| 1. |
- Haage, David, et al.
(författare)
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Allopregnanolone modulates spontaneous GABA release via presynaptic Cl- permeability in rat preoptic nerve terminals
- 2002
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Ingår i: Brain Research. - : Elsevier. - 0006-8993 .- 1872-6240. ; 958:2, s. 405-413
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Tidskriftsartikel (refereegranskat)abstract
- The endogenous neurosteroid 3alpha-hydroxy-5alpha-pregnane-20-one (allopregnanolone) affects presynaptic nerve terminals and thereby increases the frequency of spontaneous GABA release. The present study aimed at clarifying the mechanisms underlying this presynaptic neurosteroid action, by recording the frequency of spontaneous GABA-mediated inhibitory postsynaptic currents (sIPSCs) in neurons from the medial preoptic nucleus (MPN) of rat. Acutely dissociated neurons with functional adhering nerve terminals were studied by perforated-patch recording under voltage-clamp conditions. It was shown that the sIPSC frequency increased with the external K(+) concentration ([K(+)](o)). Further, the effect of allopregnanolone on the sIPSC frequency was strongly dependent on [K(+)](o). In a [K(+)](o) of 5 mM, 2.0 microM allopregnanolone caused a clear increase in sIPSC frequency. However, the effect declined rapidly with increased [K(+)](o) and at high [K(+)](o) allopregnanolone reduced the sIPSC frequency. The effect of allopregnanolone was also strongly dependent on the external Cl(-) concentration ([Cl(-)](o)). In a reduced [Cl(-)](o) (40 mM, but with a standard [K(+)](o) of 5 mM), the effect on sIPSC frequency was larger than that in the standard [Cl(-)](o) of 146 mM. The dependence of the effect of allopregnanolone on [K(+)](o) and on estimated presynaptic membrane potential was also altered by the reduction in [Cl(-)](o). As in standard [Cl(-)](o), the effect in low [Cl(-)](o) declined when [K(+)](o) was raised, but reversed at a higher [K(+)](o). The GABA(A) receptor agonist muscimol also potentiated the sIPSC frequency. Altogether, the results suggest that allopregnanolone exerts its presynaptic effect by increasing the presynaptic Cl(-) permeability, most likely via GABA(A) receptors.
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| 2. |
- Blay, Pilar, et al.
(författare)
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An in vivo study of the effect of 5-HT and sympathetic nerves on transferrin and transthyretin mRNA expression in rat choroid plexus and meninges
- 1994
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Ingår i: Brain Research. - : Elsevier BV. - 1872-6240 .- 0006-8993. ; 662:1-2, s. 148-154
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Tidskriftsartikel (refereegranskat)abstract
- Brain expression of transferrin (Tf) and transthyretin (TTR) mRNA has been demonstrated in different species, TTR being found only in the choroid plexus. We report here that both these mRNAs are also expressed in the meninges. In vitro studies have shown that Tf secretion by the rat choroid plexus is stimulated by 5-hydroxytryptamine (5-HT) while sympathetic nerves regulate different transport functions in the same tissue. We have used various in vivo models to study the neuroendocrine regulation of Tf and TTR mRNA expression in the choroid plexus and meninges. Destruction of the serotonergic nerves in the brain by either raphe nuclei lesion or intraventricular injections of 5,7-dihydroxytryptamine (5,7-DHT), which both decreased brain 5-HT levels significantly, did not affect Tf or TTR mRNA levels in choroid plexus and meninges, but increased TTR mRNA in liver. Intraventricular injection of 10 or 100 pmol 5-HT did not change the expression of these proteins in any of the tissues studied. Removal of the sympathetic innervation to the choroid plexus by cervical sympathectomy did not affect Tf or TTR mRNA levels in choroid plexus and liver, nor the incorporation of radioactive leucine into protein in various parts of the brain. In conclusion, our results do not support a regulatory role in vivo for neuronally derived 5-HT or sympathetic nerve activity on Tf and TTR mRNA expression in rat choroid plexus and meninges.
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| 3. |
- Chang, Jing-Yu, et al.
(författare)
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Serotonin uptake into cerebrovascular nerve fibers of rat, visualization by immunohistochemistry, disappearance following sympathectomy, and release during electrical stimulation
- 1989
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Ingår i: Brain Research. - : Elsevier BV. - 1872-6240 .- 0006-8993. ; 492:1-2, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- Immunohistochemistry as well as in vitro uptake and release of [3H]5-HT were performed on pial arteries of rat to investigate the nature of 5-HT containing nerve fibers. Immunoreactive fibers were constantly found only in the basilar, vertebral and superior cerebellar arteries, while in the other parts of the circle of Willis, 5-HT immunofluorescent fibers were absent. After systemic treatment with tryptophan following inhibition of monoamine oxidase with nialamide the immunofluorescence intensity was markedly enhanced. The 5-HT immunoreactive fibers disappeared after superior cervical ganglionectomy or intraventricular administration of 6-hydroxydopamine, but persisted after administration of 5,6-dihydroxytryptamine. When isolated vessels were incubated in low concentration of 5-HT (1 nM) together with nialamide, a very dense plexus of 5-HT immunoreactive fibers appeared in all branches of the circle of Willis. Uptake and release experiments were carried out by incubation of arterial preparations with 3 nM [3H]5-HT (together with nialamide), followed by electrical field stimulation, or by exposure to tyramine or 124 mM potassium, all of which induced a 100%-350% increase in the tritium release over prestimulation values. Preincubation with cocaine and bilateral superior cervical ganglionectomy abolished or markedly attenuated the release upon all modes of stimulation. The results suggested that the 5-HT observed by immunohistochemistry in pial arteries is located in sympathetic nerve terminals where it may serve as a neuromodulator that is released during nerve activation.
