Magnetic transcranial motor and somatosensory evoked potentials in cervical spondylitic myelopathy

Fourteen cervical spondylitic myelopathy (CSM) patients were clinically diagnosed and proved by MRI and surgery. The results of 11 patients showed that 8 (72.7%) had motor evoked potential (MEP) abnormality with prolongation of central motor conduction time (CMCT) in 7, and absence of motor action potentials after C7 stimulation in one. Five of the 11 patients showed normal somatosensory evoked potentials (SEPs) along the same arm. The short term (2-4 weeks) follow-up study in 10 patients showed normalization of the prolonged CMCT in one and reappearance of MEPs with C7 stimulation in another. Non-invasive and painless magnetic transcranial stimulation of the motor pathways is useful in the assessment and management of CSM patients, and is better than electrical stimulation.

Pursuit deficits in bilateral pulvinar lesions

A 58-year-old man had bilateral pulvinar infarctions. The patient developed smooth pursuit deficits in both the horizontal and vertical directions, while metrics of saccadic eye movements were normal. The gain of optokinetic nystagmus was slightly reduced. These findings strongly support the idea that the efferent fibers from the cortical pursuit center pass through the pulvinar in the human brain, in the same manner as previously described in the monkey cerebrum.

Efferent projections of the periaqueductal gray in the rabbit

The efferent projections of the periaqueductal gray in the rabbit have been described by anterograde tract-tracing techniques following deposits of tritiated leucine, or horseradish peroxidase, into circumscribed sites within dorsal, lateral or ventral periaqueductal gray. No attempts were made to place labels in the fourth, extremely narrow (medial), region immediately surrounding the aqueduct whose size and disposition did not lend itself to confined placements of label within it. These anatomically distinct regions, defined in Nissl-stained sections, corresponded to the same regions into which deposits of horseradish peroxidase were made in order for us to describe afferent projections to the periaqueductal gray. In this present study distinct ascending and descending fibre projections were found throughout the brain. Terminal labelling was detected in more than 80 sites, depending somewhat upon which of the three regions of the periaqueductal gray received the deposit. Therefore, differential projections with respect to both afferent and efferent connections of these three regions of the periaqueductal gray have now been established. Ventral deposits disclosed a more impressive system of ramifying, efferent fibres than did dorsal or lateral placements of labels. With ventral deposits, ascending fibres were found to follow two major pathways from periaqueductal gray. The periventricular bundle bifurcates at the level of the posterior commissure to form hypothalamic and thalamic components which distribute to the anterior pretectal region, lateral habenulae, and nuclei of the posterior commissure, the majority of the intralaminar and midline thalamic nuclei, and to almost all of the hypothalamus. The other major ascending pathway from the periaqueductal gray takes a ventrolateral course from the deposit site through the reticular formation or, alternatively, through the deep and middle layers of the superior colliculus, to accumulate just medial to the medial geniculate body. This contingent of fibres travels more rostrally above the cerebral peduncle, distributing terminals to the substantia nigra, ventral tegmental area and parabigeminal nucleus before fanning out and turning rostrally to contribute terminals to ventral thalamus, subthalamus and zona incerta, then continuing on to supply amygdala, substantia innominata, lateral preoptic nucleus, the diagonal band of Broca and the lateral septal nucleus. Caudally directed fibres were also observed to follow two major routes. They either leave the periaqueductal gray dorsally and pass through the gray matter in the floor of the fourth ventricle towards the abducens nucleus and ventral medulla, or are directed ventrally after passing through either the inferior colliculus or parabrachial nucleus. These ventrally directed fibres merge just dorsal to the pons on the ventral surface of the brain.(ABSTRACT TRUNCATED AT 400 WORDS)

Bronchoconstriction induced by inhaled sodium metabisulfite in the guinea pig. Effect of capsaicin pretreatment and of neutral endopeptidase inhibition

