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PubMed1988

Effect of crush lesion on radiolabelling of ganglioside in rat peripheral nerve.

Left sciatic nerves of adult male Sprague-Dawley rats were crushed and allowed to recover for 0, 1, 2, 4, 7, or 14 days. At each of these times both L-5 dorsal root ganglia were injected with 100 microCi of [3H]glucosamine. Two days later, dorsal root ganglia, lumbosacral trunks, and sciatic nerves were removed bilaterally. The amounts of radiolabelled ganglioside in crushed lumbosacral trunks were consistently higher than in the controls, with the largest difference occurring within 2 days from simultaneous crush and injection to killing (specimens labelled day 0). The largest difference in the amount of radiolabelled ganglioside between crushed and control sciatic nerve (4-9 days from crush to killing) occurred later than that of lumbosacral trunk, but no significant difference occurred within the first 3 days following crush. There was only a slightly higher radioactivity in gangliosides totalled from all three anatomical specimens of crushed than in control nerves. The neutral nonganglioside lipid and acid-precipitable fraction followed patterns of synthesis and accumulation similar to those of the gangliosides. These findings indicate that after nerve crush gangliosides, glucosamine-labelled neutral nonganglioside lipids, and glycoproteins accumulate close to the proximal end of the regenerating axon. This accumulation could serve as a reservoir to increase the ganglioside concentration in the growth cone membrane.

Animals↗
PubMedDate not supplied

Feasibility of implant driven micturition in paraplegic dogs.

OBJECTIVE: This study evaluates the feasibility of using existing technology for implant driven micturition in paralyzed dogs (part I) and also examines a less invasive technique for implant driven micturition (part II). STUDY DESIGN: Part I. Sacral nerve root dimensions and bladder and urethral pressure responses to intradural and extradural sacral nerve root stimulation were measured to determine the optimal location and size for sacral nerve root electrodes. Part II. Sacral nerve roots were stimulated via wire electrodes introduced into the S2 foramina. ANIMALS OR SAMPLE POPULATION: Ten dogs (five dogs in part I and five dogs in part II). METHODS: Part I. Microtip pressure transducers were used to monitor bladder and urethral pressure responses to sacral nerve root stimulation with tripolar hook electrodes. After euthanasia, sacral nerve root, and spinal canal dimensions were measured. Part II. Bipolar electrical stimulation of the sacral nerve roots was performed by introducing wire electrodes into the S2 foramina. Bladder and urethral pressures were recorded as in part I. RESULTS: Part I. Stimulation of SI produced an increase in urethral, but not bladder, pressure. Stimulation of S2 or S3 produced increases in bladder pressure and decreases in urethral pressure. Intradural and extradural nerve roots were not significantly different with respect to nerve dimensions or effects on nerve stimulation. Part II. High bladder pressures were achieved, but effective voiding could not be produced, primarily because of urethral resistance. CONCLUSIONS: Part I. Extradural implantation was determined to be the most appropriate site based on ease of dissection, nerve root dimensions, and decreased risk of iatrogenic trauma. Enough space is available to implant two to four tripolar spiral nerve cuffs. Part II. Transforaminal sacral nerve root stimulation did not effectively empty the bladder. CLINICAL RELEVANCE: Clinical trials in paraplegic dogs are necessary to evaluate the number of sacral nerve cuff electrodes necessary to produce effective bladder emptying.

Animals↗
PubMed1987

FES for bladder: direct or indirect means?

