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Studies on brain glutamic acid
684
INTERNATIONAL FEDERATION - 7TH CONGRESS
brane depolarization of many seconds and a massive increase in conductance, while increases in calcium concentration to 33-88 mM depressed or blocked the bursting activity. Replacement of sodium with tris blocked the long-lasting depolarizations, in contrast to the reported persistance of a depolarization in a sodium-free solution with TEA added. Changes in temperature or in external concentration of potassium and addition of ouabain or copper ions to the bathing medium had no significant influence on the described effects of strychnine. After an increase in spontaneous synaptic activity by 0.2% strychnine solution orthoand antidromic activation were depressed or even blocked possibly due to an increase in threshold of the presynaptic fibers. Furthermore, the changes in membrane potential and resistance due to iontophoretic application of acetylcholine were altered by strychnine. That is, the depolarizing (D-) response in DINI and DILDA cells, which is blocked in sodium-free solution, was significantly decreased, and the hyperpolarizing (H-) response, which is blocked by copper ions, was increased after strychnine application and reduced during the washing period. These results suggest that strychnine, in addition to its k n o w n interaction with a specific inhibitory transmitter of the mammalian motoneuron, changes properties of the spike generating and subsynaptic membrane and causes repetitive activity even in synaptically isolated neurons. 84.
Studies on brain glutamic Subbarao (Jaipur, India).
acid.-V.
V.
The metabolism of amino acids is of great interest in mental diseases. In this paper some of the changes brought about in cerebral metabolic processes by chemical agents will be presented. The experiments were performed on albino rats on exposure to cold stress, after treatment with cortisone and reserpine and also on exposure to total darkness. The brain amino acids of the animals were estimated by paper chromatographic techniques. Reserpine and cold stress caused depletion of brain glutamic acid, whereas cortisone and dark exposure increased the brain glutamic acid content. The significant rise in brain glutamic acid leads to the question whether glutamic acid is directly concerned with seizure processes, although it is not clear what metabolic area is primarily involved. 85.
A preliminary study of the evoked response
at the time of voluntary movement in normal m a n . - P . Castaigne, H. Cathala, E. PierrotDesseiligny and E. Bussel (Paris, France). The work to be presented demonstrates the great
variability of the large negative wave seen in the averaged EEG when voluntary movement occurs. It has been possible to show this variability by recording 10 to 12 times a series of 100 movements repeated for each subject. The variability affects the amplitude of the wave as well as the latency to the time of maximum negativity which indicates the beginning of muscle movement. The maximum negativity can occur 100 msec before to 100 msec after beginning of the movement but there appears to be no systematic relation in the variations. The large negative wave is probably the same pattern as that described by Kornhuber e t al. and Vaughan e t al. Although this wave might be identified with the Expectancy Wave of Walter, it shows certain differences in amplitude and topography.
86.
Cortical steady potential shifts during delayed response performance by monkeys.-S. C. Rosen and J. S. Stamm (Stony Brook,
N.Y., U.S.A.). Monkeys were trained on a two choice delayed response (DR) task which involved 2-see visual cue presentation, 8-see delay, and food reinforcement for the correct response. Pairs of non-polarizable Ag-AgC1 electrodes were chronically implanted on the surface and in underlying white matter of several cortical areas. Bipolar ECoG recordings with DC amplifiers were obtained throughout testing and were computer averaged. Recordings from cortex contralateral to the responding (preferred) hand revealed surface negative steady potential (SP) shifts of 25 to 100 /aV from: (1) occipital cortex during presentation of the cue and reinforcement lights, (2) premotor cortex in relation to the instrumental response, and (3) prefrontal cortex prior to and after the start of the delay period and again following the instrumental response. SP shifts from posterior parietal cortex were not clearly associated with events of the DR trial. When the monkeys were then tested with cues of 4, 6, and 8 sec duration, it was found that the prefrontal SP shifts reached maximum negativity at the start of the delay period, regardless of cue duration, and returned to baseline level during the last 5 sec of the delay. The magnitude of the prefrontal shift was also a function of the level of correct responses, with higher correct scores correlated with greater shifts. SP shifts from prefrontal cortex ipsilateral to the responding hand were less than those from contralateral cortex. During transfer tests with the nonpreferred hand the magnitude of prefrontal SP shifts increased in both hemispheres. The surface negative SP shifts are interpreted as reflecting increased excitation, and hence greater involvement of the underlying
INTERNATIONAL FEDERATION - 7TH CONGRESS
brane depolarization of many seconds and a massive increase in conductance, while increases in calcium concentration to 33-88 mM depressed or blocked the bursting activity. Replacement of sodium with tris blocked the long-lasting depolarizations, in contrast to the reported persistance of a depolarization in a sodium-free solution with TEA added. Changes in temperature or in external concentration of potassium and addition of ouabain or copper ions to the bathing medium had no significant influence on the described effects of strychnine. After an increase in spontaneous synaptic activity by 0.2% strychnine solution orthoand antidromic activation were depressed or even blocked possibly due to an increase in threshold of the presynaptic fibers. Furthermore, the changes in membrane potential and resistance due to iontophoretic application of acetylcholine were altered by strychnine. That is, the depolarizing (D-) response in DINI and DILDA cells, which is blocked in sodium-free solution, was significantly decreased, and the hyperpolarizing (H-) response, which is blocked by copper ions, was increased after strychnine application and reduced during the washing period. These results suggest that strychnine, in addition to its k n o w n interaction with a specific inhibitory transmitter of the mammalian motoneuron, changes properties of the spike generating and subsynaptic membrane and causes repetitive activity even in synaptically isolated neurons. 84.