Sodium metabisulfite (MBS), a commonly used preservative, induces bronchoconstriction in asthmatics, probably through the release of sulfur dioxide (SO2). The mechanisms involved in MBS- and SO2-induced bronchoconstriction are not yet certain. We aerosolized MBS or acid control solution (pH, 2.7) to anesthetized, tracheostomized guinea pigs pretreated intravenously with propranolol (1 mg/kg). MBS was given at increasing doubling concentrations (0.01, 0.02, 0.04, and 0.08 M) every 5 min. Steep concentration-response curves were observed, and most animals responded at 0.02 or 0.04 M. Tachyphylaxis was seen at high concentrations and during a subsequent MBS challenge 15 min later. For pharmacologic studies, we stopped the challenge when lung resistance (RL) had increased by at least 350%; a second challenge was found to be reproducible. MBS response was measured as the concentration needed to increase RL by 350% (PC350). Atropine (1 mg/kg given intravenously) did not affect PC350 or the peak RL response. Inhibition of neutral endopeptidase by inhaled phosphoramidon (7.5 nmol) administered before the repeated challenge did not alter PC350 value to MBS or peak RL responses (phosphoramidon, 201 +/- 49% of first peak; vehicle, 164 +/- 35%). In addition, the increase in RL was not prolonged in the phosphoramidon-treated group. Animals treated subcutaneously with capsaicin (50 mg/kg) 1 wk before the experiment, so as to deplete neuropeptides from airway sensory nerves, had PC350 values similar to those of the control animals. Our data demonstrate that inhaled MBS causes bronchoconstriction in guinea pigs by mechanisms that are due neither to a cholinergic reflex nor to the release of tachykinins from airway sensory nerves.

Development of two morphological types of retinopetal fibers in chick embryos, as shown by the diffusion along axons of a carbocyanine dye in the fixed retina

Centrifugal fibers to the retinas of chick embryos and hatched chicks have been examined and traced following staining by diffusion along their axonal membranes of the carbocyanine dye DiI in fixed tissue. In the older embryos and hatched chicks, the report of Dogiel (Arch. Mikrosk. Anat. 44:622-648, 1895) has been confirmed that there are two very different morphological types of centrifugal fiber. The restricted type ends as a relatively thick fiber, lacking varicosities, that runs for a short distance in the most sclerad level of the inner plexiform layer before terminating in a pericellular nest overlying the flask-shaped body of a single amacrine cell. Thin filaments occasionally leave the pericellular net, apparently to terminate on adjacent cells. The widespread type also runs in the most sclerad level of the inner plexiform layer, but it is thin, varicose, and highly branched, and its terminal arbor may span more than 1 mm, remaining at the same level. Both types of terminal arbor issue from parent axons in the optic fiber layer of the retina. A single parent axon gives either a single terminal fiber of the restricted type or several terminals of the widespread type, but never a mixture of the two. It is argued that the restricted and widespread types originate respectively from the neurons of the contralateral isthmo-optic nucleus and from the "ectopic" neurons scattered outside the isthmo-optic nucleus. In development, the centrifugal fibers reach the retina between E9 and E10 and initially run radially in the optic fiber layer, parallel to the retinofugal fibers but avoiding the dorsal retina. They dive into the inner plexiform layer at about E12. By E13, the terminal arbors are forming, and the widespread and restricted types can already be distinguished. The widespread type continues to increase its territory until about E18, and then appears to remain stable, whereas the restricted type attains its maximum ramification between E13 and E15 and then contracts. Prior to the retraction, the terminal territories of the restricted type fibers overlap, which may provide the anatomical basis for the interaxonal competition that apparently contributes to neuronal death in the isthmo-optic nucleus between E13 and E16. Axons of ganglion cells exhibit transient side branches between E11 and E13; these never reach as deep as the level where the centrifugal fibers run.

Effect of 5-hydroxytryptamine on gastric motility and efferent gastric vagus nerve activity in rats

Intravenous administration of 5-hydroxytryptamine (5-HT) produced a depressor effect on pyloric pressure and an increase in the duration of this depressor effect on gastric pressure dose-dependently in anesthetized rats. Pretreatment with a selective 5-HT3-receptor antagonist, ICS 205-930 (10 micrograms/kg), inhibited these effects. Intravenous administration of 5-HT produced a dose-dependent increase in efferent gastric vagus nerve activity (GVNA). A selective 5-HT3-receptor agonist, 2-methyl-5-HT, also produced a dose-dependent increase in GVNA. Pretreatment with a selective 5-HT3-receptor antagonist, ICS 205-930 (10 micrograms/kg), caused a shift to the right in both the 5-HT and 2-methyl-5-HT dose-response curves. These findings suggest that exogenous 5-HT activates efferent vagus gastric nerve activity and may trigger or mediate the gastric motility via 5-HT3-receptors.

