Search PubMed⌕ Search

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.

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

At least 361 records · Page 20Linked to original sources
PubMed1987

Cytotoxic effects of ethylene glycol monomethyl ether in the forelimb bud of the mouse embryo.

The role of cytotoxicity in digital maldevelopment in CD-1 mouse embryos was examined following dosage with ethylene glycol monomethyl ether (EGME) on gestation day (gd) 11. Patterns of cell necrosis in the forelimb buds of embryos collected from dams given EGME orally at doses of 100, 250 or 350 mg/kg were characterized by staining with Nile blue A. Cell death was induced in the mesenchymal tissue and to some extent in the limb bud ectoderm, including the apical ectodermal ridge in a dose-related manner. The area of preaxial physiological cell necrosis was enlarged by EGME, and the shape of the limb buds was altered 24 hr after treatment. Preaxial tissue and the predigital chondrocyte condensations were reduced or missing following 250 and 350 mg EGME per 1 kg. Light and electron microscope evaluations of forelimb buds revealed the presence of phagocytic vacuoles and condensed, fragmented cytoplasm, which indicate cytotoxicity, as early as 2 hr following EGME, a maximum effect being observed 6 hr after the dose was administered. Although the severity of the cytotoxic response appeared to be dose-related, comparison with the incidence of digital malformations in near-term fetuses indicates that the loss of mesenchymal tissue is partially compensated for as formation of the limb progresses.

Abnormalities, Drug-Induced↗
PubMed1999

Time-course analysis and comparison of acute and chronic intrastriatal quinolinic acid administration on forelimb reaching deficits in the rat.

Rats were trained to use a single forelimb for a food pellet retrieval task. During baseline testing all rats exhibited > 90% use of a preferred limb for the task. Following baseline, rats were subjected to chronic administration (18 day) or acute injection of quinolinic acid (QUIN) or vehicle to the striatum contralateral to the preferred limb. Rats were tested 48 h after insertion of chronic delivery probes or after acute injection and retested every 48 h over an 18-day period. Compared to vehicle, rats receiving chronic QUIN (7.6 nmol/h) exhibited an increase in the number of reach attempts required to meet task criteria. Chronic QUIN did not produce a significant change in latency to initiate the task or an increase in latency to complete the task. No rats exposed to chronic QUIN exhibited a switch in limb preference for the task. Unlike animals exposed to chronic QUIN, a significant number of animals receiving acute QUIN injections switched to exclusive use of the ipsilateral (nonpreferred) limb for the task. Quantitative histological analysis revealed no significant difference in lesion volume between acute and chronic lesion animals. These findings suggest that behavioral manifestations of histopathologically similar lesions may be vastly different depending on the methods used to produce these lesions. More specifically, the acute injection model resulted primarily in forelimb disuse, whereas the chronic model resulted in continued abnormal use of the affected limb. Understanding adaptive strategies used in these models may be particularly important when testing newly developed transgenic models of neurodegenerative diseases and the therapeutic potential of newly developed neuroprotectants.

Animals↗
PubMed2001

Functional recovery of skilled forelimb use in rats obliged to use the impaired limb after grafting of the frontal cortex lesion with homotopic fetal cortex.

The long-term effect of transplanting embryonic frontal cortex into a unilateral frontal cortex lesion has been studied in adult rats. Before surgery, activity in an open field, muscular strength of both forelimbs, and performance in a paw-reaching-for-food task were scored in 26 rats. In 21 animals a unilateral cortex lesion was then made in the forelimb motor area of the hemisphere contralateral to the preferred paw in the paw-reaching-for-food task, while the other 5 animals were sham-operated. On retesting, the lesion animals changed the preferred paw. A solid homotopic transplant of embryonic tissue (embryonic day 17) was then placed in the lesion cavity in 11 of the lesion rats. Three months later neither lesion alone nor lesion plus transplantation affected open field behavior and muscular strength, but the lesion permanently affected performance in the paw-reaching-for-food task, as shown by a change of preferred paw and a functional deficit in the paw contralateral to the lesion. Transplantation ameliorated the deficits caused by the lesion, but this was only evident when animals were forced to reach with the paw contralateral to the lesion plus transplant. The behavioral results were independent of the size of the lesion and graft. Connections between graft and host tissue were studied by means of the fluorescent tracer 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI). A dense array of labeled fibers was found in the host cortex adjacent to the transplant. The results suggest that functional recovery depends on grafting but is only evident when the animal is obliged to use the affected limb.