Efforts to restore function to the neurologically disabled lower urinary tract by direct electrical stimulation of the bladder wall have met with only very limited success. This has been due to pain and cocontraction of bladder outlet mechanisms caused by presumed spread of the large currents required to effectively directly stimulate the detrusor muscle. Stimulation at the four anatomical sites of the sacral neural outflow on the other hand has been more successful. Conus medullaris stimulation has resulted in "good results" in just over half of the 28 patients so treated. Acceptance of this technique has been limited by the poor selectivity of the intramedullary electrodes in stimulating only the target motor neurons and the resultant clinical problems with the consequent stimulus current spread. Sacral anterior root stimulation has been used in at least 88 patients with generally good results. Cocontraction of the detrusor and external urethral sphincter are circumvented by the use of an intermittent pattern of stimulation. The primary disadvantage of this technique is the obligatory placement of the electrodes within the cerebrospinal fluid compartment. Clinical experience with stimulation of the extradural sacral mixed nerves is limited. Experimental studies indicate that success with this technique requires dorsal rhizotomy and pudendal neurotomy. Preliminary clinical experience suggests that these surgical manipulations may not be necessary for a successful outcome. The literature on clinical application of pelvic nerve stimulation is too limited for detailed comment on this technique. A definitive technique for restoration of bladder function by electrical stimulation remains to be developed.

Electric Stimulation Therapy↗
PubMed1997

Delivery and pudendal nerve function.

OBJECTIVE: To assess the impact of mode of delivery and the occurrence of pelvic instability upon the pudendal nerve function and relate the pudendal nerve function to the occurrence of anal and urinary incontinence. METHODS: One hundred and forty-six pregnant women were examined during pregnancy and 12 weeks post partum with measurement of pudendal nerve terminal motor latency (PNTML), the difference between the two measurements was defined as delta PNTML. Anal and urinary continence status, details of delivery and the occurrence of pelvic instability were recorded prospectively. RESULTS: Pudendal nerve terminal motor latency increased from 1.7 msec in primiparae and 1.8 msec in multiparae during pregnancy to 2.0 msec (p < 0.001) and 2.1 (p < 0.001) respectively after delivery. The increase was significantly higher after the use of vacuum extraction (p < 0.04). Multivariate analysis showed that delta PNTML was associated with age, the presence of pelvic instability and the use of vacuum extraction. Whereas delta PNTML was not associated with factors such as infant's head circumference and weight, parity, cesarean section, pudendal block, epidural analgesia and second stage of labor. Only four women had anal incontinence after delivery. Twenty-five women with urinary incontinence had a significantly higher mean PNTML (2.20 msec) than 121 continent women (2.01 msec). CONCLUSION: Pudendal nerve terminal motor latency increases in both primiparous and multiparous women after delivery. In 10% of the women the increase resulted in a pathologic PNTML value > 2.4 msec. The delta PNTML was significantly associated with age, the occurrence of pelvic instability and the use of vacuum extraction. The group of women with urinary incontinence had a significant increased PNTML.

Adult↗
PubMed1982

Spinal evoked potentials evaluated with two relevant electrode types.

The spinal evoked potentials (SEPs) were recorded at the level of the 7th lumbar segment in five cats by stimulating the popliteal nerve separately on both sides. The recordings were performed both with silver-silver chloride cup electrodes and stainless steel needle electrodes. The shapes and latencies of the responses were highly similar, when comparing the responses recorded with the two electrode types as shown by means of transfer function: attenuation and phase curves for both electrode types are highly similar in the bandpass used in the present study. It is concluded that the properties of stainless steel needle electrodes are highly correspondent with the conventional silver-silver chloride electrodes when somatosensory evoked responses are recorded.

Animals↗
PubMed1966

The release of acetylcholine from the spinal cord of the cat by antidromic stimulation of motor nerves.

1. ACh was measured in the effluent from the perfused lumbosacral cord of the cat with or without stimulation of the central ends of the cut left sciatic and femoral nerves after section of the left dorsal roots.2. In about 30% of the preparations ACh was obtained in the samples collected at rest (average 3.3 ng/min); the amount of ACh release was increased 1.3-9 times by stimulation of the peripheral nerves. The average amount of ACh collected during stimulation of the peripheral nerves at 5/sec was 6.9 ng/min. Antidromic motor nerve impulses responsible for the ACh release were likely to be only those in alpha motor fibres.3. There was a depression in ACh release/stimulus as the stimulus frequency was increased more than 10/sec. Such changes in ACh release with various stimulus frequencies were correlated with depression in the response of Renshaw cells to excitation through motor-axon collaterals.4. Amounts of ACh release during stimulation of the peripheral nerves at 5/sec were significantly increased for 1 or 2 min after a short tetanic stimulation of the nerves.5. Intravenous injection of dihydro-beta-erythroidine did not reduce the amount of ACh release produced by stimulation of the peripheral nerves.6. It is concluded that antidromic impulses in alpha motor fibres liberate ACh from the presynaptic terminals at the central synapses on Renshaw cells.

