Experimental Brain Research

, Volume 145, Issue 4, pp 498–504 | Cite as

Effects of cholinergic and noradrenergic agents on locomotion in the mudpuppy (Necturus maculatus)

Research Article

Abstract

Some neurotransmitters act consistently on the central pattern generator (CPG) for locomotion in a wide range of vertebrates. In contrast, acetylcholine (ACh) and noradrenaline (NA) have various effects on locomotion in different preparations. The roles of ACh and NA have not been studied in amphibian walking, so we examined their effects in an isolated spinal cord preparation of the mudpuppy (Necturus maculatus). This preparation contains a CPG that produces locomotor activity when N-methyl-d-aspartic acid (NMDA), an excitatory amino acid agonist, is added to the bath. The addition of carbachol, a long acting ACh agonist, to the bath disrupted the walking rhythm induced by NMDA, while not changing the level of activity in flexor and extensor motoneurons. Adding clonidine, an α2-noradrenergic agonist, had no effect on the NMDA-induced walking rhythm. Physostigmine, an ACh-esterase inhibitor, disrupted the walking rhythm, presumably by potentiating the effects of endogenously released ACh. Atropine, an ACh antagonist that binds to muscarinic ACh receptors, blocked the effects of carbachol, indicating that the action is mediated, at least in part, by muscarinic receptors. In the absence of carbachol, atropine had no effect. Locomotion was not induced by carbachol, atropine or clonidine in a resting spinal cord preparation. Cholinergic actions do not seem to be essential to the CPG for walking in the mudpuppy, but ACh may convert a rhythmic walking state to a more tonic state with occasional bursts of EMG activity for postural adjustments.

Keywords

Acetylcholine Inhibition Amphibian Carbachol Atropine Physostigmine Muscarinic Clonidine 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  1. 1.Department of Physiology and Centre for Neuroscience, 513 Heritage Medical Research CentreUniversity of AlbertaEdmontonCanada

Personalised recommendations