Animals↗
PubMed1992

Responses of cat ventroposterolateral thalamic neurons to vibrotactile stimulation of forelimb footpads.

Responses of neurons in the ventroposterolateral nucleus of the thalamus to vibration applied to the forelimb footpads were analyzed in anesthetized cats in order to describe the signalling properties of thalamic neurons that received input from the different classes of tactile afferents innervating the glabrous skin of the distal forelimb. Seventy-six thalamic neurons, the majority of which (60 of 76) were positively identified as thalamocortical projection neurons, were classified into two broad groups according to their responses to 1-s step indentations of the skin. A minority (24%) comprised neurons that had slowly adapting (SA) responses, whereas the remainder (76%), the dynamically sensitive neurons, had transient responses to the onset and offset phase of the step and were further classified according to their sensitivity to cutaneous vibrotactile stimuli into those activated by low-frequency vibration (rapidly adapting, RA, neurons) and those activated by high frequencies (Pacinian afferent, PC, neurons). Thalamic RA neurons displayed phaselocked responses to vibration at frequencies up to approximately 100 Hz, while PC neurons displayed phaselocked responses to vibration up to 400-500 Hz. Thalamic SA neurons varied in their responses to vibrotactile stimuli; half were most sensitive to vibration frequencies of 50 Hz or less, while the others responded over a broader range of frequencies. Although three major classes of footpad-related thalamic neurons were identified, there was evidence of convergent input to a small proportion of them. The study demonstrates that thalamic neurons have the capacity for responding to cutaneous vibration with phaselocked, patterned impulse trains, which would enable them to encode information about vibrotactile frequencies up to approximately 300 Hz.

Anesthesia↗
PubMed1990

Early development of SI cortical barrel subfield representation of forelimb in normal and deafferented neonatal rat as delineated by peroxidase conjugated lectin, peanut agglutinin (PNA).

Development of the barrel field representation of the forelimb in the primary somatosensory cortex (SI) was studied in normal and deafferented neonatal rat pups by means of the peroxidase conjugated lectin peanut agglutinin (PNA), which most likely binds to radial glial cells within barrel boundaries. 1. Alterations in lectin binding were seen in animals sacrificed on postnatal day 8 (PND-8) if deafferentation took place on PND-1 (day of birth) through PND-6. 2. Deafferentation on PND-5 or on PND-6 had the least effect on lectin binding. In these animals, lectin binding was reduced, although the prospective representation was intact. 3. Deafferentation on PND-2, 3, and 4 had the greatest effect on lectin binding. In these animals, lectin binding was reduced and the prospective cortical representation was disrupted. 4. Deafferentation on PND-1 resulted in reduced lectin binding, however the prospective cortical representation was only slightly impaired compared to that in animals deafferented on PND-2, 3, and 4. 5. These results suggest that SI barrel field boundaries are important to plasticity and that a sensitive period for predevelopment of the forelimb barrels consists of postnatal days 1 through 6. Furthermore, the formation of normal SI barrel field boundaries requires an ongoing interaction between incoming afferents and radial glial cells.

Afferent Pathways↗
PubMed1993

Differential impairments in reaching and grasping produced by local inactivation within the forelimb representation of the motor cortex in the cat.

