摘要:

AbstractPsychopharmacological activation, in conjunction with positron emission tomographic measurements of regional cerebral blood flow (rCBF), was used to investigate the neurotransmitter basis of a specific cognitive function in man. Monoaminergic neurotransmission was pharmacologically manipulated during performance of auditory – verbal memory tasks. Statistical parametric mapping was used to identify the brain sites of interaction between memory‐induced increases in rCBF and active drugs. Memory task‐induced increases in rCBF in the left prefrontal cortex were attenuated by apomorphine, a non‐selective dopamine agonist, whilst buspirone, a serotonin1Apartial agonist, augmented rCBF increases in this area. In addition, apomorphine and buspirone augmented memory‐induced increases in rCBF centred in the posterior cingulate cortex, whilst buspirone alone attenuated rCBF increases in the retrosplenial cortex and posterior parahippocampal gyrus. These regionally selective interactions may represent neuromodulatory effects of monoaminergic neurotransmission on a specific cognitive functi

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00145.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractElectrical stimulation of cutaneous nerve Aδ‐fibres can lead to increases in skin blood flow (Jänig and Lisney,J. Physiol. (Lond.),415, 477–486, 1989). Here we have examined this phenomenon in adult rats treated neonatally with antisera to nerve growth factor between postnatal days 2 and 14. This treatment forces many Aδ nociceptor afferents to take on the phenotype of low‐threshold D‐hair afferents (Lewinet al., J. Neurosci.,12, 1896–1905, 1992). In animals treated this way we found a parallel decrease in the ability of Aδ‐fibres to increase skin blood flow. The increase in blood flow evoked by C‐fibre stimulation was also reduced, but no change was seen in the ability of C‐fibres to elicit neurogenic extravasation in skin. These data may be taken as evidence that in rats, amongst the cutaneous Aδ‐fibres, nociceptor but not D‐hair afferents are capable of producing blood

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00146.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWe compared the pre‐ and postoperative performance of macaque monkeys on visual discrimination tasks entailing the perception of differences in the motion of two luminous spots. Animals in which area MT and adjacent regions had been surgically removed were not significantly impaired as long as there were differences in the temporal frequency of the two stimuli. When the latter were eliminated the postoperative performance of the MT animals was significantly impaired compared to their preoperative performance and compared to the animals in the control groups. The same animals were also impaired at perceiving which of two moving dots, presented in the dark, changed its directio

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00147.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractNine macaque monkeys were trained to discriminate between a display in which all the dots moved randomly (visual dynamic noise) and an adjacent display in which a proportion of the dots oscillated coherently from side to side. Two monkeys in which area MT (middle temporal visual area) and adjacent regions were surgically removed were unable to perform even the simplest version of this task where the coherent motion was not masked by any visual dynamic noise. The other seven animals tolerated between 60% and 65% of random movement in the otherwise coherently oscillating display before they failed to discriminate between the two displays. In contrast, shape discrimination tasks containing luminance boundaries were unaffected by the removal of area MT. However, the removal of area MT did impair the animals' ability to use a kinetic boundary as the basis for shape discrimination. Their performance with a kinetic boundary between a moving and a stationary random dot field and a kinetic boundary between two random dot fields moving in opposite directions was the most severely impaired. Their performance with a kinetic boundary defined by two random dot fields moving orthogonally to each other was unimpaired. None of the animals from either group was able to use the kinetic boundary defined by coherent motion and visual dynamic noise as the basis for shape discrimination. The ease with which the control animals were able to employ the different types of kinetic boundaries to perform the shape discrimination reflected previously published proportions of cells in area MT that are specialized for detecting the different types of kinetic boundaries.

