SEARCH · Search PubMed

Results for “Forelimb”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

PubMed1992

Organization of the forelimb area in squirrel monkey motor cortex: representation of digit, wrist, and elbow muscles.

The EMG in 8 to 14 hand, forearm, and arm muscles evoked by intracortical electrical stimulation was recorded at 433 sites in layer V in the region of the forelimb area of the primary motor cortex (MI) of three squirrel monkeys during ketamine anesthesia. At each site, the EMG was recorded at movement threshold (T) and at 1.5T and 2T at each site (but less than or equal to 60 microA), and the threshold movement was noted. In the animals examined, the total MI forelimb area identified by movements or EMG occupied about 25 to 35 mm2. At most sites from which a forelimb movement was evoked, EMG activity was evoked in one or more of the recorded muscles. One group of sites located rostrolaterally to the main forelimb area was separated by an intervening zone largely related to the face. The average area from which digit, wrist, elbow, or shoulder movement was evoked at threshold was nearly the same, and their movement thresholds were not significantly different. Average movement thresholds across the anterior-posterior extent of MI were also similar. All muscles recorded could be activated by cortical stimulation. Most commonly more than one muscle was activated from a single site. The highest individual EMG levels were produced at sites from which more than one muscle was activated. These results suggest that small regions of MI influence multiple muscles. Individual muscles were typically activated at multiple, spatially separated locations. For many muscles, increasing the stimulation intensity revealed additional separate areas of activation. Spatial locations of different muscles showed considerable interanimal variation. The size of most muscle representations was relatively large. The smallest representations always included the intrinsic hand muscles and the largest included the proximal muscles. Orderly topographic relationships among forelimb joints or muscles within the MI forelimb area were not apparent. Although distal muscle activation tended to be found posteriorly in the forelimb area and proximal muscles tended to be activated from anterior sites, both could be activated from broadly distributed and overlapping areas. The broad, overlapping nature of the muscle representation supports the concept that a small region of cortex is involved in controlling functional groups of muscles. The intermingling of muscle representations may provide a substrate for local cortical interactions among territories representing various muscle synergies or for changing associations of muscle groups. The representation plan derived from these mappings contains elements of all previously described summaries of MI organization.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2000

Individual speed dependency of forelimb lameness in trotting horses.

Using a system for motion analysis, linear correlation of speed and forelimb lameness was measured in 16 horses trotting on a treadmill at a minimum of three different trotting speeds. Forelimb lameness was determined as asymmetry of vertical head motion during left and right forelimb stance. In seven horses with a moderate forelimb lameness (head motion asymmetry >40%), lameness increased significantly with trotting speed. In a further seven horses with mild or subclinical forelimb lameness (head motion asymmetry <40%) and in two horses with a moderate forelimb lameness, no significant correlation between speed and motion asymmetry was found. The results indicate that moderate forelimb lameness measured as head motion asymmetry depends on the speed at which the measurements are taken. If head motion asymmetry is measured at two trotting speeds, it can be standardized to any speed within the trotting speed range.

Animals↗

PubMed1980

Effects of intravenously infused histamine on canine forelimb transvascular protein efflux following adrenergic receptor blockade.

The intravenous infusion of high doses of histamine (400 micrograms base/min) produced only small increases in weight (approximately equal to +30 g) and lymph total protein concentration (+ 0.9 g/100 ml) in canine forelimbs perfused at constant inflow. The weight gain was associated with profound decreases in aortic pressure (112 to 30 mm Hg) and in forelimb perfusion pressure (105 to 75 mm Hg) and marked increases in forelimb skin small-vein pressure (from 12 to 25 mm Hg). After treatment with phentolamine, the intravenous infusion of these doses of histamine under the same conditions produced marked decreases in forelimb perfusion pressure (120 to 60 mm Hg) and failed to increase forelimb skin small-vein pressure, yet still produced only minimal increases in weight (+ 12 g) and lymph total protein concentration (+ 0.8 g/100 ml). Following treatment with both phentolamine and propranolol, the intravenous infusion of histamine caused very marked increases in forelimb weight (approximately equal to +75 g) and lymph total protein concentration (+ 2.9 g/100 ml). These marked increases in forelimb weight and lymph formation were associated with profound decreases in perfusion pressure (112 to 60 mm Hg) but no change in skin small-vein pressure relative to control. These same increases in weight and lymph total protein concentration were observed after treatment with propranolol alone. Thus, treatment with propranolol markedly increased net fluid filtration and protein efflux during intravenous infusions of massive doses of histamine, idicating that this edemogenic agent causes an endogenous release of catecholamines which tend to antagonize the direct actions of histamine on the microvascular membrane via stimulation of beta-adrenergic receptors.