This study analyzed changes in the performance of a reaching task and its adaptive modification produced by reversible inactivation of three sites within the forelimb representation of the motor cortex (MCx, area 4 gamma) in five cats by microinjections of muscimol. Two sites were located in the lateral MCx, rostral (RL-MCx) and caudal (CL-MCx) to the end of the cruciate sulcus, where intracortical microstimulation (ICMS) produced contraction of the most distal muscles. The third site was located more medially, in the anterior sigmoid gyrus (RM-MCx) where ICMS primarily produced contraction of more proximal muscles. The task required the animals to reach into a horizontal target well, located in front of them at one of three possible heights, to grasp and retrieve a small piece of food. The height of the reach was primarily achieved by elbow flexion. Grasping consisted primarily of digit flexion, and food retrieval consisted of forearm supination and shoulder extension. In some blocks of trials, an obstacle was placed in the path of the limb to assess the animal's ability to adaptively adjust the kinematic characteristics of their response trajectory. In normal animals, contact with the bar on the first trial triggered a corrective response at short latency that allowed the paw to circumvent the bar. On all subsequent trials, the trajectory was adapted to prevent contact with the obstacle, with a safety margin of about 1 cm. Inactivation at all sites produced a slowing of movement, a protracted and extended forelimb posture, and increased variability of initial limb position. In addition, inactivation of RL-MCx immediately produced systematic reaching errors, consisting of hypermetric movements, as well as impaired grasping and food retrieval. The degree of hypermetria was similar for all target heights and was not associated with alterations in trajectory control. During inactivation, animals did not compensate for the hypermetria by reducing paw path elevation, suggesting a defect in kinematic planning or in adaptive control. This was confirmed by finding that trajectory adaptation to avoid bar contact was impaired during RL-MCx inactivation. The short latency corrective response, triggered by contact of the limb with the obstacle was, however, preserved. Inactivation of CL-MCx did not impair aiming, grasping, or adaptation immediately after injection. However, impairments occurred after about 1 h postinjection, and at that time mimicked the effects of RL-MCx inactivation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Automatic postural responses in the cat: responses of proximal and distal hindlimb muscles to drop of support from a single hind- or forelimb.

Cats respond to drop of the support from beneath a single limb with the "diagonal stance response" (Coulmance et al. 1979). They load the limbs on the diagonal opposite to the one containing the dropped limb and unload the third supporting limb in the diagonal containing the dropped limb. Characteristic biomechanical delays in limb motion and in vertical force changes imposed upon the limbs are observed. These delays range from 30 to 45 ms, depending upon the location of the dropped limb. This study describes the kinematics of the "diagonal stance response" and the activation of selected agonist-antagonist muscle pairs acting on the joints of the hindlimb during the response. Proximal and distal hindlimb muscles respond to perturbations in groups that are appropriate to the vertical forces imposed upon the limb. When the hindlimb containing the recording electrodes is loaded by drop of the contralateral hindlimb or the ipsilateral forelimb medium latency (25-45 ms) EMG responses occur in the extensors. This response serves to stiffen the limb against the increased vertical force of loading. A similar response is observed when the hindlimb is reloaded after being dropped. In this case, however, short latency responses precede the medium latency responses in muscles that are passively stretched by the limb drop. When drop of the diagonal forelimb unloads the hindlimb containing the electrodes, medium latency responses are observed in the distal hindlimb flexors, which indicates that the unloading is evoked in part by active lifting of the limb. In most cases, the medium latency responses precede or are coincident with the changes in force imposed on the limb, suggesting that the observed responses are centrally programmed.

Animals↗
PubMed1985

Distribution of neurons related to a hindlimb as opposed to forelimb movement in the monkey premotor cortex.

Single cell recordings were made from the premotor cortex (lateral part of area 6) of a monkey trained to perform either a distal hindlimb or forelimb movement separately. Out of 175 movement-related neurons, 59 neurons showed modulation of activity only prior to the hindlimb movement, and the majority of them was distributed in a focal region around the superior precentral sulcus, several mm posteromedial to the genu of the arcuate sulcus. The hindlimb focus was separate from a focal region for forelimb movement-related neurons, which lay immediately posterior to the genu of the arcuate sulcus.