Non-invasive brain stimulation reveals reorganized cortical outputs in amputees

EMG responses to non-invasive electromagnetic brain stimulation (EMS) were recorded from arm muscles of congenital amputees. Responses were obtained with lower thresholds on the amputated than on the intact side and were evoked from a larger cortical area. Contracting muscles showed increased responses to EMS; the increase was more pronounced on the amputated side. Similar findings were obtained in one traumatic amputee who suffered an early amputation, but not in another patient with a late amputation. We conclude that in congenital amputees there is substantial reorganisation of the corticospinal system and that this may also occur in early traumatic cases.

Identification of motoneurons in the spinal cord of the zebrafish (Brachydanio rerio), with special reference to motoneurons that innervate intermediate muscle fibers

We investigated the location and size distribution of motoneurons that innervate red, intermediate and white muscle fibers in the axial musculature of the zebrafish (Brachydanio rerio). Motoneurons were identified by retrograde labeling from the respective myotomal compartments with horseradish peroxidase applied either in small polyacrylamide gel fragments or as pure crystals. We found a spatial relationship between the three myotomal muscle fiber types and the corresponding motoneurons. The white motoneurons are grouped in the dorsal part of the motorcolumn, near the central canal. Motoneurons of the red and intermediate muscle are clustered in the ventral part of the motorcolumn. The average position of the red motoneurons is ventral to that of the intermediate motoneurons. Some sizes are distributed over wide overlapping ranges, spanning from 41 to 352 microns 2 for red and intermediate and from 56 to 894 microns 2 for white motoneurons. These data are discussed in relation to the recruitment order of myotomal muscle fibers of different types as revealed by electromyographic recordings in fish, and the so called "size principle" for motoneuron recruitment.

Immunoelectron microscopic localization of neurotransmitters in the cochlea

This paper presents the works and methods of our respective laboratories using electron microscopic immunocytochemistry to identify and localize cochlear neurotransmitters. Antibodies to various prospective neurotransmitters and associated enzymes have been used to study the ultrastructural localization of several candidates for olivocochlear efferent neurotransmitters previously suggested by light microscopic immunocytochemistry. Antibodies against enkephalins label lateral olivocochlear efferent fibers. Antibodies against choline acetyltransferase (ChAT) (an enzyme marker for acetylcholine) label a major population of both lateral and medial efferent fibers and terminals, whereas antibodies to gamma-aminobutyric acid (GABA) label what might be a small subpopulation of both the lateral and medial efferent systems. The GABA-like immunostained medial efferent fibers are preferentially located in the upper turns of the guinea pig cochlea, particularly the third turn. Immunoelectron microscopy shows that neither GABA nor ChAT immunolabels all medial efferent terminals, regardless of cochlear turn. All the different types of immunolabeled efferent terminals have been observed to make characteristic synaptic contacts; lateral efferent terminals on afferent dendrites and medial efferent terminals on outer hair cells and occasionally on type II afferent dendrites. Other types of contacts involving GABA-like, and sometimes met-enkephalin-like, immunostained fibers are occasionally seen particularly in the upper turns of the cochlea. Immunoelectron microscopic results suggest that both medial and lateral efferent systems might be further subdivided on the basis of differences in neurotransmitters. Future trends of immunocytochemical research on cochlear neurotransmitters are proposed, particularly colocalization studies, which show a complex pattern of coexistence of neurotransmitters in the lateral efferent system.

Origins and terminations of bulbospinal axons that contain serotonin and either enkephalin or substance-P in the North American opossum

We have shown previously that some enkephalin, substance-P, and serotoninergic neurons in the medullary raphe and adjacent reticular formation project to the spinal cord in the opossum. In the present study we have combined the retrograde transport of True Blue and immunofluorescence histochemistry to determine whether methionine enkephalin or substance-P containing bulbospinal neurons are serotoninergic. Furthermore, we have used the same immunofluorescence protocol to determine whether spinal axons contain the same substances. Neurons that immunostained for both enkephalin and serotonin were observed in many brainstem nuclei. However, those that projected to the spinal cord were limited to the nuclei raphe magnus and obscurus, and the ventral part of nucleus reticularis gigantocellularis, pars ventralis. Neurons that immunostained for both substance P and serotonin were fewer in number, but some of the ones in the above nuclei and within the nucleus raphe pallidus, projected to the spinal cord. Spinal axons exhibiting both enkephalin- and serotonin-like immunoreactivity were observed in the superficial laminae of the dorsal horn, lamina X, and the intermediolateral cell column, whereas those showing both substance-P and serotonin-like immunoreactivity were seen primarily in lamina X, the intermediolateral cell column, and the ventral horn. Some of the axons in the ventral horn were in close apposition to presumed motoneurons. Comparison of the above results with those obtained from previous studies of bulbospinal projections has allowed us to infer the origins of axons that innervate different spinal targets.

