Recurrent inhibition to and from motoneurons innervating the flexor digitorum and flexor hallucis longus muscles of the cat

1990 ◽  
Vol 63 (3) ◽  
pp. 395-403 ◽  
Author(s):  
T. M. Hamm
Keyword(s):  
Tibialis Anterior ◽  
Recurrent Inhibition ◽  
Medial Gastrocnemius ◽  
Flexor Hallucis Longus ◽  
Flexor Digitorum Longus ◽  
Lateral Gastrocnemius ◽  
Hindlimb Muscles ◽  
Inhibitory Postsynaptic Potentials ◽  
Flexor Digitorum ◽  
Stimulation Of

1. Recurrent inhibitory postsynaptic potentials (IPSPs) to and from motoneurons innervating the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) muscles of the cat were investigated to determine whether recurrent inhibitory projections involving these motoneurons are similar--as would be consistent with the Ia and anatomic synergism of FDL and FHL--or are dissimilar, as are the activities of these muscles during locomotion (O'Donovan et al. 1982). 2. Composite recurrent IPSPs were recorded in several species of motoneurons innervating hindlimb muscles in response to stimulation of a number of muscle nerves in cats allowed to become unanesthetized after ischemic decapitation. 3. No recurrent IPSPs from stimulation of the FDL nerve were observed in motoneurons innervating FDL, FHL, lateral gastrocnemius-soleus (LG-S), medial gastrocnemius (MG), plantaris (Pl), tibialis anterior (TA), or extensor digitorum longus (EDL). 4. The recurrent IPSPs produced by stimulation of FHL were larger and found more frequently in LG-S than in FDL motoneurons. Recurrent inhibition from FHL was also greater in Pl than in FDL motoneurons. 5. The recurrent IPSPs produced by stimulation of LG-S, PL, and MG were larger in FHL than in FDL motoneurons, and those from LG-S and MG were found more frequently in FHL than in FDL motoneurons. 6. Stimulation of the TA nerve produces recurrent IPSPs in FDL but not in FHL motoneurons. A few FDL and FHL cells (6 of 23 and 9 of 34, respectively) received small (less than 0.5 mV) recurrent IPSPs from stimulation of the EDL nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrent collaterals of motoneurons projecting to distal muscles in the cat hindlimb

1992 ◽  
Vol 67 (5) ◽  
pp. 1359-1366 ◽  
Author(s):  
M. L. McCurdy ◽  
T. M. Hamm
Keyword(s):  
Recurrent Inhibition ◽  
Flexor Hallucis Longus ◽  
Flexor Digitorum Longus ◽  
First Order ◽  
Hindlimb Muscles ◽  
Ankle Muscles ◽  
Anterior Tibial ◽  
Recurrent Collateral ◽  
Recurrent Collaterals ◽  
Flexor Digitorum

1. Recurrent collaterals of motoneurons innervating muscles that have a role in control of the hindlimb digits were studied with neuroanatomic tracing methods to determine whether these motoneurons have simple recurrent collateral arbors in comparison with those of hip, knee, and ankle muscles. 2. Motoneurons innervating the hindlimb muscles plantaris (Pln), flexor hallucis longus (FHL), or flexor digitorum longus (FDL) were injected with 10% horseradish peroxidase. Recurrent collaterals were reconstructed from serial transverse sections. 3. No recurrent collaterals were observed in a sample of 10 FDL motoneurons. 4. FHL motoneurons had simple recurrent collateral arbors as assessed by number of first-order collaterals, number of collateral swellings, number of end branches, and the highest-order branch of individual collateral trees. Recurrent collateral arbors of Pln motoneurons were more complex than those of FHL motoneurons. Pln and FHL recurrent collateral arbors were less complex than those described for gastrocnemius-soleus, anterior tibial, and posterior biceps motoneurons. 5. These anatomic findings correspond well with electrophysiological results indicating that the recurrent inhibition produced by FHL motoneurons is weak and that FDL motoneurons do not produce recurrent inhibition. In addition, Pln motoneurons are reported to produce stronger recurrent inhibition than FHL motoneurons in many motor pools. 6. Consideration of these results with respect to the mechanical actions and patterns of motor activity observed in FDL, FHL, and Pln suggests that the complexity of recurrent collaterals of a motoneuron pool and the extent of its contribution to recurrent inhibition diminish with its involvement in the individualized control of the digits.

