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Does L-dopa depolarize motoneurons in the isoalted spinal cord of neonatal rat?
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L-DOPA-IMHUNOREACTIVITY IN HYPOTHALAMIC MAGNOCELLULAR NEURONS OF HYPOTHALAMO-NEUROHYPOPHYSIALSYSTEM KAWAKAM14 NICOLE -5, HICHEL GEFFARD5, HITOSHI OKAMURAl, -.__.--_I--* KUNIO KITAHAKA3 FIJI410 MASAKI TANAKA' --* YASUHIKO -t IBATA' Departments of 'Anesthesioloa, 2Anatome and 4Psychiatryc Kyoto Prefectural University of Medicine, Kawaramachi-Hiroko.ii,Kamikyo-ku. Kyoto 602. Japan; 3Departaent de Medicine Exuerimentale, CNRS U1195- INSERM U52. Faculte de Medicine. Universite Claude Bernard, 69373 Lyon Cedex Q& France; 'Laboratoire &g Neuroimmunologie. IBCN-CNRS. Universite de Bordeaux II, 33077 Bordeaux Cedex. France Catecholaminergic properties of magnocellular neurons of hypothalamo-neurohypophysialin normal and salt-loaded conditions were investigated in the present study. Normal rats were given food and water ad libitum, and salt-loaded rats were given food and 2% NaCl to drink for 1 week prior to death. In normal
? rats, tyrosine hydroxylase (TH)-immunoreactiveneurons were occasionaly detected in the ?agnocellular In these rats, L-DOPAneurons of the paraventricular nucleus (PVN) and supraoptic nucleus (SON). immunoreactivities were detected weakly in magnocellular neurons of PVN and SON, and the internal layer of the median eminence. In salt-loaded rats, inmunoreactivitiesof TH and L-DOPA in magnocellular neurons of PVN and SON and the internal layer of the ME were greatly enhanced. In both conditions, no aromatic L-amino acid decarboxylase-, dopamine-, hydroxylase-, phenylethanolamine N-methyl transferase-, and dopamine-immunoreactivities were detected in these structures. These findings have suggest that LWPA may be produced in magnocellular hypothalamic neurons, particularly in salt-loaded conditons.
BEHAVIORAL AND,PHARMACDLOGICAL !jiODULATIONOF MESOLSMBIC DOPAMINERGIC SYSIEM STUDIED BY MICRODI+LYSIS PSAMI YOSHIDA , HIDEYASU YOKOO , HIROSHI KAWAHARA , KATSUHIRO MIZOGUCHI AND MASAT SHI TANAKA Department of Pharmacology, Kurume University School of Medicine, Kurume 830, and ! Department of Kitakyushu 803.Japan. Dental Anesthesiology, Kyusu-Dental College, Dopamlne (DA) neurons in the ventral tegmental area (VTA) proJect their nerve fibers to the nucleus accumbens (NAC), To examine functional properties of the mesolimbic .DA neurons, the microdialysis probes were implanted into the NAC and VTA of rats. During microdialysis perfusion rats were treated behaviorally or pharmacologically, and the dialysis samples (6 or 9 X 2Omin) were collected for the following 2 or 3 hrs. DA and its metabolites in the perfusate were measured by HPLC-ECD. Behavioral manipulations (deprivation-induced feeding and.drinking) induced significant increases in extracellular DA levels in both the NAC and VTA, showing that DA is released somatodendritically in the cell body site as well as in terminal fields during spontaneous behaviors with goaldirected nature. Pharmacological treatment (intra-NAC via the probe r i..p. application of drugs i.e., ketamine 20mg/kg, MK801, nicotine, amantadine and morphine(lO' G-8 M, 20 min) produced a marked increase in DA outflow from the NAC. Infusion of opiate analogue, DAGO (lo-6M, 40 min) through the VTA probe caused pronounced increases in DA release in the NAC. These results suggest that rewarding stimuli or some drugs inducing abuse increase the mesolimbic DAergic activity, and also indicate that the possible site of opioid action on the mesolimbic DA neuron is located at least in the VTA
DOES L-DOPA DEPOLARIZE MOTONEURONS IN THE ISOALTED SPINAL CORD OF NEONATAL RAT ? MASAFUMI SAICUMA,KUMIKO UI, AND YUHEI MIYATA, Department of Pharmacology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku. Tokvo 113, Japan. It has recently been reported that L-dopa potentiates spinal monosynaptic reflexes (MSR) _in vivo and suggested that this effect is mediated by release of noradrenaline (NA) from the descending NAergic fibers (Tanabe et al., Japan. J. However, another possibility is remaining that Pharmacol., 54, 69-77, 1990). the L-dopa effect is due to its direct action on motoneurons. The present study was undertaken to test this possibility. Under ether anesthesia, a lumbar spinal cord was isolated from 5-6 days old rats and perfused with artificial cerebra-spinal fluid (ACSF). Although MSR was depressed in this preparation, L-dopa applied in a bath induced depolarization of motoneurons recorded from a ventral root with a suction electrode. In the spinal cord of which lower thoracic level was sectioned 2-3 days previously to allow degeneration of the descending NAergic inputs, L-dopa similary depolarized motoneurons. It was reduced to about 60 % of control in an ACSF containing low Ca and high Mg ions which completely abolished MSR. Tetrodotoxin (0.2 )JM)greatly reduced the L-dopa-induced depolarization to about 7%. These results suggest that L-dopa depolarize motoneurons directly besides by its indirect action.