Studies on brain glutamic Subbarao (Jaipur, India).
acid.-V.
V.
The metabolism of amino acids is of great interest in mental diseases. In this paper some of the changes brought about in cerebral metabolic processes by chemical agents will be presented. The experiments were performed on albino rats on exposure to cold stress, after treatment with cortisone and reserpine and also on exposure to total darkness. The brain amino acids of the animals were estimated by paper chromatographic techniques. Reserpine and cold stress caused depletion of brain glutamic acid, whereas cortisone and dark exposure increased the brain glutamic acid content. The significant rise in brain glutamic acid leads to the question whether glutamic acid is directly concerned with seizure processes, although it is not clear what metabolic area is primarily involved. 85.
A preliminary study of the evoked response
at the time of voluntary movement in normal m a n . - P . Castaigne, H. Cathala, E. PierrotDesseiligny and E. Bussel (Paris, France). The work to be presented demonstrates the great
variability of the large negative wave seen in the averaged EEG when voluntary movement occurs. It has been possible to show this variability by recording 10 to 12 times a series of 100 movements repeated for each subject. The variability affects the amplitude of the wave as well as the latency to the time of maximum negativity which indicates the beginning of muscle movement. The maximum negativity can occur 100 msec before to 100 msec after beginning of the movement but there appears to be no systematic relation in the variations. The large negative wave is probably the same pattern as that described by Kornhuber e t al. and Vaughan e t al. Although this wave might be identified with the Expectancy Wave of Walter, it shows certain differences in amplitude and topography.
86.
Cortical steady potential shifts during delayed response performance by monkeys.-S. C. Rosen and J. S. Stamm (Stony Brook,
N.Y., U.S.A.). Monkeys were trained on a two choice delayed response (DR) task which involved 2-see visual cue presentation, 8-see delay, and food reinforcement for the correct response. Pairs of non-polarizable Ag-AgC1 electrodes were chronically implanted on the surface and in underlying white matter of several cortical areas. Bipolar ECoG recordings with DC amplifiers were obtained throughout testing and were computer averaged. Recordings from cortex contralateral to the responding (preferred) hand revealed surface negative steady potential (SP) shifts of 25 to 100 /aV from: (1) occipital cortex during presentation of the cue and reinforcement lights, (2) premotor cortex in relation to the instrumental response, and (3) prefrontal cortex prior to and after the start of the delay period and again following the instrumental response. SP shifts from posterior parietal cortex were not clearly associated with events of the DR trial. When the monkeys were then tested with cues of 4, 6, and 8 sec duration, it was found that the prefrontal SP shifts reached maximum negativity at the start of the delay period, regardless of cue duration, and returned to baseline level during the last 5 sec of the delay. The magnitude of the prefrontal shift was also a function of the level of correct responses, with higher correct scores correlated with greater shifts. SP shifts from prefrontal cortex ipsilateral to the responding hand were less than those from contralateral cortex. During transfer tests with the nonpreferred hand the magnitude of prefrontal SP shifts increased in both hemispheres. The surface negative SP shifts are interpreted as reflecting increased excitation, and hence greater involvement of the underlying