Brain research bulletin
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Brain research bulletin · Apr 1998
Postsynaptic integration of cholinergic and dopaminergic signals on medium-sized GABAergic projection neurons in the neostriatum.
The effects of cholinergic drugs and the interaction between cholinergic and dopaminergic compounds were studied on electrically evoked [3H]gamma-aminobutyric acid (GABA) overflow in slices of the rat neostriatum. Slices were prepared and loaded with [3H]GABA in the presence of beta-alanine and then superfused with Krebs-bicarbonate buffer containing aminooxyacetic acid and nipecotic acid to inhibit GABA uptake and metabolism, respectively. The nonselective muscarinic agonist oxotremorine (0.1-10 microM) increased the release of [3H]GABA and the selective M1 receptor agonist McN-A-343 (0.1-10 microM) exerted similar effect. ⋯ McN-A-343 and sulpiride also increased the KCl-induced [3H]GABA overflow from superfused neostriatal slices and tetrodotoxin (1 microM) did not affect these stimulations. These data indicate that the release of GABA in the neostriatum is under the control of M1 stimulatory and M3 inhibitory muscarinic receptors. Dopamine, which exerts inhibition on GABA release via D2 receptors, may counteract the M1 facilitation, and M1 and D2 receptors involved in the cholinergic-dopaminergic interaction may be located postsynaptically on medium-sized spiny GABAergic projection neurons.
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Brain research bulletin · Jan 1997
Submodality-selective hyperalgesia adjacent to partially injured sciatic nerve in the rat is dependent on capsaicin-sensitive afferent fibers and independent of collateral sprouting or a dorsal root reflex.
We studied submodality dependence of sensory changes produced by unilateral ligation of the sciatic or the saphenous nerve in the rat. We focused especially on sensory changes in the skin area adjacent to the innervation area of the injured nerve. Moreover, we examined the roles of capsaicin-sensitive nociceptive fibers, collateral sprouting and a dorsal root reflex in sensory changes observed behaviorally. ⋯ At the peripheral level, the mechanical hyperalgesia adjacent to the innervation area of the injured nerve was mediated by capsaicin-sensitive nociceptive fibers. Collateral sprouting of nociceptive fibers from the uninjured to the injured innervation area did not contribute to the present sensory findings. The sciatic nerve injury did not induce a dorsal root reflex in nociceptive fibers innervating the hyperalgesic saphenous nerve area.
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Brain research bulletin · Jan 1997
Anticonvulsant activity of new and potent inhibitors of nitric oxide synthase.
The effects of new and potent NOS inhibitors, S-methyl-L-thiocitrulline (S-Me-TC), 3-bromo 7-nitro indazole (3-Br-7-NI), and 1-(2-trifluoromethylphenyl) imidazole (TRIM), were examined on the pilocarpine-induced seizures in mice. 3-Br-7-NI and TRIM decreased the frequency of status epilepticus and mortality, while TRIM. In addition, significantly reduced the incidence of seizures. The latencies to onsets of seizures, status epilepticus, and mortality were significantly prolonged by all three NOS inhibitors, while duration of seizures was reduced by 3-Br-7-NI and TRIM. These data suggest an excitatory effect of NO in the neuronal structure involved in the pilocarpine-induced seizures.
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Brain research bulletin · Jan 1995
Immunolocalization of putative neurotransmitters innervating autonomic regulating neurons (correction of neurones) of cat ventral medulla.
This study investigated possible sites of contact of nerve fibers containing a range of putative neurotransmitter substances onto neurons in the cat ventral medulla oblongata concerned with autonomic, particularly cardiovascular, regulation. The parasympathetic preganglionic neurons of the nucleus ambiguous (correction of ambiguus) were identified by retrograde horseradish peroxidase tracing from the vagus nerve, and the groups of neurons in the A1 and C1 cell areas and the raphe nucleus by catecholamine enzyme or 5-hydroxytryptamine (5-HT) immunohistochemistry, respectively. Immunoreactive (-ir)nerve fibers and terminals in the vicinity if these neurons were visualized by subjecting the sections to a dual-staining technique using a brown peroxidase-diaminobenzidine reaction product and a blue alkaline phosphatase-Fast blue reaction product. ⋯ The catecholamine cells of the rostral C1 and caudal A1 groups showed a broadly similar pattern of innervation, most noticeably by fibers immunoreactive for DBH, GABA, 5-HT, cholecystokinin (CCK), CGRP, ENK, GAL, NPY, and SP. The 5-HT-ir neurons of the raphe nucleus, some also containing SP, TRH, ENK, or corticotropin-releasing factor (CRF)-ir, were most prominently innervated by terminals containing DBH, GABA, CCK, ENK, NPY, TRH, somatostatin (SRIF), and vasoactive intestinal polypeptide (VIP)-ir. Although the proof that these groups of neurons receive functional synaptic contacts from the immunoreactive fibers awaits further ultrastructural studies, the results do suggest that a wide range of putative transmitters may influence the activity of efferent neurons in the cat medulla controlling autonomic functions.
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Brain research bulletin · Jan 1995
Topographic organization of projections from the thalamic reticular nucleus to the anterior thalamic nuclei in the rat.
We have investigated connections between the thalamic reticular nucleus (TRN) and the anterior thalamic nuclei (ATN) in the rat, following injections of horseradish peroxidase (HRP) into subnuclei of the ATN and different regions of the rostral TRN. Three nonoverlapping groups of neurons in the dorsal part of the ipsilateral rostral TRN project to, and receive reciprocal projections from, specific subnuclei of the ATN. A vertical sheet of neurons in the most dorsal part of the rostral TRN projects to the dorsal half of the posterior subdivision of the anteroventral thalamic nucleus (AVp), the dorsal region of the medial subdivision of the anteroventral thalamic nucleus (AVm), and the dorsolateral part of the rostral anterodorsal thalamic nucleus (AD). ⋯ The medial sheet projects to the ventral part of AVm, the ventral part of rostral AD, and to the caudal portions of both AV and AD. There appears to be no input to the anteromedial thalamic nucleus (AM) from the TRN. These findings shed new light on the anatomy of the rostral TRN, the ATN, and the connections between the two, and are relevant to emerging hypotheses about the functional organization of the TRN and reticulo-thalamic projections.