A kinematic comparison of L-DOPA-induced air-stepping and swimming in developing rats

Acute mid-thoracic spinal cord transection eliminates hindlimb air-stepping in neonatal rats suspended in harnesses and administered L-DOPA. Because spinal cord transection eliminates all descending inputs to the hindlimb locomotor circuits, this experiment determined if coadministration of L-DOPA and quipazine (serotonin receptor agonist) would induce hindlimb air-stepping in rat pups 24 hr after transection. Hindlimb steps of spinally transected pups that received L-DOPA or quipazine alone were infrequent and slow; hindlimb steps induced by L-DOPA + quipazine occurred more frequently and were faster than those elicited by either drug alone. These findings suggest that catecholaminergic and serotonergic systems both contribute to hindlimb stepping.     

Requirement for Brn-3b in early differentiation of postmitotic retinal ganglion cell precursors

Postnatal development of the spinal cord serotonergic (5-HT) system and of swimming movements were studied in newborn Sprague-Dawley rats, in which the serotonin level in the central nervous system was lowered in the prenatal period. For this purpose, para-chlorophenylalanine (PCPA) (300 mg/kg) was administered intraperitoneally to pregnant mother rats on day 8 of gestation, followed by a daily injection of PCPA (80 mg/kg) from day 9 of gestation to delivery. The postnatal development of the 5-HT system in the spinal cord of the pups (PCPA-treated pups) born from the PCPA-administered mothers was markedly delayed during the period between PND 1 and PND 10 in comparison to that in the control pups born from healthy mothers. Postnatally, the control pups developed their swimming movements regularly through three distinct phases: forelimb dominant, forelimb and hindlimb well coordinated, hindlimb dominant. In contrast, in the PCPA-treated pups, swimming movements were disorganized during the period in which the development of 5-HT system was delayed. However, between PND 17 and 22 in which the 5-HT system developed to that extent observed in the control pups, the pups eventually developed swimming movements as observed in the control pups. These results suggest that the disorganized developmental process of swimming movements in the PCPA-treated pups is due to the possible failure in the prenatal and postnatal development of the 5-HT system and its target system in the brain stem and the spinal cord.     

L-DOPA and quipazine elicit air-stepping in neonatal rats with spinal cord transections.

Acute mid-thoracic spinal cord transection eliminates hindlimb air-stepping in neonatal rats suspended in harnesses and administered {l}-DOPA. Because spinal cord transection eliminates all descending inputs to the hindlimb locomotor circuits, this experiment determined if coadministration of {l}-DOPA and quipazine (serotonin receptor agonist) would induce hindlimb air-stepping in rat pups 24 hrs after transection. Hindlimb steps of spinally transected pups that received {l}-DOPA or quipazine alone were infrequent and slow; hindlimb steps induced by {l}-DOPA?+?quipazine occurred more frequently and were faster than those elicited by either drug alone. These findings suggest that catecholaminergic and serotonergic systems both contribute to hindlimb stepping. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Morphometric ultrastructural evaluation of the axonal endings in the neuromuscular junctions of pigeons after long lasting limitation of movement

To analyze the discharge patterns of the reticulospinal (R-S) neurons associated with four-limb movement, we recorded the unit spikes of 108 R-S neurons in 18 thalamic cats. (1) Unit spikes of R-S neurons exhibited alternating firings during leg movements, not only stepping on the treadmill but also upon passive flexion and extension movement by the experimenter's hand. (2) R-S neurons manifested firing patterns associated with diagonal, reciprocal and quadrupedal leg movements. About half of the neurons showed reciprocal patterns upon bilateral forelimb movements; spikes were increased when the ipsilateral forelimb was in a backward position; they were decreased when that leg was in a forward position. In contrast, the spikes were increased when the contralateral forelimb was placed forward and decreased when it was backward. About 15% of the R-S neurons showed discharge patterns correlated with quadrupedal leg movements. Firing increased when the left forelimb and right hindlimb were placed backward and the left hindlimb and right forelimb were forward. In contrast, when the position of all 4 limbs was reversed, firing rates decreased. (3) When brief touch stimulation was applied to the skin around the leg, bursting spikes were obtained; these were suppressed upon touching the skin of the contralateral limb. Even after transection of the muscle nerves, alternating firings were observed. (4) Local anesthesia to the shoulder joint resulted in a marked reduction of spontaneous discharges and alternating firings. (5) Our results indicate that afferents of joints and of cutaneous origins in individual limbs ascend to the brainstem reticular formation, that integrative action is organized as pattern generation in that region, and that this patterned information is sent to the spinal cord via the reticulospinal tracts.     