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| 4. |
- Elmer, Eskil, et al.
(författare)
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Delayed kindling development after rapidly recurring seizures: relation to mossy fiber sprouting and neurotrophin, GAP-43 and dynorphin gene expression
- 1996
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Ingår i: Brain Research. - : Elsevier BV. - 1872-6240 .- 0006-8993. ; 712:1, s. 19-34
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Tidskriftsartikel (refereegranskat)abstract
- Development of kindling and mossy fiber sprouting, and changes of gene expression were studied after 40 seizures produced during about 3 h by electrical stimulation every 5 min in the ventral hippocampus. As assessed by 5 test stimulations, enhanced responsiveness was present already after 6-24 h but from 1 week post-seizure increased gradually up to 4 weeks without additional stimuli. Sprouting of mossy fibers in the dentate gyrus was demonstrated only at 4 weeks with Timm's staining. In situ hybridization showed a transient increase (maximum at 2 h) of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), TrkB and TrkC mRNA levels and reduction (maximum at 12-24 h) of neurotrophin-3 (NT-3) mRNA expression in dentate granule cells after the seizures. In addition, BDNF mRNA levels were elevated in CA1 and CA3 regions, amygdala and piriform cortex. Marked increases of mRNA for growth-associated protein (GAP-43), with maximum expression at 12-24 h, were observed in dentate granule cells and in amygdala-piriform cortex. Dynorphin mRNA levels showed biphasic changes in dentate granule cells with an increase at 2 h followed by a decrease at 24 h. No long-term alterations of gene expression were observed. These findings indicate that increased responsiveness develops rapidly after recurring seizures but that the kindled state is reached gradually in about 4 weeks. Mossy fiber sprouting occurs in parallel to epileptogenesis and may play a causative role. Short-term changes of neurotrophin and Trk, GAP-43 and dynorphin mRNA levels and the assumed alterations of the corresponding proteins could trigger structural rearrangements underlying kindling but might also contribute to the initial increase of seizure susceptibility.
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| 5. |
- Grabowski, Martin, et al.
(författare)
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Sensorimotor performance and rotation correlate to lesion size in right but not left hemisphere brain infarcts in the spontaneously hypertensive rat
- 1991
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Ingår i: Brain Research. - : Elsevier BV. - 1872-6240 .- 0006-8993. ; 547:2, s. 249-257
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Tidskriftsartikel (refereegranskat)abstract
- In order to correlate behavioural deficits to lesion size and to reveal possible functional asymmetries in the rat brain, locomotor activity, rotation and sensorimotor integration to touch were studied in spontaneously hypertensive rats (SHR) subjected to right or left middle cerebral artery occlusion. Control and infarcted rats showed no difference in locomotor activity. Infarcted rats tended to rotate towards the side of the lesion. A large sensorimotor deficit was found contralateral to the infarcted hemisphere. The absolute values of the side-biases for the rotation and sensorimotor tests were of the same degree irrespective of lesion side. Whereas the left hemisphere lesion size did not correlate to the behavioural outcome, the size of the right hemisphere lesion was highly correlated to the total sensorimotor deficit. Furthermore, the sensorimotor deficit of specific body parts was found to correlate to the damage of certain brain regions in a rostrocaudal fashion, reminiscent of a somatotopical organization. The extent of ipsilateral rotation correlated to brain tissue loss at the level of the posterior caudate-putamen. The present results indicate an asymmetrical organization for brain functions involved in the performance of the rotation and sensorimotor tests.
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| 6. |
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| 7. |
- Schouenborg, Jens, et al.
