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2320 Inhibitory long-term potentiation underlying long-lasting habituation of goldfish escape response
S244
2318
ROLE OF THE THALAMO-STRIATAL PROJECTION IN ACQUISITION OF STRIATE NEURON ACTIVlTY THROUGH BEHAVIORAL LEARNING IN THE MONKEY. NAOYUKI MATSUMOTO. TAKAFUMI MINAMIMOTO AND MINORU KIMURA. Facultv of Health and Sport Sci., Osaka Univ. Toyonaka Osaka, 560 Jarian. Previously we reported that activity of tonically active neurons (TANS) in the primate striatum which is conditionally related to sensory events used in behavioral tasks is acquired through the behavioral learning. Aim of this study was to identify structures supplying the conditioning input to the TANS. In a monkey (Macaca fuscata), click sound of solenoid valve was followed by a delivery of liquid reward. About 60% (74112 1) of TANS in the putamen and caudate nucleus became responsive to the click through 3 to 4 weeks of conditioning. In the thalamus ipsilateral to the striate recording, neurons were found to respond to the conditioning stimuli spec&cally in the centromedian and parafascicular nuclei. Then, we injected GABAA receptor agonist muscimol(38.l/15min.) to inactivate these structures. Most of TANS became non-responsive to the conditioning stimuli (8149 cells) after the muscimol injection. These results suggested that intralaminar nucleus of the thalamus supply sensory event-related information to the striatum, and that the TANS acquire conditioned responses to the sensory events through behavioral learning which includes involvement ofnigrostriatal dopamine system.
2319
LONG-LASTING
RESPONSE
HABITUATION OF GOLDFISH.
OF MAUTHNER
CELL-INITIATED
ESCAPE
r
-The reflex The goldfish Mautbner (M-) cell initiates a fast startle reflex in response to sound stimulus. is produced by excitatory transmission from the auditory (VIII) nerve to the spinal motoneuron via the MIt has been demonstrated that the cell, which is concurrently modulated by feedforward inhibition. inhibitory synaptic connection exhibits long-term potentiation (LTP) aRer tetanization of the VIII nerve (Kern et al., 1992, Oda et al., 1995). Therefore, if such LTP occurs in free swimming fish, it should result in depression of M-cell triggered behavior. In the present study, we examined whether the startle response can The escape response evoked by a ball falling onto the be modified by applying a repeated sound stimulus. water was tested before and after applying subthreshold sound stimulus (50 msec duration, 566 to 800 Hz) every 4 set for 3-5 minutes with an underwater loudspeaker. The score of escape response measured every 10 min was stable for more than 70 minutes in control. After sound stimulus it decreased to 26*10 % (9 By contrast, neither latency fish) of control and the habituation was maintained for more than 40 minutes. (1 lkO.5 msec, n=36) nor stage 1 flexion angle (81#, n=15) was different from control, indicating that the These results suggest that repeated sound stimulation gives rise to a behavioral kinetics were unaffected. long-lasting habituation of the M-cell initiated startle response with decreased probability of M-cell firing presumably caused by enhanced feedforward inhibition.
2320
INHIBITORY HAJJITUA!I’ION
LONG-TERM POTFJWIATION OF GOLDFISH ESCAPE
UNDERLYING RESPONSE.
LONGIBWING
Tetanization of the auditory (VIII) nerve in gold&h produces a long-term potentiation (LTP) of the glycinergic inhibitory (Kom et al., 1992; Oda et al., 1995) as well as the electrotonic and glutamatergic excitatory (Yang et al., 1990) synapses of the Mauthner (M-) cell As shown in the preceding report (Kawasaki et al.), application of repeated high frequency sound to swimming fish induces long-lasting habituation of the M-cell initiated escape response. In the present study, we examined whether the conditioning sound could give rise to an LTP of synaptic connections onto the M-cell. A sound stimulus for conditioning was applied (40 msec duration, 90 dB, 306 to 806 Hz) every 4 set for 3 to 5 minutes to goldfish fixed after anesthesia. The test responses were evoked in the M-cell by electrical stimulation of posterior branch of VIII nerve. The inhibitory synaptic conductance in the test response evoked in M-cells on both sides increased after sound conditioning by 75*21% ContralateralIy (14 out of 17 cells) and 71*9% ipsilaterally (12 out of 18 cells). In contrast, electrotonic coupling potential recorded in the lateral dendrite of the ipsilateral M-cell did not show any potentiation (-1.6&l%, n=7). These findings suggest that natural sensory input induces an inhibitory LTP of the identified pathway, which possibly contributes to establishment of long-lasting behavioral habituation.