Brachially innervated ectopic hindlimbs in the chick embryo. I. Limb motility and motor system anatomy during the development of embryonic behavior

The functional status of brachially innervated hindlimbs, produced by transplanting hindlimb buds of chick embryos in place of forelimb buds, was quantified by analyzing the number and temporal distribution of spontaneous limb movements. Brachially innervated hindlimbs exhibited normal motility until E10 but thereafter became significantly less active than normal limbs and the limb movements were more randomly distributed. Contrary to the findings with axolotls and frogs, functional interaction between brachial motoneurons and hindlimb muscles cannot be sustained in the chick embryo. Dysfunction is first detectable at E10 and progresses to near total immobility by E20 and is associated with joint ankylosis and muscular atrophy. Although brachially innervated hindlimbs were virtually immobile by the time of hatching (E21), they produced strong movements in response to electrical stimulation of their spinal nerves, suggesting a central rather than peripheral defect in the motor system. The extent of motoneuron death in the brachial spinal cord was not significantly altered by the substitution of the forelimb bud with the hindlimb bud, but the timing of motoneuron loss was appropriate for the lumbar rather than brachial spinal cord, indicating that the rate of motoneuron death was dictated by the limb. Measurements of nuclear area indicated that motoneuron size was normal during the motoneuron death period (E6-E10) but the nuclei of motoneurons innervating grafted hindlimbs subsequently became significantly larger than those of normal brachial motoneurons. Although the muscle mass of the grafted hindlimb at E18 was significantly less than that of the normal hindlimb (and similar to that of a normal forelimb), electronmicroscopic examination of the grafted hindlimbs and brachial spinal cords of E20 embryos revealed normal myofiber and neuromuscular junction ultrastructure and a small increase in the number of axosomatic synapses on cross-sections of motoneurons innervating grafted hindlimbs compared to motoneurons innervating normal forelimbs. The anatomical data indicate that, rather than being associated with degenerative changes, the motor system of the brachial hindlimb of late-stage embryos is intact, but inactive.     

Adult opossums (Didelphis virginiana) demonstrate near normal locomotion after spinal cord transection as neonates

When the thoracic spinal cord of the North American opossum (Didelphis virginiana) is transected on postnatal day (PD) 5, the site of injury becomes bridged by histologically recognizable spinal cord and axons which form major long tracts grow through the lesion. In the present study we asked whether opossums lesioned on PD5 have normal use of the hindlimbs as adults and, if so, whether that use is dependent upon axons which grow through the lesion site. The thoracic spinal cord was transected on PD5 and 6 months later, hindlimb function was evaluated using the Basso, Beattie, and Bresnahan (BBB) locomotor scale. All animals supported their weight with the hindlimbs and used their hindlimbs normally during overground locomotion. In some cases, the spinal cord was retransected at the original lesion site or just caudal to it 6 months after the original transection and paralysis of the hindlimbs ensued. Surprisingly, however, these animals gradually recovered some ability to support their weight and to step with the hindlimbs. Similar recovery was not seen in animals transected only as adults. In order to verify that descending axons which grew through the lesion during development were still present in the adult animal, opossums subjected to transection of the thoracic cord on PD5 were reoperated and Fast blue was injected several segments caudal to the lesion. In all cases, neurons were labeled rostral to the lesion in each of the spinal and supraspinal nuclei labeled by comparable injections in unlesioned, age-matched controls. The results of orthograde tracing studies indicated that axons which grew through the lesion innervated areas that were appropriate for them.     

The Serotonergic Agonists Quipazine, CGS-12066A, and α-Methylserotonin Alter Motor Activity and Induce Hindlimb Stepping in the Intact and Spinal Rat Fetus.

