Linked Life Data

7509856

Source:http://linkedlifedata.com/resource/pubmed/id/7509856

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
6
pubmed:dateCreated
1994-4-6
pubmed:abstractText
1. Intracellular microelectrode current-clamp technique was used to study the steady-state membrane properties of single intact large primary afferent axons (conduction velocity > 10 m/s) attached to isolated hemisected frog spinal cord. 2. Hyperpolarizing electrotonic potentials (ETPs) had a slow complex multiphasic charging. This complex charging could be approximated by two time constants: one in the range of 70-210 ms, the other of < 20 ms. 3. Two regions of outward and inward rectification hyperpolarized to the resting membrane potential were observed, in addition to the previously characterized outward rectification active at potentials depolarized to resting membrane potential. The peak and steady-state input resistance of these axons in tetrodotoxin Ringer solution was on average 65.6 +/- 21.1 and 31.1 +/- 10.8 M omega, mean +/- SE, respectively. 4. Application of external tetraethylammonium (10-20 mM) significantly depolarized the axon and decreased the outward rectification just hyperpolarized to the resting membrane potential. This outward rectification could also be blocked by external barium ions (2-10 mM). 5. Activation of an inward or anomalous rectification in these axons was observed 300-600 ms after the start of a current pulse. In addition, a depolarizing afterpotential (DAP) (1-3 mV in amplitude, 500 ms-10 s in duration) was evident after a current pulse in which inward rectification had been activated. This DAP most likely reflected the slow inactivation of the inwardly rectifying conductance. 6. Inward rectification was blocked by external application of cesium ions (1-3 mM) but it was insensitive to external application of barium ions (2-10 mM). The blockade of the voltage attenuation was accompanied by a disappearance of the DAP and an increase in the charging time constant of the axon. This blockade resulted in a single linear voltage-current (V-I) relationship. Axons now had, on average, an input resistance of 114 +/- 19.1 M omega. 7. Reducing the concentration of external potassium ions increased both the peak and steady-state slope resistance. Reducing the external sodium concentration altered the ETPs and the V-I relationship little but it consistently reduced the magnitude and length of the DAP. These results are compatible with the hypothesis that anomalous rectification is a mixed ionic conductance dependent on potassium and sodium ions in the external media. 8. Overall, the V-I relationship of these intact axons had both linear and nonlinear regions reflecting the activity of numerous slowly activating and inactivating conductances. (ABSTRACT TRUNCATED AT 400 WORDS)
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0022-3077
pubmed:author
pubmed:issnType
Print
pubmed:volume
70
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
2301-12
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1993
pubmed:articleTitle
An examination of frog myelinated axons using intracellular microelectrode recording: the role of voltage-dependent and leak conductances on the steady-state electrical properties.
pubmed:affiliation
Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't