Animals↗
PubMed1981

Integration in descending motor pathways controlling the forelimb in the cat. 7. Effects from the reticular formation on C3-C4 propriospinal neurones.

Effects of stimulation in the medullary reticular formation (RF) on C3-C4 propriospinal neurones (PNs) were investigated in two series of experiments: (1) indirectly by analyzing how propriospinal transmission to forelimb motoneurones is modified by reticular stimuli; (2) directly by intracellular recording from C3-C4 neurones, which were identified as propriospinal by their antidromic activation from the C6 segment. Propriospinally mediated disynaptic EPSPs evoked in motoneurones from the pyramid (Pyr) and the red nucleus (NR) were effectively facilitated by conditioning stimulation in the RF with a time course of facilitation indicating monosynaptic linkage to the PNs. Propriospinally mediated trisynaptic IPSPs were facilitated less regularly and sometimes instead depressed by conditioning stimulation in the RF. The depression is at least partly due to inhibition of the first order PNs. Recording from C3-C4 PNs revealed that many of them were excited or inhibited by single stimuli in the RF. The brief latency of the EPSPs evoked in these neurones shows monosynaptic linkage from fast reticulospinal fibres. Some IPSPs were similarly monosynaptically evoked from fast fibres and observations are presented suggesting that longer latency IPSPs are monosynaptically mediated by slower fibres. Facilitation of propriospinal transmission to motoneurones as well as the EPSPs and IPSPs in PNs were evoked from a region within or close to the nucleus reticularis gigantocellularis. Convergence of monosynaptic EPSPs from Pyr, NR, tectum, and RF was common in C3-C4 PNs. Linear summation of the EPSPs from RF with those evoked from cortico-, rubro-, or tectospinal tracts shows that the former are not due to stimulation of collaterals which the latter tracts may have in RF. Mediation of the EPSPs and IPSPs by descending, rather than by antidromically activated ascending fibres, was indicated by temporal facilitation produced by RF stimuli, subliminal for evoking monosynaptic PSPs in the PNs. Stimulation of the labyrinth did not evoke disynaptic PSPs in any of the PNs investigated. It is concluded that the C3-C4 PNs projecting to forelimb motoneurones can be excited not only from the cortico-, rubro-, and tectospinal tracts (Illert et at. 1977, 1978) but also by reticulospinal fibres.

Animals↗
PubMed1979

Effects of ventrolateral thalamic nucleus cooling on initiation of forelimb ballistic flexion movements by conditioned cats.

Five cats were trained to perform a forelimb ballistic flexion on a reaction time paradigm including an upper limit of about 400 ms for reinforcement (food pellets). They were implanted with a cyrogenic probe thermically insulated, except at the tip, by a vacuum jacket (outer diameter, 1.1 mm). Four cats had the probe inserted into the ventrolateral thalamic nucleus (VL), contralateral to the moving limb. During cooling they showed increased reaction times, which remained constant throughout daily sessions performed during many weeks, independent of the foreperiod but varying from 25 to 100 ms according to the subject. The temperatures used to upset the reaction times varied from +10 decrees C to -8 degrees C, depending on the localisation of the probe and on the insulation of the silver tip used to prevent nervous tissue reaction, but for each subject the reaction times always increased when the temperature was lowered. The fifth cat, with a probe inserted between VL and the Centre Median, showed a decrease of reaction times on cooling to 0 degrees C and an increase of the reaction times for a cooling at -10 degrees C. For one of the four cats with a probe properly inserted into the VL, strain-gauges were stuck on the lever to measure the latency of the decrease of the pressure exerted by the subject when the subject initiated the forelimb flexion in response to the CS. Reaction times and latencies of pressure changes were closely correlated with the movement onset, and they were equally delayed during cooling. This result demonstrates that it is not by slowing down movement velocity that reaction times are upset during VL cooling but by delaying the movement onset.

Animals↗
PubMed1988

The nucleus accumbens and forelimb muscular rigidity in rats.

