Dopamine modulation of phasing of activity in a rhythmic motor network: Contribution of synaptic and intrinsic modulatory actions

Document Type

Article

Publication Date

11-1-2005

Abstract

The phasing of neuronal activity in a rhythmic motor network is determined by a neuron's intrinsic firing properties and synaptic inputs; these could vary in their relative importance under different modulatory conditions. In the lobster pyloric network, the firing of eight follower pyloric (PY) neurons is shaped by their intrinsic rebound after pacemaker inhibition and by synaptic input from the lateral pyloric (LP) neuron, which inhibits all PY neurons and is electrically coupled to a subset of them. Under control conditions, LP inhibition is weak and has little influence on PY firing. We examined modulation that could theoretically enhance the LP's synaptic contribution to PY firing. We measured the effects of dopamine (DA) on LP→PY synapses, driving the LP neuron with trains of realistic waveforms constructed from prerecorded control and DA LP oscillations, which differed in shape and duration. Under control conditions, chemical inhibition underwent severe depression and disappeared; in the mixed synapses, electrical coupling dominated. Switching between control and DA LP waveforms (with or without DA present) caused only subtle changes in synaptic transmission. DA markedly enhanced synaptic inhibition, reduced synaptic depression and weakened electrical coupling, reversing the sign of the mixed synapses. Despite this, removal of the LP from the intact network still had only weak effects on PY firing. DA also enhances PY intrinsic rebound properties, which still control the onset of PY firing. Thus in a rhythmic network, the functional importance of synaptic modulation can only be understood in the context of parallel modulation of intrinsic properties. Copyright © 2005 The American Physiological Society.

Identifier

27144462658 (Scopus)

Publication Title

Journal of Neurophysiology

External Full Text Location

https://doi.org/10.1152/jn.00440.2005

ISSN

00223077

PubMed ID

16014790

First Page

3101

Last Page

3111

Issue

5

Volume

94

Grant

R01MH060605

Fund Ref

National Institute of Mental Health

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