Selective blockade of components of potassium activation in Myxicola axons

The K+ conductance in Myxicola giant axons activates in two phases which are pharmacologically separable. The fast phase of K+ activation is specifically inhibited by 4-aminopyridine and by the substitution of D2O for H2O. We suggest Myxicola giant axons, like the amphibian node of Ranvier, may possess more than one variety of K+ channel.     

Depletion of synaptic vesicles at the frog (Rana pipiens) neuromuscular junctions by tetraphenylboron

Summary At the frog neuromuscular junction tetraphenylboron produced a decrease in miniature endplate potential amplitude, accompanied by a decrease in the number but not the size of synaptic vesicles.This work was supported by NIH Grants Nos NS-07740 and NS-05707 to R. L. P. and was done during the tenure of a Research Fellowship of Muscular Dystrophy Associations of America, a Wellcome Research Travel Grant and a grant from the Carnegie Trust for the Universities of Scotland to I. G. M. The assistance of Dr.R. M. Schnitzler, W. G. Boldosser andP. M. Spannbauer is gratefully acknowledged.     

Heterogeneous effects of sinusoidal muscular stretching on frequency grams of primary endings due to stimulation of static gamma axons]

The action of sinusoidal stretching at 1,5 Hz on primary ending frequencygrams due to repetitive stimulation of static gamma axons has been studied, in nembutalized cats, on flexor hallucis longus muscle spindles. Whenever, in static conditions, driving is elicited by the repetitive stimulation of gamma axons, the elementary components of the frequencygrams increase in amplitude during muscle stretch. This effect is not observed when the stimulation of the gamma axons gives a regular acceleration of the primary endings without "driving".     

Depletion of synaptic vesicles at the frog (Rana pipiens) neuromuscular junctions by tetraphenylboron.

At the frog neuromuscular junction tetraphenylboron produced a decrease in miniature endplate potential amplitude, accompanied by a decrease in the number but not the size of synaptic vesicles.     

Monosynaptic inhibition of thalamic neurons produced by stimulation of the substantia nigra

Summary Electrical stimulation to the substantia nigra (Pars reticulata) produced a monosynaptic inhibition of the neurons of the ventromedial necleus of the thalamus in anesthetized cats.     

Antidromic inhibition of presumed fusimotor neurones by repetitive stimulation of the ventral root in the decerebrate cat

Résumé On a enregistré des décharges de 17 fibres fusimotrices dont on suppose l'existence dans les filaments de racines ventrales des chats décérébrés. 8 fibres ont été inhibées par stimulation répétée de la portion centrale isolée du reste de la racine ventrale. Ces résultats montrent qu'il existe une inhibition antidromique dans les neurones fusimoteurs.     

Study of the cortical field potentials produced by weak light stimulation in adult rabbits]

On a chronic preparation of an adult Rabbit, the cortical visual evoked response, produced by a weak luminous stimulation activating only the scotopic system is characterized by the suppression of the early surface-positive phase and by a lengthening of the latencies of the following deflection. The profile of the fields of potential corresponding to the various defletions in relation to the depth, has been investigated.     

The influence of reserpine upon the changes in femoral blood flow produced by stimulation of the lumbar sympathetic chain

Zusammenfassung Die durch sympathische Nervenreizung ausgelöste Vasoconstriktion im Hinterbein des Hundes wird durch Reserpinvorbehandlung aufgehoben. Die dazu benötigten Reserpindosen entsprechen denen, die am Herzen Verlust der Nervenfunktion und des Noradrenalingehaltes hervorrufen.

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This work was supported by grants from the U.S. Public Health Service H-2205, the American Heart Association 59-G-11, and the Eugene Higgins Trust.     

Modulation of transmission in different electronic junctions by aminopyridine

Summary 4 distinct electronic inputs can be identified in amphibian motoneurons perfused with calcium-free solution containing manganese. The differential effect of 4-aminopyridine on different electrotonic junctions may reflect the peculiarities of molecular architecture of potassium channels in different electrically excitable presynaptic membranes.We thank Prof. D. R. Curtis, of National University Canberra, for the gift of 4-aminopyridine.     

The effect of asphyxia and re-oxygenation on bilateral dorsal root potentials produced by stimulation of the cutaneous afferents

Résumé Les potentiels conditionnants et les tests effectués sur la racine dorsale des deux cotés de la moelle montrent une sensibilité différenciée à l'asphyxie. Après le rétablissement de l'oxygénation la dépression du potentiel ipsilatéral testé est augmentée et les potentiels contralatéraux n'apparaissent qu'après un retard prolongé.     

Modulation of transmission in different electronic junctions by aminopyridine.

4 distinct electronic inputs can be identified in amphibian motoneurons perfused with calcium-free solution containing manganese. The differential effect of 4-aminopyridine on different electronic junctions may reflect the peculiarities of molecular architecture of potassium channels in different electrically excitable presynaptic membranes.     

Degeneration of unmyelinated axons in the dental root canal induced by 6-OH-dopamine

Summary The pulpal nerve fibres of feline incisors were examined ultrastructurally after i.v. administration of 6-OH-dopamine. The presence of degenerating unmyelinated fibres at this site provides conclusive morphological evidence that sympathetic fibres enter the dental pulp.     

Zinc ions block the second but not the first phasic response to repetitive application of carbachol and histamine in guinea-pig taenia caeci

In the presence of Zn²⁺ (0.3 mM), carbachol (10^–6 M) or histamine (10^–5 M) induced the phasic response in guinea-pig taenia caeci while the tonic response was markedly inhibited. However, when the muscles were kept in Zn²⁺-containing medium following the first stimulation with either carbachol or histamine, neither application of carbachol nor of histamine elicited another phasic contraction. Caffeine (25 mM) did not induce contraction in the presence of Zn²⁺. After the washing out of caffeine in the presence of Zn²⁺, however, the muscle did then develop the phasic response on the application of carbachol or histamine. In conclusion, Zn²⁺ did not affect the carbachol or histamine-induced Ca²⁺ release from the storage sites. However, when Zn²⁺ was continuously present, Ca²⁺ was not supplied to the storage sites. Furthermore, carbachol and histamine mobilized a common cellular Ca²⁺ store, but they activated Ca²⁺ release channels different from the ones activated by caffeine in the Ca²⁺ storage sites.