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractRecent experiments have shown that after lesions of the inferior olive or of the flocculus and paraflocculus of the cerebellum, in the pigmented rat, spontaneous saccades made when the head is completely restrained are followed by a large postsaccadic drift. The aims of the present paper were to study (i) the strategies and the characteristics of spontaneous eye – head coordinated gaze shifts in intact pigmented rats and to compare them with those described in other mammals, (ii) how they are affected by inferior olive and flocculus – paraflocculus lesions, and (iii) whether in these groups of animals the stability of the gaze is more deficient when the head is free to rotate in the horizontal plane (head‐free condition) relative to the head‐fixed condition. Three types of gaze shift strategy of intact rats are described and characterized. Following inferior olive or flocculus – paraflocculus lesion the dynamic parameters of such gaze shifts (the main sequences of head, gaze and eye and the timing of eye and head movement onset) are not significantly affected. The main deficits of lesioned animals affect the stability of gaze at the end of gaze shifts. After inferior olive lesion the amplitude of the postsaccadic drift of the gaze is 43.2% of the gaze saccade in the head‐fixed condition, which is reduced to 22.9% in the head‐free condition. Following flocculus – paraflocculus lesion the postsaccadic drift of gaze is even more reduced than after inferior olive lesion, changing from 39.2% in the head‐fixed condition to only 9.7% in the he

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00149.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe process of regulated secretion in PC‐12 cells is tightly coupled to calcium entry, which is absolutely dependent on extracellular Ca2+([Ca2+]ex). Tunicamycin treatment of the cells dissociated depolarization‐triggered Ca2+influx from depolarization (high K+)‐induced transmitter release into two distinct and independent phases. Deplarization‐evoked Ca2+influx was not affected by tunicamycin treatment (1 μg/ml, 72 h), whereas depolarization‐evoked transmitter release was strongly inhibited (>60%), suggesting at least a two‐step process, and the participation of glycosylated protein(s) in the actual fusion/secretion step. Similarly, bradykinin‐mediated transmitter release was linearly related to and absolutely dependent on Ca2+entry, and was inhibited by tunicamycin treatment (>80%), whereas bradykinin‐evoked Ca2+entry was not impaired, indicating that glycosylated protein(s) are essential for bradykinin‐evoked release at a step subsequent to Ca2+influx. The heavily glycosylated α2subunit of the dihydropyridine‐sensitive channel, which was used to monitor tunicamycin inhibition of glycosylation, was not expressed in the tunicamycin‐treated cells, as shown by Western blot analysis. This observation allowed us to conclude that the a, subunit of the heteromeric dihydropyridine voltage‐sensitive Ca2+channel, which is responsible for Ca2+entry, is also fully functional when not assembled with its corresponding α2subunit. The molecular properties of the α2subunit, whose role in the complex structure of the channel is not yet understood, are shown for the first time for the L‐type Ca2+channel of PC‐12 cells. Similar to cardiac and skeletal muscle cells, the α2subunit appears to be a glycosylated polypeptide of molecular weight 170 kD and to display a characteristic mobility shift to

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00150.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractNeuroendocrine chromaffin cells of the adrenal gland express certain molecular markers either transiently during development or permanently. In the present study, the expression of neuromodulin (GAP‐43), a neuronal protein often associated with neurite outgrowth, was examined in adult adrenals. Neuromodulin was detected by Western blot analysis in extracts of both rat adrenals and cultured bovine chromaffin cells, and was localizedin situin a subpopulation of chromaffin cells, as well as in nerve fibres and Schwann cells. The use of anti‐tyrosine hydroxylase or anti‐phenylethanolamineN‐methyltransferase antibodies in combination with anti‐neuromodulin antibodies in double immunofluorescent labelling of cryostat sections of rat glands demonstrated that neuromodulin is expressed by noradrenergic, and not by adrenergic chromaffin cells. The results provide further evidence that neuromodulin is not limited to neurons; it is also expressed in a subpopulation of neuroendocrine chromaffin cells. Neuromodulin may play a role in the development of the adrenal medulla or in the specific regulation of noradrenalin secretion from chromaf