Acetylcholine↗
PubMed1966

Algebraical summation in synaptic activation of motoneurones firing within the 'primary range' to injected currents.

1. In intracellular studies of cat lumbar motoneurones constant synaptic stimuli such as stretch, contraction or a high-frequency stimulation of a cut afferent nerve have been superimposed on firing in response to injected currents.2. As long as the slope relating spike frequency to injected current remained constant, which by definition is the ;primary range' of firing, algebraical summation of superimposed synaptic stimulation prevailed. Added quantities in these experiments were then between 2.0 and 56.2 impulses/sec for excitation, between -2.8 and -21.8 impulses/sec for inhibition.3. Data were obtained correlating firing rates with amount of synaptic potential and current respectively.4. Theoretical implications are dealt with in the Discussion.

Animals↗
PubMed1966

Synaptic stimulation superimposed on motoneurones firing in the 'secondary range' to injected current.

1. This paper extends the work on the ;primary range' of firing (Granit, Kernell & Lamarre, 1966), in lumbar motoneurones to the ;secondary range'. By definition the latter begins when, with stronger currents, the linear curve relating firing rate to injected current in the primary range undergoes a fairly sudden increase of slope.2. It was shown that motoneurones firing at the higher frequencies of the secondary range were partially inactivated. Yet such firing rates were within the physiological range.3. Algebraical summation of firing rates, when present in the secondary range, implied at the same time that the synaptic amount added was diminished by comparison with what it had been within the primary range.4. Superimposed synaptic excitatory stimuli did not (as in the ;primary range') regularly add their effect algebraically on to the rate of firing achieved by injected currents alone. More commonly the synaptic effect of the constant input underwent a progressive increase throughout the secondary range.5. Superimposed inhibitory stimuli regularly reduced the slope constant as determined by trans-membrane current alone and, by counter-acting inactivation, made the motoneurone approach the mode of firing characteristic of the ;primary range'.6. The latter finding emphasizes the significance of analysing firing motoneurones with the aid of ;slope constants' and provides inhibition with a new role in the integrative behaviour of motoneurones, as considered in the Discussion.

Animals↗
PubMed1967

The distribution of acetylcholine in normal and in regenerating nerves.

1. The distribution of acetylcholine (ACh) in various nerves which had been regenerating for different periods after crushing has been compared with that in uncrushed nerves.2. Normal ventral roots from cats contained 78.1 +/- 22.7 (S.D.) mumole ACh/kg (blotted wet wt.); rabbit ventral roots contained 48.0 mumole/kg +/- 19.0 (S.D.) and rabbit sciatic nerves 16.6 +/- 7.3 (S.D.) mumole/kg. In the sciatic nerves the distal cm of 5 cm lengths taken from the thigh contained 30% more ACh than the most central cm portion. Possible explanations for this difference have been discussed.3. After both sciatic nerves and ventral roots had been crushed, there was an initial build-up (4 times control) of ACh central to the lesion and a decline ((1/4) control) distal to the lesion. These changes were maximum around 5 days after crushing. In sciatic nerves in which long periods of regeneration were investigated, the central build-up fell off to 1(1/2) times control by 25 days and the distal decline reversed to 2 times control in about 10 days. It then again decreased towards the control level by 25 days after crushing. These changes have been discussed in relation to the morphological changes which occur in a nerve following crushing.4. A peak of ACh content moved distally along the nerve from the crushed region at a rate of 1.0-1.5 mm/day. This was considered to represent an average rate of regeneration of the bulk of the axons. The amplitude of the peak declined progressively with time in the more distal parts of the nerve, probably because of dispersion as axons regenerated at different rates.

