- Email: [email protected]
Spontaneous antidromic activity in primary afferent fibers after chronic axotomy
S201
SPONTANEOLJS ANTIDRCMIC ACTIVITY IN PRIMARYAFFERENT FIBERS AFTERCHRONIC AXOTCMY. L.C. Russell and K.J. Burchiel, Dept ( ~~~;~~~~I” 1 of Neurological Surgery, University of Washington, and VA Hospital, Seattle, WA, 98195, USA. Spontaneous antidromic action potentials (AI?.) have Aim of Investigation: been reported in primary afferent axons following axotomy of their peripheral processes. We wished to verify this, quantitate the fiber conduction velocity (CV) spectrum, and determine if such activity was affected by a potassium channel-blocking agent (Gallamine). anesthesia, 28 rats underwent unilateral Methods : Under pentobarbital One to eight weeks later, the rats were again anessa$iZZii? neurotomy. thetized, and microfilament recordings were carried out in the proximal stump of the nerve after removal of the neuroma. Spike-triggered averaging was used to determine the direction of propagation and velocity of recorded APs. Gallamine (20 mg initial dose, 10 mg every 30 minutes) was given (IV) and the nerve was reexamined for spontaneous activity. Control recordings were performed in six rats. Results : Compared to controls, significantly more antidromic activity in bominated and unmyelinated fibers occurred in chronically axotomized nerves. This was further increased by gallamine in A fibers, but not in C fibers . Receptive fields could be demonstrated in 4% of axons with spontaneous activity. The average CV of these active fibers (16.85 + 20.73 m/s) was significantly slower than similarly active fibers in neuroiiias (p< .OOl). Conclusions: Axotomy produces spontaneous activity in A and C fibers _ central to a nerve section. Such activitv in mvelinated fibers is increased by potassium channel blockade. Rarely, this activity may be accounted for by the presence of peripherally dichotomizing axons. This activity occurs in a relatively slower conducting population of axons than does similar activity in neuromas. I
390 Pcstcr
INHIBITORY AND FACILITATORYEFFECTSOF PERIPHERAL ELECTRICAL STIMULATION ON AUTOTOMYINDUCED BY DEAFFERENTATIONIN THE RAT. Y. Yamaguchi, H. Mivaoawa*, H. w and W. Yasumo*. Department of Health Sciences, University of Osaka Prefecture, Sakai, Osaka, 59 1JAPAN. AilR Autotomy of daafferented areas of the rat has bean considered to occur related with phantom sensation including pain. It is notad that peripheral electrical stimulation delivered to the daafferented rat has certain effects on autotomy. This study examines the details of stimulating effects concerning the stimulation parameters. Methods: The unilateral median, ulnar end radial nerves were sectioned in Wister rats. The autotomy of dwfferentad areas wss observed for six weeks after the section. The deefferentad rats were divided into two groups : control and peripheral stimulation ones. The stimulation group was divided into three subgroups according to the site of stimulation. Stimulating electrodes were implanted nesr the nerve stump, to the proxtmal parts of tha sectioned nerve and to the subcutaneous tissue of the hindpaw contralateral to the section, respectively. Frequency of the stimulation was 30 c/sac and two sorts of intensity, strong and weak, were usad. Stimulation was given for one hour a de/ during three weeks after the section. Results : A significant delay of autotomy latency was generally observed, excepting for weak stimulation of the nerve stump, which facilitated autotomy. Stimulation of proximal parts of the sectioned nerves had the most significant inhibitory effects on autotomy. Stimulating effects of the hindpsw contralateral to the section was next to it. After finishing stimuletion session, the inhibitory effects disappesred and autotomy reached to the control level. @@&&Dg : Peripheral electrical stimulation generally inhibits autotomy during stimulation period. But stimulation around the sectioned nerves has facilitatory as well as inhibitory effects on autotomy.
I
SPONTANEOLJS ANTIDRCMIC ACTIVITY IN PRIMARYAFFERENT FIBERS AFTERCHRONIC AXOTCMY. L.C. Russell and K.J. Burchiel, Dept ( ~~~;~~~~I” 1 of Neurological Surgery, University of Washington, and VA Hospital, Seattle, WA, 98195, USA. Spontaneous antidromic action potentials (AI?.) have Aim of Investigation: been reported in primary afferent axons following axotomy of their peripheral processes. We wished to verify this, quantitate the fiber conduction velocity (CV) spectrum, and determine if such activity was affected by a potassium channel-blocking agent (Gallamine). anesthesia, 28 rats underwent unilateral Methods : Under pentobarbital One to eight weeks later, the rats were again anessa$iZZii? neurotomy. thetized, and microfilament recordings were carried out in the proximal stump of the nerve after removal of the neuroma. Spike-triggered averaging was used to determine the direction of propagation and velocity of recorded APs. Gallamine (20 mg initial dose, 10 mg every 30 minutes) was given (IV) and the nerve was reexamined for spontaneous activity. Control recordings were performed in six rats. Results : Compared to controls, significantly more antidromic activity in bominated and unmyelinated fibers occurred in chronically axotomized nerves. This was further increased by gallamine in A fibers, but not in C fibers . Receptive fields could be demonstrated in 4% of axons with spontaneous activity. The average CV of these active fibers (16.85 + 20.73 m/s) was significantly slower than similarly active fibers in neuroiiias (p< .OOl). Conclusions: Axotomy produces spontaneous activity in A and C fibers _ central to a nerve section. Such activitv in mvelinated fibers is increased by potassium channel blockade. Rarely, this activity may be accounted for by the presence of peripherally dichotomizing axons. This activity occurs in a relatively slower conducting population of axons than does similar activity in neuromas. I
390 Pcstcr
INHIBITORY AND FACILITATORYEFFECTSOF PERIPHERAL ELECTRICAL STIMULATION ON AUTOTOMYINDUCED BY DEAFFERENTATIONIN THE RAT. Y. Yamaguchi, H. Mivaoawa*, H. w and W. Yasumo*. Department of Health Sciences, University of Osaka Prefecture, Sakai, Osaka, 59 1JAPAN. AilR Autotomy of daafferented areas of the rat has bean considered to occur related with phantom sensation including pain. It is notad that peripheral electrical stimulation delivered to the daafferented rat has certain effects on autotomy. This study examines the details of stimulating effects concerning the stimulation parameters. Methods: The unilateral median, ulnar end radial nerves were sectioned in Wister rats. The autotomy of dwfferentad areas wss observed for six weeks after the section. The deefferentad rats were divided into two groups : control and peripheral stimulation ones. The stimulation group was divided into three subgroups according to the site of stimulation. Stimulating electrodes were implanted nesr the nerve stump, to the proxtmal parts of tha sectioned nerve and to the subcutaneous tissue of the hindpaw contralateral to the section, respectively. Frequency of the stimulation was 30 c/sac and two sorts of intensity, strong and weak, were usad. Stimulation was given for one hour a de/ during three weeks after the section. Results : A significant delay of autotomy latency was generally observed, excepting for weak stimulation of the nerve stump, which facilitated autotomy. Stimulation of proximal parts of the sectioned nerves had the most significant inhibitory effects on autotomy. Stimulating effects of the hindpsw contralateral to the section was next to it. After finishing stimuletion session, the inhibitory effects disappesred and autotomy reached to the control level. @@&&Dg : Peripheral electrical stimulation generally inhibits autotomy during stimulation period. But stimulation around the sectioned nerves has facilitatory as well as inhibitory effects on autotomy.
I