2318
ROLE OF THE THALAMO-STRIATAL PROJECTION IN ACQUISITION OF STRIATE NEURON ACTIVlTY THROUGH BEHAVIORAL LEARNING IN THE MONKEY. NAOYUKI MATSUMOTO. TAKAFUMI MINAMIMOTO AND MINORU KIMURA. Facultv of Health and Sport Sci., Osaka Univ. Toyonaka Osaka, 560 Jarian. Previously we reported that activity of tonically active neurons (TANS) in the primate striatum which is conditionally related to sensory events used in behavioral tasks is acquired through the behavioral learning. Aim of this study was to identify structures supplying the conditioning input to the TANS. In a monkey (Macaca fuscata), click sound of solenoid valve was followed by a delivery of liquid reward. About 60% (74112 1) of TANS in the putamen and caudate nucleus became responsive to the click through 3 to 4 weeks of conditioning. In the thalamus ipsilateral to the striate recording, neurons were found to respond to the conditioning stimuli spec&cally in the centromedian and parafascicular nuclei. Then, we injected GABAA receptor agonist muscimol(38.l/15min.) to inactivate these structures. Most of TANS became non-responsive to the conditioning stimuli (8149 cells) after the muscimol injection. These results suggested that intralaminar nucleus of the thalamus supply sensory event-related information to the striatum, and that the TANS acquire conditioned responses to the sensory events through behavioral learning which includes involvement ofnigrostriatal dopamine system.
2319
LONG-LASTING
RESPONSE
HABITUATION OF GOLDFISH.
OF MAUTHNER
CELL-INITIATED
ESCAPE
r
-The reflex The goldfish Mautbner (M-) cell initiates a fast startle reflex in response to sound stimulus. is produced by excitatory transmission from the auditory (VIII) nerve to the spinal motoneuron via the MIt has been demonstrated that the cell, which is concurrently modulated by feedforward inhibition. inhibitory synaptic connection exhibits long-term potentiation (LTP) aRer tetanization of the VIII nerve (Kern et al., 1992, Oda et al., 1995). Therefore, if such LTP occurs in free swimming fish, it should result in depression of M-cell triggered behavior. In the present study, we examined whether the startle response can The escape response evoked by a ball falling onto the be modified by applying a repeated sound stimulus. water was tested before and after applying subthreshold sound stimulus (50 msec duration, 566 to 800 Hz) every 4 set for 3-5 minutes with an underwater loudspeaker. The score of escape response measured every 10 min was stable for more than 70 minutes in control. After sound stimulus it decreased to 26*10 % (9 By contrast, neither latency fish) of control and the habituation was maintained for more than 40 minutes. (1 lkO.5 msec, n=36) nor stage 1 flexion angle (81#, n=15) was different from control, indicating that the These results suggest that repeated sound stimulation gives rise to a behavioral kinetics were unaffected. long-lasting habituation of the M-cell initiated startle response with decreased probability of M-cell firing presumably caused by enhanced feedforward inhibition.
2320
INHIBITORY HAJJITUA!I’ION
LONG-TERM POTFJWIATION OF GOLDFISH ESCAPE
UNDERLYING RESPONSE.
LONGIBWING
Tetanization of the auditory (VIII) nerve in gold&h produces a long-term potentiation (LTP) of the glycinergic inhibitory (Kom et al., 1992; Oda et al., 1995) as well as the electrotonic and glutamatergic excitatory (Yang et al., 1990) synapses of the Mauthner (M-) cell As shown in the preceding report (Kawasaki et al.), application of repeated high frequency sound to swimming fish induces long-lasting habituation of the M-cell initiated escape response. In the present study, we examined whether the conditioning sound could give rise to an LTP of synaptic connections onto the M-cell. A sound stimulus for conditioning was applied (40 msec duration, 90 dB, 306 to 806 Hz) every 4 set for 3 to 5 minutes to goldfish fixed after anesthesia. The test responses were evoked in the M-cell by electrical stimulation of posterior branch of VIII nerve. The inhibitory synaptic conductance in the test response evoked in M-cells on both sides increased after sound conditioning by 75*21% ContralateralIy (14 out of 17 cells) and 71*9% ipsilaterally (12 out of 18 cells). In contrast, electrotonic coupling potential recorded in the lateral dendrite of the ipsilateral M-cell did not show any potentiation (-1.6&l%, n=7). These findings suggest that natural sensory input induces an inhibitory LTP of the identified pathway, which possibly contributes to establishment of long-lasting behavioral habituation.