SEARCH · PubMed Health

Results for “Sensorimotor Cortex”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 649 records · Page 36Linked to original sources

PubMed2004

Subthalamic nucleus stimulation reduces abnormal motor cortical overactivity in Parkinson disease.

BACKGROUND: Based on the basal ganglia model, it has been hypothesized that the efficacy of high-frequency stimulation of the subthalamic nucleus (STN) against parkinsonian symptoms relies on the activation of cortical premotor regions. In previous positron emission tomography activation studies, STN high-frequency stimulation was associated with selective activation of midline premotor areas during hand movements but mainly reduced the regional cerebral blood flow in movement-related areas, peculiarly at rest. OBJECTIVE: To investigate with positron emission tomography the role of regional cerebral blood flow reduction in the clinical improvement provided by STN high-frequency stimulation. METHODS: Seven patients with advanced Parkinson disease, who were markedly improved by bilateral STN high-frequency stimulation, underwent positron emission tomography with H2(15)O while the right STN electrode was turned off. The patients were studied at rest and during right-hand movements in 3 electrode conditions: no stimulation, inefficient low-frequency stimulation, and efficient high-frequency stimulation. RESULTS: The main effect of high-frequency stimulation was to reduce regional cerebral blood flow in the left primary sensorimotor cortex, the lateral premotor cortex, the right cerebellum, and the midline premotor areas. The selective activation of the anterior cingulate cortex and the left primary sensorimotor cortex during hand movement under STN high-frequency stimulation was attributed to decreased regional cerebral blood flow at rest, rather than increased activation induced by STN high-frequency stimulation. Akinesia was correlated with the abnormal overactivity in the contralateral primary sensorimotor cortex and the ipsilateral cerebellum. CONCLUSION: High-frequency stimulation of the STN acts through the reduction of abnormal resting overactivity in the motor system, allowing selective cortical activation during movement.

Aged↗

PubMed1990

Convergence of cortical and cerebellar projections on single basilar pontine neurons: a light and electron microscopic study in the rat.

A protocol that involved a combination of two orthogradely transported tracer substances, wheat agglutinin-horseradish peroxidase and Phaseolus vulgaris leucoagglutinin injected at separate locations in the same animal was utilized to investigate the possible congruence of axonal projection fields formed by the cerebral cortical and cerebellar afferents to the basilar pontine nuclei. When large placements of tracer material were made in the cerebellar nuclei to label the cerebellopontine projections and a second tracer was injected in one of several cerebral cortical areas to visualize certain corticopontine projections, it was noted that axon terminal zones of the cortical and cerebellar systems occupied greater or lesser amounts of the same basilar pontine territory depending on the location of the cerebral cortical injection. Cerebellopontine terminal fields exhibited their greatest congruency with projections from the motor cortex containing the representation for facial musculature and with projections from the forelimb sensorimotor cortex. A lesser degree of overlap was observed when cerebellar projection zones were visualized in combination with basilar pontine projections from sensory face cortex, hindlimb sensorimotor cortex, visual cortex and auditory cortex. In addition, it was apparent that portions of the cerebellopontine and corticopontine terminal fields did not overlap at all. A related series of electron microscopic experiments was undertaken to establish that within the zones of overlapping cerebellar and cortical projections, there was in fact a convergence of the two afferent systems on single basilar pontine neurons. Boutons of the corticopontine system were labeled by the orthograde transport of wheat germ agglutinin horseradish peroxidase injected into the sensorimotor cortex while cerebellopontine terminals were marked for electron microscopic identification in the same animal by transecting the brachium conjunctivum and allowing sufficient time for boutons in the pontine nuclei to exhibit degeneration. Although the number of definitive examples of convergence was small, nonetheless it was possible to observe single basilar pontine neuron dendrites receiving synaptic contacts from both the cortical and cerebellar afferents systems. Taken together these observations indicate that some basilar pontine neurons receive a dual or convergent input from the cerebral cortex and cerebellar nuclei. It is difficult to estimate the prevalence of such convergence since cortical and cerebellar inputs typically contact distal and proximal pontine neuron dendrites, respectively, thus limiting the chances that both types of boutons can be observed in contact with a single basilar pontine neuron dendrite.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1994

Difference of regional cerebral metabolic pattern between presenile and senile dementia of the Alzheimer type: a factor analytic study.

