摘要:

AbstractThe stimulation of cortical dopaminergic D1 receptors can counteract the increased locomotor activity evoked by D‐amphetamine application in the nucleus accumbens (Vezinaet al., Eur. J. Neurosci.,3, 1001–1007, 1991). Moreover, an α1 antagonist, prazosin, prevents the locomotor hyperactivity induced by electrolytic lesions of the ventral tegmental area (Troveroet al., Neuroscience,47, 69–76, 1992). Attempts were thus made to see whether blockade of α1‐adrenergic receptors in the rat prefrontal cortex could reduce nucleus accumbens D‐amphetamine‐evoked locomotor activity. Rats implanted chronically and bilaterally with cannulae into the medial prefrontal cortex and the nucleus accumbens were used for this purpose and locomotor activity was monitored in circular corridors. Preliminary experiments indicated that intraperitoneal injection of prazosin (0.06 mg/kg) reduces the locomotor hyperactivity induced by the peripheral administration of D‐amphetamine (0.75 mg/kg). This effect of prazosin was not observed when locomotor hyperactivity was obtained by an intraperitoneal injection of scopolamine (0.8 mg/kg). Bilateral nucleus accumbens injections of D‐amphetamine (4.0 nmol/side) markedly increased locomotor activity, as estimated in a 30 min period. Prior (20 min) bilateral injections of either prazosin or WB‐4101 (0.16 pmol) into the medial prefrontal cortex abolished the nucleus accumbens D‐amphetamine‐evoked response. The recovery of the nucleus accumbens D‐amphetamine‐evoked response was closely dependent on the amount of prazosin used, very prolonged inhibitory effects of the drug being seen with a high amount (>4 days with 160 pmol). In contrast, whatever the amount of WB‐4101 used (0.16–160 pmol), recovery occurred within 3 days. It is suggested that the blockade of cortical d‐adrenergic receptors facilitates locally dopaminergic D1 transmission. This latter effect may counteract the increased locomotor activity induced by the application of D‐amp

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00272.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractNeurons projecting to the parietal cortex or striatum and neurons showing immunoreactivity for the calcium‐binding proteins parvalbumin and 28KD‐calbindin were examined in the anterior intralaminar nuclei (IL) of the cat. Retrograde tracing from deep or superficial parietal cortical layers or from the caudate nucleus was coupled with immunohistochemistry to determine which of these proteins were expressed in the projection neurons. It was found that IL neurons project to deep as well as to superficial layers of the parietal cortex, that IL‐cortical neurons could be differentiated into two populations according to their cortical projection pattern and their soma size, and that IL neurons projecting to the parietal cortex or to the striatum express 28KDcalbindin immunoreactivity but not parvalbumin immunoreactivity. The distribution of immunoreactivity to 28KDcalbindin and parvalbumin in the neuropil showed a consistent complementary distribution pattern in the IL. The compartments based on differential parvalbumin and 28KDcalbindin expression may indicate the presence of functionally segregated units

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00273.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractDay‐old‐chicks can be trained in one trial to avoid a methylanthranilate‐coated bead (methyl‐chicks). The lobus parolfactorius of the chick forebrain is an important structure for memory of this avoidance response. To examine training‐induced electrophysiological changes in this structure, spontaneous neuronal bursting activity was measured from the lobus parolfactorius of anaesthetized, day‐old methyl‐ and water‐chicks (the latter chicks trained to peck at a water‐coated bead) over the period 1 – 10 h post‐test. Bursting was significantly higher in methyl‐chicks over this period. This post‐test increase was time‐dependent: bursting in methyl‐chicks was significantly higher only during the period 4–7 h post‐test. In a second experiment, methyl‐chicks were subjected to brief, subconvulsive electroshock 5 min post‐training. When tested 1 h later about half of these chicks showed recall (avoided the bead) and half were amnesic (pecked the bead). These chicks were anaesthetized and bursting was recorded from the lobus parolfactorius. Chicks that showed recall exhibited a significantly higher level of bursting over the period 1 – 10 h post‐test when compared to chicks that were amnesic. The time course of bursting was similar to that seen in non‐electroshocked methyl‐chicks. These results suggest that passive avoidance training induces a memory‐specific, time‐dependent increase in neuronal activity within the lobus parolfactorius of day‐old chicks. This increase may be directly associated

