Effects of pancuronium and hexamethonium on paraoxon‐induced twitch potentiation and antidromic firing in rat phrenic nerve diaphragm preparations

Clark, Amanda; Hobbiger, F.; Terrar, D A

doi:10.1111/j.1476-5381.1983.tb10720.x

Cited by 5 publications

(1 citation statement)

References 19 publications

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“…The possible mechanisms for neuromast sensitivity to the acceleration component are discussed in detail by Kroese et al (1980). Since Pancuronium was used for relaxation in the present study which is known to block the cholinergic synapses of the nicotinergic type (Clark et al 1983), the muscarinergic lateral line efferent synapses (Russell 1976) are probably active. In their studies Kroese et al (1978Kroese et al ( , 1980 and Strelioff and Honrubia (1978) used isolated lateral line skin preparations, the intracellular studies were partly made on isolated head preparations (Flock and Russell 1973).…”

Section: Discussionmentioning

confidence: 89%

Single unit activity in the peripheral lateral line system of the cichlid fishSarotherodon niloticus L.

Münz

1985

J. Comp. Physiol.

117

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The activities of single afferent fibers were recorded in the trunk lateral line nerve of the cichlid fish Sarotherodon niloticus L. Using both electrophysiological recordings and neuroanatomical tracing techniques, the number, arrangement, and innervation of superficial (SNs) and canal (CNs) neuromasts were determined. Both, SNs and CNs, are innervated by several afferent fibers of different diameters and efferent fibers. The CNs and SNs are neuronally separated: afferent fibers which innervate both CNs and SNs were not found. Whereas the single CN is innervated by a separate set of afferent fibers, fibers innervating the SNs within rows often branched to reach all or several SNs. The SNs within a row were thus considered to form a functional unit. With the exception of SNs on the tail fin, functional units of neuromasts were in general topographically restricted to single scales.The majority of lateral line units had resting activity. On the basis of the time interval distribution of the resting activity, 4 types of units were classified: these were labelled irregular (type I), regular (type II), bimodal (type III) and silent (type IV). Type I was the most common type of resting activity (obtained in 47.8% of the recorded units). Units with this resting activity type were identified as afferents innervating either SNs or CNs. Units with resting activity of type II represented mostly afferents of CNs if their mean activity was high (around 40 imp/s). If the mean activity of this type was below 20 imp/s the units were unresponsive to local water movements and at least some were identified as efferent fibers. Resting activity of type III was found only in units originating from CNs. Only 4% of the units were silent (type IV). These units were often identified as injured neuromasts.Abbreviations." SN superficial neuromast; CN canal neuromast Units originating from CNs show higher mean resting activity than those from SNs. For both SN and CN units, the mean discharge rate of the resting activity correlated with the sensitivity to stimulation for sinusoidal water movements.During stimulation of the neuromasts by sinusoidal water movements of small amplitude and different frequencies, the response characteristics of SN and CN units were determined by linear frequency analysis under steady state conditions. Most units responded linearly to small stimulus amplitudes. In this amplitude range the units' resting activity was modulated according to the stimulus frequency. Small stimulus amplitudes proportionally changed the amount of modulation but did not alter the phase of the response. CN and SN units that responded linearly produce differing frequency responses. Whereas CNs were most sensitive at frequencies of up to 200 Hz (center frequencies between 100 and 200 Hz), the center frequencies of SNs were distributed between 10 and 70 Hz with a maximum number at about 30 Hz. Bode plots for many CN and SN units indicated that the neuromasts were sensitive to the acceleration component of the water movement.The functional si...

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Section: Discussionmentioning

confidence: 89%

Single unit activity in the peripheral lateral line system of the cichlid fishSarotherodon niloticus L.

Münz

1985

J. Comp. Physiol.

117

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High pancuronium sensitivity of axonal nicotinic‐acetylcholine receptors in humans during organophosphate intoxication

et al. 1991

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The effect of low-dose pancuronium on neuromuscular transmission was studied in 2 patients during the early and late stages of severe organophosphate intoxication. Single evoked compound muscle action potentials (CMAP) were followed by repetitive discharges and a decrement-increment (D-I) phenomenon with 10-, 20-, and 50-Hz supramaximal nerve stimulation. Intravenous pancuronium, 1 mg, abolished the D-I phenomenon, while the repetitive discharges of the CMAP were only partially reduced. It is postulated, that the disappearance of the D-I phenomenon with persistence of the CMAP repetitive discharges results from blockade of nicotinic-acetylcholine receptors located on the terminal axon responsible for stimulus-induced antidromic backfiring. This response to a very low dose of pancuronium indicates a high sensitivity of the axonal nicotinic-acetylcholine receptor to pancuronium in humans, as had been previously postulated from animal experiments.

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Attenuation of soman-induced lesions of skeletal muscle by acetylcholinesterase reactivating and non-reactivating antidotes

A¹,

Sket²,

Sketelj³

et al. 1989

Acta Neuropathol

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It has been reported recently that some oximes reactivating acetylcholinesterase (AChE) exhibit concomitant ganglion-blocking effects which presumably could contribute independently to their powerful antidotal action in organophosphate inhibitor (OPI) poisoning, thus mimicking some unrelated substances which are effective antidotes without reactivating AChE. This raises the question whether OPI-induced muscle lesions, like some other symptoms could also be attenuated by oximes and other antidotes in the absence of AChE reactivation. To test this possibility, the oxime HI-6 was applied at increasing time intervals after the injection of soman until and beyond the point when soman-AChE complex becomes completely "aged" and not capable of reactivation. As the examples of OPI antidotes which do not reactivate AChE, the muscarinic antagonist atropine and the ganglion-blocking agent hexamethonium were also tested on possible attenuation of muscle lesions. The proportions of fibers with lesions, AChE inhibition and muscle fasciculations in experimental groups relative to the controls treated with soman only were evaluated. The results show that HI-6 can attenuate lesions only if AChE is partially reactivated and muscle fasciculations are permanently eliminated. However, atropine does not affect either AChE inhibition or muscle fasciculations and is also ineffective in counteracting the lesions in spite of its potency as an effective general antidote. Hexamethonium also does not affect AChE inhibition, but abolishes fasciculations and effectively attenuates muscle lesions. The latter findings reveal the existence of lesion-protecting mechanisms unrelated to AChE reactivation, which if further elucidated might become potentially relevant for additional treatment in OPI poisoning.

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Effects of pancuronium and hexamethonium on paraoxon‐induced twitch potentiation and antidromic firing in rat phrenic nerve diaphragm preparations

Cited by 5 publications

References 19 publications

Single unit activity in the peripheral lateral line system of the cichlid fishSarotherodon niloticus L.

Single unit activity in the peripheral lateral line system of the cichlid fishSarotherodon niloticus L.

High pancuronium sensitivity of axonal nicotinic‐acetylcholine receptors in humans during organophosphate intoxication

Attenuation of soman-induced lesions of skeletal muscle by acetylcholinesterase reactivating and non-reactivating antidotes

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