Positron emission tomographic studies using metabolic ratios to represent the contrast between certain brain regions have shown differences of cerebral glucose metabolism between presenile and senile dementia of Alzheimer type (DAT). In this study, factors for regional variance of cerebral metabolism in 61 patients with probable Alzheimer's disease were obtained using principal component analysis (PCA). The difference between two age groups of DAT patients according to age at onset < or = 65 years (n = 30) and > 65 years (n = 31) were investigated. A PCA using nine pairs of cerebral regions normalized to cerebellum for reduction of intersubject variability identified five regional factors for cerebral metabolism: one each for the left and right temporo-parietal cortex, and the other three for frontal cortex, primary visual and sensorimotor cortex, and mesial temporal sensorimotor cortex, and mesial temporal cortex. The age groups differed significantly only in the factor for the right temporo-parietal cortex, with a more prominent metabolic reduction in presenile than senile DAT. Severity of dementia was correlated with the factors for the right and left temporo-parietal cortex. The effect of age at onset on glucose metabolism of the right temporo-parietal cortex was independent from that of dementia severity in DAT.

Age Factors↗

PubMed1984

Reevaluation of motor cortex and of sensorimotor overlap in cerebral cortex of albino rats.

The organization of motor cortex and the sensorimotor overlap zone was examined by in-depth electrical stimulation using micromapping procedures in rats. The cutaneous somatic sensory, as well as the efferent motor projections to the hindlimb and forelimb sensorimotor overlap zone were studied in the same animals. Low-threshold movements were elicited from portions of 3 architectonic areas: the lateral agranular, dysgranular and granular areas. Cutaneous light touch projections occur only within the granular area. Cutaneous projections to, and motor projections from individual punctures in the granular overlap zone did not always involve homologous body parts. The total motor cortex exhibits a general musculotopic pattern of organization.

Animals↗

PubMed1994

The cerebral cortex origin of enflurane-induced generalized seizure in cats.

The role of sensorimotor cortex (anterior and posterior sigmoid gyri) as the origin of enflurane-induced generalized seizures was examined and compared to that of lidocaine-induced seizures in cats. The inhaled enflurane concentration was adjusted at 3.5% in oxygen, the maximum potency to induce generalized seizures. Repetitive electrical stimulation with supramaximum intensity at a forepaw (2 Hz, 0.5 ms, 10 V) induced generalized seizures, which ended with a sudden appearance of isoelectricity in the electroencephalogram (EEG), the so-called "postictal depression." Repetitive auditory stimuli also induced similar grand mal-type EEGs. Unilateral ablation of the sensorimotor cortex completely blocked the induction of generalized seizures by contralateral somatosensory stimuli. However, it had little effect on the induction of seizures by ipsilateral somatosensory stimuli or bilateral auditory stimuli. In contrast, bilateral ablation of the sensorimotor cortex did not have a significant effect on the lidocaine-induced seizures. These findings indicate that the involvement of the sensorimotor cortex is essential for the development of enflurane-induced but not lidocaine-induced seizures.

Acoustic Stimulation↗

PubMed1976

Amine-responsive adenylate cyclase activity from brain: comparisons between rat and rhesus monkey and demonstration of dopamine-stimulated adenylate cyclase in monkey neocortex.

The effects of biogenic amines on adenylate cyclase from rhesus monkey brain have been surveyed. Dopamine-responsive cyclase activity was found throughout the subcortical limbic area and limbic cortex, as well as in the sensorimotor cortex, where stimulation by dopamine was blocked by fluphenazine. Cyclase activity from caudate nucleus in rat and rhesus monkey was very similar in relative responsiveness to stimulation by dopamine and norepinephrine. Some response of the enzyme from cingulate and sensorimotor cortex to isoproterenol was observed. The inhibition by fluphenazine of dopamine-responsive cyclase activity from sensorimotor cortex raises the possibility of a cerebrocortical locus of action for antipsychotic agents.

Adenylyl Cyclases↗

PubMed2004

Histochemical characterization of skeletal muscles in rats with photochemically-induced stroke.

PRIMARY OBJECTIVE: The aim of this study was to assess skeletal muscle showing a complete functional recovery after induction of pan-necrotic lesions in the right sensorimotor cortex in rats. RESEARCH DESIGN AND METHODS: A focal lesion of the right sensorimotor cortex was induced photochemically. Rats were divided into three groups; the sham-operated group (CON), Stroke (RB) and Stroke plus severed right sciatic nerve (RBD). MAIN OUTCOMES AND RESULTS: All RB rats showed complete functional recovery in the beam-walking test within 10 days. The score of CON rats was 7 for 21 days. The wet weight of the soleus muscle (SOL) only in the RB and RBD was significantly greater than in the CON. The cross-sectional area of type I fibres was increased in SOL. CONCLUSIONS: It was concluded that the functional recovery was mainly due to increased wet weight and cross-sectional area of type I SOL fibres, which probably reflected the functional reorganization and neuromodulation in the non-damaged contralateral sensorimotor cortex and ipsilateral sensorimotor cortex lateral to the lesion identified in a previous study.

Animals↗

PubMed1983

Corticobulbar projections and orofacial and muscle afferent inputs of neurons in primate sensorimotor cerebral cortex.

In barbiturate-anesthetized monkeys, single cortical neurons were found that could be antidromically activated by brain stem stimulation in the contralateral trigeminal motor, facial, and hypoglossal nuclei. The corticobulbar neurons were localized in the precentral gyrus and anterior bank of the central sulcus, and 20% of them could be excited by muscle afferent stimulation; none were excited by cutaneous or intraoral stimuli. However, many "nonprojection" neurons situated at the bottom of the anterior bank of the central sulcus, especially in area 3a, received a low-threshold afferent input from jaw, facial, and tongue muscles, and neurons with cutaneous or intraoral afferent inputs predominated further caudally, in areas 3b and 1. The results provided electrophysiologic evidence of a direct projection from primate face motor cortex to the brain stem and of an excitatory input from low-threshold afferent fibers of the jaw, facial, and tongue muscles to the primate sensorimotor cortex.

Animals↗

PubMed2006

Facilitated beam-walking recovery during acute phase by kynurenic acid treatment in a rat model of photochemically induced thrombosis causing focal cerebral ischemia.

We previously demonstrated the presence of activated areas in the non-injured contralateral sensorimotor cortex in addition to the ipsilateral sensorimotor cortex of the area surrounding a brain infarction, using a rat model of focal photochemically induced thrombosis (PIT) and functional magnetic resonance imaging. Using this model, we next applied gene expression profiling to screen key molecules upregulated in the activated area. RNA was extracted from the ipsilateral and contralateral sensorimotor cortex to the focal brain infarction and from the sham controlled cortex, and hybridized to gene-expression profiling arrays containing 1,322 neurology-related genes. Results showed that glycine receptors were upregulated in both the ipsilateral and contralateral cortex to the focal ischemic lesion. To prove the preclinical significance of upregulated glycine receptors, kynurenic acid, an endogenous antagonist to glycine receptors on neuronal cells, was administered intrathecally. As a result, the kynurenic acid significantly improved behavioral recovery within 10 days from paralysis induced by the focal PIT (p < 0.0001), as evaluated with beam walking. These results suggest that intrathecal administration of a glycine receptor antagonist may facilitate behavioral recovery during the acute phase after brain infarction.

Animals↗

PubMed1986

The contributions of motor cortex, nigrostriatal dopamine and caudate-putamen to skilled forelimb use in the rat.

Skilled forelimb use was studied in rats with unilateral lesions of the sensorimotor cortex, the caudate-putamen, or the dopaminergic nigrostriatal bundle, in a task involving reaching for food. Limb preference and efficiency were evaluated, as well as the relationship between limb use, spontaneous, and methamphetamine-induced rotation bias, both preoperatively and postoperatively. To induce use of the nonpreferred limb, a bracelet, which prevented reaching but not other movements, was attached to the forearm of the preferred forelimb. Whereas small cortical lesions of the forepaw area of the sensorimotor cortex mildly influenced limb preference and use, larger lesions changed preference. Furthermore, medium-sized sensorimotor cortex lesions impaired contralateral limb use, although surprising recovery occurred on the forced tests with the bracelet. Large cortical lesions abolished effective reaching even on the forced tests. Impairments similar to those following sensorimotor cortex lesions were also obtained following small and large caudate-putamen lesions. By contrast, unilateral dopamine depletions not only blocked use of the limb contralateral to the depletion but also impaired use of the ipsilateral limb. There was recovery in use of the ipsilateral forelimb but not the contralateral forelimb. Correlational analysis showed a weak relation between methamphetamine-induced rotation and limb preference preoperatively but no significant relation between these two variables postoperatively. The similarity in the deficits following sensorimotor cortex lesions and basal ganglia lesions suggests that skilled forelimb use depends upon a shared neural organization within the two systems.