Heterogeneous atrophy occurs within individual lower limb muscles during 60 days of bed rest

2012 ◽  
Vol 113 (10) ◽  
pp. 1545-1559 ◽  
Author(s):  
Tanja Miokovic ◽  
Gabriele Armbrecht ◽  
Dieter Felsenberg ◽  
Daniel L. Belavý
Keyword(s):  
Lower Limb ◽  
Bed Rest ◽  
Cross Sectional Area ◽  
Medial Gastrocnemius ◽  
Flexor Hallucis Longus ◽  
Sectional Area ◽  
Flexor Digitorum Longus ◽  
Cross Sectional ◽  
Lateral Gastrocnemius ◽  
Flexor Digitorum

To better understand disuse muscle atrophy, via magnetic resonance imaging, we sequentially measured muscle cross-sectional area along the entire length of all individual muscles from the hip to ankle in nine male subjects participating in 60-day head-down tilt bed rest (2nd Berlin BedRest Study; BBR2–2). We hypothesized that individual muscles would not atrophy uniformly along their length such that different regions of an individual muscle would atrophy to different extents. This hypothesis was confirmed for the adductor magnus, vasti, lateral hamstrings, medial hamstrings, rectus femoris, medial gastrocnemius, lateral gastrocnemius, tibialis posterior, flexor hallucis longus, flexor digitorum longus, peroneals, and tibialis anterior muscles ( P ≤ 0.004). In contrast, the hypothesis was not confirmed in the soleus, adductor brevis, gracilis, pectineus, and extensor digitorum longus muscles ( P ≥ 0.20). The extent of atrophy only weakly correlated ( r = −0.30, P < 0.001) with the location of greatest cross-sectional area. The rate of atrophy during bed rest also differed between muscles ( P < 0.0001) and between some synergists. Most muscles recovered to their baseline size between 14 and 90 days after bed rest, but flexor hallucis longus, flexor digitorum longus, and lateral gastrocnemius required longer than 90 days before recovery occurred. On the basis of findings of differential atrophy between muscles and evidence in the literature, we interpret our findings of intramuscular atrophy to reflect differential disuse of functionally different muscle regions. The current work represents the first lower-limb wide survey of intramuscular differences in disuse atrophy. We conclude that intramuscular differential atrophy occurs in most, but not all, of the muscles of the lower limb during prolonged bed rest.

Determination of afferent fibers mediating oligosynaptic group I input to cat medial gastrocnemius motoneurons

1985 ◽  
Vol 53 (2) ◽  
pp. 518-529 ◽  
Author(s):  
R. K. Powers ◽  
M. D. Binder
Keyword(s):  
Electrical Stimulation ◽  
Medial Gastrocnemius ◽  
Flexor Hallucis Longus ◽  
Selective Activation ◽  
Group I ◽  
Afferent Fibers ◽  
Series Of Experiments ◽  
Group Ii ◽  
Flexor Digitorum ◽  
Stimulation Of