Central motor conduction to hand and leg muscles in Huntington's disease

Using electromagnetic stimulation of motor cortex and cervical or lumbar roots, central conduction times to the thenar and abductor hallucis muscles bilaterally were determined in a population of 32 patients with definite Huntington's disease (HD) and 14 subjects at risk. The HD patients showed a wide variety of different severity of choreatic movements, disease duration, and total disability. None of the stimulation parameters (latency after cortical stimulation, amplitude, threshold, or central conduction time) revealed statistically significant abnormalities compared with a normal control group as well as between patient subgroups. The data indicate that central motor conduction to upper and lower extremity muscles remains normal in Huntington's disease irrespective of the severity of the disorder.

Descending modulation of dorsal horn biogenic amines as determined by in vivo dialysis

Bipolar concentric stimulating electrodes were placed medially within the nucleus raphe magnus and laterally within the nucleus gigantocellularis. The levels of norepinephrine (NE), serotonin (5-HT), and 5-hydroxyindolacetic acid (5-HIAA) within the dorsal horn of the spinal cord were measured before and after electrical stimulation of these brainstem nuclei using in vivo dialysis coupled with high pressure liquid chromatography and electrochemical detection. Stimulation medially significantly increased the levels of all three amines. While simulation laterally also increased NE, both 5-HT and 5-HIAA were significantly reduced. The relevance of these findings to descending modulation of ascending nociceptive neural activity within the dorsal horn is discussed.

Do injuries to the developing human brain alter corticospinal projections?

Experimental lesions of the mammalian brain involving the developing corticospinal pathways may cause these pathways to become redirected. In humans, injury to the developing brain results in disorders of movement known collectively as 'cerebral palsy'. These motor disorders differ from those produced by similar lesions in adults. We present evidence that abnormal corticospinal projections exist in subjects who have had an injury to the brain in the perinatal period. These aberrant connections, which may represent misdirected corticospinal fibers, help to explain the impairment of voluntary movements experienced by these subjects.

Baroreflex control of renal sympathetic nerve activity is preserved in heart failure despite reduced arterial baroreceptor sensitivity

The purpose of this study was to determine if arterial baroreflex control of sympathetic nerve traffic is impaired in heart failure. We recorded renal nerve activity during changes in arterial pressure while simultaneously recording from aortic baroreceptor afferent fibers in 10 dogs with heart failure induced by rapid ventricular pacing and in 10 sham animals. Sensitivity of the aortic baroreceptors (percent change in nerve activity per millimeters mercury change in mean arterial pressure) was reduced in the heart failure group (heart failure, 2.3 +/- 0.3; sham, 3.6 +/- 0.4, p = 0.02). Despite the reduced sensitivity of aortic baroreceptors in heart failure, there was no difference in the baroreflex gain of renal nerve activity (heart failure, -5.5 +/- 1.4; sham, -5.8 +/- 1.3, p = NS). These values tended to decrease in both groups after vagotomy. The relation between baroreceptor input and renal sympathetic output, or central baroreflex gain (percent change in renal nerve activity divided by percent change in aortic nerve activity) was similar in both groups before vagotomy (heart failure, -2.4 +/- 0.6; sham, -2.3 +/- 0.5, p = NS). Vagotomy reduced central gain in the sham group (-0.9 +/- 0.1, p = 0.03) but not in the heart failure group (-1.7 +/- 0.5, p = NS), suggesting that the contribution of vagal afferents in the baroreflex arc is reduced in heart failure. Baroreflex control of R-R interval was attenuated in heart failure when assessed by blood pressure elevation but not reduction, indicating abnormal parasympathetic but preserved cardiac sympathetic mechanisms in heart failure. Thus, dogs with heart failure exhibit reduced sensitivity of aortic baroreceptors but preserved baroreflex control of renal nerve activity. Reduced baroreceptor sensitivity with preservation of baroreflex control of sympathetic nerve activity may contribute to the sympathoexcitatory state known to exist in heart failure.

