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Titolo:
WAVE-FORM PARAMETERS OF RECURRENT INHIBITORY POSTSYNAPTIC POTENTIALS IN CAT MOTONEURONS DURING TIME-VARYING ACTIVATION PATTERNS
Autore:
BOORMAN G; WINDHORST U; KIRMAYER D;
Indirizzi:
UNIV CALGARY,FAC MED,DEPT CLIN NEUROSCI,3330 HOSP DR NW CALGARY T2N 4N1 AB CANADA UNIV CALGARY,FAC MED,DEPT CLIN NEUROSCI CALGARY T2N 4N1 AB CANADA UNIV CALGARY,FAC MED,DEPT MED PHYSIOL CALGARY T2N 4N1 AB CANADA
Titolo Testata:
Neuroscience
fascicolo: 3, volume: 63, anno: 1994,
pagine: 747 - 756
SICI:
0306-4522(1994)63:3<747:WPORIP>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
POST-SYNAPTIC POTENTIALS; RANDOM STIMULATION; RENSHAW CELLS; MOTO-NEURONS; PROBABILITY; RESPONSES; AXONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
37
Recensione:
Indirizzi per estratti:
Citazione:
G. Boorman et al., "WAVE-FORM PARAMETERS OF RECURRENT INHIBITORY POSTSYNAPTIC POTENTIALS IN CAT MOTONEURONS DURING TIME-VARYING ACTIVATION PATTERNS", Neuroscience, 63(3), 1994, pp. 747-756

Abstract

A considerable number of theoretical and experimental studies have been undertaken to establish quantitative relationships between the timecourse of postsynaptic potentials in a neuron and the change in firing probability thereby induced. Depending on background synaptic noise level, the time course of the postsynaptic potential per se as well asits time derivative are both of importance in varying proportion. We have recently begun to study recurrent inhibitory potentials in cat hindlimb motoneurons during rhythmically varying rates of stimulation ofmotor axons. The amplitude-rate relationship exhibits hysteresis in that amplitudes are usually larger during augmenting than decrementing rates in the cycle. We here report results on the other important variable, that is the slope of recurrent inhibitory potential development,which need not a priori be correlated with amplitude. We found that the slope has a relation to stimulus rate similar to amplitude, so thatboth parameters are correlated. In pentobarbitone anaesthetized or decerebrate cats, intracellular recordings were obtained from hindlimb skeleto-motoneurons. Various hindlimb muscle nerves were prepared for electrical stimulation to elicit recurrent inhibitory potentials, with dorsal roots cut. Test stimulus patterns consisted of repetitive pulsetrains whose rates varied, at modulation frequencies between 0.1 and 1.0 Hz, in one of two waveforms: triangular or sinusoidal. Modulation depths were either ''full'', with rates varying between a minimum of less than 10 and a maximum of around 50 pulses per s. Or they were about ''half'' this depth, with mean rates shifted into a ''low'', ''medium'' or ''high'' rate region. Recurrent inhibitory potentials were averaged with respect to stimuli occurring during different phases of the stimulation cycle. Most often when, throughout the cycle, the amplitude changed in a consistent way, so did the slopes of the inhibitory potentials. That is, when the amplitudes rhythmically declined with increasing and recovered with decreasing stimulus rate, the rate of hyperpolarization followed the same pattern. With prominent hysteresis in amplitude, a corresponding hysteresis appeared in slopes. Hence, amplitude and slopes were correlated, occasionally showing a hysteresis among themselves. To a certain extent, these results can be explained by Renshaw cell behavior, the contribution of the Renshaw cell-motoneuron synapse being unknown and difficult to assess experimentally. For the inhibitory effect of Renshaw cells on motoneurons (and reciprocal Ia inhibitory interneurons), both its magnitude and its time course probablyplay an important role in determining the efficacy of counteracting local excitatory inputs. The change in slope of inhibitory potentials, and likely its underlying conductance, during cyclic motoneuron activation can be presumed to significantly contribute to the temporal pattern of discharge of motoneurons, in particular in relation to the prevention of synchronization leading to enhanced tremor.

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Documento generato il 27/11/20 alle ore 22:10:34