In the experiments described in the preceding paper electrical stimulation of the quadriceps (QUAD), medial tibial (MTIB), and flexor digitorum and hallucis longus (FDHL) muscle nerves was used to evoke oligosynaptic group I postsynaptic potentials (PSPs) in medial gastrocnemius (MG) motoneurons. In the present study, we attempted to specify the types of afferent fibers which mediate that oligosynaptic activity (FDHL to MG only). In one series of experiments, isolated single flexor digitorum longus (FDL) and flexor hallucis longus (FHL) afferents were identified as Ia, Ib, or group II fibers according to their conduction velocities, responses to muscle contraction, and mechanical thresholds to small amplitude triangular stretches applied to the parent muscles. We also determined the electrical thresholds of the identified afferent fibers by applying graded electrical stimulation to their muscle nerve. These results were used as criteria to define the types of afferents that mediated the electrically and stretch-evoked FDHL oligosynaptic PSPs recorded in MG motoneurons during a second series of experiments. The amplitudes of the oligosynaptic PSPs evoked in MG motoneurons increased as the strength of the electrical stimuli applied to the FDHL muscle nerves was raised to activate greater numbers of Ia- and Ib-fibers, but showed little or no additional increase when the stimulus intensity was raised further to include the majority of group II fibers. On this basis, a significant contribution by group II fibers to these oligosynaptic PSPs was considered unlikely. Simultaneous electrical activation of both Ia- and Ib-fibers produced distinct oligosynaptic PSPs in MG motoneurons, but these were likely due primarily to Ib-afferent activity, since selective activation of Ia-afferents (by stretch) rarely produced oligosynaptic PSPs in the same motoneurons. There was, however, evidence for some Ia contribution to these oligosynaptic PSPs. This is consistent with the demonstration that Ia- and Ib-afferent fibers converge onto common interneurons and that selective activation of Ia-fibers can produce PSPs similar to those evoked by concurrent stimulation of Ia- and Ib-fibers. On the basis of the present results and those of several related studies it is argued that the oligosynaptic PSPs evoked in MG motoneurons by submaximal group I stimulation of the FDHL, MTIB, or QUAD muscle nerves can be ascribed predominantly to the activation of Ib-afferent fibers, with only minimal Ia and probably no group II contribution.

Topography of recurrent inhibitory postsynaptic potentials between individual motoneurons in the cat

1994 ◽  
Vol 72 (1) ◽  
pp. 214-226 ◽  
Author(s):  
M. L. McCurdy ◽  
T. M. Hamm
Keyword(s):  
Input Resistance ◽  
Biceps Femoris ◽  
Recurrent Inhibition ◽  
Medial Gastrocnemius ◽  
Lateral Gastrocnemius ◽  
Postsynaptic Potentials ◽  
Inhibitory Postsynaptic Potentials ◽  
Extensor Muscles ◽  
Regulation Of Activity ◽  
Motor Nuclei

1. The amplitude of recurrent inhibitory postsynaptic potentials (RIPSPs) was examined in pairs of lumbosacral motoneurons that were separated by a known distance and were identified by antidromic stimulation of muscle nerves. One motoneuron was stimulated by injecting depolarizing current pulses, and postsynaptic responses were recorded and averaged in the second motoneuron. Input resistance, rheobase, and conduction velocity were determined for many motoneurons. Most motoneurons innervated extensor muscles. 2. RIPSP values as large as -283 microV were recorded, but most were between -10 and -40 microV. RIPSPs from individual motoneurons of a pool are distributed to several heteronymous motor nuclei and have a range of amplitudes comparable with homonymous RIPSPs. 3. A specific spatial distribution of RIPSP amplitudes was found whereby the largest RIPSP amplitudes (> 40 microV) occurred in motoneurons located within +/- 1.4 mm of the stimulated motoneuron. A significant correlation was found between RIPSP amplitude and the distance between motoneurons for all motoneuron pairs. This correlation was also found within individual groups of motoneuron pairs that innervate the lateral gastrocnemius, medial gastrocnemius, anterior-middle biceps femoris, or soleus muscles. 4. The dependency of RIPSP amplitude on the motoneuron species, which is the particular muscle a motoneuron innervates, is less distinct than the dependency of RIPSP amplitude on topography. Pooling all motoneuron species of close motoneuron pairs indicated that RIPSPs measured in homonymous motoneuron pairs were greater in amplitude than RIPSPs measured in heteronymous pairs. In addition, homonymous RIPSPs of anterior middle biceps femoris or lateral gastrocnemius motoneurons were greater than heteronymous RIPSPs of those motoneurons in all heteronymous combinations. However, homonymous and heteronymous RIPSPs were not significantly different when heteronymous pairs were restricted to individual combinations of species. These findings indicate that RIPSP amplitudes within a set of motor nuclei interconnected by recurrent inhibition are dependent in some cases on the species of motoneurons, but this effect is less important than the effect of topography on RIPSP amplitude. 5. These results indicate that recurrent inhibition in motoneuron pools that innervate hindlimb extensor muscles has a strong topographic organization, such that the strongest recurrent inhibition is produced by each motoneuron in a restricted rostrocaudal zone that includes both homonymous and heteronymous motor nuclei. This suggests that recurrent inhibition is organized for the control of several motor nuclei engaged in common motor activity as well as regulation of activity within individual motor pools.

