Disease relevance of Muscle Spindles

• METHODS: We used the vibration induced facilitation of an MEP of the sternocleidomastoid muscle (SCM) as a surrogate marker for muscle spindle function in 20 healthy subjects and 10 patients with idiopathic rotational torticollis in whom BTX was injected unilaterally [1].

Psychiatry related information on Muscle Spindles

• Toe flexor muscle spindle discharge and stretch modulation during locomotor activity in the decerebrate cat [2].
• Blockade of the tonic hindlimb extensor component of maximal electroshock and pentylenetetrazol-induced seizures by drugs acting on muscle and muscle spindle systems: a perspective on method [3].
• Each of the two joints in this system is independently controlled by a neurological control model for single joint movements, consisting of an idealized pair of antagonistic muscles (flexor and extensor), their common load, and proprioception from the muscle spindles [4].

High impact information on Muscle Spindles

• Egr3 was highly expressed in developing muscle spindles, but not in Ia afferent neurons or their terminals during developmental periods that coincided with the induction of spindle morphogenesis by sensory afferent axons [5].
• Although extrafusal skeletal muscle fibers appeared normal, Egr3-deficient animals lacked muscle spindles, a finding that is consistent with their profound gait ataxia [5].
• Importantly, the number of muscle spindles in heterozygous mutant mice was half of that in control mice, indicating that NT-3 is present at limiting concentrations in the embryo [6].
• Recent molecular studies have identified the gonadotropin subunit, luteinizing hormone beta, as an EGR1-regulated gene in vivo and uncovered an essential role for EGR3 in muscle-spindle development [7].
• The diversity of the heavy-chain subunits of myosin (MyHCs) in intrafusal fibers is thought to reflect a pathway of differentiation that is unique to muscle spindles [8].

Chemical compound and disease context of Muscle Spindles

• From comparison of the effect of procaine and diazepam on the phasic and static responses of the muscle spindle it was concluded that directly after the injection of diazepam the gamma motor activity was completely abolished at a dose as low as 0.1 mg/kg whereas the alpha motor system was only partly depressed even at higher doses [9].

Biological context of Muscle Spindles

• Baclofen, a specific GABAB receptor agonist, was used to study the functional role of activation of GABAB receptors in synaptic transmission between muscle spindle afferents and motoneurons in the isolated spinal cord of bullfrogs [10].
• Dantrolene, a muscle contraction antagonist, and MI-65-S, a muscle spindle suppressant, significantly delayed THE [3].
• By means of tungsten microelectrodes, action potentials from axons within the dorsal spino-cerebellar tract (DSCT) and from muscle spindle afferents were recorded [11].
• The cross-correlation analysis suggested that the membrane potentials of both tonic and phasic motoneurons are equally lowered by eperisone or that monosynaptic transmission from primary afferents of muscle spindles to motoneurons is inhibited by eperisone [12].
• Diphenylhydantoin, 10 mg/kg, suppressed only the cerebellar potentials evoked by muscle stretch indicating a suppression of muscle spindle function leading to a reduced cerebellar input [13].

Anatomical context of Muscle Spindles

• Finally, neurotrophin 3 released from muscle spindles regulates the strength of sensory-motor connections within the spinal cord postnatally [14].
• DiI staining of dorsal roots indicated that limb injections of anti-NT3 reduced the spinal projection of muscle spindle afferents [15].
• Achilles tendon reflexes and the dynamic discharge from primary muscle spindles were evaluated after five or ten injections of acrylamide [16].
• Lesions of the posterior column pathways, in which muscle spindle afferents run towards the brain, are associated with loss of servo responses in the long flexor of the thumb, in the absence of motor weakness and with tendon jerks preserved [17].
• We show here that in the chick oculomotor system, endogenous GDNF is derived largely from extraocular muscle but less from glial cells and not from muscle spindles [18].

Associations of Muscle Spindles with chemical compounds

• More than 30 years ago, Frank and Fuortes proposed that the synaptic effectiveness of muscle spindle afferents associated with spinal motoneurones could be diminished by the activation of nerves from flexor muscles [19].
• Phenytoin and carbamazepine reduce the afferent output of muscle spindles [20].
• Quantal analysis, performed using a deconvolution technique, of the monosynaptic EPSPs in brachial motoneurons evoked by activity in single triceps muscle spindle afferents showed that transmission at these synapses was quantal, and baclofen lowered the quantal content without altering the quantal size [10].
• 1. A method of classification of muscle spindle afferents using succinylcholine (SCh) and ramp stretches has recently been described, which appears to estimate separately the strength of influence of bag1 (b1) and of bag2 (b2) intrafusal fibres [21].
• Activation of cat muscle spindle primary, secondary and intermediate sensory endings by suxamethonium [22].

Gene context of Muscle Spindles

• Sensory ataxia and muscle spindle agenesis in mice lacking the transcription factor Egr3 [5].
• We provide genetic evidence that Neuregulin1 (Nrg1) is required for proprioceptive afferent-evoked induction of muscle spindle differentiation in the mouse [23].
• Erbb2 regulates neuromuscular synapse formation and is essential for muscle spindle development [24].
• Peripherally, muscle spindles are absent and TrkC-positive axons do not enter their target muscles [25].
• We have monitored the expression of three transcription factors, Egr3, Pea3, and Erm, that delineate early muscle spindle development in an assay of muscle spindle-inducing signals [23].

Analytical, diagnostic and therapeutic context of Muscle Spindles

• Unitary recordings were made from 20 primary and 17 secondary muscle spindle afferents via a tungsten microelectrode inserted percutaneously into the peroneal nerve in 10 awake, healthy subjects seated with the legs supported in the extended position [26].
• Noradrenaline and serotonin were applied ionophoretically close to a selected neuron, and their effects were tested on extracellularly recorded responses of this neuron to electrical stimulation of low-threshold skin afferents and group II muscle spindle afferents [27].
• Sensory denervation of the plantar lumbrical muscle spindles in pyridoxine neuropathy [28].
• Intravenous injection of succinylcholine showed no increase in whole nerve activity attributable to muscle spindles, and had a negligible effect on identified receptors in the wrist joint capsule [29].
• Isolated muscle spindles from lower lumbrical muscles of rats were used to study the 3-dimensional organization of intrafusal structures by scanning electron microscopy following (a) complete denervation, (b) reinnervation after a single crush lesion of the sciatic nerve, or (c) reinnervation after transection and immediate suture of this nerve [30].

References