Acetylcholine↗
PubMed1971

The time course of minimal excitory post-synaptic potentials evoked in spinal motoneurones by group Ia afferent fibres.

1. Group Ia EPSPs were recorded from lumbosacral motoneurones in anaesthetized cats after almost complete section of the relevant dorsal roots. The EPSPs were usually of small amplitude (median value of 230 muV) and an averaging device was used to improve the definition of their time course.2. From a total of over 500 averaged EPSPs a smaller number (342) were subjected to analysis. The other EPSPs were rejected either because they showed signs of multiple origin in the rising phase of their time course (see Methods) or because the resting membrane potential of the cell was less than 50 mV. All the selected EPSPs had their rise time (from the 10 to the 90% level) and half-width measured, and a semilogarithmic plot of their decay time course was made.3. 252 of the EPSPs showed an exponential decline in their later time course and the slope of this line was used to give an estimate of the membrane time constant. The range of the time constant for different motoneurones was 2.3-12.9 msec, with a mean value of 5.8 msec.4. In ten cells an EPSP was recorded which was judged to be generated exclusively by synaptic knobs located on the soma. On this assumption measurements of the normalized rise time, half-width and break point time were used to estimate alpha, rho(infinity) and L by the method suggested in Jack & Redman (1971b). The estimated value of alpha ranged from 18 to 65. A positive correlation was found between alpha and tau(m), indicating that for these EPSPs the duration of current injection was independent of the membrane time constant. The peak time of the wave form of current injection was between 0.1 and 0.25 msec. The estimates of rho(infinity) were not thought to be very accurate. A lower limit of 4 was assumed and the highest measured value was 12, but in three cells the time course of the EPSP could not be fitted even with a very high value of rho(infinity). Some possible explanations for this discrepancy are mentioned in the Discussion. The electrotonic length of the dendrites (L) was usually greater than 1.0 lambda and ranged between 0.75 and 1.5 lambda. Evidence for an open-circuit termination of the dendrites was found in some cells.5. The normalized values of the rise time and half-width were used to make an electrotonic distance allocation to the 246 EPSPs which were judged to be non-somatic. The method of allocation was not precise because individual values of rho(infinity) and L were not available for these motoneurones. Instead, a maximum possible range was assumed: for rho(infinity), 4-25; for L, 0.75-1.5. The range of alpha was also assumed, from 12 to 100. With these values the motoneurone model (Jack & Redman, 1971b) was used to set limits within which the normalized rise time and half-width of all EPSPs, generated by current at a single point, should lie. Twenty of the 246 EPSPs lay outside these boundary lines and hence they did not receive a distance allocation. The remaining 226 were assigned values between 0.2 and 1.6 lambda (in 0.2 lambda steps); the majority of the allocations (183) were to the proximal electrotonic part of the dendrites (0.2, 0.4 or 0.6 lambda). The relationship of these distance allocations to the histological results of Conradi (1969) is discussed.6. It is concluded that there is no good evidence against the view that the main time course of minimal Ia EPSPs can be explained by their generation by a brief pulse of synaptic current and subsequent passive spread.

Animals↗
PubMed1972

The effects of stimulation of the left atrial receptors on sympathetic efferent nerve activity.

1. Activation of left atrial receptors by distension of balloons at the pulmonary vein-atrial junctions caused an increase in the cardiac sympathetic nerve activity, a decrease in the renal sympathetic nerve activity, and no change in the lumbar and splenic sympathetic nerve activity.2. The cardiac and renal nerve responses to balloon distension were abolished by vagal blockade in the neck.3. The results provide additional evidence that the reflex increase in the heart rate following stimulation of the left atrial receptors is mediated by selective activation of cardiac sympathetic nerve fibres.4. The inhibitory effect of atrial receptor activation on the renal sympathetic nerve activity suggests that a neural factor, possibly involving renal haemodynamics, may be a component of the diuretic response to the activation of the left atrial receptors.5. The results provide further evidence for the selective nature of the pattern of reflex responses to left atrial receptor activation and show for the first time a directionally fractionated response from sympathetic efferent neurones.

Action Potentials↗