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Strychnine effect on cord dorsum potentials
702
INTERNATIONAL FEDERATION - 7TH CONGRESS
tested using an olfactory discrimination task. Results suggest that spindling is not directly related to the central processing of olfactory information per se. The significance of nasal air-flow and arousal factors in the control of amygdala activity will be discussed.
135. Slow changes in the membrane potentials of glial cells and neurons following nerve impulses.-J. G. Nicholls (Boston, Mass., U.S.A.). Neurons in the central and peripheral nervous system are closely in contact with glial or Schwann cells. Potassium (K) can collect in this intercellular space. This paper discusses the effect of K accumulation from action potentials and of a slow neurona! hyperpolarization. Since the membrane potential of a glial cell behaves like a K electrode, this potential follows changes in external K and an intra-glial cell electrode follows the K levels in the space between nerve and glial cell. Leech ganglia have been used since they permit simultaneous recording of glial cells and neurons. Due to the high propagation safety factor in the fiber, removal of glial cells and change in surrounding K concentration are unlikely to produce demonstrable change• However, at synapses, variation of surrounding K concentrations might produce effects on release of transmitter substances, postsynaptic potentials and the initiation of impulses. It has been found that small increases in K (around 3 raM) can cause changes in the frequency of spontaneously active cells and in the frequency of synaptic potentials. It is possible that the activity of one neuron could influence the activity of some adjacent ones and shield others. Furthermore, since prolonged trains of impulses can produce hyperpolarization of up to 20 mV which declines over 15 rain and since evidence suggests this is related to some electrogenic pump, a glial depolarization with a neuronal hyperpolarization might interact to produce some of the recorded extracellular potentials.
augmentation was found. Following strychnine injection, however (0.2 mg/kg i.v.), even with 50-100 msec intervals, amplitude of the N1 wave was greatly reduced and the P component completely abolished. Further increasing the intervals up to 175-300 msec the P wave clearly emerged again. The described behavior of the cord dorsum potentials corresponded in phase to those induced by strychnine on the cerebral cortex but with opposite polarity. Intracellular recording during strychnine injection revealed increased amplitude and duration of the polysynaptic EPSPs. At the same time, the negative N 1 wave was followed by a positive P wave which was fully synchronous with secondary EPSPs in intracellular records. Following strychninisation, 50-100 mg/kg of guaiacol-glycerinether (MY-301) was administered and change of the polysnyaptic EPSPs in the opposite direction from that induced by strychnine was seen, Le., there was a reduction of their amplitude and also a normalization of the cord dorsum potentials with a decrease and abolishment of the P component.
137. Variability of visual evoked responses in epileptic patients.-C. H. Lucking (Munich, W. Germany). Visual evoked potentials (VEP) were studied in 45 epileptic patients and compared with those from 30 normal persons. The purpose of this investigation was to look for typical alterations and a diagnostic value of the VEP in epilepsy. In contrast to the relatively high inter-individual stability of the VEP in normal persons, epileptic patients showed a great variability of amplitude, shape and latency of the VEP. Patients with epileptiform patterns in the EEG showed a larger alteration of the evoked responses than those without such patterns. But no typical alteration could be shown which may be related to the different types and etiologies of epilepsy except in patients with spike-wave patterns who often had a pronounced negativity corresponding to wave V of Clganek, and the photosensitive epileptics, who showed a high voltage VEP of up to 80 /~V. No significant differences of the VEPs of both sides were found in patients with a unilateral temporal focus. The majority of the VEPs from epileptic patients showed a slightly longer latency of waves IV - VI than normals. This has no diagnostic significance but may be interesting for pathophysiological considerations. The correlation between the amplitude of EEG and VEP was close no matter whether the person was epileptic or not. •
136. Strychnine effect on cord dorsum potentials. --A. Wagner (Frankfurt am Main, W. Germany). The experiments were performed on 40 cats, anesthetized with Nembutal, using conventional methods for recording from motoneurons and the dorsal surface of the spinal cord. Either muscle nerve or the cut end of dorsal root L 6 were stimulated. Activity was displayed on an oscilloscope and filmed and also fed directly into a CAT computer. Before strychnine, with 10 msec stimulus intervals, refractory phase of the N 1 wave did not exist. With 0.5 - 1.5 msec intervals a distinct
S
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.
.
.