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00274.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe two major afferents of the substantia nigra pars reticulata are the subthalamic nucleus and the striatum. Stimulation of these afferents has opposing physiological effects on the output neurons of the substantia nigra pars reticulata. In order to better understand the role of these afferents in the flow of information through the basal ganglia and to better understand the ways in which they might interact, experiments have been performed to test the possibility that single‐output neurons of the substantia nigra pars reticulata receive convergent synaptic input from the subthalamic nucleus and the neostriatum. To address this, rats received iontophoretic deposits of the anterograde tracerPhaseolus vulgarisleucoagglutinin in the subthalamic nucleus, injections of the anterograde tracer biocytin in the neostriatum and injections of the retrograde tracer horseradish peroxidase conjugated to wheat‐germ agglutinin in the ventral medial nucleus of the thalamus. Following appropriate survival times the animals were perfusion‐fixed and sections of the substantia nigra were processed to reveal the transported tracers and prepared for electron microscopy. Light microscopic examination revealed that the substantia nigra contained rich plexuses of anterogradely labelled subthalamic and striatal terminals, as well as many retrogradely labelled nigrothalamic neurons. The anterogradely labelled terminals were often seen apposed to the retrogradely labelled neurons. In the electron microscope the subthalamic terminals were seen to form asymmetrical synaptic contacts (subthalamic type 1) with the identified nigrothalamic neurons as well as unlabelled perikarya and both proximal and distal dendrites. In confirmation of previous findings, the striatal terminals made symmetrical synaptic contact with the nigrothalamic neurons as well as unlabelled neurons. In areas of overlap between the two classes of terminals, identified nigrothalamic neurons and unlabelled nigral neurons were found to receive convergent synaptic input from the subthalamic nucleus and the neostriatum. In addition to the anterogradely labelled subthalamic terminals that formed asymmetrical synaptic specializations, a second, much rarer class was also observed (subthalamic type 2). These terminals were much larger and formed symmetrical synapses; several lines of evidence suggest that they originated not in the subthalamic nucleus but in the globus pallidus. These terminals were found to make synaptic contacts with identified nigrothalamic neurons and non‐labelled neurons and to form convergent synaptic contacts with subthalamic type 1 terminals and striatal terminals. It is concluded that the topographical and synaptic organization of the so‐called direct (striatum to substantia nigra pars reticulata) and indirect pathways (i.e. pathways involving the subthalamic nucleus andlor the globus pallidus) of information flow through the basal ganglia underlies the inhibition and excitation of the output neurons of the substantia nigra pars reticulata that occur following stimulation of the

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00275.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe properties and characteristics of calcium channel openings in cerebellar granule cells were analysed by the cell‐attached patch‐clamp technique. At depolarized potentials, with 110 mM Ba2+ as the divalent charge carrier, 36% of the patches displayed activity that consisted of elementary events whose amplitude ranged from – 0.3 to –1. 75 pA at 0 mV, giving rise to a high threshold current. In this population of events at least four different types of channel openings were identified by their distinct biophysical and pharmacological properties. Two types of channel openings, with conductances around 24 and 7 pS, had similar characteristics in that both opened following two modes of gating characterized by brief (˜ 2 ms) and longer openings (˜ 8 ms) and both were sensitive to dihydropyridines. A further type of channel opening, with a conductance around 11 pS gated mainly with brief openings (∼1 ms), was shown to be insensitive to dihydropyridines but was undetectable in recordings from the cells that had been treated with ω‐conotoxin. The last type of event was revealed after treatment of the cell with nicardipine or nifedipine and ω‐conotoxin. The corresponding channel had a conductance of 19 pS and opened in one dominant mode characterized by brief openings (∼1 ms). The data obtained on single‐channel activity of cerebellar granule cells are compared with the properties of the total current recorded in