The effects of serotonergic agonists were examined in intact and spinal fetuses, using an in vivo fetal rat preparation. On Gestational Day 20, fetuses were prepared with a midthoracic or sham spinal transection. Dose-response curves were obtained for quipazine (nonselective 5-hydroxytryptamine [5-HT] agonist; 1.0-10.0 mg/kg), CGS-12066A (5-HT1B agonist; 1.0-30.0 mg/kg), and α-methylserotonin (α-Me-5-HT; 5-HT? agonist; 0.2-15.0 mg/kg). During a 10-min test, each of the agonists (delivered via intraperitoneal injection) influenced fetal behavior: They increased the occurrence of head movements, mouthing, and hindlimb stepping. Quipazine and α-Me-5-HT also promoted hindlimb activity in spinal fetuses. Thus, stimulation of the fetal 5-HT system modulates motor activity at multiple levels of the developing central nervous system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gait analysis of adult paraplegic rats after spinal cord repair

This study presents a novel detailed method of analysis of rat gait and uses this method to demonstrate recovery of forward locomotion patterns in adult rats made paraplegic by surgical spinal cord transection and subjected to a novel strategy for spinal cord repair. Six normal rats were compared to five animals in which the cord was transected at T8-T9, and a 5-mm segment of the spinal cord removed, and to seven animals in which, following spinal cord transection and removal of a spinal cord segment, multiple intercostal peripheral nerve bridges were implanted, rerouting pathways from white to gray matter in both directions. The implanted area was filled with fibrin glue containing acidic fibroblast growth factor. Details of the repair strategy have been published (H. Cheng, Y. Cao, and L. Olson, 1996, Science 273: 510-513). Gait analysis was carried out 3 and 4 months after surgery and once in the normal animals. Animals were allowed to walk across a runway with a transparent floor. Each test consisted of five trials, and each trial was videorecorded from underneath. Using frame-by-frame playback, individual footprints were then recorded regarding location and order of limb use, as well as step quality (degree of weight bearing, etc.). These data allowed measuring runway transit time, five different measures of step numbers, all possible temporal patterns of limb use, stride length, and base of support. Transected controls remained paralyzed in the hindlimbs with only occasional reflex hindlimb movements without weight bearing. Animals subjected to the full repair procedure were significantly faster than the controls, used their hindlimbs for 25-30% of the movements, and regained several of the specific limb recruitment patterns used by normal rats. Taken together, the gait analysis data demonstrate remarkable recovery of coordinated gait in the repaired animals, which was significantly better than controls for all relevant parameters, while at the same time clearly inferior to normal rats for most of the examined parameters. We conclude that normal rats use a multitude of interchangeable step sequence patterns, and that our spinal cord repair strategy leads to recovery of some of these patterns following complete spinal cord transection. These data suggest functionally relevant neuronal communication across the lesion.     

Red nucleus stimulation inhibits within the inferior olive

Red nucleus stimulation inhibits within the inferior olive. J. Neurophysiol. 80: 3127-3136, 1998. In the anesthetized cat, electrical stimulation of the magnocellular red nucleus (RNm) inhibits responses of rostral dorsal accessory olive (rDAO) neurons to cutaneous stimulation. We tested the hypothesis that RNm-mediated inhibition occurs within the inferior olive by using stimulation of the ventral funiculus (VF) of the spinal cord in place of cutaneous stimulation of the hindlimb. Fibers in the VF terminate on hindlimb rDAO neurons, so inhibition of this input would have to occur within the olive. rDAO responses elicited by VF stimulation were inhibited by prior stimulation of the RNm, indicating that inhibition occurs within the olive. In contrast, evoked potentials recorded from the VF or dorsal columns following hindlimb stimulation were not affected by prior stimulation of RNm, indicating that stimulation of the RNm does not inhibit olivary afferents at spinal levels. RNm stimulation that inhibited rDAO responses had little effect on evoked somatosensory responses in thalamus, indicating that inhibition generated by activity in RNm may be specific to rDAO. To test limb specificity of RNm-mediated inhibition, conditioning stimulation was applied to the dorsolateral funiculus at thoracic levels, which selectively activates RNm neurons projecting to the lumbar cord. Stimulation at thoracic levels inhibited evoked responses from hindlimb but not forelimb regions of rDAO, suggesting that inhibitory effects of RNm activity are limb specific. Several studies have reported that olivary neurons have reduced sensitivity to peripheral stimulation during movement; it is likely that RNm-mediated inhibition occurring within the olive contributes to this reduction of sensitivity. Inhibition of rDAO responses by descending motor pathways appears to be a salient feature of olivary function.     