Accessory museulus soleus

1926 ◽  
Vol 22 (5-6) ◽  
pp. 511-513
Author(s):  
V. N. Ternovsky ◽  
M. Sadykova
Keyword(s):  
Lower Limb ◽  
Lower Leg ◽  
Flexor Hallucis Longus ◽  
Posterior Surface ◽  
Flexor Digitorum Longus ◽  
Accessory Muscle ◽  
Peroneus Brevis ◽  
The Right ◽  
Flexor Digitorum

Dissecting the muscles of the right lower limb of an unknown corpse, we found an accessory muscle on the posterior surface of the lower leg. This muscle (see Fig.) Was bordered behind in. soleus and with the tendon m. plantaris, in front - with in. flexor hallucis longus, medially - c m. flexor digitorum longus and laterally - c m. peroneus brevis.

Homosynaptic depression and transmitter turnover in spinal monosynaptic pathway

1977 ◽  
Vol 40 (1) ◽  
pp. 95-105 ◽  
Author(s):  
R. Capek ◽  
B. Esplin
Keyword(s):  
Transmitter Release ◽  
Motor Nerve ◽  
Drug Effects ◽  
Medial Gastrocnemius ◽  
Lateral Gastrocnemius ◽  
Homosynaptic Depression ◽  
Dorsal Root Reflex ◽  
Frequency Of Stimulation ◽  
Fractional Release ◽  
Stimulation Of

1. The transmission in the spinal monosynaptic pathway was studied during repetitive stimulation of a motor nerve by 10 stimuli at 2, 5, or 10 Hz in spinal cats. Initially, the amplitudes of the monosynaptic responses rapidly declined, reaching a plateau after a few stimuli. The level of the plateau was inversely related to the frequency of stimulation. 2. This depression of monosynaptic response was seen only when the same pathway was stimulated; the response elicited from the lateral gastrocnemius was not depressed when preceded by stimulation of the medial gastrocnemius nerve and vice versa. Pretreatment with semicarbazide left the homosynaptic depression unchanged while suppressing the dorsal root reflex. The participation of a depolarization of primary afferents in the described depression is, therefore, unlikely. 3. The decrease of transmitter release by successive volleys, which is the cause of the observed depression, could conceivably be related to the depletion of transmitter stores. 4. A procedure is described, based on this assumption, which allows the calculation of transmitter turnover. The input-output relation in the spinal monosynaptic pathway is used to convert the amplitudes of monosynaptic responses to the amounts of transmitter, both relative to the maximum response. The changes of transmitter release are analyzed under the assumption that each volley releases instantaneously a constant fraction of the transmitter store available for release and that this store is replenished at a constant fraction of the depleted part per second. 5. The values of fractional release per volley were about 0.4, irrespective of frequency of stimulation. 6. The values of fractional replenishment per second ranged from about 1 to 5 on the average, depending directly on the frequency of stimulation. 7. It is suggested that the described procedure might be useful in analyzing drug effects on synaptic transmission.