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00276.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe dorsal horn of the spinal cord, which forms the locus of first synapses in pain pathways, is an important site of interaction between calcitonin gene‐related peptide (CGRP), substance P and enkephalin—the neuropeptides considered to be especially involved in the regulation of pain perception. Since adjuvant‐induced arthritic rats provide a suitable model for peripheral inflammation and hyperalgesia, the possible alterations of immunoreactive CGRP, substance P and enkephalin as well as the binding sites for [125I]hCGRPα, [125I]substance Plneurokinin‐1, (NK1) and [125I]FK‐33‐824/μ‐opioid receptors were studied in the dorsal horn of the spinal cord receiving projections from the inflamed limbs. In arthritic rats compared to control animals, a bilateral increase in CGRP‐ and substance P‐immunoreactive fibres and the presence of enkephalin‐immunoreactive cell bodies were noted in the dorsal horn of the spinal cord. As for receptors, while a significant decrease in [125I]hCGRPα and [125I]substance P/NK1 binding sites was observed in selective layers, no measurable alteration in [125I]FK‐33‐824/μ‐opioid binding sites was noted in any regions of the arthritic rat dorsal horn compared to the unaffected control rats. Following unilateral section of the peripheral nerve prior to induction of arthritis, CGRP‐ and substance P‐immunoreactive fibres were markedly depleted and no enkephalin‐positive neurons were observed in the ipsilateral dorsal horn. Analysis of receptor binding sites in denervated arthritic rats, however, exhibited differential responses, i.e. a significant increase in [125I]hCGRPα, a marked decrease in [125I]FK‐33‐824/μ‐opioid and apparently no alteration in [125I]substance P/NK1 receptor binding sites were observed in the ipsilateral dorsal horn compared to the intact contralateral side. These results taken together provide anatomical evidence for a concerted role of these peptides in the regulation of adjuvant‐induced hype

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00277.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the central nervous system (CNS), nerve regeneration after traumatic injury fails. The formation of a dense fibrous scar is thought to restrict in part the growth of axonal projections, providing one of the many reasons that complete lesions of neural pathways in the adult mammalian CNS are rarely followed by significant functional recovery. In order to determine which mechanisms mediate scar formation in the CNS and to investigate whether they can be modulatedin vivo, we have attempted to define the potential role of trophic factors. Our previous studies have shown the focal elevation of transforming growth factor β1(TGFβ1) expression in lesioned CNS tissue. In the studies described here, we demonstrate that TGFβ1participates in the scarring response in the rat brain. First, the elevated protein levels of TGFβ1are localized to specific populations of injury‐responsive cells in the traumatized CNS. Furthermore, the injection of TGFβ1into the brains of injured rats causes a dramatic increase in the scarring response. Conversely, when neutralizing TGFβ1antibodies are administered, the deposition of fibrous scar tissue and the formation of a limiting glial membrane that borders the lesion is significantly attenuated, thus establishing a role for the endogenous growth factor in regulation of the non‐glial component of the scar. In implicating TGFβ1in the scarring response in the CNS, the potential use for TGFβ1antagonists as inhibitors of scar formation in the injured mammalian CNS is s