Thoughts about spinal actions and cerebral reflections in movement

Some thoughts about the co-ordination in movement are given and how our communication organ may be able to adapt to the disaster of an interruption in the information chain.

Vestibulospinal evoked potential versus motor evoked potential monitoring in experimental spinal cord injuries of cats

Changes in vestibulospinal evoked potentials (VsEP) and motor evoked potentials (MEP) were examined in 10 cats before and after two different weight-dropping spinal cord injuries. In six animals somatosensory evoked potentials (SEP) were also monitored. The recordings were done from epidural spinal cord electrodes. Before and after severe and light weight-dropping spinal cord injuries all 3 modalities were recorded at the same time intervals till the end of 4th hour postinjury. According to a scoring system, evoked potential changes below and above the level of injury were monitored, and compared with each other. This study showed that the different motor stimulation methods use different descending spinal tracts, and both can be useful as a monitoring tool. Both descending tracts carrying VsEP and MEP had similarly remarkable changes after severe spinal cord injury. These consisted of major deformation, development of an evoked injury potential and complete potential loss. During the 4 hour monitoring period, no case showed EP recovery in the severe injury group. Light spinal cord injury caused somewhat more deterioration in MEPs than VsEP. The higher numbers of severe potential alterations in the lightly injured animals suggest that MEP is a more sensitive method for spinal cord monitoring compared to VsEP and also to SEP. On the other hand, this sensitivity might be a disadvantage during intraoperative monitoring, if MEP alone were used.

[Brain stem projections of afferent fibres form the salivary gland]

The sensory nerve fibres and terminals exist in the salivary gland. However, the projection sites of these sensory fibres have not been clarified. The present study was examined electrophysiologically the projection site of the afferent fibres in the brain stem in urethane-chloralose anesthetized cats. The sensory fibres from the sublingual and submandibular glands were passing through the trigeminal nerve. The afferent fibres projected to the caudal end of subnucleus interpolaris of trigeminal spinal tract nucleus, then send the secondary neurons to the lateral and medial of bulbar reticular formation and pontine reticular formation. The sensory afferents from the salivary gland would control the salivary secretion and other autonomic functions.

The effect of distension of the urinary bladder on activity in efferent vagal fibres in anaesthetized dogs

Experiments were performed in anaesthetized dogs to find out whether the response of decreases in vagus nerve activity to distension of the urinary bladder is affected by changes in carotid sinus pressure. The carotid sinuses were vascularly isolated and perfused with blood at constant flow. Both ureters were cannulated and the urinary bladder was distended with warm Ringer solution. In eight dogs, all eleven efferent vagus fibres which responded to changes in carotid sinus pressure also responded to distension of the urinary bladder by a decrease in activity. This response of a decrease in activity was obtained at all levels of carotid sinus pressure between 8.4 and 30 kPa, and was greater at high than at low carotid sinus pressure. In the same vagus fibres, a relation was shown between progressive decreases in activity and either increases in intravesical pressure up to 8.7 kPa or reductions in carotid sinus pressure between 9 and 30 kPa. The decreases in activity were greater at high than at low carotid sinus pressure. These findings have shown that the inhibition of vagus nerve activity caused by bladder distension was affected by the level of carotid sinus pressure.

Efferent limb of the atrial receptor reflex decrease in plasma renin activity in anaesthetized dogs

The efferent limb of the reflex response of a decrease in plasma renin activity in response to stimulation of atrial receptors was examined in two groups of experiments in anaesthetized dogs. The atrial receptors were discretely stimulated by distension of small balloons in the left pulmonary vein-atrial junction and in the atrial appendage. In the first group, in which the responses of tachycardia and natriuresis were blocked, the diuretic response was accompanied by decreases in plasma renin activity. This decrease was abolished in the second group by renal denervation. The results have shown that the efferent limb of the response of a decrease in plasma renin activity involved the renal nerves.

Responses of vagal efferent fibres to stimulation of gastric mechano- and chemoreceptors in the anaesthetized ferret

The involvement of gastric tension receptors and mucosal chemoreceptors in vagal reflexes was assessed directly by recording single efferent fibres from the cervical vagus nerve in the urethane anaesthetised ferret. 32/39 fibres responded to distension of the gastric corpus, mainly with excitation of firing, 24/39 fibres responded to antral distension, with a higher proportion showing a reduction in firing. Fifty-seven percent of fibres showed a convergent input from corpus and antrum. The magnitude of these responses was large (usually greater than 50%) and of short latency (less than 1 s). Responses to chemical perfusions in the antrum were seen in 14/31 efferent fibres, most of which showed excitation. Latency of response was variable (5-120 s) and may have been influenced by diffusion through the antral mucous barrier. These data indicate a complex arrangement of vagal reflexes involved in pre-pyloric regulation of gastric emptying by mechanical and chemical stimuli in the lumen.