Adrenergic beta-Antagonists↗

PubMed1983

Pattern regulation in the anterior half of the embryonically produced symmetrical forelimb of the axolotl, Ambystoma mexicanum.

Symmetrical forelimbs were created in the axoltl by performing surgery on embryos at stages 32-34. The technique of J.M.W. Slack (J. Embryol. Exp. Morphol., 39:151-168, 1977) was utilized. Several experiments were then performed to test the ability of these symmetrical forelimbs to participate in pattern formation. When symmetrical limbs were amputated without previous surgery, 58% failed to regenerate. When symmetrical limbs were wounded in the plane of symmetry and permitted to heal for 30 days prior to amputation, 75% failed to regenerate. When the anterior half of the symmetrical limb was exchanged with the posterior half of the contralateral forelimb followed by amputation 30 days later, both limbs failed to regenerate. When the anterior half of the symmetrical limb was exchanged with the anterior half of an asymmetrical limb followed by amputation 30 days later, the previously symmetrical limbs regenerated asymmetrical hands, and previously asymmetrical limbs failed to regenerate. These results indicate that wounding increases the occurrence of regenerative failure in embryonically produced symmetrical forelimbs. The anterior half of the embryonically produced symmetrical forelimb behaves unpredictably and in a manner not easily described with any of the current models of pattern regulation. The posterior half of the embryonically produced symmetrical forelimb behaves predictably during pattern formation.

Ambystoma mexicanum↗

PubMed1978

The failure of double-half forelimbs to undergo distal transformation following amputation in the axolotl, Ambystoma mexicanum.

Although capable of initiating early regenerative responses, axolotl forelimb stumps which are composed of double-half limb tissues fail to undergo the events that normally lead to the replacement of missing parts. In the present study, the posterior halves of right forelimbs were exchanged with the anterior halves of left forelimbs, or the dorsal halves of right forelimbs were exchanged with the ventral halves of left forelimbs. Forelimbs were amputated through the graft region 30 days after grafting. Limb stumps bearing double-dorsal, double-ventral or double-posterior tissues either produced hypomorphic regenerates or failed to form any externally visible outgrowth. When the limb stump bore double-anterior tissues, no externally visible structures were formed. Normal and multiple regenerates were never formed by double-half limbs. These results are discussed in terms of the polar coordinate model and suggest that the regeneration blastema requires a complete circumference of positional values in order to complete distal transformation.

Ambystoma↗

PubMed1995

Insulin receptors in Xenopus laevis liver and forelimb regenerates and the effects of local insulin deprivation on regeneration.

As forelimb regeneration in Xenopus laevis is mainly a cell proliferative event which results in a spike-shaped appendage, we set out to examine the possibility that insulin is a growth-promoting factor in this process. The objectives were 1) to detect the presence of insulin receptors (IRs) in the liver (a specific target organ for insulin) and IRs in the forelimb regenerates of X. laevis, 2) to determine whether the receptor is similar to IRs identified in other organisms, and 3) to absorb insulin locally by implanting anti-insulin antibody-soaked hydrolyzed polyacrylamide beads into regenerating forelimb outgrowths in order to assess the effects of insulin deprivation on regeneration. The results show that IRs are present in Xenopus liver plasma membranes (XLPM) as well as in plasma membranes of 21 day forelimb regenerates. Insulin binding to this receptor is time-dependent and specific, as unlabeled bovine insulin competes with radioiodinated insulin for binding to XLPM more effectively than insulin-like growth factor-I, guinea pig insulin, or glucagon. Scatchard analysis of insulin binding to XLPM describes a two binding site receptor possessing a low affinity (0.16 nM-1), high capacity (3.2 +/- 0.9 pM/mg) binding site and a high affinity (2.7 nM-1), low capacity (0.5 +/- 0.3 pM/mg) binding site. The holoreceptor has a molecular mass of 380 kDa. The reduced receptor has subunits of 130 kDa and 95 kDa. The 95 kDa subunit undergoes autophosphorylation following insulin stimulation. Implantation of hydrolyzed polyacrylamide beads, saturated with anti-insulin antibody, into regenerating Xenopus forelimbs significantly impeded development of the regenerates and, therefore, demonstrates that insulin is required for growth of Xenopus forelimb regenerates.