The present set of experiments were performed to evaluate the role of the nucleus accumbens in the regulation of forelimb muscle tone. Rats were chronically implanted with cannulae aimed at the nucleus accumbens or the neostriatum and with EMG electrodes in the triceps or the gastrocnemius soleus muscle. The experiments were all performed in non-anaesthetised freely moving animals. The results show that haloperidol induced an increase in triceps muscle tone when injected into the nucleus accumbens but not when injected into the neostriatum. Likewise it was found that haloperidol induced an increase in gastrocnemius soleus muscle tone when injected into the neostriatum but not when injected into the nucleus accumbens. The increase in triceps muscle tone seen after intra-accumbens haloperidol was only briefly attenuated by apomorphine, whereas phenylephrine produced a more long lasting antagonism. The present data show that in addition to the cortex, subcortical structures also appear to possess a certain topography, with forelimb rigidity being mediated, at least in part, by the nucleus accumbens, and hindlimb rigidity, at least in part by the neostriatum. In addition it appears that the effects of haloperidol in the nucleus accumbens on triceps muscle tone are primarily mediated by alpha 1 adrenergic receptors, although a minor role of dopamine D2 receptors cannot be fully excluded.

Animals↗
PubMed1990

Movement and muscle activity during contact placing of the forelimb and their relations to other postural reactions in the cat.

Forelimb trajectory and the activity of eight muscles operating at the elbow, wrist and digit joints were compared during the contact placing reaction, during the swing phase of locomotion and during reactions induced by swing perturbations, to verify the hypothesis that common neural mechanisms are involved in these reactions. Both the patterns of muscle activation and forelimb kinetics during the placing reaction greatly differed from those during the swing phase of locomotion. Both similarities and differences have been found between the placing reaction and the reaction to swing perturbations. Similar latencies, patterns of muscle activation and trajectories have been found for elbow movements while considerable differences were seen in the movements of distal joints. Both reactions started with a backward and upward movement at the proximal joints which was accompanied by a locking at the elbow. At the distal joints, tactile stimuli evoked first a wrist ventroflexion during the placing reaction, whereas they induced wrist dorsiflexion to swing perturbations. A further difference between these two reactions appeared at the beginning of the extension which was highly passive during the reaction to swing perturbation and active during contact placing. These results suggest that some common, most likely spinal, reflexes are involved at the beginning of the two reactions while their extension phases are controlled in a different way.

Animals↗
PubMed1994

Microcatalepsy and disruption of forelimb usage during operant behavior: differences between dopamine D1 (SCH-23390) and D2 (raclopride) antagonists.

In an experiment designed to distinguish between the behavioral consequences of treatment with SCH-23390, a D1 dopamine receptor blocker, and raclopride, a D2 antagonist, rats were trained to perform a water-reinforced forelimb operant response. Response rate and the duration of each forelimb contact with the operandum were recorded. In addition, the durations of the rat's visits to the reward well were detected by a photobeam which was blocked by the rat's muzzle as it remained at the reward well. In a between-groups dosing design, separate groups of rats (11-13 rats/group) received SCH-23390 (0, 0.01, 0.02, 0.04, 0.08, 0.12 mg/kg, IP, 30 min) or raclopride (0. 0.05, 0.1, 0.2, 0.4, 0.8 mg/kg, IP, 30 min) for 21 consecutive days. Quantitative analyses indicated that for comparable amounts of operant rate reduction, raclopride had a significantly greater tendency than SCH-23390 to increase the duration of operant responses and to increase the maximum muzzle entry duration (i.e., to induce microcatalepsy). The results support the idea that at relatively low doses D2 antagonism is more likely than D1 antagonism to produce effects identified preclinically with extrapyramidal side effects.

Animals↗
PubMed1992

Contractile properties of single motor units in two multi-tendoned muscles of the cat distal forelimb.

