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1705 Long-term potentiation in auditory cortex slices
S190
1703
MENBRANE PROPERTIES OF THE NEURONS OF THE CHICK AUDITORY NUCLEUS: NUCLEUS MAGNOCELLULARIS. KONOMI KOYANO AND KAZUO FUNABIKI, Department of Physiology., Faculty of Medicine, Kyoto University, Ky.oto, 606-01, Japan.
It has been known that the neurons of the avian second auditory nucleus:Nucleus magunocellularis (NMC) lock the phase of sound and transmit the information about phase angle to the higher auditory nucleus. Our present study was undertaken to determine the membrane properties of the NMC neuron that underlie this "phase locking" character. Whole cell recording from the NMC neuron was made in the brainstem slice preparation (130 lain thick) from the chick embryo (14-16E). Under the current-clamp condition, the resting membrane potential was -67.4+_1.4 mV (n=9).The input resistance and capacitance were 636+38 Mohm and 23.5+7.7 pF, respectively. The neurons elicited an action potential in response to the brief depolarization pulse with a relatively high threshold (-40 mV). The neurons exhibited the phasic response with only a single action potential at the onset of the long (>100 ms) suprathreshold depolarizing current pulse. Under voltage clamp, these cells showed the TTX sensitive Na current, low and high threshold Ca currents. The cells also had a low voltage activated, transient K current and a delayed rectifying K current. These K currents might account for the phasic response that allows the phase locking function of the NMC neurons.
1704
DISTRIBUTION OF THE OLIVOCOCHLEAR NEURONS IN THE SUPERIOR OLIVARY NUCLEAR COMPLEX OF THE HOUSE MUSK SHREW, S U N C U S M U R I N U S . A K I R A T O K U N A G A , HIDEAKI TANAKA, TAKASHI M A E B A R A , W A N G YAN, YOUKO OKAMOTO, THIRD DEPT." OF ANATOMY, OKAYAMA UNIV. MEDICAL SCHOOL, 2-5-1 Shikata-cho, Okayama 700, Japan. Distribution of the o l i v o c o c h l e a r neurons in the superior o l i v a r y nuclear complex (SON) was studied in the suncus murinus, by means of the r e t r o g r a d e l a b e l i n g and immunohistochemical methods. The o l i v o c o c h l e a r neurons were found in the ventral half of the ventral nucleus of the t r a p e z o i d body (VNTB) on both sides after u n i l a t e r a l injection of HRP into the cochlea. Very few neurons were l a b e l e d i p s i l a t e r a l l y in the marginal part of the lateral superior o l i v a r y subnucleus (LSO). However, no l a b e l e d neurons were found in the central core of the LSO. Immunoreactive neurons to the choline a c e t y l t r a n s f e r a s e were found in all subnuclei of the SON. On the other hand, m e t - e n k e p h a l i n (mENK)-Iike and calcitonin gene r e l a t e d p e p t i d e (CGRP)-Iike i m m u n o r e a c l i v e neurons were d e t e c t e d in the medial and lateral parts of the VNTB, r e s p e c t i v e l y . No neurons in other SON subnuclei showed the immunoreactity to either mENK or CGRP.
1 705
LONG-TERM POTENTIATION IN AUDITORY CORTEX SLICES. MASAHARU KUDOH AND KATSUEI SHIBUKI. Department of Neuroohvsiology. Research Institute. Niiaata University. Niiaata 951, Japan
Brain
It is known that the receptive field of auditory cortical neurons are changed after discrimination training. Plasticity of synaptic transmission in the auditory cortex is thought to be the base for such changes. To investigate synaptic plasticity, we studied field potential changes after tetanic stimulation in a slice preparation of the auditory cortex of adult rats (4 - 7 w). Electrical stimulation of the white matter produced field potentials of two negative components (latency: 2 msec and 3.5 msec, respectively) at layer III radial to stimulation site. Long-term potentiation (LTP) of the slow component was elicited after a tetanic stimulation (i00 Hz, 1 sec) and maintained for 60 min, at least, while first negative component unchanged. Induction of LTP was blocked by bath application of D-2-amino-5-phosphonopentatonic acid (AP5, i00 ~M). From these results, it is concluded that LTP in the auditory cortex is evoked by activation of NMDA ~eceptors following tetanic White matter stimulation.