L-DOPA-IMHUNOREACTIVITY IN HYPOTHALAMIC MAGNOCELLULAR NEURONS OF HYPOTHALAMO-NEUROHYPOPHYSIALSYSTEM KAWAKAM14 NICOLE -5, HICHEL GEFFARD5, HITOSHI OKAMURAl, -.__.--_I--* KUNIO KITAHAKA3 FIJI410 MASAKI TANAKA' --* YASUHIKO -t IBATA' Departments of 'Anesthesioloa, 2Anatome and 4Psychiatryc Kyoto Prefectural University of Medicine, Kawaramachi-Hiroko.ii,Kamikyo-ku. Kyoto 602. Japan; 3Departaent de Medicine Exuerimentale, CNRS U1195- INSERM U52. Faculte de Medicine. Universite Claude Bernard, 69373 Lyon Cedex Q& France; 'Laboratoire &g Neuroimmunologie. IBCN-CNRS. Universite de Bordeaux II, 33077 Bordeaux Cedex. France Catecholaminergic properties of magnocellular neurons of hypothalamo-neurohypophysialin normal and salt-loaded conditions were investigated in the present study. Normal rats were given food and water ad libitum, and salt-loaded rats were given food and 2% NaCl to drink for 1 week prior to death. In normal
? rats, tyrosine hydroxylase (TH)-immunoreactiveneurons were occasionaly detected in the ?agnocellular In these rats, L-DOPAneurons of the paraventricular nucleus (PVN) and supraoptic nucleus (SON). immunoreactivities were detected weakly in magnocellular neurons of PVN and SON, and the internal layer of the median eminence. In salt-loaded rats, inmunoreactivitiesof TH and L-DOPA in magnocellular neurons of PVN and SON and the internal layer of the ME were greatly enhanced. In both conditions, no aromatic L-amino acid decarboxylase-, dopamine-, hydroxylase-, phenylethanolamine N-methyl transferase-, and dopamine-immunoreactivities were detected in these structures. These findings have suggest that LWPA may be produced in magnocellular hypothalamic neurons, particularly in salt-loaded conditons.
BEHAVIORAL AND,PHARMACDLOGICAL !jiODULATIONOF MESOLSMBIC DOPAMINERGIC SYSIEM STUDIED BY MICRODI+LYSIS PSAMI YOSHIDA , HIDEYASU YOKOO , HIROSHI KAWAHARA , KATSUHIRO MIZOGUCHI AND MASAT SHI TANAKA Department of Pharmacology, Kurume University School of Medicine, Kurume 830, and ! Department of Kitakyushu 803.Japan. Dental Anesthesiology, Kyusu-Dental College, Dopamlne (DA) neurons in the ventral tegmental area (VTA) proJect their nerve fibers to the nucleus accumbens (NAC), To examine functional properties of the mesolimbic .DA neurons, the microdialysis probes were implanted into the NAC and VTA of rats. During microdialysis perfusion rats were treated behaviorally or pharmacologically, and the dialysis samples (6 or 9 X 2Omin) were collected for the following 2 or 3 hrs. DA and its metabolites in the perfusate were measured by HPLC-ECD. Behavioral manipulations (deprivation-induced feeding and.drinking) induced significant increases in extracellular DA levels in both the NAC and VTA, showing that DA is released somatodendritically in the cell body site as well as in terminal fields during spontaneous behaviors with goaldirected nature. Pharmacological treatment (intra-NAC via the probe r i..p. application of drugs i.e., ketamine 20mg/kg, MK801, nicotine, amantadine and morphine(lO' G-8 M, 20 min) produced a marked increase in DA outflow from the NAC. Infusion of opiate analogue, DAGO (lo-6M, 40 min) through the VTA probe caused pronounced increases in DA release in the NAC. These results suggest that rewarding stimuli or some drugs inducing abuse increase the mesolimbic DAergic activity, and also indicate that the possible site of opioid action on the mesolimbic DA neuron is located at least in the VTA
DOES L-DOPA DEPOLARIZE MOTONEURONS IN THE ISOALTED SPINAL CORD OF NEONATAL RAT ? MASAFUMI SAICUMA,KUMIKO UI, AND YUHEI MIYATA, Department of Pharmacology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku. Tokvo 113, Japan. It has recently been reported that L-dopa potentiates spinal monosynaptic reflexes (MSR) _in vivo and suggested that this effect is mediated by release of noradrenaline (NA) from the descending NAergic fibers (Tanabe et al., Japan. J. However, another possibility is remaining that Pharmacol., 54, 69-77, 1990). the L-dopa effect is due to its direct action on motoneurons. The present study was undertaken to test this possibility. Under ether anesthesia, a lumbar spinal cord was isolated from 5-6 days old rats and perfused with artificial cerebra-spinal fluid (ACSF). Although MSR was depressed in this preparation, L-dopa applied in a bath induced depolarization of motoneurons recorded from a ventral root with a suction electrode. In the spinal cord of which lower thoracic level was sectioned 2-3 days previously to allow degeneration of the descending NAergic inputs, L-dopa similary depolarized motoneurons. It was reduced to about 60 % of control in an ACSF containing low Ca and high Mg ions which completely abolished MSR. Tetrodotoxin (0.2 )JM)greatly reduced the L-dopa-induced depolarization to about 7%. These results suggest that L-dopa depolarize motoneurons directly besides by its indirect action.