Heterosynaptic modulation by the octopaminergic OC interneurons increases the synaptic outputs of protraction phase interneurons (SO, NIL) in the feeding system of Lyainaea stagnalis

TY - JOUR

T1 - Heterosynaptic modulation by the octopaminergic OC interneurons increases the synaptic outputs of protraction phase interneurons (SO, NIL) in the feeding system of Lyainaea stagnalis

AU - Vehovszky, A

AU - Elliott, C J H

PY - 2002

Y1 - 2002

N2 - We examined the cholinergic synapses between protraction phase interneurons (SO or NIL) and their targets (NIM interneuron, B1 motoneuron) in the buccal ganglia of the pond snail Lymnaea stagnalis. We have tested the hypothesis that the OC (octopamine-containing) interneuron, an intrinsic modulator of the feeding network, can increase the synaptic efficacy from the SO or NIL to their targets. Prestimulation of the OC interneuron, 4 s before the activation of the SO or NIL increases the strength of their output synapses by 75% (SO)-110% (NIL). The individual excitatory postsynaptic potentials evoked by SO or NIL stimulation increase in size. OC prestimulation also produces an increase in the firing rate of these presynaptic Interneurons: SO 40%: NIL 33%. The facilitation lasts up to 6 s after the end of the OC burst. The enhancement of PSPs is seen at all the Output synapses (both excitatory and inhibitory) of the SO and NIL interneurons. The output synapses of the non-cholinergic swallowing phase N3p interneuron are not affected, even when the same postsynaptic target is selected. The SO --> NIM, SO --> B1 and NIL --> NIM synapses are also strengthened by bath application of 1-5 muM octopamine (average increase 60%). The major effect is an increased excitability of the SO: the B1 motoneuron response to the main transmitter of the SO, acetylcholine, is unaffected. Increased synaptic outputs of the protraction phase SO and NIL interneurons is functionally significant for generation of feeding pattern in the Lymnaea CNS. Strengthening the connections of SO and NIL to the central pattern generator (NIM) interneurons enhances their ability to drive fictive feeding. Thus heterosynaptic facilitation by the octopaminergic OC interneurons in the central pattern generator network may contribute to the behavioral plasticity of feeding in the intact animal, (C) 2002 IBRO. Published by Elsevier Science Ltd. All rights reserved.

AB - We examined the cholinergic synapses between protraction phase interneurons (SO or NIL) and their targets (NIM interneuron, B1 motoneuron) in the buccal ganglia of the pond snail Lymnaea stagnalis. We have tested the hypothesis that the OC (octopamine-containing) interneuron, an intrinsic modulator of the feeding network, can increase the synaptic efficacy from the SO or NIL to their targets. Prestimulation of the OC interneuron, 4 s before the activation of the SO or NIL increases the strength of their output synapses by 75% (SO)-110% (NIL). The individual excitatory postsynaptic potentials evoked by SO or NIL stimulation increase in size. OC prestimulation also produces an increase in the firing rate of these presynaptic Interneurons: SO 40%: NIL 33%. The facilitation lasts up to 6 s after the end of the OC burst. The enhancement of PSPs is seen at all the Output synapses (both excitatory and inhibitory) of the SO and NIL interneurons. The output synapses of the non-cholinergic swallowing phase N3p interneuron are not affected, even when the same postsynaptic target is selected. The SO --> NIM, SO --> B1 and NIL --> NIM synapses are also strengthened by bath application of 1-5 muM octopamine (average increase 60%). The major effect is an increased excitability of the SO: the B1 motoneuron response to the main transmitter of the SO, acetylcholine, is unaffected. Increased synaptic outputs of the protraction phase SO and NIL interneurons is functionally significant for generation of feeding pattern in the Lymnaea CNS. Strengthening the connections of SO and NIL to the central pattern generator (NIM) interneurons enhances their ability to drive fictive feeding. Thus heterosynaptic facilitation by the octopaminergic OC interneurons in the central pattern generator network may contribute to the behavioral plasticity of feeding in the intact animal, (C) 2002 IBRO. Published by Elsevier Science Ltd. All rights reserved.

KW - octopamine

KW - heterosynaptic facilitation

KW - mollusc

KW - synapse

KW - neuromodulation

KW - central pattern generator

KW - SNAIL LYMNAEA-STAGNALIS

KW - LOBSTER STOMATOGASTRIC GANGLION

KW - CENTRAL PATTERN GENERATOR

KW - POND SNAIL

KW - AMINE MODULATION

KW - EXTRINSIC MODULATION

KW - HELISOMA-TRIVOLVIS

KW - MEDICINAL LEECH

KW - PYLORIC NETWORK

KW - MOTOR-NEURONS

M3 - Article

SN - 0306-4522

VL - 115

SP - 483

EP - 494

JO - Neuroscience

JF - Neuroscience

IS - 2

ER -