Distribution of oligosynaptic group I input to the cat medial gastrocnemius motoneuron pool

1985 ◽  
Vol 53 (2) ◽  
pp. 497-517 ◽  
Author(s):  
R. K. Powers ◽  
M. D. Binder
Keyword(s):  
Sural Nerve ◽  
Afferent Input ◽  
Medial Gastrocnemius ◽  
Resting Potential ◽  
Tibialis Posterior ◽  
Medial Branch ◽  
Motoneuron Pool ◽  
Group I ◽  
Flexor Digitorum ◽  
Stimulation Of

To characterize the oligosynaptic group I afferent input to the cat medial gastrocneumius (MG) motoneuron pool, the medial branch of the tibial nerve (MTIB: flexor digitorum and hallucis longus, popliteus, tibialis posterior and interosseous nerves), the nerves to flexor digitorum and hallucis longus (FDHL), or the nerves to the quadriceps muscles (QUAD) were stimulated at submaximal group I strength while recording intracellularly from MG motoneurons. Since previous work indicates that stimulation of these nerves at group I strength produces no significant monosynaptic Ia excitation or Renshaw inhibition of MG motoneurons, group I effects were assumed to be predominantly, though not exclusively, due to the action of Ib-fibers. Evidence supporting this assumption is presented in the following paper. MTIB, FDHL, and QUAD postsynaptic potentials (PSPs) were most commonly inhibitory. Since the MTIB, FDHL, and QUAD nerves are composed predominantly of fibers innervating muscles with extensor action, their inhibitory effect on MG motoneurons is consistent with previous findings that stimulation of Ib-afferents in nerves to extensor muscles produces di- and trisynaptic inhibition of extensor motoneurons. However, excitatory effects were observed in about one third of the motoneurons, indicating that oligosynaptic group I input is not homogeneously distributed within the MG motoneuron pool. Variations in QUAD, FDHL, and MTIB PSP pattern and amplitude were correlated with variations in the PSP pattern evoked by stimulation of the sural nerve: excitatory oligosynaptic group I PSPs generally appeared in motoneurons receiving excitatory cutaneous (sural nerve) input, whereas inhibitory PSPs generally appeared in motoneurons receiving some inhibitory cutaneous input and were largest in motoneurons receiving predominantly inhibition from the sural nerve. These variations in QUAD, FDHL, and MTIB PSP pattern and amplitude were not due to variations in resting potential and were only partly due to variations in intrinsic motoneuron properties or motoneuron "type." Our results indicate that activation of these cutaneous and group I muscle afferents can exert similar effects on the MG motoneuron pool. Moreover, the presence of a strong correlation between the distributions of cutaneous and oligosynaptic group I PSPs within a single motoneuron pool is consistent with the results of previous studies that have shown that some of the input to motoneurons from these peripheral afferents is mediated through common interneurons.

Communications between the tendons of flexor hallucis longus and flexor digitorum longus: a cadaveric study

2019 ◽  
Vol 41 (12) ◽  
pp. 1411-1419
Author(s):  
T. K. Vasudha ◽  
P. C. Vani ◽  
G. Sankaranarayanan ◽  
S. S. S. N. Rajasekhar ◽  
V. Dinesh Kumar
Keyword(s):  
Cadaveric Study ◽  
Flexor Hallucis Longus ◽  
Flexor Digitorum Longus ◽  
Flexor Digitorum

Tonic and Phasic Discharge Patterns in Toe Flexor γ-Motoneurons During Locomotion in the Decerebrate Cat

2002 ◽  
Vol 87 (1) ◽  
pp. 286-294 ◽  
Author(s):  
P. R. Murphy
Keyword(s):  
Mechanical Action ◽  
Emg Activity ◽  
Flexor Hallucis Longus ◽  
Plantar Flexor ◽  
Step Cycle ◽  
Decerebrate Cat ◽  
Hindlimb Muscles ◽  
Discharge Patterns ◽  
Flexor Digitorum ◽  
Α Activity

