A study of spontaneous miniature potentials in spinal motoneurones

Katz, Bernard; Miledi, Ricardo

doi:10.1113/jphysiol.1963.sp007199

Cited by 318 publications

(150 citation statements)

References 40 publications

(42 reference statements)

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“…The observations of Eccles and co-workers (Eccles et al 1957a) & Nelson, 1966). With moderately deep barbiturate anaesthesia as used here the 'spontaneous' synaptic activity impinging on these neurones (see Katz & Miledi, 1963;Hubbard, Stenhouse & Eccles, 1967) was reduccxd to a rather low level and the mEPSP activity elicited by small amounts of muscle stretch could be examined against a relatively quiet background (Fig. 2, upper record).…”

Section: Methodsmentioning

confidence: 86%

Group Ia synaptic input to fast and slow twitch motor units of cat triceps surae

Burke¹

1968

The Journal of Physiology

189

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SUMMARY1 The characteristics of the group Ia synaptic input to triceps surae motoneurones have been examined in pentobarbitone-anaesthetized cats, using intracellular recording techniques. The mechanical properties of the muscle units innervated by the cells were determined and the motoneurone input resistance values were also measured.2. A significant positive correlation was found between the maximum amplitudes of homonymous composite (electrically evoked) monosynaptic excitatory post-synaptic potentials (EPSPs) and the motoneurone input resistance values across the entire population of units sampled. The same correlation in the case of heteronymous EPSPs was also significant although somewhat less strong.3. The distribution of the amplitudes of unitary miniature EPSPs (mEPSPs) of presumed group Ia origin, elicited by small static stretches of the homonymous muscles, were also studied. A significant positive correlation was found between the median amplitudes of the mEPSP distributions and the input resistance values in the motoneurones studied. Positive correlation was also observed between the amplitudes of the median mEPSPs and the maximum homonymous composite EPSPs in the cells for which both data points were available.4. In each of these correlations, the synaptic potential amplitudes tended to be larger in the relatively high resistance type S (slow twitch muscle unit) motoneurones from both gastrocnemius and soleus motor pools, than in the lower resistance type F (fast twitch muscle unit) gastrocnemius cells.

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Section: Methodsmentioning

confidence: 86%

Group Ia synaptic input to fast and slow twitch motor units of cat triceps surae

Burke¹

1968

The Journal of Physiology

189

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“…In spite of this they have to be considered as inhibitory postsynaptic potentials (IPSP) for reasons demonstrated in Figures 2 and 3. In spinal motoneurons of the frog it is a common feature, that only depolarizing PSPs are recordable (Katz and Miledi, 1963). However, a depolarization of the membrane potential by intracellular current injection reverses one component of the PSP into a hyperpolarizing direction, thus charac-terizing it as an IPSP ( Fig.2; Sonnhof et al, 1975).…”

Section: Resultsmentioning

confidence: 99%

“…As can be seen in Figure 1 B1 also under normal conditions the membrane potential showed small irregular appearing oscillations. These small postsynaptic potentials of frog motoneurons were first described by Katz and Miledi (1963) and were called "spontaneous miniature potentials". Some minutes after the application of guanidine into the bath solution (5 9 10 .4 M/7 min) these potentials strongly increased in amplitude and frequency ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The increase in the amplitude of inhibitory postsynaptic potentials induced by dorsal root stimulation (DR-IPSP) in the spinal cord of the frog is comparable with the enhancement in the amplitude of endplate potentials caused by guanidine in nervemuscle preparations (Otsuka and Endo, 1960;Kamenskaya et al, 1975a, b;Terfivfiinen and Larsen, 1975). The small postsynaptic potentials in spinal motoneurons of the frog originate from action potentials of spontaneously active interneurons and, similar to the miniature endplate potentials of neuromuscular transmission, from a spontaneous transmitter release in the nerve terminals (Katz and Miledi, 1963;Colomo and Erulkar, 1968). Guanidine, however, only enhanced the action potential induced transmitter release, since in contrast to the spontaneous transmitter release, which is resistant to high magnesium concentrations (Katz and Miledi, 1963;Erulkar et al, 1974), stimulus induced synaptic activation, as well as the action of guanidine were blocked by addition of magnesium ions (15 mM) into the Ringer solution (see Fig.…”

Section: Discussionmentioning

confidence: 98%

“…Only some very small postsynaptic potentials could be recorded also in the presence of magnesium ions (Fig.4B). These potentials may originate from a spontaneous transmitter release in synaptic terminals, which cannot be blocked by magnesium (Katz and Miledi, 1963;Erulkar et al, 1974).…”

Section: Effects Of Guanidine During High Magnesium Concentrationmentioning

confidence: 99%

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Effects of guanidine on synaptic transmission in the spinal cord of the frog

Grafe

Sonnhof

Kühner³

1977

Naunyn-Schmiedeberg's Arch. Pharmacol.

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Summary. The effects of guanidine on motoneurons of the isolated frog spinal cord were studied by adding the drug to the solution bathing the cord during intracellular recording. Guanidine (5.10 -4 M) did not alter the membrane potential of motoneurons.The main effect was a marked increase of the amplitudes and frequencies of small spontaneously occurring inhibitory postsynaptic potentials. The hyperpolarizing component of postsynaptic potentials evoked by stimulation of dorsal roots was also enhanced by guanidine. Higher concentrations of guanidine (5 9 10 -3 M) resulted in a very large and irreversible increase of the small spontaneously occurring inhibitory potentials, which now appeared in a regular, rhythmic pattern.The effects of guanidine could easily be blocked by increasing the magnesium ions (15 raM) in the bath solution.These results indicate that guanidine facilitates the release of an inhibitory transmitter in afferent terminals of the frog spinal cord either by a direct action on these terminals or indirectly by an action on nerve endings impinging on inhibitory interneurons.

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The anatomical organization of hindlimb motoneurons in the lumbar spinal cord of the frog, Rana catesbiana

Cruce

1974

J of Comparative Neurology

117

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The precise location of lumbar spinal motoneurons was studied in the bullfrog by observing the retrograde reaction following injury to nerves which innervate different hindlimb muscles. The results were confirmed and their usefulness for physiological studies was demonstrated by iontophoretically injecting dye through an intracellular recording micropipette into motoneurons which were identified by antidromic spike invasion. The effects of plexus variation upon the location of motoneuron pools was considered in order to standardize the results and make possible comparisons between different frogs.New determinations were made of frog hindlimb muscle function with reference to jumping in order to assess the possible functional significance of motoneuron organization. In general, motoneurons acting upon proximal joints are located rostrally to motoneurons acting upon distal joints and flexor motoneurons are located rostrally to extensors. The somatotopic significance of motoneuron organization was also assessed and it was found that within the lateral motoneuron column there are three groups of cells, each of which innervates different, but somatotopically related groups of muscles. This organization is quite similar to that found in cats. The developmental and functional implications of this similarity are considered.

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A study of spontaneous miniature potentials in spinal motoneurones

Cited by 318 publications

References 40 publications

Group Ia synaptic input to fast and slow twitch motor units of cat triceps surae

Group Ia synaptic input to fast and slow twitch motor units of cat triceps surae

Effects of guanidine on synaptic transmission in the spinal cord of the frog

The anatomical organization of hindlimb motoneurons in the lumbar spinal cord of the frog, Rana catesbiana

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