Affinity Labels↗

PubMed1986

Descending pathways eliciting forelimb stepping in the lateral funiculus: experimental studies with stimulation and lesion of the cervical cord in decerebrate cats.

The funicular pathways that elicit forelimb stepping were investigated with stimulation and lesion of the cervical white matter in decerebrate cats with the lower thoracic cord transected. We localized cross-sectional areas where stimulation evoked rhythmic motor-nerve discharges imitating those of stepping (fictive locomotion) in the immobilized animal, and further examined whether or not lesions made in the corresponding areas abolished actual locomotor movements. Stimulation of the C3 lateral funiculus (LF) produced fictive locomotion in the ipsilateral forelimb. The effective areas of stimulation were located separately in the dorsolateral funiculus (DLF) and in the ventrolateral funiculus (VLF), while the VLF was more effective than the DLF. Effective stimuli were pulse trains with a frequency of about 30 Hz, with a rather wide pulse duration of about 0.5 ms. Blocking axonal conduction through the lower thoracic cord by cooling reproducibly facilitated fictive locomotion in both amplitude and frequency. In the lesion experiments, forelimb locomotor movements were elicited spontaneously or by stimulation of the mesencephalic locomotor region (MLR). The locomotor movements were abolished by complete lesions of the C2-C3 LFs on both sides, but these remained when either the DLF or the VLF was intact on one side. These findings together suggested that the descending pathways for the activation of the spinal locomotor network of the single forelimb are located ipsilaterally in the DLF as well as in the VLF. Both the DLF and the VLF pathways can initiate locomotion, while the VLF pathways have a higher potential for its initiation. Lesion experiments further showed that cats can walk with both forelimbs, even though the spinal locomotor network of the single forelimb was deprived of its main descending input by unilateral lesions of the LF. However, when the unilateral lesion extended to the medial part of the LF, the bilateral walking was abolished; the limb on the lesioned side showed only rhythmic extension movements without active flexion movements, which was out of phase with the stepping movements on the intact side. This finding suggested that the medial part of the LF is important for producing flexion movements during the swing phase of stepping.

Animals↗

PubMed1986

A chronic unit study of the sensory properties of neurons in the forelimb areas of rat sensorimotor cortex.

The sensory properties of neurons in the several forelimb areas of rat sensorimotor cortex were examined using the technique of extracellular single-unit recording in the awake, head-restrained rat. Cells with peripheral receptive fields were tested for the amount and modality of sensory input during joint manipulation and brushing and tapping of limbs, face and trunk. Input-output correlations were made on the basis of the results of receptive field mapping and intracortical microstimulation in the same electrode penetration. It was found that neurons (n = 117) in the rostral forelimb area receive virtually no sensory input while 30% of neurons (n = 114) in the caudal forelimb primary motor area do receive such input. The inputs to caudal forelimb motor area neurons were primarily (83%) from single joints; along perpendicular electrode penetrations the same joint that activated a cortical cell also moved when microstimulation was delivered along the same electrode penetration. In the granular and dysgranular zones of somatic sensory forelimb cortex, 70% of neurons (n = 82) were responsive to peripheral sensory inputs, with most of the cells in the granular cortex responsive to cutaneous inputs while cells in the dysgranular cortex were more responsive to deep inputs. The lack of sensory inputs to the rostral forelimb motor area is consistent with the proposal that this region may be a part of the supplementary motor area of the rat.

Afferent Pathways↗

PubMed1986

A study of forelimb movements evoked by intracortical microstimulation after hemicerebellectomy in newborn, young and adult rats.

Microstimulation of the cerebral motor cortex in normal adult rats evokes low-threshold contralateral and high-threshold ipsilateral forelimb movements. The present study examined the effects of hemicerebellar ablation at different postnatal ages on the current threshold values needed to evoke forelimb movements by intracortical stimulation. Animals that received hemicerebellar lesions at various ages were electrophysiologically tested 4-6 months postoperatively. In all groups, including non-lesion control animals, forelimb movements contralateral to the stimulating electrode were evoked at threshold values of 7-11 microA. Ipsilateral forelimb movements for control animals as well as those receiving cerebellar lesions at 45 or 120 days of age showed significantly higher mean threshold current values, ranging from 38 to 45 microA. In contrast, the mean threshold current values for ipsilateral forelimb movements in adult animals sustaining hemicerebellar lesions at 2, 10 or 21 days of age were significantly lowered, ranging from 16 to 22 microA. Secondary lesions of spared cerebellar tissue or callosal fibers in adult animals that had sustained hemicerebellectomy at two days of age had no effect on the current intensities needed to evoke forelimb responses. In comparison, lesions of the cerebral cortex contralateral to the stimulated cortex increased the threshold for ipsilateral movements and medullary pyramidal lesions ipsilateral to the stimulated cortex both reduced the number of responses and increased the threshold current intensities needed to evoke them. These data indicate that hemicerebellectomy within 3 weeks of age can induce electrophysiological alterations in the responses mediated by the corticospinal tract. These results support previous suggestions of the cerebral cortical involvement in compensation for neonatal cerebellar lesions.