Roles of ascending inhibition during two rhythmic motor patterns in Xenopus tadpoles

We have investigated the effects of ascending inhibitory pathways on two centrally generated rhythmic motor patterns in a simple vertebrate model, the young Xenopus tadpole. Tadpoles swim when touched, but when grasped respond with slower, stronger struggling movements during which the longitudinal pattern of motor activity is reversed. Surgical spinal cord transection to remove all ascending connections originating caudal to the transection (in tadpoles immobilized in alpha-bungarotoxin) did not affect "fictive" swimming generated more rostrally. In contrast, cycle period and burst duration both significantly increased during fictive struggling. Increases were progressively larger with more rostral transection. Blocking caudal activity with the anesthetic MS222 (pharmacological transection) produced equivalent but reversible effects. Reducing crossed-ascending inhibition selectively, either by midsagittal spinal cord division or rostral cord hemisection (1-sided transection) mimicked the effects of transection. Like transection, both operations increased cycle period and burst duration during struggling but did not affect swimming. The changes during struggling were larger with more rostral hemisection. Reducing crossed-ascending inhibition by spinal hemisection also increased the rostrocaudal longitudinal delay during swimming, and the caudorostral delay during struggling. Weakening inhibition globally with low concentrations of the glycine antagonist strychnine (10-100 nM) did not alter swimming cycle period, burst duration, or longitudinal delay. However, strychnine at 10-60 nM decreased cycle period during struggling. It also increased burst duration in some cases, although burst duration increased as a proportion of cycle period in all cases. Strychnine reduced longitudinal delay during struggling, making rostral and caudal activity more synchronous. At 100 nM, struggling was totally disrupted. By combining our results with a detailed knowledge of tadpole spinal cord anatomy, we conclude that inhibition mediated by the crossed-ascending axons of characterized, glycinergic, commissural interneurons has a major influence on the struggling motor pattern compared with swimming. We suggest that this difference is a consequence of the larger, reversed longitudinal delay and the extended burst duration during struggling compared with swimming.     

Functional reorganization of the rat motor cortex following motor skill learning

Functional reorganization of the rat motor cortex following motor skill learning. J. Neurophysiol. 80: 3321-3325, 1998. Adult rats were allocated to either a skilled or unskilled reaching condition (SRC and URC, respectively). SRC animals were trained for 10 days on a skilled reaching task while URC animals were trained on a simple bar pressing task. After training, microelectrode stimulation was used to derive high resolution maps of the forelimb and hindlimb representations within the motor cortex. In comparison with URC animals, SRC animals exhibited a significant increase in mean area of the wrist and digit representations but a decrease in elbow/shoulder representation within the caudal forelimb area. No between-group differences in areal representation were found in either the hindlimb or rostral forelimb areas. These results demonstrate that motor skill learning is associated with a reorganization of movement representations within the rodent motor cortex.     

Restitution of functional neural connections in chick embryos assessed in vitro after spinal cord transection in Ovo

Functional neural reconnection is not common after spinal cord transection in the CNS of adult higher vertebrates but has been demonstrated in embryonic avian and neonatal mammalian CNS. Chick brainstem spinal cord preparations from nontransected controls and embryos transected at the cervical level on embryonic days (E) 8, 9, or 10 in ovo were assessed in vitro between E12 and E20 for their ability to produce and maintain episodic motor activity (EMA) using electrophysiological, voltage sensitive dye and anatomical tract-tracing techniques. After 3 to 4 days recovery, cycle-by-cycle coupling of EMA between segments separated by a transection was absent or inconsistent, although otherwise normal bouts of locally stimulated and spontaneous EMA were routinely observed restricted to segments of a cord separated by a transection site. After 5-7 days recovery in ovo the cross-transection coordination during bouts of EMA approached that of nontransected controls. The delay between the initiation of EMA in cervical segments to its initiation in lumbosacral segments caudal to a transection was an indicator of reconnection strength. The delay shortened from 0.5 to a few seconds after 3 days of recovery to around 150 ms (i.e., normal) after 5 days of recovery. We conclude that the reconnection of spinal central pattern generators for EMA across the transection was served mainly by axons which established connections with local circuits after extending 1-3 segments through a transection. Propriospinal axons that originated within 1-3 segments rostral to the transection then served to serially initiate EMA in distal caudal segments.     