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00151.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe present study was designed to examine the cellular localization and biosynthetic machinery of the broad‐spectrum excitatory amino acid receptor antagonist kynurenic acid in the lesioned rat hippocampus. Seven days after an intrahippocampal injection of 120 nmol quinolinic acid, which causes massive neurodegeneration in the dorsal hippocampus, kynurenic acid tissue levels and the activity of kynurenic acid's anabolic enzyme, kynurenine aminotransferase, were increased by 92% and 67%, respectively, as compared to controls. The steady‐state levels of extracellular kynurenic acid, examined by microdialysis in unanaesthetized rats, were also increased in the lesioned tissue (from 93.6 ± 10.2 to 207.6 ± 18.6 fmol/30 μl dialysate). Using microdialysis, three compounds which are known to decrease kynurenic acid production from its bioprecursorl‐kynurenine in brain slices andin vivowere tested for their ability to reduce the levels of endogenous kynurenic acid. In unlesioned tissue, aminooxyacetic acid (300 μM), veratridine (50 μM) and glutamate (5 mM), all administered through the dialysis probe, decreased extracellular kynurenic acid concentrations by 30 – 40%, i.e. to a lesser degree than in previous experiments in which kynurenine was used as a bioprecursor. Only the effect of veratridine was abolished in the quinolinate‐lesioned hippocampus. These data indicate that kynurenic acid is produced in and liberated from astrocytes, and that aminooxyacetic acid and glutamate (but not veratridine) exert their action by directly affecting glial kynurenic acid biosynthesis. The results also suggest the existence of two distinct intracellular kynurenic acid pools, which are responsible for kynurenic acid storage and rapid kynurenic acid mobilization, respectively. Taken together, these features of kynurenic acid neurobiology may be of relevance in the control of excitatory amino acid receptor function under physiological and pathologi

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00152.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWe studied Na+and Ca2+currents in glial cells during the development of the corpus callosumin situ.Glioblasts and oligodendrocytes from frontal brain slices of postnatal day (P) 3 to P18 mice were identified based on morphological and ultrastructural features after characterization of the currents with the patch‐clamp technique. Slices from P3‐P8 mice contained predominantly glioblasts with immature morphological features. These cells showed Na+and Ca2+currents, but the population with these currents decreased between P3 and P8. Na+currents were blocked in Na+‐free bathing solution and in the presence of tetrodotoxin, Ca2+currents were only observed when a high concentration of extracellular Ba2+was present. The cells from the corpus callosum of P10 – P18 mice predominantly had morphological features of oligodendrocytes. In these cells, which in some cases were shown to form myelin, neither Na+nor Ca2+currents were detected. To compare thesein situresults with those from the electrophysiologically and immunocytochemically well‐characterized cultured glial cells, we determined the expression pattern of stage‐specific antigens in the corpus callosumin situ.The first O4 antigen‐positive glial precursors were observed at P1, the earliest stage examined. The oligodendrocytic antigens O7 and O10 appeared at P6 and P14, respectively, and prominent labelling with the corresponding markers was seen at P12 and P18, respectively. Despite the existence of numerous mature, O10‐positive oligodendrocytes at P18, which expressed Ca2+channelsin vitro, we failed to detect Ca2+currentsin si

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00153.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractPrevious experiments in the rat have demonstrated that field CA1 and the subiculum project to the prefrontal cortex and that this direct unilateral pathway is excitatory. In the present study, anatomical and electrophysiological approaches were used to determine the transmitter mediating the excitatory responses in prefrontal cortex neurons to low‐frequency stimulation of the hippocampus. The method of selective retrograded‐[3H]aspartate labelling was used to identify putative glutamatergic and/or aspartatergic hippocampal afferent fibres to the prefrontal cortex. Unilateral microinjection ofd‐[3H]aspartate into the prelimbic area of the prefrontal cortex resulted in the retrograde labelling of a fraction of hippocampal neurons. Some labelled cell bodies were distributed in field CA1 and the subiculum but larger numbers of neurons were detected in the ventral and intermediary subiculum. In a second series of experiments, the excitatory transmission from the hippocampus to the prefrontal cortex was pharmacologically analysed to provide further evidence for the involvement of glutamate and/or aspartate in the pathway. All prefrontal cortex neurons responding to the stimulation of the hippocampus were activated by selective agonists of the glutamate receptor subtypes α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole‐propionic acid (AMPA) andN‐methyl‐d‐aspartate (NMDA), and these effects were selectively antagonized by 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) and 2‐amino‐5‐phosphonopentanoic acid (APV) respectively. Most of the excitatory responses of prefrontal cortex neurons to single and paired‐pulse stimulation of the hippocampus were antagonized by CNQX. APV only affected the excitatory response in a few cells. These results suggest that the hippocampal input to the prefrontal cortex utilizes glutamate and/or aspartate as a transmitter. Even though prefrontal cortex neurons responding to the stimulation of the hippocampus appear to have both AMPA and NMDA receptors, low‐frequency stimulation of the hippocampo‐prefrontal cortex pathway activa

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1992.tb00154.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY