Neuronal Firing Pattern Following Amygdaloid Kindling in Unrestrained Rats

Chronic recordings of amygdaloid neurons were performed on freely moving rats following kindling. Satisfactory recordings were obtained from 22 amygdaloid neurons of the contralateral amygdala before, during, and after unilateral kindling. Kindling stimulations were given once per hour. Seven cells disappeared during kindling. Seven cells were recorded during the full course of kindling. These units showed (a) an increase in spontaneous firing, (b) a development of high-frequency bursts (the peak interval of the interval histogram decreased from 18 to 2 ms), and (c) high-frequency firings during spontaneous activity that were similar to the firings recording during afterdischarge.     

Changes in muscle activity determine progression of clinical symptoms in patients with chronic spine-related muscle pain. A complex clinical and neurophysiological approach

Spine-related muscle pain can affect muscle strength and motor unit activity. This study was undertaken to investigate whether surface electromyographic (sEMG) recordings performed during relaxation and maximal contraction reveal differences in the activity of muscles with or without trigger points (TRPs). We also analyzed the possible coexistence of characteristic spontaneous activity in needle electromyographic (eEMG) recordings with the presence of TRPs. Thirty patients with non-specific cervical and back pain were evaluated using clinical, neuroimaging and electroneurographic examinations. Muscle pain was measured using a visual analog scale (VAS), and strength using Lovett's scale; trigger points were detected by palpation. EMG was used to examine motor unit activity. Trigger points were found mainly in the trapezius muscles in thirteen patients. Their presence was accompanied by increased pain intensity, decreased muscle strength, increased resting sEMG amplitude, and decreased sEMG amplitude during muscle contraction. eEMG revealed characteristic asynchronous discharges in TRPs. The results of EMG examinations point to a complexity of muscle pain that depends on progression of the myofascial syndrome.     

Proteolytic enzyme activities during regeneration of the rat gastrocnemius muscle

The enzymatic activity of creatine phosphokinase and the lysosomal enzymes cathepsin D and acid phosphatase was followed during skeletal muscle regeneration after partial excision to the gastrocnemius muscle in the rat. For each time interval (1, 2, 5, 14 and 45 days) following injury, the activity of the regenerated muscle was compared with the activity in the contralateral sham operated muscle. The specific activity of creatine phosphokinase of the regenerated muscle showed a significant decrease (25%) during the first 2 days post injury and thereafter was comparable to that of the uninjured control muscle. The activity of cathepsin D was 2.3-4-fold significantly higher in the regenerated muscle than in the control intact muscle from day 1 until day 14 post-injury. At 45 days after partial excision, the activity of this enzyme was comparable to a normal muscle. However, the activity of another lysosomal enzyme (acid phosphatase) did not show any distinct changes from the level of this enzyme in the uninjured muscle during the course of muscle regeneration. It is suggested that elevation of lysosomal enzymes in skeletal muscle may not be confined to conditions of muscle wasting and degradation but also to differentiation and development processes such as during muscle regeneration following injury.     

Assessment of fusimotor contribution to reflex reinforcement in humans

The contribution of the fusimotor system to reflex reinforcement such as the Jendrassik manoeuvre was investigated by recording single unit activity with tungsten electrodes from muscle spindle afferent nerves in unanaesthetized normal human subjects. Muscle spindle afferent activity was recorded before, during, and after the reinforcement test. When the leg muscles remained relaxed during the Jendrassik manoeuvre, spindle activity recorded in the tibial nerve was accelerated. Also in the median nerve, activity from muscle spindle afferent fibres was increased during a remote contraction of the ipsilateral quadriceps muscle. Comparing the time course of the phasic reflex reinforcement and the muscle spindle facilitation during the remote contraction, a marked after-effect was recorded in both responses. Present results show an increased spontaneous muscle spindle activity in relaxed muscles during a remote muscle contraction, and provide evidence for the contribution of the fusimotor system to the enhancement of phasic reflexes by reinforcement manoeuvres.     

Increased activity of creatine phosphokinase and aldolase activity in the acute psychoses: Case reports

Two acutely psychotic patients, one a manic-depressive, the other and acute schizophrenic, who both had marked increases in the activity of creatine phopphokinase (CPK) and aldolase in serum are presented and discussed. The increases in serum enzyme activity were significantly correlated with clinical course, occuring at times of severe stress which preceded or coincided with psychotic behavior. The type of CPK and aldolase present was the muscle type. No increase in CPK and aldolase activity in spinal fluid was noted. Some of the factors which might be expected to effect serum CPK and aldolase activity were considered: physical activity, catecholamines, secretion of steroids, medication and weight loss. These factors do not appear to account for the increased activity of CPK and aldolase. The increased enzyme activity is discussed as a manifestation of subtle myopathic changes in acutely psychotic patients.     

CD8 and CD4 T cell-mediated polymyositis complicating the HTLV-1 associated myelopathy. Quantitative evaluation of corticosteroid treatment

Introduction – Inflammatory myopathy is a treatable cause of worsening in the spectrum of neurological conditions that may develop during the course of HTLV-1 infection. Material and methods — To investigate the cause of subacute worsening in the strength of a 46-y-old black male with HTLV-1 associated myelopathy we performed electrodiagnostic examination and a muscle biopsy which was studied with histochemistry, immunocytochemistry and electron microscopy. Serial measurements of isometric muscle strength were performed during the course of corticosteroid treatment. Results — The muscle biopsy showed evidence of denervation atrophy and prominent inflammatory changes with autoaggressive features. Lymphocyte typing showed a predominance of CD8+ T cells. The patient had sustained, marked improvement in strength, especially of the upper extremities, with oral, high single-dose, alternate-day prednisone therapy. Conclusion — A muscle biopsy should be considered in all patients with HTLV-1 associated weakness, especially when electromyography indicates possible coexisting primary muscle involvement and/or serum creatine kinase levels are elevated. HTLV-1-associated polymyositis can be successfully treated with corticosteroids.     

Scn2a sodium channel mutation results in hyperexcitability in the hippocampus in vitro

PURPOSE: To investigate in vitro, the cellular network activity of the hippocampus in Q54 mice that display spontaneous seizures because of a gain-of-function mutation of the Scn2a sodium channel gene. METHODS: Extacellular recordings were obtained from CA1 and CA3 pyramidal neurons in hippocampal slices prepared from Q54 transgenic and nontransgenic littermates (WT) under physiologic conditions as well as during periods of orthodromic stimulation of the Schaffer collaterals. Cerebral spinal fluid samples were analyzed and cresyl violet histology of the hippocampus was conducted. RESULTS: Increased spontaneous extracellular activity was found in both CA1 and CA3 regions of Q54 hippocampal slices. Q54 slices also demonstrated significantly greater spontaneous and afterdischarge activity as well as population spike amplitude and duration following tetanic stimulus in comparison to WT slices. Frequency analysis of tetanically stimulated recordings indicated high-frequency components (100 and 200 Hz) unique to Q45 slices. Analysis of cresyl violet histology supports healthy Q54 slices up to 10 weeks, while Q54 cerebral spinal fluid shows elevated osmolarity. CONCLUSION: Evidence for hyperexcitability and increased synaptic efficacy in Q54 mice was found by observing spontaneous activity as well as evoked activity. Response to tetanic stimulation included unique high-frequency oscillations, and resulted in an increased population spike amplitude and duration. Histological assessment shows equivalent neuronal development in both experimental groups. The data support the hypothesis that modified Scn2a channels in Q54 mice result in network hyperexcitability of the hippocampus necessary for the development and maintenance of temporal lobe seizures.     

fMRI methods for proximal upper limb joint motor testing and identification of undesired mirror movement after stroke

fMRI has been used to characterize the abnormal brain activity after stroke during attempted motor tasks, the change in brain activity accompanying spontaneous motor recovery, and response to interventions. However, many patients after stroke exhibit abnormally high effort during attempted movements, including undesired movements of the supposed quiescent, uninvolved limb, which could confound fMRI measures. We developed a method of identifying the potentially confounded scans, using EMG measures of muscle activity in the supposed quiescent limb. We found that there was no interference in the MRI signal from the EMG data acquisition system, during simultaneous use of both MRI and EMG. For EMG signal acquisition, as expected, we were able to identify EMG signal free of MRI noise contamination during the inter-scan interval between any given scan and its subsequent scan. We tested movement of the involved limb. We determined that when undesired muscle activation was present in the uninvolved, supposed quiescent limb, there was an over-estimation of the number of active voxels ranging from 10 to 11, depending upon the ROI.     

Monitoring of anaesthesia in neurophysiological experiments

Cortical activity can be substantially changed by the type of anaesthetic used, and by its dose level. For easy monitoring of depth of anaesthesia we describe the changes in electroencephalogram and electrocardiogram accompanying changes in depth of anaesthesia in the cat. Anaesthesia was induced by the volatile anaesthetic isoflurane. The high-frequency components (around 30 Hz) in the electroencephalogram disappear in deep anaesthesia. The electrocardiogram also shows substantial changes in contamination due to muscle fasciculations with anaesthesia level. Fasciculations appear as noise in the electrocardiogram. The amplitude of the electrical muscle activity contaminating the ECG can be easily used for the maintainance of a constant level of anaesthesia during a neurophysiological experiment.     

Choline acetyltransferase activity in skeletal muscles after denervation

The activity of choline acetyltransferase (ChAc) in rat hind-limb muscles started to decrease rapidly between 10 and 24 hr after transection of the mixed nerve supply. The time course of changes in the tibialis anterior, extensor digitorum longus, and soleus muscles was very similar. Semilogarithmic plots of ChAc changes vs time revealed that the changes in enzyme activity proceed in two steps, both of which have an exponential time course. A steep decline occurs during the first 72–96 hr after denervation; this is followed by a slow decline. During the period of steep decline the activity of ChAc in the muscles decreased by 79–92%. After 7 mo, the mean ChAc activity in denervated tibialis anterior was 3.4 and in extensor digitorum longus 3.3% of that in contralateral control muscles. It is suggested that the ChAc disappearing from the muscles during the period of steep decline is the enzyme present in the motor nerve terminals and intramuscular branches of the motor nerve, whereas the enzyme remaining in the muscle after 4 days of denervation constitutes a different pool (or different pools) of ChAc. It appears likely that this pool of ChAc is also present in the muscle before denervation. No secondary increase of ChAc at later stages of denervation was observed. The level of nerve transection affected the time course of the steep ChAc decline; a 50% decrease of ChAc was attained 9 hr earlier when the nerve was cut near the muscle than when it was cut 34 mm away from the muscle.