| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Velocity changes following single and double conditioning impulses were studied by microneurography in single human C fibres to provide information about axonal membrane properties. C units were identified as mechano-responsive (n = 19) or mechano-insensitive (12) nociceptors, cold-sensitive (8) or sympathetic fibres (9), and excited by single, double and triple electrical stimuli to the skin at mean rates of 0.25-2 Hz. The interval between single or paired (20 ms apart) conditioning stimuli and test stimulus was then varied between 500 and 2 ms, and recovery curves of velocity change against inter-spike interval constructed, allowing for changes in these variables with distance. All fibres exhibited an initial (4-24 ms) relative refractory phase, and a long-lasting (>500 ms) 'H2' phase of reduced velocity, attributed to activation of Na+/K+-ATPase. Mechano-responsive nociceptors exhibited an intermediate phase of either supernormality or subnormality, depending on stimulation rate. Mechano-insensitive nociceptors behaved similarly, but all were supernormal at 1 Hz. Sympathetic units exhibited only a long-lasting supernormality, while cold fibres exhibited a briefer supernormal and a late subnormal phase (H1), similar to A fibres. A pre-conditioning impulse doubled H2 and increased H1, but did not augment supernormality or the subnormality of similar time course. Like A fibre supernormality, these phenomena were explained by a passive cable model, so that they provide an estimate of membrane time constant. Nociceptor membrane time constants (median 110 ms, n = 17) were rather insensitive to membrane potential, indicating few active voltage-dependent potassium channels, whereas sympathetic time constants were longer and reduced by activity-dependent hyperpolarisation.
This article has been cited by other articles:
|
|
 |
|
  R. De Col, K. Messlinger, and R. W. Carr Conduction velocity is regulated by sodium channel inactivation in unmyelinated axons innervating the rat cranial meninges J. Physiol., February 15, 2008; 586(4): 1089 - 1103. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Burke The properties of axons differ according to their function J. Physiol., January 1, 2007; 578(1): 1 - 2. [Full Text] [PDF]
|
|
|
|
|
|
A. George, J. Serra, X. Navarro, and H. Bostock Velocity recovery cycles of single C fibres innervating rat skin J. Physiol., January 1, 2007; 578(1): 213 - 232. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. M. Lang, G. Moalem-Taylor, D. J. Tracey, H. Bostock, and P. Grafe Activity-Dependent Modulation of Axonal Excitability in Unmyelinated Peripheral Rat Nerve Fibers by the 5-HT(3) Serotonin Receptor J Neurophysiol, December 1, 2006; 96(6): 2963 - 2971. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. D Baker Protein kinase C mediates up-regulation of tetrodotoxin-resistant, persistent Na+ current in rat and mouse sensory neurones J. Physiol., September 15, 2005; 567(3): 851 - 867. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Bostock, M. Campero, J. Serra, and J. L. Ochoa Temperature-dependent double spikes in C-nociceptors of neuropathic pain patients Brain, September 1, 2005; 128(9): 2154 - 2163. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. R. Light "Nocifensor" System Re-Revisited. Focus on "Two Types of C Nociceptor in Human Skin and Their Behavior in Areas of Capaicin-Induced Secondary Hyperalgesia" J Neurophysiol, June 1, 2004; 91(6): 2401 - 2403. [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