Animals↗

PubMed1991

The pathway from Ia forelimb afferents to the motor cortex: a new hypothesis.

Forelimb target-reaching and food-taking in cats depend on different interneuronal circuitry in the spinal cord. On the basis of previous findings regarding the effect of transection of the corticospinal tract in the spinal cord, of high dorsal column (DC) transection, of low pyramidotomy and of pyramidotomy after previous DC transection, it is proposed that the food-taking movement is temporally linked to target-reaching as follows: During target-reaching, the position of the paw is signalled by the pathway from forelimb proprioceptors (mainly Ia) to the motor cortex with a relay in the main cuneate nucleus. The command for food-taking is issued by the motor cortex only when the pathway from the forelimb signals that the paw approaches the target correctly, as may be determined by a comparison of the information from the forelimb with an efference copy of the motor program for target-reaching. The hypothesis is based on previous results regarding the organization of the pathway from the forelimb to area 3a and the motor cortex, and regarding the cortico-cuneate pathway with selective projection from area 3a and motor cortex to the basal caudal part of the cuneate nucleus, where the proprioceptive information from the forelimb is relayed. Results relevant to the present hypothesis regarding responses of precentral neurones during active and passive movements in awake animals are briefly discussed.

Animals↗

PubMed2003

Cortical field potentials preceding self-paced forelimb movements and influences of cerebellectomy upon them in rats.

Seven rats were well trained to move lever to the left by right forelimb at self-pace (self-paced forelimb movements). Cortical field potentials associated with self-paced forelimb movements were recorded by electrodes implanted chronically on the surface and at a 2.0 mm depth in the forelimb motor cortex on the left side. A surface-negative, depth-positive potential starting about 1.0 s prior to the movement was recorded in the rostral part of the forelimb motor cortex. Further we found that the premovement potential was eliminated by the cerebellar hemispherectomy on the right side. This suggests the participation of the cerebellar hemisphere in preparing the activity of the motor cortex before self-paced forelimb movements in rats, by cerebello-thalamo-cortical projections.

Action Potentials↗

PubMed1998

Differences in acquisition and full performance in skilled forelimb use as measured by the 'staircase test' in five rat strains.

Skilled forelimb use was examined in five different rat strains (DA/Ztm, LEW/Ztm-ci, LEW.1W/Ztm, SD/Ztm, SPRD/Ztm-Cu3) by means of the 'staircase test', as originally described by Montoya et al. [20] (C.P. Montoya, H.L. Campbell, K.D. Pemberton, S.B. Dunnett, The 'staircase test': A measure of independent forelimb reaching and grasping abilities in rats, J. Neurosci. Methods 36 (1991) 219-228). Strain-dependent differences were observed most prominently during the acquisition phase, and less pronounced, at the full performance level. SD/Ztm and DA/Ztm rat strains seemed to be particularly skilled in their forelimb use, although with varying levels of activity. Interestingly, significant differences in skilled forelimb movements were found between the related Sprague-Dawley derived and Lewis congenic rat strains. No clear-cut correlation was found between skilled forelimb use and basic nutrition-dependent measures, such as pretest body weight or weightloss during the test period. Based on previous observations on strain-dependent behavioral variations it seems likely that the differences in skilled forelimb use, as observed in the present study, might be caused by morphological and/or functional strain-dependent alterations in the involved neuronal circuitries, such as motor cortex, caudate-putamen unit and mesotelencephalic dopamine system. However, they should also be considered as potentially influencing parameters in studies related to the behavioral effects of lesions and restorative therapies in the central nervous system.

Animals↗

PubMed1997

Amphetamine and task-specific practice augment recovery of vibrissae-evoked forelimb placing after unilateral sensorimotor cortical injury in the rat.