138. Wave length analysis of the EEG-the alpha profile.-J. D. Frost (Houston, Tex., U.S.A.). Clinical EEG reports usually include some state-
INTERNATIONAL FEDERATION - 7TH CONGRESS
tested using an olfactory discrimination task. Results suggest that spindling is not directly related to the central processing of olfactory information per se. The significance of nasal air-flow and arousal factors in the control of amygdala activity will be discussed.
135. Slow changes in the membrane potentials of glial cells and neurons following nerve impulses.-J. G. Nicholls (Boston, Mass., U.S.A.). Neurons in the central and peripheral nervous system are closely in contact with glial or Schwann cells. Potassium (K) can collect in this intercellular space. This paper discusses the effect of K accumulation from action potentials and of a slow neurona! hyperpolarization. Since the membrane potential of a glial cell behaves like a K electrode, this potential follows changes in external K and an intra-glial cell electrode follows the K levels in the space between nerve and glial cell. Leech ganglia have been used since they permit simultaneous recording of glial cells and neurons. Due to the high propagation safety factor in the fiber, removal of glial cells and change in surrounding K concentration are unlikely to produce demonstrable change• However, at synapses, variation of surrounding K concentrations might produce effects on release of transmitter substances, postsynaptic potentials and the initiation of impulses. It has been found that small increases in K (around 3 raM) can cause changes in the frequency of spontaneously active cells and in the frequency of synaptic potentials. It is possible that the activity of one neuron could influence the activity of some adjacent ones and shield others. Furthermore, since prolonged trains of impulses can produce hyperpolarization of up to 20 mV which declines over 15 rain and since evidence suggests this is related to some electrogenic pump, a glial depolarization with a neuronal hyperpolarization might interact to produce some of the recorded extracellular potentials.
augmentation was found. Following strychnine injection, however (0.2 mg/kg i.v.), even with 50-100 msec intervals, amplitude of the N1 wave was greatly reduced and the P component completely abolished. Further increasing the intervals up to 175-300 msec the P wave clearly emerged again. The described behavior of the cord dorsum potentials corresponded in phase to those induced by strychnine on the cerebral cortex but with opposite polarity. Intracellular recording during strychnine injection revealed increased amplitude and duration of the polysynaptic EPSPs. At the same time, the negative N 1 wave was followed by a positive P wave which was fully synchronous with secondary EPSPs in intracellular records. Following strychninisation, 50-100 mg/kg of guaiacol-glycerinether (MY-301) was administered and change of the polysnyaptic EPSPs in the opposite direction from that induced by strychnine was seen, Le., there was a reduction of their amplitude and also a normalization of the cord dorsum potentials with a decrease and abolishment of the P component.
137. Variability of visual evoked responses in epileptic patients.-C. H. Lucking (Munich, W. Germany). Visual evoked potentials (VEP) were studied in 45 epileptic patients and compared with those from 30 normal persons. The purpose of this investigation was to look for typical alterations and a diagnostic value of the VEP in epilepsy. In contrast to the relatively high inter-individual stability of the VEP in normal persons, epileptic patients showed a great variability of amplitude, shape and latency of the VEP. Patients with epileptiform patterns in the EEG showed a larger alteration of the evoked responses than those without such patterns. But no typical alteration could be shown which may be related to the different types and etiologies of epilepsy except in patients with spike-wave patterns who often had a pronounced negativity corresponding to wave V of Clganek, and the photosensitive epileptics, who showed a high voltage VEP of up to 80 /~V. No significant differences of the VEPs of both sides were found in patients with a unilateral temporal focus. The majority of the VEPs from epileptic patients showed a slightly longer latency of waves IV - VI than normals. This has no diagnostic significance but may be interesting for pathophysiological considerations. The correlation between the amplitude of EEG and VEP was close no matter whether the person was epileptic or not. •
136. Strychnine effect on cord dorsum potentials. --A. Wagner (Frankfurt am Main, W. Germany). The experiments were performed on 40 cats, anesthetized with Nembutal, using conventional methods for recording from motoneurons and the dorsal surface of the spinal cord. Either muscle nerve or the cut end of dorsal root L 6 were stimulated. Activity was displayed on an oscilloscope and filmed and also fed directly into a CAT computer. Before strychnine, with 10 msec stimulus intervals, refractory phase of the N 1 wave did not exist. With 0.5 - 1.5 msec intervals a distinct
S
.
.
.
.
138. Wave length analysis of the EEG-the alpha profile.-J. D. Frost (Houston, Tex., U.S.A.). Clinical EEG reports usually include some state-