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Titolo:
Medullary reticulospinal tract mediating the generalized motor inhibition in cats: Parallel inhibitory mechanisms acting on motoneurons and on interneuronal transmission in reflex pathways
Autore:
Takakusaki, K; Kohyama, J; Matsuyama, K; Mori, S;
Indirizzi:
Asahikawa Med Coll, Dept Physiol, Asahikawa, Hokkaido 0788510, Japan Asahikawa Med Coll Asahikawa Hokkaido Japan 0788510 kkaido 0788510, Japan Tokyo Med & Dent Univ, Dept Pediat, Bunkyo Ku, Tokyo 1130034, Japan Tokyo Med & Dent Univ Tokyo Japan 1130034 unkyo Ku, Tokyo 1130034, Japan Sapporo Med Coll, Dept Physiol, Sapporo, Hokkaido 0608543, Japan Sapporo Med Coll Sapporo Hokkaido Japan 0608543 , Hokkaido 0608543, Japan Natl Inst Physiol Sci, Okazaki, Aichi 4448585, Japan Natl Inst Physiol Sci Okazaki Aichi Japan 4448585 i, Aichi 4448585, Japan
Titolo Testata:
NEUROSCIENCE
fascicolo: 2, volume: 103, anno: 2001,
pagine: 511 - 527
SICI:
0306-4522(2001)103:2<511:MRTMTG>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEUS-RETICULARIS GIGANTOCELLULARIS; INTACT UNANESTHETIZED CAT; NON-RECIPROCAL INHIBITION; LUMBAR MOTONEURONS; SYNAPTIC POTENTIALS; SPINAL-CORD; FUNCTIONAL-ORGANIZATION; CHOLINERGIC PROJECTIONS; DESCENDING PROJECTIONS; SPINDLE AFFERENTS;
Keywords:
spinal interneurons; alpha-gamma linkage; decerebrate preparation; REM sleep; locomotion;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
68
Recensione:
Indirizzi per estratti:
Indirizzo: Takakusaki, K Asahikawa Med Coll, Dept Physiol, Asahikawa, Hokkaido 0788510, Japan Asahikawa Med Coll Asahikawa Hokkaido Japan 0788510 , Japan
Citazione:
K. Takakusaki et al., "Medullary reticulospinal tract mediating the generalized motor inhibition in cats: Parallel inhibitory mechanisms acting on motoneurons and on interneuronal transmission in reflex pathways", NEUROSCIENC, 103(2), 2001, pp. 511-527

Abstract

The present study was designed to elucidate the spinal interneuronal mechanisms of motor inhibition evoked by stimulating the medullary reticular formation. Two questions were addressed. First, whether there is a parallel motor inhibition to motoneurons and to interneurons in reflex pathways. Second, whether the inhibition is mediated by interneurons interposed in known reflex pathways. We recorded the intracellular activity of hindlimb motoneurons in decerebrate cats and examined the effects of medullary stimulation on these neurons and on interneuronal transmission in reflex pathways to them. Stimuli (three pulses at 10-60 muA and 1-10 ms intervals) delivered to the nucleus reticularis gigantocellularis evoked inhibitory postsynaptic potentials in a-motoneurons (n = 147) and gamma -motoneurons (n = 5) with bothearly and late latencies. The early inhibitory postsynaptic potentials were observed in 66.4% of the motoneurons and had a latency of 4.0-5.5 ms witha segmental delay of more than 1.4 ms. The late inhibitory postsynaptic potentials were observed in 98.0% of the motoneurons and had a latency of 30-35 ms, with a peak latency of 50-60 ms. Both types of inhibitory postsynaptic potentials were evoked through fibers descending in the ventrolateral quadrant. The inhibitory postsynaptic potentials were not influenced by recurrent inhibitory pathways, but both types were greatly attenuated by volleysin flexor reflex afferents. Conditioning medullary stimulation, which was subthreshold to evoke inhibitory postsynaptic potentials in the motoneurons, neither evoked primary afferent depolarization of dorsal roots nor reduced the input resistance of the motoneurons. However, the conditioning stimulation often facilitated non-reciprocal group I inhibitory pathways (Tt,inhibitory pathways) to the motoneurons in early (<20 ms) and late (30-80 ms) periods. In contrast, it attenuated test postsynaptic potentials evoked through reciprocal Ia inhibitory pathways, and excitatory and inhibitory pathways from flexor reflex afferent and recurrent inhibitory pathways. The inhibitory effects were observed in both early and late periods. The present results provide new information about a parallel inhibitory process from the medullary reticular formation that produces a generalized motor inhibition by acting on <alpha>- and gamma -motoneurons, and on interneurons in reflex pathways. Interneurons receiving inhibition from flexor reflex afferents and a group of Ib interneurons may mediate the inhibitory effects upon motoneurons. (C) 2001 IBRO. Published by Elsevier Science Ltd. AUrights reserved.

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Documento generato il 18/02/20 alle ore 05:18:41