Cricoid pressure: are two hands better than one?

A two-year-old, neutered male Labrador retriever was anesthetized with intravenous propofol for bronchoscopy to remove a bronchial foreign body. The dog previously had been diagnosed with idiopathic epilepsy. During anesthetic recovery, the dog exhibited excitatory movements characterized by forelimb extensor rigidity, opisthotonos, generalized tremors, paddling, horizontal nystagmus, and facial twitching. Intravenous administration of pentobarbital temporarily stopped the motor activity. The excitatory movements persisted for 20 hours. The dog went on to recover completely, although he remained an epileptic, having one brief, generalized grand mal seizure every three-to-four months.     

Effects of drugs affecting endogenous amines or cyclic nucleotides on ethanol withdrawal head twitches in mice

1 Twenty-four hours after ethanol withdrawal, dependent mice exhibited frequent head twitching. Naive mice exhibited similar twitching 15 min after treatment with 5-hydroxytryptophan (5-HTP) or 6 h after alpha-methyl-p-tyrosine (AMPT). Ethanol lessened the incidence of head twitches induced by any of these treatments. 5-HTP and AMPT each increased the incidence of head twitches induced by withdrawal of ethanol from dependent mice. 2 Drugs that affect the amount or activity of endogenous amines or cyclic nucleotides modified the incidence of head twitches. Nearly all drugs acted in the same direction on twitching elicited by any of these three treatments. 3 The incidence was lessened by: (a) methysergide, methergoline, MA 1420, p-chlorophenylalanine and p-chloroamphetamine; (b) dopamine, noradrenaline, L-DOPA, amphetamine and apomorphine; (c) hyoscine and nicotine; and (d) adenosine triphosphate, dibutyryl cyclic adenosine-3',5'-monophosphate (db cyclic AMP) and prostaglandins E1 and E2. 4 The incidence was increased by: (a) acetylcholine, carbachol and physostigmine; and (b) guanosine triphosphate, dibutyryl cyclic guanosine monophosphate (db cyclic GMP), theophylline and 3-isobutyl-1-methyl-xanthine. 5 These findings suggest that head twitching induced by these three treatments arises from a common biochemical mechanism, which may ultimately be a change in favour of cyclic GMP of the balance between this nucleotide and cyclic AMP within appropriate neurones. This imbalance appears to be elicited or increased by 5-hydroxytryptamine and acetylcholine and to be decreased by dopamine, noradrenaline and E prostaglandins. 6 Neither actinomycin D nor cycloheximide, given during the induction of ethanol dependence, altered the incidence of head twitches after ethanol withdrawal.     

Reconstruction of flexor/extensor alternation during fictive rostral scratching by two-site stimulation in the spinal turtle with a transverse spinal hemisection

Analyses of fictive scratching motor patterns in the spinal turtle with transverse hemisection provided support for the concept of bilateral shared spinal cord circuitry among neurons responsible for generating left- and right-side rostral, pocket, and caudal fictive scratching. Rhythmic bursts of hip flexor activity, the hip extensor deletion variation of fictive rostral scratching, were elicited by ipsilateral stimulation in the rostral scratch receptive field of a spinal turtle [transection at the segmental border between the second (D2) and third (D3) postcervical spinal segments] with a contralateral transverse hemisection one segment anterior to the hindlimb enlargement (at the D6-D7 segmental border). In addition, other sites were stimulated in this preparation: (1) contralateral sites in a rostral, pocket, or caudal scratch receptive field or (2) ipsilateral sites in a caudal scratch receptive field. A reconstructed fictive rostral scratch motor pattern of rhythmic alternation between hip flexor and hip extensor activation was produced by simultaneous stimulation of one site in the ipsilateral rostral scratch receptive field and another site in one of the other scratch receptive fields. This reconstructed rostral scratch motor pattern resembled the normal rostral scratch motor pattern produced by one-site rostral scratch stimulation of a spinal turtle (D2-D3 transection) with no additional transections. The observation of a reconstructed rostral scratch motor pattern produced by two-site stimulation in the spinal turtle with transverse hemisection supports the concept that hip extensor circuitry activated by stimulation of other scratch receptive fields is shared with circuitry activated by ipsilateral rostral scratch receptive field stimulation.     