1703
MENBRANE PROPERTIES OF THE NEURONS OF THE CHICK AUDITORY NUCLEUS: NUCLEUS MAGNOCELLULARIS. KONOMI KOYANO AND KAZUO FUNABIKI, Department of Physiology., Faculty of Medicine, Kyoto University, Ky.oto, 606-01, Japan.
It has been known that the neurons of the avian second auditory nucleus:Nucleus magunocellularis (NMC) lock the phase of sound and transmit the information about phase angle to the higher auditory nucleus. Our present study was undertaken to determine the membrane properties of the NMC neuron that underlie this "phase locking" character. Whole cell recording from the NMC neuron was made in the brainstem slice preparation (130 lain thick) from the chick embryo (14-16E). Under the current-clamp condition, the resting membrane potential was -67.4+_1.4 mV (n=9).The input resistance and capacitance were 636+38 Mohm and 23.5+7.7 pF, respectively. The neurons elicited an action potential in response to the brief depolarization pulse with a relatively high threshold (-40 mV). The neurons exhibited the phasic response with only a single action potential at the onset of the long (>100 ms) suprathreshold depolarizing current pulse. Under voltage clamp, these cells showed the TTX sensitive Na current, low and high threshold Ca currents. The cells also had a low voltage activated, transient K current and a delayed rectifying K current. These K currents might account for the phasic response that allows the phase locking function of the NMC neurons.
1704
DISTRIBUTION OF THE OLIVOCOCHLEAR NEURONS IN THE SUPERIOR OLIVARY NUCLEAR COMPLEX OF THE HOUSE MUSK SHREW, S U N C U S M U R I N U S . A K I R A T O K U N A G A , HIDEAKI TANAKA, TAKASHI M A E B A R A , W A N G YAN, YOUKO OKAMOTO, THIRD DEPT." OF ANATOMY, OKAYAMA UNIV. MEDICAL SCHOOL, 2-5-1 Shikata-cho, Okayama 700, Japan. Distribution of the o l i v o c o c h l e a r neurons in the superior o l i v a r y nuclear complex (SON) was studied in the suncus murinus, by means of the r e t r o g r a d e l a b e l i n g and immunohistochemical methods. The o l i v o c o c h l e a r neurons were found in the ventral half of the ventral nucleus of the t r a p e z o i d body (VNTB) on both sides after u n i l a t e r a l injection of HRP into the cochlea. Very few neurons were l a b e l e d i p s i l a t e r a l l y in the marginal part of the lateral superior o l i v a r y subnucleus (LSO). However, no l a b e l e d neurons were found in the central core of the LSO. Immunoreactive neurons to the choline a c e t y l t r a n s f e r a s e were found in all subnuclei of the SON. On the other hand, m e t - e n k e p h a l i n (mENK)-Iike and calcitonin gene r e l a t e d p e p t i d e (CGRP)-Iike i m m u n o r e a c l i v e neurons were d e t e c t e d in the medial and lateral parts of the VNTB, r e s p e c t i v e l y . No neurons in other SON subnuclei showed the immunoreactity to either mENK or CGRP.
1 705
LONG-TERM POTENTIATION IN AUDITORY CORTEX SLICES. MASAHARU KUDOH AND KATSUEI SHIBUKI. Department of Neuroohvsiology. Research Institute. Niiaata University. Niiaata 951, Japan
Brain
It is known that the receptive field of auditory cortical neurons are changed after discrimination training. Plasticity of synaptic transmission in the auditory cortex is thought to be the base for such changes. To investigate synaptic plasticity, we studied field potential changes after tetanic stimulation in a slice preparation of the auditory cortex of adult rats (4 - 7 w). Electrical stimulation of the white matter produced field potentials of two negative components (latency: 2 msec and 3.5 msec, respectively) at layer III radial to stimulation site. Long-term potentiation (LTP) of the slow component was elicited after a tetanic stimulation (i00 Hz, 1 sec) and maintained for 60 min, at least, while first negative component unchanged. Induction of LTP was blocked by bath application of D-2-amino-5-phosphonopentatonic acid (AP5, i00 ~M). From these results, it is concluded that LTP in the auditory cortex is evoked by activation of NMDA ~eceptors following tetanic White matter stimulation.