The contractile properties of motor units (MUs) in two multi-tendoned forelimb muscles were investigated. In anesthetized cats single MUs of the extensor carpi ulnaris (ECU) and extensor digitorum communis (EDC) muscles were selectively activated by stimulation of cervical ventral root filaments. MUs were characterized by various tests including single twitches, series of tetanic contractions providing a tension-frequency relation and a fatigue test. They were classified by the parameters contraction time (CT, time-to-peak within unpotentiated single twitches) and fatigue-index (RB, according to Burke). The ECU muscle is composed of 38% type FR MUs (fast, fatigue-sensitive; CT less than 38 ms; RB less than 0.5), 35% type FR MUs (CT less than 38 ms, RB greater than 0.5) and 27% type S MUs (slow; CT greater than 38 ms, RB greater than 0.5). 46% of the EDC MUs were classified as FF (RB less than or equal to 0.25), 29% as FI (fast, intermediately fatiguable; 0.25 less than RB less than 0.75) and 25% as FR/S (fatigue-resistant, fast or slow; RB greater than or equal to 0.75). The latter group was devised since most MUs appeared as fast and the unequivocal presence of slow MUs could neither be demonstrated nor excluded. Normalized tension-frequency relations of fast ECU and EDC MUs were nearly identical and similar to those reported for fast MUs of other muscles. In contrast to this, the tension-frequency relation of slow ECU MUs has a different shape supporting the use of this function to distinguish fast from slow MUs. The distribution of different types of MUs is discussed with regard to the structure and function of the parent muscles and in relation to hindlimb muscles of comparable architecture. As revealed by comparison to EMG data gained in behaving animals (Fritz et al. 1985; Hoffmann et al. 1986, Botterman et al. 1985), the three muscles of the cat distal forelimb investigated so far seem to be adapted to different tasks: the EDC to rapid movements with a high proportion of type FF MUs, flexor carpi radialis to sustained contractions during the body support with a high proportion of fatigue-resistant MUs; the ECU which changes synergism between both muscles has an intermediate composition.

Animals↗
PubMed1990

Integration in descending motor pathways controlling the forelimb in the cat. 17. Axonal projection and termination of C3-C4 propriospinal neurones in the C6-Th1 segments.

Collateralization and termination of single C3-C4 propriospinal neurones (PNs) have been studied in the C6-Th1 segments of the cat using two methods: threshold mapping for antidromic activation of C3-C4 PNs and intra-axonal injection of horseradish peroxidase. Low threshold points for antidromic activation of C3-C4 PNs were found in the region of different motor nuclei in lamina IX both at one level and at different segmental levels, in all parts of lamina VII, in the lateral part of lamina VI and in the dorsal and ventral parts of lamina VIII. Collaterals were found from C6 to Th1. A marked decrease of conduction velocity of the stem axon occurred in the caudal region of termination, while it was almost constant in the rostral region of termination. HRP was injected iontophoretically in C6-Th1 into stem axons of neurones, which were activated antidromically from the ventral part of the lateral funiculus in C5/C6, from the lateral reticular nucleus (LRN) and monosynaptically from the corticospinal fibres (stimulated in the contralateral pyramid) which were transected in C5/C6. Reconstruction of successfully stained stem axons, revealed collaterals with terminals on presumed motoneurones in different parts of lamina IX and on interneurones in laminae IV-VIII. These findings confirm previous results which showed monosynaptic projections from C3-C4 PNs to forelimb motoneurones and Ia inhibitory interneurones. With respect to termination in the region of the motoneurones in lamina IX and in the region of Ia inhibitory interneurones in lamina VII, three patterns were found: 1) termination mainly in lamina IX (n = 1) 2) termination in laminae IX and VII (n = 15) and 3) termination mainly in lamina VII (n = 2). However, in some cases the same stem axon gave off collaterals which terminated either on motoneurones in lamina IX or on presumed Ia inhibitory interneurones in lamina VII. Furthermore, when the stem axons had collaterals which terminated in different motor nuclei only some of these collaterals had additional terminations on presumed Ia inhibitory interneurones. This result suggest that C3-C4 PNs do not follow a strict Ia pattern of reciprocal innervation. It is tentatively proposed that the difference of innervation may be related to the type of multi-joint movement, such as target-reaching with the forelimb, which has been shown to be controlled by the C3-C4 PNs. Termination in laminae VI, VIII and different parts of lamina VII indicates that C3-C4 PNs also project to other types of neurones than motoneurones and Ia inhibitory interneurones.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Facilitation of transmission via inhibitory pathway 1a to spinal extensor motoneurons in response to stimulation of the forelimb nerves in cats.