[Pressor response induced by glutamate injection into caudal ventrolateral part of periaqueductal gray matter and its efferent pathway in brain-stem]

In urethane-anesthetized, tubocurarine-immobilized artificially ventilated rats, the following results were observed: (1) Sodium glutamate (Glu) microinjection into the caudal ventrolateral part of the periaqueductal gray matter (PAG) produced a marked rise in blood pressure. (2) This effect was attenuated by phentolamine or propranolol but not by atropine, injected bilaterally into the rostral ventrolateral medulla (RVL), indicating that this pressor response is mediated by RVL and alpha- and beta-receptors. (3) Propranolol-injection into RVL also attenuated the pressor response induced by electrical stimulation of the nucleus parabrachialis ventralis (NPV), while the pressor response initiated by injecting Glu into the same area (NPV) was not affected. Taken together with the previous findings that phentolamine blocks the pressor response produced by NPV-electrostimulation, but not of Glu-injection into NPV, the above results suggest that neurons in the caudal ventrolateral part of PAG may either send axons passing through the nucleus parabrachialis (NPB) and directly acting upon beta-receptors in RVL, or relay in NPB and act indirectly on alpha-receptors in RVL to produce the pressor response.

[Inhibition of renal sympathetic efferent activities induced by stimulation of the paraventricular nucleus of the hypothalamus(PVH) in rabbits]

Experiments were performed on rabbits anesthetized with chloralose-urethane mixture, paralyzed with gallamine triethiodide, and ventilated artificially. Bilateral vagi, aortic and carotid sinus nerves were severed. Renal sympathetic efferent discharge (RSED) and its histogram were recorded, while the blood pressure (BP) of the femoral artery was monitored. When PVH was strongly stimulated, a transient increase of RSED was observed, which was followed by an inhibition of RSED. The inhibition of RSED was divided into two phases: the initial inhibitory phase without change in BP and the late inhibitory phase with an increase of BP. It was found that both the duration of total inhibition and the late, but not initial, inhibitory phase were positively correlated with the alterations of BP. When PVH was weakly stimulated, no change in BP was observed, but the inhibition of RSED still appeared. The inhibition duration was shortened remarkably following cutting of baroreceptor nerves. In some experiments, the RSED inhibition was not accompanied by a definite excitatory response. The present results indicate that 1) an inhibitory mechanism of PVH-renal sympathetic efferent system is present in the central nervous system; 2) the initial inhibitory phase of RSED originates from central mechanisms, while the late inhibitory phase is associated with the baroreceptor reflex and a direct action of the central nervous system; 3) the inhibition of RSED seems not to be a post-excitation depression, but an active inhibition exerted by the PVH on the spinal sympathetic preganglionic neurons.

Ascending projections of long descending propriospinal tract (LDPT) neurons

Ascending projections of long descending propriospinal tract (LDPT) cells were investigated using the technique of double retrograde labeling. In rat, injection of one fluorescent dye was made into either the reticular formation or the cerebellum, and a second dye was injected into the lumbosacral enlargement (LSE). In cat, injections were made into the reticular formation and into the lumbosacral enlargement. Using fluorescence microscopy, observation of neurons in the cervical enlargement (CE) revealed single- and double-labeled cells which were either spinoreticular or spinocerebellar tract cells and/or LDPT cells. In both cat and rat, the location of double-labeled LDPT-spinoreticular cells were in the ventromedial spinal gray matter of the CE and were coextensive with single-labeled LDPT and spinoreticular cells. The locations of double-labeled LDPT-spinocerebellar cells in rat were in the ventromedial gray and were coextensive with single-labeled LDPT cells, but not with single-labeled spinocerebellar cells. The latter group was located in central lamina VII and medial laminae V and VI. Overall, the mean number of double-labeled cells was 40% of rat and 7% of cat LDPT cells, indicating projections to either the brainstem reticular formation or cerebellum as well as to the lumbosacral enlargement. Thus, a subpopulation of LDPT cells apparently also serves as a spinoreticular (SR) and spinocerebellar (SC) projection system.