Animals↗

PubMed1994

Development of specificity in corticospinal connections by axon collaterals branching selectively into appropriate spinal targets.

Corticospinal projections in adult rodents arise exclusively from layer V neurons in the sensorimotor cortex. These neurons are topographically organized in their connections to spinal cord targets. Previous studies in rodents have shown that the mature distribution pattern of corticospinal neurons develops during the first 2 weeks postnatal from an initial widespread pattern that includes the visual cortex to a distribution restricted to the sensorimotor cortex. To determine whether specificity in corticospinal connections also emerges from an initially diffuse set of projections, we have studied the outgrowth of corticospinal axons and the formation of terminal arbors in developing hamsters. The sensitive fluorescent tracer 1,1',dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was used to label corticospinal axons from the visual cortex or from small regions of the forelimb or hindlimb sensorimotor cortex in living animals at 4-17 days postnatal. Initially axon outgrowth was imprecise. Some visual cortical axons extended transiently beyond their permanent targets in the pontine nuclei, by growing through the pyramidal decussation and in some cases extending as far caudally as the lumbar enlargement. Forelimb sensorimotor axons also extended past their targets in the cervical enlargement, in many cases growing in the corticospinal tract to lumbar levels of the cord. By about 17 days postnatal these misdirected axons or axon segments were withdrawn from the tract. Despite these errors in axon trajectories within the corticospinal tract, terminal arbors branching into targets in the spinal gray matter were topographically appropriate from the earliest stages of innervation. Thus visual cortical axons never formed connections in the spinal cord, forelimb sensorimotor axons arborized only in the cervical enlargement, and hindlimb cortical axons terminated only in the lumbar cord at all stages of development examined. Corticospinal arbors formed from collaterals that extended at right angles from the shafts of primary axons, most likely by the process of interstitial branching after the primary growth cone had extended past the target. Once collaterals extended into the spinal gray matter, highly branched terminal arbors formed within 2-4 days, beginning at about 4 and 8 days postnatal for the cervical and lumbar enlargements, respectively. These results show that specificity in corticospinal connectivity is achieved by selective growth of axon collaterals into appropriate spinal targets from the beginning and not by the later remodeling of initially diffuse connections. In contrast, errors occur in the initial outgrowth of axons in the corticospinal tract, which are subsequently corrected.

Animals↗

PubMed2006

Is the ipsilateral cortex surrounding the lesion or the non-injured contralateral cortex important for motor recovery in rats with photochemically induced cortical lesions?

PRIMARY OBJECTIVE: To determine whether the ipsilateral cortex surrounding the lesion or the non-injured contralateral cortex is important for motor recovery after brain damage in the photochemically initiated thrombosis (PIT) model. RESEARCH DESIGN: We induced PIT in the sensorimotor cortex in rats and examined the recovery of motor function using the beam-walking test. METHODS AND PROCEDURES: In 24 rats, the right sensorimotor cortex was lesioned after 2 days of training for the beam-walking test (group 1). After 10 days, PIT was induced in the left sensorimotor cortex. Eight additional rats (group 2) received 2 days training in beam walking, then underwent the beam-walking test to evaluate function. After 10 days of testing, the left sensorimotor cortex was lesioned and recovery was monitored by the beam-walking test for 8 days. MAIN OUTCOMES AND RESULTS: In group 1 animals, left hindlimb function caused by a right sensorimotor cortex lesion recovered within 10 days after the operation. Right hindlimb function caused by the left-side lesion recovered within 6 days. In group 2, right hindlimb function caused by induction of the left-side lesion after a total of 12 days of beam-walking training and testing recovered within 6 days as with the double PIT model. The training effect may be relevant to reorganization and neuromodulation. Motor recovery patterns did not indicate whether motor recovery was dependent on the ipsilateral cortex surrounding the lesion or the cortex of the contralateral side. CONCLUSION: The results emphasize the need for selection of appropriate programs tailored to the area of cortical damage in order to enhance motor functional recovery in this model.

