (dorsal-left buccal posterior neurone). The axonal pathways of the neurones were studied by the intracellular injection of Lucifer Yellow; their pharmacological characteristics with respect to common putative neurotransmitters were also investigated. 2. The axonal pathways of d-LBAN and d-LBCN were simple, innervating some left lateral buccal nerves or the left accessory connective buccal nerve. On the other hand, those of d-LBMN and d-LBPN were much more widespread, projecting not only to the left buccal nerves, but also to the right buccal nerves through the buccal commissure. 3. No direct axonal pathway from any of the four buccal neurones tested to the other ganglioncomplexes through the cerebral buccal connectives was demonstrated. 4. The pharmacological characteristics of the four neurones tested were not identical. Only 5-hydroxytryptamine excited all of the neurones, whereas dopamine, l-epinephrine and acetylcholine inhibited all of them. However, the other effective substances, such as dl-octopamine, GABA, l-homocysteic acid, erythro-β-hydroxy- l-glutamic acid and histamine, were either excitatory or inhibitory according to the neurone.