This study investigated the relative contribution of amphetamine administration and task-specific practice during the period of drug action to recovery of forelimb-placing ability after unilateral electrolytic lesions of the sensorimotor cortex (SMC) in rats. Subjects were divided into groups receiving amphetamine plus postinjection forelimb-placing practice, amphetamine only, saline plus postinjection forelimb-placing practice, or saline only. The results revealed that groups of subjects receiving either amphetamine, postinjection practice, or a combination of these treatments exhibited the greatest enhancement of rates of vibrissae-evoked forelimb-placing recovery. These data suggest that these treatments can have an enduring beneficial effect on vibrissae-evoked forelimb-placing recovery without any immediate restorative effect on forelimb-placing ability. The recovery patterns and experimental evidence (see Feeney and Sutton, 1988; Chaouloff, 1989) suggest that the beneficial effect of the two therapies may be mediated by catecholamine release.

Amphetamine↗

PubMed2006

Delayed intervention with transplants and neurotrophic factors supports recovery of forelimb function after cervical spinal cord injury in adult rats.

The adult central nervous system is capable of considerable anatomical reorganization and functional recovery after injury. Functional outcomes, however, vary greatly, depending upon size and location of injury, type and timing of intervention, and type of recovery and plasticity evaluated. The present study was undertaken to assess the recovery of skilled and unskilled forelimb function in adult rats after a C5/C6 spinal cord over-hemisection and delayed intervention with fetal spinal cord transplants and neurotrophins. Recovery of forelimb function was evaluated during both target reaching (a skilled behavior) and vertical exploration (an unskilled behavior). Anatomical tracing and immunohistochemistry were used to assess the growth of descending raphespinal, corticospinal, and rubrospinal fibers at the injury site, tracts that normally confer forelimb function. Delayed intervention with transplants and either brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3) restored skilled left forelimb reaching to pre-injury levels. Animals showed recovery of normal reaching movements rather than compensation with abnormal movements. Transplants and NT-3 also improved right forelimb use during an unskilled vertical exploration, but not skilled right reaching. Intervention with fetal transplant tissue supported the growth of descending serotonergic, corticospinal, and rubrospinal fibers into the transplant at the lesion site. The addition of neurotrophins, however, did not significantly increase axonal growth at the lesion site. These studies suggest that the recovery of skilled and unskilled forelimb use is possible after a large cervical spinal cord injury following delayed intervention with fetal spinal cord and neurotrophins. Plasticity of both spared and axotomized descending pathways likely contributes to the functional recovery observed.

Animals↗

PubMed2005

Structure of the excitatory receptive fields of infragranular forelimb neurons in the rat primary somatosensory cortex responding to touch.

We quantitatively studied the excitatory receptive fields of 297 neurons recorded from the forelimb infragranular somatosensory cortex of the rat while touch stimuli were applied to discrete locations on the forelimbs. Receptive fields were highly heterogeneous, but they were regulated, on average, by an underlying spatio-temporal structure. We found the following. (i) Neurons responded with decreasing magnitude and increasing latency when the stimulus was moved from the primary location to secondary locations and to far ispilateral locations of their excitatory receptive fields, displaying smooth transitions from the primary location to secondary locations. (ii) Receptive field patterns revealed functional connectivity between the digits and ventral palm, which did not depend on whether the digits were stimulated dorsally or ventrally. (iii) The structure of the receptive fields (i.e. the neural responses to stimulation of secondary locations compared to the neural responses to stimulation of the primary location), reflected cortical (rather than body) distances. (iv) There was a functional separation between the forepaw and the rest of the forelimb. Namely: if the primary location was in the digits or palm, secondary locations were biased toward the digits and palm; if the primary location was in rest of the forelimb, secondary locations appeared equally distributed over forelimb, digits and palm. (v) More than 40% of neurons extended their receptive field to the ipsilateral forelimb, without any evident spatial organization. Overall, the stimuli evoked approximately 3 times more spikes from secondary responses than from primary responses. These results suggest that a rich repertoire of spatio-temporal responses is available for encoding tactile information. This highly distributed receptive field structure provides the electrophysiological architecture for studying organization and plasticity of cortical somatosensory processing.

Animals↗

PubMed2002

Distal forelimb cross-innervation effectively induces formation of corticorubral synapses.