Animals↗

PubMed1991

Regional cerebral blood flow during voluntary arm and hand movements in human subjects.

1. Regional cerebral blood flow (rCBF) was measured using positron emission tomography in six normal volunteers while at rest and while performing four different repetitive movements of the right arm. 2. The four movements were performed in random order and consisted of abduction of the index finger, making a fist, sequential thumb to digit opposition, and shoulder flexion. All the movements were done at the same rate, using an auditory cue and involved displacements through similar amounts of the physiological range at each joint. 3. Increases in rCBF were interpreted as evidence of local neural activation and all four movements were associated with significant increases in CBF in the contralateral sensorimotor and premotor areas and in the supplementary motor area (SMA). 4. The average increase in blood flow in the contralateral sensorimotor cortex was significantly greater for the shoulder movement (31%) than for the three other movements. The increases with finger opposition (21%) and fist-making (24%) were not significantly different, and both were significantly greater than with index finger movement (13%). These data indicate that neither "fractionation" nor distal movement per se cause selective activation of sensorimotor cortex. 5. Significantly greater increases in blood flow in both the contralateral premotor cortex and the SMA ("nonprimary motor areas") occurred with shoulder movement than with the other movements. Because this difference may be related to the significantly greater activation occurring concurrently in the sensorimotor cortex, this finding does not prove unequivocally a "selective" role of the nonprimary motor areas in proximal movement. 6. Neither of the two nonprimary motor areas showed selective activation when a simple sequence of finger movements was performed compared with repetitive contractions of the same fingers. 7. Shoulder movement alone was associated with significant increases in rCBF in the ipsilateral sensorimotor cortex (10%), the superior vermis of the cerebellum (19%), and Brodmann areas 5 and 40 in the contralateral hemisphere. 8. The average location of the center of excitation in the sensorimotor cortex and SMA differed for the four movements and was interpreted as evidence of within-limb somatotopy. The shoulder focus lay highest in the sensorimotor cortex and lowest in the SMA.

Adult↗

PubMed1999

Intracisternal antisense oligonucleotide to growth associated protein-43 blocks the recovery-promoting effects of basic fibroblast growth factor after focal stroke.

Focal infarction (stroke) of the lateral cerebral cortex of rats (including the sensorimotor cortex) produces deficits in sensorimotor function of the contralateral limbs that recover partially over time. In previous studies, we found that the intracisternal injection of basic fibroblast growth factor (bFGF), a potent neurotrophic growth factor, starting at 1 day after stroke, significantly enhanced recovery of sensorimotor function of the contralateral forelimb and hindlimb. Moreover, immunoreactivity (IR) for growth-associated protein-43 (GAP-43), a molecular marker of new axonal growth, was increased in the intact contralateral sensorimotor cortex following bFGF treatment. In the current study, we found that the intracisternal administration of antisense, but not missense, oligonucleotide to GAP-43 blocked the recovery-enhancing effects of bFGF and blocked the increase in GAP-43 IR in the contralateral cortex. These results suggest that upregulation of GAP-43 expression and consequent enhanced axonal sprouting in intact uninjured parts of the brain are likely mechanisms for the recovery-promoting effects of bFGF.

Animals↗

PubMed1993

Unilateral locus coeruleus lesions facilitate motor recovery from cortical injury through supersensitivity mechanisms.

Previous research has indicated that noradrenergic infusions into the cerebellum contralateral to a sensorimotor cortex injury facilitate recovery of motor function. In the present study, the locus coeruleus was lesioned at 2 weeks prior to, 1 week prior to, or simultaneous with a right sensorimotor cortex injury, and functional recovery in response to noradrenergic cerebellar infusions was measured using the beam-walk task. When the locus coeruleus lesion was separated from the sensorimotor cortex lesion by 1 week or more, noradrenergic-induced facilitation of functional recovery occurred with the greater effects observed at the 2-week interval. Simultaneous locus coeruleus and sensorimotor cortex injury with cerebellar noradrenergic infusions revealed no difference in functional recovery. The results suggest that denervation supersensitivity and/or sprouting developed in the cerebellum following the locus coeruleus lesions if a sufficient amount of time elapsed before the sensorimotor cortex injury. The heightened sensitivity to noradrenergic infusions in the contralateral cerebellum suggests that noradrenergic changes in this structure underlie the acceleration of functional recovery from the cortical injury.

