Neuroscience research
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Neuroscience research · Jun 1996
Comparative StudyDual effect of serotonin on formalin-induced nociception in the rat spinal cord.
To examine the role of the descending serotonergic system in the regulation of spinal nociceptive processing, the effects of serotonin (5-HT) and selective ligands for 5-HT receptor subtypes on persistent nociception were investigated. Formalin (5% formaldehyde) injected into the plantar region of the rat hindpaw induced two phases of aversive responses such as licking and biting. Intrathecal administration of selective 5-HT3 receptor antagonists, granisetron (0.1-100 pmol/rat) and ondansetron (1-1000 pmol/rat), reduced the second phase of the formalin-induced aversive responses without affecting the first one. ⋯ Intrathecal administration of 5-HT showed a dual effect on the second phase of the aversive responses in the 5,7-DHT-treated rats; 5-HT inhibited the aversive responses when administered at a low dose (0.1 nmol/rat) but facilitated them at a high dose (1 nmol/rat). In addition, the inhibitory and facilitatory effects of intrathecal 5-HT were blocked by its co-administration with NAN190, a 5-HT1A receptor antagonist, and granisetron, respectively. These results suggest that 5-HT suppresses formalin-induced nociception in the spinal cord via the 5-HT1A receptor and facilitates it via the 5-HT3 receptor.
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Neuroscience research · Mar 1996
Effects of judgement process on motor evoked potentials in Go/No-go hand movement task.
We examined the motor evoked potentials (MEP) of the forearm muscles following transcranial magnetic stimulation after the Go/No-go reaction-time hands movement in ten normal subjects. Facilitation of MEP of the agonistic muscles and suppression of MEP of the antagonistic muscles were recognized during the 'Go' session, while the MEPs of both muscles were markedly suppressed in the 'No-go' session. We considered that this MEP changes reflected the inhibition on the pyramidal tract during the 'No-go' session.
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Neuroscience research · Mar 1996
The distribution of two calcium binding proteins, calbindin D-28K and parvalbumin, in the entorhinal cortex of the adult mouse.
The immunohistochemical localization of two specific calcium binding proteins, parvalbumin (PV) and calbindin D-28K (CB), were examined in the entorhinal cortex (EC) of the adult mouse. The PV and CB immunoreactivities exhibited a conspicuous regional and laminar distribution in the EC. The overall immunostaining pattern of PV and CB appeared to be complementary in the EC, especially in the medial entorhinal area (MEA). ⋯ Furthermore, we also recognized a particular region at the most medial part of the MEA, where layer 2 was different from the other portion of the MEA regarding CB immunoreactivity and the cells containing another calcium binding protein, calretinin, were clustered in layer 3. Both the adjacent section technique and the fluorescent double-staining technique clearly revealed that a relatively large number of presumable interneurons contained both PV and CB immunoreactivities. Furthermore, the three neuron groups that were immunoreactive for both PV and CB, immunoreactive for PV alone and immunoreactive for CB alone were heterogeneous in their structural features such as shape and size, and no particular difference was found in their structural features among these three groups.
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Neuroscience research · Feb 1996
Mild electrical stimulation of pontine tegmentum around locus coeruleus reduces rapid eye movement sleep in rats.
The norepinephrinergic neurons in the locus coeruleus (LC) cease firing during REM sleep (REMS) and increase firing during REMS deprivation. Most of the earlier studies used lesion and transection techniques which could not confirm the role of LC in REMS generation and/or its maintenance, if at all. Hence, in this study it was hypothesized that if the LC REM-off neurons must cease firing before the onset of REMS, its continuous activation should eliminate or at least reduce REMS. ⋯ Total duration of REMS was significantly reduced during stimulation and showed a rebound increase during the post stimulation period. This reduction in REMS duration was primarily due to a significant reduction in the REMS frequency/h while the mean REMS duration/episode was not affected. Thus, the results of this study suggest that the stimulated area (LC) affects REMS, most likely by suppression of REMS generation process.
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Neuroscience research · Oct 1994
Terminal distribution of projections from the retrosplenial area to the retrohippocampal region in the rat, as studied by anterograde transport of biotinylated dextran amine.
The terminal distribution of projections from the retrosplenial area to the retrohippocampal region was examined in the rat with anterograde transport of biotinylated dextran amine. Projections from the retrosplenial granular area (RSG) to the retrohippocampal region terminate predominantly ipsilaterally in layers I, III, V and VI of the presubiculum, layers I and IV-VI of the parasubiculum, the molecular and pyramidal cell layers of the subiculum, and layers I, III, V and VI of the entorhinal area. ⋯ The results show that projections from the RSG to the retrohippocampal region are as massive as those from the RSA, and that each retrosplenial area has distinct projection fields in the retrohippocampal region. This suggests that each retrosplenial area may play some distinct functional roles in memory and learning processes such as spatial behavioral learning.