Search results for "Antidromic"
showing 9 items of 9 documents
Origin of impulse initiation in the slowly adapting stretch receptor of the crayfish
1974
Characteristic for the crayfish stretch receptor is a gradual decrease in axon diameter up to a stretch of axon about 350 μm away from the soma-axon border. In response to depolarizing currents applied at different positions along the axon this stretch of axon can be localized as the most excitable membrane region. When depolarizing current steps of 10–25 nA intensity are injected into the soma the first impulse is always triggered in the soma (due to sudden rise in the membrane potential) while the second impulse originates at the axon region of highest escitability. As the intensity of the stimulus is increased the site of impulse initiation along the axon shifts nearer to the receptor so…
EFFERENT CONNECTIONS OF THE CEREBELLUM OF THE WEAKLY ELECTRIC FISH EIGENMANNIA SP. (GYMNOTODEI)
1981
An efferent connection of lobus caudalis cells of the cerebellum of the electric fish Eigenmannia sp. has been verified by means of electrical stimulation and recording techniques. Stimulating in the lobus caudalis, an orthodromic activation has been found in the reticular formation of the midbrain tegmentum. Switching recording and stimulating electrodes led to an antidromic activation in cells of the lobus caudalis. The area identified in the midbrain corresponds to what, in higher vertebrates, is called the red nucleus.
Neuropeptides in Primary Afferent Neurons
1990
Traditionally, the primary sensory neurons, having their perikarya in the spinal or cranial sensory ganglia with processes directed towards the periphery and the central nervous system, have been regarded to function as receptive and afferent systems which reflexly activate central effector systems.1 This, however, does not apply to the small diameter primary afferents as suggested by the observation made about a century ago that antidromic stimulation of transected dorsal roots or sensory nerves caused vasodilatation and inflammatory signs in the skin.2,3 The novel concept which has been confirmed by many investigators ascribes to small diameter (particularly unmyelinated C) primary sensor…
Impaired neuromuscular transmission during partial inhibition of acetycholinest-erase: The of stimulus-induced antiromic backfiring in the generation…
1992
Neuromuscular transmission was studied in the rat phrenic nerve-hemidiaphragm preparation with acetylcholinesterase (AChE) partially inactivated. Enzyme inhibition resulted in (1) increased single-twitch tension of the diaphragm; (2) compound muscle action potential (CMAP) containing repetitive discharges; (3) stimulus-induced antidromic backfiring (SIAB) seen in the phrenic nerve; and (4) repetitive nerve stimulation (RNS) eliciting a decrement-increment (D-I) phenomenon (i.e., amplitude reduction maximal with the second CMAP). Using a high-calcium and low-magnesium solution, SIAB and the decrement of the second CMAP during RNS were intensified, whereas closely spaced trains and (+)-tubocu…
Conditioning effect of transcranial magnetic stimulation evoking motor‐evoked potential on V‐wave response
2014
Abstract The aim of this study was to examine the collision responsible for the volitional V‐wave evoked by supramaximal electrical stimulation of the motor nerve during voluntary contraction. V‐wave was conditioned by transcranial magnetic stimulation (TMS) over the motor cortex at several inter‐stimuli intervals (ISI) during weak voluntary plantar flexions (n = 10) and at rest for flexor carpi radialis muscle (FCR; n = 6). Conditioning stimulations were induced by TMS with intensity eliciting maximal motor‐evoked potential (MEPmax). ISIs used were ranging from −20 to +20 msec depending on muscles tested. The results showed that, for triceps surae muscles, conditioning TMS increased the V‐…
Presence of muscarinic inhibitory and absence of nicotinic excitatory receptors at the terminal sympathetic nerves of chicken hearts.
1976
Nicotine (2 X 10(-4) M) or acetylcholine (5.5 X 10(-4) M) in the presence of 3 X 10(-6) M atropine did not increase the rate or amplitude of contraction in isolated atria or ventricular strips of the chicken heart; both drugs also did not cause an output of noradrenaline or adrenaline and did not evoke antidromic discharges in the right sympathetic nerves of isolated perfused chicken hearts. In contrast, "high K+-solutions" evoked an output of noradrenaline and adrenaline and caused a burst of antidromic discharges. Dimethylphenylpiperazine (DMPP; 3.1 X 10(-4) M), by a tyramine-like action, elicited a small output of noradrenaline and increased rate and amplitude of contraction" but did not…
Pancuronium improves the neuromuscular transmission defect of human organophosphate intoxication.
1990
Two patients with acute severe organophosphate intoxication showed (1) single evoked compound muscle action potentials (CMAP) with repetitive discharges and (2) prominent decremental responses of CMAP with 20 and 50 Hz supramaximal nerve stimulation. Following the intravenous injection of single small doses of pancuronium, marked improvement in these abnormalities occurred and persisted for several hours. We postulate that the physiologic improvement following low-dose pancuronium results from blockade of acetylcholine receptors, especially those located on the terminal axon responsible for antidromic backfiring.
Backfiring of the isolated rat phrenic nerve does not collide with impulse propagation following repetitive nerve stimulation at 1-50 Hz.
1991
Acetylcholinesterase inhibition with neostigmine in the isolated rat phrenic nerve-hemidiaphragm preparation induced axonal backfiring and repetitive compound muscle action potentials following single nerve stimulation. The duration of backfiring and the repetitive compound muscle action potentials did not exceed 55 ms. With repetitive nerve stimulation at frequencies ranging from 1 to 50 Hz, backfiring was present only with the first stimulus and the amplitude of the second compound muscle action potential was maximally reduced, while the subsequent responses recovered gradually. However, the amplitudes of the concommitant antidromic nerve action potentials remained unchanged during the en…
High pancuronium sensitivity of axonal nicotinic-acetylcholine receptors in humans during organophosphate intoxication.
1991
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 respo…