Animals↗

PubMed1998

Preoperative functional magnetic resonance imaging (fMRI) of the motor system in patients with tumours in the parietal lobe.

Intracranial lesions may compromise structures critical for motor performance, and mapping of the cortex, especially of the motor hand area, is important to reduce postoperative morbidity. We investigated nine patients with parietal lobe tumours and used functional MRI sensitized to changes in blood oxygenation to define the different motor areas, especially the primary sensorimotor cortex, in relation to the localization of the tumour. Activation was determined by pixel-by-pixel correlation of the signal intensity time course with a reference waveform equivalent to the stimulus protocol. All subjects showed significant activation of the primary sensorimotor cortex while performing a finger opposition task with the affected and unaffected side. In five patients the finger opposition task additionally activated the ipsilateral sensorimotor cortex and the supplementary motor area (SMA). Extension and flexion of the foot, additionally performed in two patients, also activated the sensorimotor cortex, in one case within the perifocal oedema of the tumour. Tumour localization near the central sulcus induced displacement of the sensorimotor cortex as compared to the unaffected side in all patients with a relevant mass effect. The results of our study demonstrate that functional MRI at 1.5 T with a clinically used tomograph can reproducibly localize critical brain regions in patients with intracranial lesions.

Adult↗

PubMed1999

Identification of the cerebral loci processing human swallowing with H2(15)O PET activation.

Lesional and electrophysiological data implicate a role for the cerebral cortex in the initiation and modulation of human swallowing, and yet its functional neuroanatomy remains undefined. We therefore conducted a functional study of the cerebral loci processing human volitional swallowing with 15O-labeled water positron emission tomography (PET) activation imaging. Regional cerebral activation was investigated in 8 healthy right handed male volunteers with a randomized 12-scan paradigm of rest and water swallows (5 ml/bolus, continuous infusion) at increasing frequencies of 0.1, 0.2, and 0.3 Hz, which were visually cued and monitored with submental electromyogram (EMG). Group and individual linear covariate analyses were performed with SPM96. In five of eight subjects, the cortical motor representation of pharynx was subsequently mapped with transcranial magnetic stimulation (TMS) in a posthoc manner to substantiate findings of hemispheric differences in sensorimotor cortex activation seen with PET. During swallowing, group PET analysis identified increased regional cerebral blood flow (rCBF) (P < 0.001) within bilateral caudolateral sensorimotor cortex [Brodmann's area (BA) 3, 4, and 6], right anterior insula (BA 16), right orbitofrontal and temporopolar cortex (BA 11 and 38), left mesial premotor cortex (BA 6 and 24), left temporopolar cortex and amygdala (BA 38 and 34), left superiomedial cerebellum, and dorsal brain stem. Decreased rCBF (P < 0.001) was also observed within bilateral posterior parietal cortex (BA 7), right anterior occipital cortex (BA 19), left superior frontal cortex (BA 8), right prefrontal cortex (BA 9), and bilateral superiomedial temporal cortex (BA 41 and 42). Individual PET analysis revealed asymmetric representation within sensorimotor cortex in six of eight subjects, four lateralizing to right hemisphere and two to left hemisphere. TMS mapping in the five subjects identified condordant interhemisphere asymmetries in the motor representation for pharynx, consistent with the PET findings. We conclude that volitional swallowing recruits multiple cerebral regions, in particular sensorimotor cortex, insula, temporopolar cortex, cerebellum, and brain stem, the sensorimotor cortex displaying strong degrees of interhemispheric asymmetry, further substantiated with TMS. Such findings may help explain the variable nature of swallowing disorders after stroke and other focal lesions to the cerebral cortex.

Adult↗

PubMed1979

Topographical distribution of ATP in rat brain.

Studies on the distribution of ATP in microdissected segments of the rat brain indicate that the nucleotide is concentrated in gray matter, and especially in the thalamus, hippocampus, entorhinal cortex and sensorimotor cortex. These distribution studies in conjunction with previous neuropharmacological studies, support the concept that adenine nucleotides may function as intercellular mediators in various regions of the brain.

Adenosine Triphosphate↗