Distribution of N-cadherin and NCAM in neurons and endocrine cells of the human embryonic and fetal gastroenteropancreatic system

When the thoracic spinal cord of the North American opossum is transected early in development, supraspinal axons grow through the lesion. In the experiments reported here, we asked whether regeneration of cut axons contributes to such growth. Fast Blue (FB) was injected into the lumbar cord on postnatal day (PD)5, 8, 15, or 20. Five days later, FB was removed by gentle suction, and the spinal cord was transected at thoracic levels. Fourteen days later, rhodamine B dextran was injected between the site of the FB injection and the lesion. The pups were maintained for an additional 7-10 days before killing and perfusion. We assumed that supraspinal neurons that contained FB survived axotomy and those that contained both FB and rhodamine B dextran supported regenerating axons. In the PD5 group (lesioned at PD10), regenerative growth was documented for axons originating in all of the supraspinal nuclei that innervate the lumbar cord by PD10. When the injections were made at the later ages, however, neurons that supported regenerative growth were fewer in number and regionally restricted. In some cases, they were limited primarily to the red nucleus, the medullary raphe, and the adjacent reticular formation. Our results show that regeneration of cut axons contributes to growth of supraspinal axons through the lesion after transection of the thoracic cord in developing opossums and that the critical period for regenerative growth is not the same for all axons.     

Instrumental Learning Within the Rat Spinal Cord: Localization of the Essential Neural Circuit.

Following spinal transection of the upper thoracic spinal cord, male Sprague-Dawley rats given legshock whenever a hindlimb is extended learn to maintain the leg in a flexed position. The region of the cord that mediates this instrumental learning was isolated using neuroanatomical tracing, localized infusion of lidocaine, and surgical transections. DiI and Fluoro-Gold microinjection at the site of shock application labeled motor neuron bodies of lamina IX in the lower lumbar region. Local application of the Na++ channel blocker lidocaine disrupted learning when it was applied over a region extending from the lower lumbar (L3) to upper sacral (S2) cord. The drug had no effect rostral or caudal to this region. Surgical transections as low as L4 had no effect on learning. Learning also survived a dual transection at L4 and S3, but not L4 and S2. The results suggest that the essential neural circuit lies between L4 and S3. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous motor activity in fetal and infant rats is organized into discrete multilimb bouts.

Spontaneous motor activity (SMA) is a ubiquitous feature of fetal and infant behavior. Although SMA appears random, successive limb movements often occur in bouts. Bout organization was evident at all ages in fetal (embryonic day [E] 17–21) and infant (postnatal day [P] 1–9) rats, with nearly all bouts comprising 1–4 movements of different limbs. A computational model of SMA, including spontaneous activity of spinal motor neurons, intrasegmental and intersegmental interactions, recurrent inhibition, and descending influences, produced bouts with the same structure as that observed in perinatal rats. Consistent with the model, bouts were not eliminated on E20 after cervical spinal transection, suggesting that the brain is not necessary to produce bout organization. These investigations provide a foundation for understanding the contributions of SMA to neuromuscular and motor development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compensatory movements of horses with a stance phase lameness

In order to study the mechanism of lameness transfer from fore- and hindlimb lamenesses 2 hypotheses were investigated. Hypothesis 1: Horses with a true supporting limb lameness in one hindlimb show a false supporting limb lameness in the ipsilateral forelimb. Hypothesis 2: Horses with a true supporting limb lameness in one forelimb show a false supporting limb lameness in the contralateral hindlimb. Fourteen horses with fore- or hindlimb lameness were used for this study. Each horse was measured at the trot on a treadmill with standardised speed, before and after diagnostic blocks (9 horses), or with and without induced lameness (5 horses). The head acceleration asymmetry (HAAS) and the sacrum acceleration asymmetry (SAAS) were used for quantification of fore- and hindlimb lameness respectively. Changes were documented by changes of the HAAS or the SAAS. In all 4 horses with a true hindlimb lameness a synchronous false lameness of the ipsilateral forelimb was documented. In 6 of 10 horses with a forelimb lameness a lameness transfer could be assessed according to hypothesis 2. The results of this study show, that horses with a true severe lameness in the forelimb show a false lameness in the contralateral hindlimb, and horses with a true hindlimb lameness show a false lameness in the ipsilateral forelimb. This indicates that the location of the truly lame limb can be deduced from the distribution of 2 lamenesses on a sagittal or diagonal axis.