We investigated whether cross-innervation of the distal forelimb extensor and flexor muscles effectively induced formation of corticorubral synapses in cats. The average time-to-peak of the corticorubral EPSPs in the red nucleus (RN) neurons innervating cervicothoracic segments (C-cells) of animals with distal forelimb cross-innervation was significantly less than that of animals with elbow cross-innervation. These fast-rising corticorubral EPSPs were shown to be induced by newly formed synapses located on the proximal soma-dendritic membrane of RN neurons, indicating that distal forelimb cross-innervation is more effective for inducing synapse formation in C-cells than elbow cross-innervation. Thus corticorubral synapse formation after forelimb cross-innervation appears to be related to direct rubrospinal connections to distal forelimb motoneurons and of functional importance to RN neurons for performing voluntary distal forelimb movement.

Animals↗

PubMed2006

Properties of propriospinal neurons in the C3-C4 segments mediating disynaptic pyramidal excitation to forelimb motoneurons in the macaque monkey.

Candidate propriospinal neurons (PNs) that mediate disynaptic pyramidal excitation to forelimb motoneurons were studied in the C3-C4 segments in anesthetized macaque monkeys (n = 10). A total of 177 neurons were recorded (145 extracellularly, 48 intracellularly, and 16 both) in laminae VI-VII. Among these, 86 neurons (73 extracellularly, 14 intracellularly and 1 both) were antidromically activated from the forelimb motor nucleus or from the ventrolateral funiculus just lateral to the motor nucleus in the C6/C7 segments and thus are identified as PNs. Among the 73 extracellularly recorded PNs, 60 cells were fired by a train of four stimuli to the contralateral pyramid with segmental latencies of 0.8-2.2 ms, with most of them (n = 52) in a monosynaptic range (<1.4 ms including one synaptic delay and time to firing). The firing probability was only 21% from the third pyramidal volley but increased to 83% after intravenous injection of strychnine. In most of the intracellularly recorded PNs, stimulation of the contralateral pyramid evoked monosynaptic excitatory postsynaptic potentials (EPSPs, 12/14) and disynaptic inhibitory postsynaptic potentials (14/14), which were found to be glycinergic. In contrast, cells that did not project to the C6-Th1 segments where forelimb motoneurons are located were classified as segmental interneurons. These were fired from the third pyramidal volley with a probability of 71% before injection of strychnine. It is proposed that some of these interneurons mediate feed-forward inhibition to the PNs. These results suggest that the C3-C4 PNs receive feed-forward inhibition from the pyramid in addition to monosynaptic excitation and that this inhibition is stronger in the macaque monkey than in the cat. Another difference with the cat was that only 26 of the 86 PNs (30%, as compared with 84% in the cat) with projection to the forelimb motor nuclei send ascending collaterals terminating in the lateral reticular nucleus (LRN) on the ipsilateral side of the medulla. Thus we identified C3-C4 PNs that could mediate disynaptic pyramidal excitation to forelimb motoneurons in the macaque monkey. The present findings explain why it was difficult in previous studies of the macaque monkey to evoke disynaptic pyramidal excitation via C3-C4 PNs in forelimb motoneurons and why-as compared with the cat-the monosynaptic EPSPs evoked from the LRN via C3-C4 PNs were smaller in amplitude.

Animals↗

PubMed2004

Local GABA receptor blockade reveals hindlimb responses in the SI forelimb-stump representation of neonatally amputated rats.

In adult rats that sustained forelimb amputation on the day of birth, there are numerous multi-unit recording sites in the forelimb-stump representation of primary somatosensory cortex (SI) that also respond to cutaneous stimulation of the hindlimb when cortical receptors for GABA are blocked. These normally suppressed hindlimb inputs originate in the SI hindlimb representation and synapse in the dysgranular cortex before exciting SI forelimb-stump neurons. In our previous studies, GABA (A + B) receptor blockade was achieved by topically applying a bicuculline methiodide/saclofen solution (BMI/SAC) to the cortical surface. This treatment blocks receptors throughout SI and does not allow determination of where along the above circuit the GABA-mediated suppression of hindlimb information occurs. In this study, focal injections of BMI/SAC were delivered to three distinct cortical regions that are involved in the hindlimb-to-forelimb-stump pathway. Blocking GABA receptors in the SI hindlimb representation and in the dysgranular cortex was largely ineffective in revealing hindlimb inputs ( approximately 10% of hindlimb inputs were revealed in both cases). In contrast, when the blockade was targeted at forelimb-stump recording sites, >80% of hindlimb inputs were revealed. Thus GABAergic interneurons within the forelimb-stump representation suppress the expression of reorganized hindlimb inputs to the region. A circuit model incorporating these and previous observations is presented and discussed.

Amputation Stumps↗