Activation of forelimb flexor reflex afferent in cats anesthetized with a mixture of Chloralose and Nembutal evoked temporospatial facilitation in the reciprocal inhibitory pathways to spinal extensor motoneurons. The amplitude of disynaptic reciprocal 1a inhibitory postsynaptic potentials (IPSP) evoked in the extensor motoneurons by activation of the most excitable fibers of the nerve supplying the antagonist muscle increased several-fold using conditioning stimulation of the forelimb nerve. Facilitation of 1a IPSP occurred on a background of IPSP evoked by descending inter-limb discharges. Facilitation of 1a IPSP had a latent period of 18-20 msec and could last to 60 msec. The possible role of inhibitory 1a interneurons in interlimb coordination is discussed.

Animals↗
PubMed2005

Impairment of skilled forelimb use after ablation of striatal interneurons expressing substance P receptors in rats: an analysis using a pasta matrix reaching task.

Local injection of substance P (SP)-saporin can cause selective ablation of striatal interneurons expressing SP receptors (SPR). In this study, we evaluated quantitatively the impairment of skilled forelimb use after unilateral ablation of the striatal interneurons using a pasta matrix reaching task in rats. We found a significant decrease of the number of the pasta pieces (uncooked spaghetti) retrieved using the paw of the experimental side contralateral to the ablation, whereas the number of the pasta pieces retrieved using the paw of the intact side increased significantly. These findings, with our previous reports, suggest that the modulation of the cortico-striato-entopeduncular direct pathway by striatal interneurons is important for maintaining normal basal-ganglia control for skilled forelimb movements.

Animals↗
PubMed2001

Large-scale cortical reorganization following forelimb deafferentation in rat does not involve plasticity of intracortical connections.

Physiological mapping of the body representation 1 month or longer after forelimb removal in adult rats revealed new pockets of shoulder representation in the forepaw barrel subfield (FBS) in the first somatosensory cortex (SI). These "new" shoulder representations have longer evoked response latencies than sites in the shoulder representation within the trunk subfield, hereafter referred to as the "original" shoulder representation. We postulated that the "new" shoulder representations in the FBS were relayed from the "original" shoulder representation. We investigated this hypothesis by studying anatomical connectivity between the "original" shoulder representation and the FBS in intact control and forelimb deafferented adult rats using Phaseolus vulgaris leucoagglutinin (PHA-L), biocytin, and biotin dextran-amine (BDA) as anterograde tracers. The retrograde tracer cholera toxin beta subunit (CT-B) injected into the FBS was also used to study connectivity between the "original" shoulder representation and the FBS. Using these anatomical tracing techniques, we were unable to show the existence of a direct corticocortical connection between the "original" shoulder representation in the trunk subfield and the FBS in either intact or deafferented rats. Functional connectivity between the two cortical regions was studied by ablating the "original" shoulder representation alone or in combination with the shoulder representation in the second somatosensory cortex (SII) while recording evoked responses in the FBS following electrical stimulation of the shoulder. Both ablations failed to eliminate the evoked responses at the "new" shoulder sites in the FBS, suggesting that SI and SII are not necessary for "new" shoulder input in the FBS. It is suggested that subcortical sites may play a major role in large-scale cortical reorganization. Results of projections from the "original" shoulder representation to parietal medial (PM), parietal lateral (PL), SII, parietal ventral (PV), and parietal rhinal (PR) sensory fields and agranular lateral (AgL) and agranular medial (AgM) motor fields are also described.

Afferent Pathways↗