(författare)
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Long-lasting neuronal activity in rat dorsal horn evoked by impulses in cutaneous C fibres during noxious mechanical stimulation
- 1988
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Ingår i: Brain Research. - : Elsevier BV. - 1872-6240 .- 0006-8993. ; 439:1-2, s. 56-63
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Tidskriftsartikel (refereegranskat)abstract
- The responses of 44 nociceptive neurones in the lumbar dorsal horn evoked by controlled mechanical stimulation of the skin, with or without conduction block in myelinated afferent fibres, were studied in the halothane-anaesthetized rat, in order to evaluate the effects of impulses in cutaneous nociceptive C fibres on dorsal horn neurones. Continuous non-noxious pinch of the skin evoked a short-latency discharge (mean latency 15 ms) in all the 13 class 2 neurones (i.e. neurones responding to both non-noxious and noxious stimulation of the skin) tested. The short-latency discharge was followed by weak prolonged activity in 6 neurones. Following noxious pinch of the skin a prominent late discharge (peak latency 150 ms-2 s) was evoked, which in all but two class 2 neurones outlasted the stimulation period (5-10 s). The discharge evoked by noxious pinch in class 3 neurones (i.e. neurones responding to noxious stimulation only) did not usually outlast the stimulation period. In all but two nociceptive neurones tested (n = 26) the late activity evoked by noxious pinch remained, albeit at a lower frequency in some neurones, during a conduction block in A fibres2.3. Hence this late discharge is probably mainly generated by impulses in nociceptive C fibres. It is concluded that nociceptive C fibres have an important role in sustaining long-lasting activation of class 2 neurones during noxious stimulation of the skin and that long-lasting discharges in these neurones indicates tissue damage to their receptive fields.
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| 8. |
- Bergenheim, M, et al.
(författare)
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Ensamble coding of muscle stretches in afferent populations containing different types of muscle afferents
- 1996
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Ingår i: Brain Research. - : Elsevier BV. - 0006-8993 .- 1872-6240. ; 734:1-2, s. 157-166
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Tidskriftsartikel (refereegranskat)abstract
- Ensemble coding of simple mechanical stimuli (small sinusoidal stretches) was studied in simultaneously recorded mixed ensembles of primary- and secondary muscle spindle afferents (MSAs), and Golgi tendon organ (GTO) afferents recorded from L7-S1 dorsal root filaments. The experiments were made on 48 recorded afferents (29 primary MSAs, 6 secondary MSAs and 13 GTO afferents) in chloralose anaesthetised cats. For the analyses, we used a combination of principal component analysis and algorithms for quantification of stimulus discrimination. Mixed ensembles of primary- and secondary MSAs, and GTO afferents, discriminated significantly better between different muscle stretches than ensembles of only one or two types of these afferents. All kinds of ensembles showed a successive increase in discriminative ability with increased ensemble size, and this ability seemed to level at larger populations. However, the increase in discriminative ability was significantly greater for the mixed ensembles. It is hypothesised that the main reason for the greater discriminative ability achieved by mixed ensembles, might be that the variation in response profiles (sensitivity tuning) among the individual afferents of the mixed ensemble will be larger than that for ensembles of only one type of afferent. Finally, the results in the present study give experimental support to some of the teleological arguments in favour of the ensemble coding theory.
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| 9. |
- Bytner, Beta, et al.
(författare)
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Nociceptin/orphanin FQ into the rat periaqueductal gray decreases the withdrawal latency to heat and loading, an effect reversed by (Nphe1)nociceptin(1-13)NH2
- 2001
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Ingår i: Brain Research. - 0006-8993 .- 1872-6240. ; 922:1, s. 118-124
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigated the effect of intraperiaqueductal grey injection of nociceptin/orphanin FQ (N/OFQ) and an antagonist (Nphe(1))nociceptin(1-13)NH(2) on the hindpaw withdrawal response to thermal and mechanical stimulation in rats. N/OFQ (5 nmol) significantly decreased the nociceptive thresholds in both tests and 1, 5 and 10 nmol of (Nphe(1))nociceptin(1-13)NH(2) significantly reversed this effect in a dose dependent way. Our results demonstrate, that N/OFQ has a nociceptive action, possibly through inhibition of PAG neurons. This effect is blocked by the antagonist (Nphe(1))nociceptin(1-13)NH(2) probably via ORL1 receptors in the periaqueductal grey.
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| 10. |
- Decety, Jean, et al.
(författare)
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The cerebellum participates in mental activity : tomographic measurements of regional cerebral blood flow
- 1990
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Ingår i: Brain Research. - 0006-8993 .- 1872-6240. ; 535:2, s. 313-317
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Tidskriftsartikel (refereegranskat)abstract
- Measurements in man of regional cerebral blood flow (rCBF) have demonstrated a number of cortical and subcortical events coupled to sensory stimulation or motor performance. It has also been shown that local activity changes take place in the cortex during 'pure' mental activity such as motor imagery (unaccompanied by sensory input or motor output). Thus, our group has previously shown that imagination of hand movements gives predominantly a frontal cortical rCBF activation while the corresponding hand movement activates the rolandic hand area mainly. In this paper we report tomographic rCBF measurements with a 133-Xenon SPECT technique during imagined tennis movements and silent counting. Both procedures gave rise to a significant cerebellar activation in addition to cortical rCBF changes. Apparently, the cerebellum may participate in pure mental activity. It possibly plays a role for the temporal organization of neuronal events related to cognition.
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