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00278.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractA previous electrochemical study showed that the increase in the tyrosine hydroxylase (TH) content of the locus coeruleus (LC) produced by RU24722 administration was associated with a relative decrease in the catecholaminergic metabolic reactivity of this nucleus to a hypotensive stimulus. Since α2receptors participate in the regulation of the activity of both LC neurons and TH, the aim of the present work was to evaluate the possible involvement of the autoinhibition mediated by α2, autoreceptors in the inverse relationship between the reactivity of the LC and its TH content. Our study was divided into two successive steps: (i) the electrochemical measurement of thein vivometabolic activation of LC cells in response to α2,‐adrenergic receptor blockade, and (ii) the evaluation of the quantity of TH every 100 μm along the caudo‐rostra1 axis in each recorded LC. The capacity of TH protein to be activated was evaluated by the measurement, using differential normal pulse voltammetry, of thein vivovariations of the extracellular 3, 4‐dihydroxyphenylacetic acid concentrations in response to six cumulated doses of the α2,‐antagonist piperoxane. The corresponding dose‐response curves, determined in control‐and RU24722‐treated rats, were expressed as a function of the quantity of TH contained either in the whole recorded LC or in the 100 μm‐wide coronal interval surrounding the recording site. It was established that the slopes of the dose‐response curves were significantly (P<0.01) and inversely related to the quantity of TH at the level of the recording site. This result suggests that the negative control of the catecholaminergic metabolic reactivity in a restricted area of the LC could be directly or indirectly dependent on the level of expression of TH protein

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00279.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase unilateral injections in various neocortical areas (prefrontal, somatosensory, auditory, visual) of the hedgehog (Erinaceus europaeus) brain resulted in labelling of nuclei in the ipsilateral thalamus known from studies in other species and in the hedgehog to project to these areas. However, injections in the motor area resulted in retrograde and anterograde labelling of nuclei in both the ipsilateral and contralateral thalamus. These nuclei included the ventral lateral nucleus (VL), the intralaminar nuclei (ILN), the mediodorsal nucleus (MD) and midline nuclei. Large unilateral injections located mainly laterally in the thalamus labelled cells, contralaterally, in the ventral lateral geniculate nucleus, the intergeniculate leaflet and the reticular nucleus of the thalamus but never in VL, ILN and MD. The present results confirm previously described bilateral thalamocortical projections from the VL to the somatosensorimotor area in this species (Regidor and Divac,Brain Behav. Evol.,39, 265–269, 1992) and in addition demonstrate that (i) bilateral thalamocortical projections are established preferentially with the motor area, (ii) several nuclei are involved in such connections, (iii) these connections are reciprocal and topographically organized, and (iv) labelling in the contralateral thalamus observed in the present study is not a result of transneuronal transport of the tracer through thalamothalamic connections. This organization is unique among mammals and supports previous anatomical and electrophysiological findings, on the basis of which it has been suggested that the hedgehog retains a primitive character in neocortical and thalamic evolutio

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00280.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe studied, in rat sensory neurons, the modulation of high voltage‐activated Ca2+currents (ICamediated by the pertussis toxin‐sensitive activation of muscarinic receptors, which were found to be of subtypes M2, or M4. Muscarine reversibly blocked somatic Ca2+spikes but strong predepolarizations only partially relieved the inhibited Ca2+current. On the other hand, the putative coupling messenger could not rapidly diffuse towards channels whose activity was recorded from a macro‐patch. The perforated patch technique virtually prevented the response rundown present during whole‐cell experiments. Both ω‐conotoxin GVIA (ω‐CgTx)‐sensitive channels and ω‐CgTx‐ and dihydropyridine‐resistant channels are coupled to the muscarinic receptor, but not the L‐channel. When measured in the same neuron, dose ‐ response relationships for the first and subsequent agonist applications differed; maximal inhibition, the reciprocal of half‐maximal concentration and the Hill coefficient were always highest in the first trial. Muscarine and oxotremorine exhibited monotone dose ‐ response curves, but oxotremorine‐M showed non‐linear relationships which became monotonic when cells were intracellularly perfused with inhibitors of protein kinase A (PKA) and C (PKC), suggesting that either PKA or receptor‐induced PKC could phosphorylate and thus inactivate G‐proteins or other unknown proteins involved in inhibitory muscarinic actions on ICa. In summary, these data provide a preliminary pharmacological characterization of the muscarinic inhibition of the Ca2+channels in sensory neurons, with implications about agonist specificity and the

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1994.tb00281.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY