The hybrid modulatory/pattern generating N1L interneuron in the buccal feeding system ofLymnaea is cholinergic |
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Authors: | àgnes Vehovszky Christopher J H Elliott |
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Institution: | (1) Present address: Balaton Limnological Institute, H-8237 Tihany, Hungary;(2) Department of Biology, University of York, PO Box 373, YO1 5YW York, UK |
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Abstract: | This study examines neurotransmission between identified buccal interneurons in the feeding system of the snailLymnaea stagnalis. We compare the pharmacology of the individual synaptic connections from a hybrid modulatory/pattern generating interneuron
(N1L) to a pattern generating interneuron (N1M) with that from a modulatory interneuron (SO) to the same follower cell (N1M).
The pharmacological properties of the N1L to N1M and the SO to N1M connections closely resemble each other. Both interneurons
produce fast cholinergic EPSPs as judged by the blocking effects of cholinergic antagonists hexamethonium,d-tubocurarine and the cholinergic neurotoxin AF-64A. A slower, more complex but non-cholinergic component of the synaptic
response is also present after stimulating either the presynaptic N1L or SO interneurons. This second component of the postsynaptic
response is not dopaminergic, on the basis of its persistence in the presence of dopaminergic antagonists ergometrine and
fluphenazine and the dopaminergic neurotoxin MPP+.
We conclude that, although there has been an evolutionary divergence in function, the modulatory SO and the hybrid modulatory/pattern
generating N1L are pharmacologically similar. Neither of them contributes directly to dopaminergic modulation of the feeding
activity. These neurons also resemble the N1M protraction phase pattern generating neurons which are cholinergic (Elliott
and Kemenes, 1992). |
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Keywords: | Lymnaea feeding interneurons pharmacology synaptic connections acetylcholine dopamine |
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