Linked Life Data

7472497

Source:http://linkedlifedata.com/resource/pubmed/id/7472497

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
11
pubmed:dateCreated
1995-12-26
pubmed:abstractText
The isolated spinal cord of the chick embryo generates episodes of rhythmic bursting in which sartorius (hip flexor) and femorotibialis (knee extensor) motoneurons exhibit characteristic patterns of activity. At the beginning of each cycle both sets of motoneurons discharge synchronously. Following this brief synchronous activation sartorius motoneurons stop firing at the time of peak femorotibialis activity, producing a period of alternation between the two sets of motoneurons. Intracellular recording from motoneurons has suggested that the pause is mediated by a synaptically induced shunt conductance. However, the pharmacological basis for this shunt and the nature of the excitatory drive to motoneurons is unknown. To address these questions we have investigated the pharmacology of the rhythmic, synaptic drive to lumbosacral motoneurons using local and bath application of several excitatory and inhibitory antagonists, and documenting their effects on motor output in E10-E12 chick embryos. Local application of bicuculline or picrotoxin over sartorius motoneurons abolished the pause in firing recorded from the sartorius muscle nerve. As a consequence, the pattern of sartorius and femorotibialis activity was similar and the motoneurons were coactive. The pause in sartorius firing was shortened following local application of the glycine antagonist strychnine the nicotinic, cholinergic antagonists mecamylamine, and dihydro-beta-erythroidine and several excitatory amino acid antagonists. Application of the GABA uptake inhibitor nipecotic acid depressed the slow potentials and discharge recorded from the sartorius muscle nerve. These findings suggest that the pause is determined primarily by synaptic inputs acting at motoneuron GABAA receptors with contributions from glycinergic, cholinergic, and glutamatergic inputs. The actions of locally applied GABA onto spinal neurons are consistent with these findings because the neurotransmitter depolarizes spinal neurons and reduces their input resistance. Local application of bicuculline, but not strychnine, onto segments containing femorotibialis motoneurons altered the amplitude and duration of femorotibialis discharge and changed the profile of the slow potentials recorded from the muscle nerve. This finding implicates GABAergic inputs in the regulation of femorotibialis discharge. The pause in sartorius firing was still present and a pause in firing appeared in each cycle of femorotibialis discharge following bath application of bicuculline or strychnine. The pause in both sets of motoneurons could be abolished by local application of the NMDA receptor antagonist AP-5 onto the motoneurons, but not by local application of bicuculline. This action of AP-5 was in contrast to its activity in normal Tyrode's solution where it shortened the pause slightly.(ABSTRACT TRUNCATED AT 400 WORDS)
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0270-6474
pubmed:author
pubmed:issnType
Print
pubmed:volume
15
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7452-64
pubmed:dateRevised
2003-11-14
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Pharmacological characterization of the rhythmic synaptic drive onto lumbosacral motoneurons in the chick embryo spinal cord.
pubmed:affiliation
Laboratory of Neural Control, NINDS, NIH, Bethesda, Maryland 20892, USA.
pubmed:publicationType
Journal Article