To investigate the specificity of fusimotor (γ) drive during locomotion, γ-efferents were recorded from the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) nerves in a decerebrate cat preparation. These nerves innervate hindlimb muscles that differ in some aspects of their mechanical action. For both FHL and FDL two stereotyped patterns of γ activity were distinguished. Tonic units fired throughout the step cycle and had less modulation, but higher minimum rates, than phasic units, which were mainly recruited with ankle extensor [soleus (SOL)] electromyogram (EMG) activity. Differences in the relative timing of these patterns were apparent. In FHL the activity of phasic and most tonic neurons peaked after EMG onset. With FDL, tonic units generally reached maximum rate before, while phasic units peaked after, the beginning of EMG activity. During locomotion FHL and FDL α activity were rhythmically recruited with SOL. However, consistent with previous reports, FHL and FDL differed in their patterns of α activity. FHL was stereotyped while FDL was variable. Both FHL and FDL had activity related to ankle extensor EMG, but only FDL exhibited a peak around the end of this phase. No corresponding γ activity was observed in FDL. In conclusion, 1) FHL and FDL received tonic and phasic fusimotor drive; 2) there was no α/γ linkage for the late FDL α burst; 3) phasic γ-efferents in both muscles received similar inputs, linked to plantar flexor α activity; and 4) tonic γ-efferents differed, to the extent that they were modulated at all. The FHL units peaked with the plantar flexor alphas. The FDL neurons generally peaked before α activity even began.

Synaptic organization of defined motor-unit types in cat tibialis anterior

1980 ◽  
Vol 43 (6) ◽  
pp. 1631-1644 ◽  
Author(s):  
R. P. Dum ◽  
T. T. Kennedy
Keyword(s):  
Motor Unit ◽  
Tibialis Anterior ◽  
Muscle Afferents ◽  
Medial Gastrocnemius ◽  
Synaptic Organization ◽  
Ia Afferents ◽  
Group I ◽  
Ia Epsp ◽  
Group I Afferents ◽  
Stimulation Of

1. Synaptic potentials were recorded intracellularly in tibialis anterior (TA) motoneurons following stimulation of a descending brain stem pathway, the medial longitudinal fasciculus (MLF), and three segmental inputs, the homonymous and heteronymous group Ia afferents, the group I afferents from the antagonist, and the cutaneous and muscle afferents. Intracellular stimulation of the motoneurons was used to classify them, based on the properties of the innervated muscle units, into types FF, F(int), FR, and S (6, 16). 2. The sum of the monosynaptic EPSP amplitudes resulting from stimulation of homonymous and heteronymous group Ia afferents (summed group Ia EPSP) was inversely related to motoneuron size, as assessed by motoneuron input resistance, and was inversely related to motor-unit tetanic tension. Type-FF, -FR, and -S motoneurons showed significant differences in the mean amplitude of their summed group Ia EPSPs. 3. The amplitudes of disynaptic IPSPs resulting from stimulation of group I afferents in the antagonist muscle also showed an inverse relationship to motoneuron size. The observed relationships between motoneuron size and the monosynaptic group Ia EPSP amplitude or the disynaptic group I IPSP amplitude are compatible with the “size principle” of motor-unit recruitment (26). 4. The amplitudes of the monosynaptic EPSPs evoked in TA motoneurons by stimulation of the MLF were distributed rather randomly among all types of TA motoneurons. A slight tendency of larger monosynaptic EPSPs to occur in motoneurons with larger tetanic tensions was observed. 5. The polysynaptic effects from cutaneous and muscle afferents in sural and gastrocnemius-soleus nerves were frequently excitatory on type-FF motoneurons, but were primarily inhibitory on type-FR and -S motoneurons. Clearly, the polysynaptic cutaneous and muscle inputs and the monosynaptic MLF input onto TA motoneurons show a different pattern of synaptic organization than the group I inputs. 6. In general, the synaptic organization of the TA motor nucleus is similar to that of its extensor antagonist, medial gastrocnemius (MG) (2--5, 7, 8), when analogous neural circuits are compared. This parallel organization suggests a commonality of motor-control systems for both flexor and extensor muscles.

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