摘要:

AbstractK‐252b, a potent inhibitor of protein kinases blocked a late phase of long‐term potentiation (LTP) in area CA1 of rat hippocampal slices, resulting in decremental LTP. It also prevented the slowly developing increase in sensitivity of CA1 neurons to iontophoretically administered α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) which was seen in control slices that exhibit nondecremental LTP. However, K‐252b applied 60–180 min after the induction of LTP had no effect on the potentiated synaptic and AMPA‐induced responses. A K‐252b‐sensitive protein kinase may therefore be involved in a slowly developing p

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe hypothesis that B‐50/GAP43, a membrane‐associated phosphoprotein, is involved in process outgrowth has been tested by studying the developmental pattern of expression of B‐50/GAP43 mRNA and protein during mouse neuroembryogenesis. B‐50/GAP43 mRNA is first detectable at embryonic day 8.5 (E8.5) in the presumptive acoustico‐facialis ganglion. Subsequently, both B‐50/GAP43 mRNA and protein were co‐expressed in a series of neural structures: in the ventral neural tube (from E9.5) and dorsal root ganglia (from E10.5), in the marginal layer of the neuroepithelium surrounding the brain vesicles and in the cranial ganglia (from E9.5), in the autonomic nervous system (from E10.5), in the olfactory neuroepithelium and in the mesenteric nervous system (from E11.5), in a continuum of brain regions (from E12.5) and in the retina (from E13.5). Immunoreactive fibers were always seen arising from these regions when they expressed B‐50/GAP43 mRNA. The spatial and temporal pattern of B‐50/GAP43 expression demonstrates that this protein is absent from neuroblasts and consistently appears in neurons committed to fiber outgrowth. The expression of the protein in immature neurons is independent of their embryological origin. Our detailed study of B‐50/GAP43 expression during mouse neuroembryogenesis supports the view that this protein is involved in a process common to all neurons

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe anterograde transport ofPhaseolus vulgaris‐leucoagglutinin (PHA‐L) was combined with postembedding immunocytochemistry for gamma‐aminobutyric acid (GABA) to study the topography, the synaptic organization and the neurotransmitter content of the pallidosubthalamic projection in the rat. After injections of PHA‐L in different parts of the globus pallidus a rich plexus of anterogradely labelled fibres and terminals was found in the ipsilateral subthalamic nucleus. The immunoreactive elements were distributed according to a mediolateral and rostrocaudal topography. Injections of PHA‐L restricted to the lateral two‐thirds of the globus pallidus gave rise to a massive anterograde labelling confined to the lateral half of the subthalamic nucleus. On the other hand, injections of PHA‐L strictly confined to the medial part of the globus pallidus resulted in anterograde labelling that occupied the ventromedial pole of the subthalamic nucleus. In some cases a few retrogradely labelled cells were found in the subthalamic nucleus after PHA‐L injections in the globus pallidus. The perikarya and the primary dendrites of these labelled cells were sometimes surrounded by anterogradely labelled terminals suggesting a close reciprocal connection between the globus pallidus and the subthalamic nucleus. Electron microscopic analysis of the PHA‐L‐labelled terminals revealed that they contain many mitochondria, numerous small round or slightly pleomorphic vesicles and occasionally one or two large dense core vesicles. They form symmetrical synaptic contacts predominantly with the proximal dendrites (39%) and less frequently with the perikarya (31%) and the distal dendrites (30%) of the subthalamic cells. Quantitative measurements showed that the pallidosubthalamic varicosities have a diameter ranging from 0.7 to 4.5 μm and a mean cross‐sectional area of 0.79 ± 0.26 μm2(Mean ± SD). Postembedding immunocytochemistry for GABA revealed that the PHA‐L‐immunoreactive pallidosubthalamic axon terminals display GABA immunoreactivity. The results of our study demonstrate that the pallidosubthalamic projection is organized according to a mediolateral and rostrocaudal topography and that the proximal dendrites of the subthalamic cells are the major targets of the GABA‐immunoreactive pallidosubthalamic terminals. This suggests that the globus pallidus exerts a powerful control over the subthalamic cells through

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe expression of tyrosine hydroxylase mRNA in the rat brain was examined using a novel alkaline phosphatase labelled antisense oligodeoxynucleotide probe. The alkaline phosphatase labelled probe revealed the presence of tyrosine hydroxylase mRNA in all the major cell groups and cell bodies previously described as containing catecholamine fluorescence or known to contain tyrosine hydroxylase immunoreactivity. Using standardized development protocols qualitative comparisons between the amount of mRNA signal in different adrenergic, noradrenergic or dopaminergic cell groups could be made. These studies showed that of the three known catecholaminergic cell types the level of tyrosine hydroxylase mRNA signal was high in the noradrenergic and dopaminergic cells, but much lower in the adrenergic cell groups. The sensitivity of this nonradioactive method ofin situhybridization is excellent and has considerable potential for studies of coexistence or coexpression of two mRNA signals for the localization of mRNA signals at the electron—microscope leve

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractWe have investigated the modulatory action of excitatory amino acids (EAA) on vasoactive intestinal polypeptide (VIP)‐stimulated cAMP formation in mouse cerebral cortical slices. Glutamate and aspartate potentiate in a concentration‐dependent manner the effect of VIP. In order to characterize the type of receptor involved, we have used three prototypical EAA receptor agonists, that is, kainate, N‐methyl‐D‐aspartate (NMDA) and quisqualate. Kainate mimicked the effect of glutamate, NMDA was inactive and quisqualate displayed an inhibitory action. Furthermore, ibotenate also potentiated the effect of VIP on cAMP formation, while L‐homocysteate exhibited an inhibitory action. Ibotenate was 4‐fold more potent and 2.5 times more effective than glutamate. However, the effects of kainate and ibotenate were not additive, suggesting the activation of a common receptor. Thus, based on this metabotropic action, EAA can be categorized into the following classes: (i) those that potentiate the effect of VIP, such as glutamate, aspartate, kainate and ibotenate; (ii) those that inhibit the effect of VIP, such as L‐homocysteate and quisqualate; and (iii) those that are ineffective, such as NMDA and D‐homocysteate. The effects of glutamate or ibotenate on VIP‐stimulated cAMP formation were completely inhibited by L‐phosphoserine and only partially by kynurenate. In a low chloride medium, or in the presence of 8‐(N,N‐diethylamino) octyl‐3,4,5‐trimethoxybenzoate‐hydrochloride (TMB‐8), an inhibitor of calcium release from internal stores, EAA did not potentiate the effect of VIP, thus stressing the importance of these ions for the transduction of the glutamatergic signal. Our results indicate the existence of marked interactions between EAA and VIP on cAMP formation; the pharmacology of these interactions is, however, clearly distinct from the classical pharmacology of EAA which is mainly based on electro

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00443.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe release of amino acids and the hydrolysis of inositol phospholipids were examined in parallel in three hippocampal areas following classical conditioning. Paired or unpaired tone(CS) ‐ shock(US) presentations were given to animals engaged in a previously acquired food‐motivated lever‐pressing task. Conditioned suppression of lever‐pressing was the behavioural measure of conditioning. Twenty‐four hours after the last conditioning session, the dentate gyrus and areas CA3 and CA1 of the hippocampus were removed bilaterally from conditioned and pseudoconditioned animals, and slices cut and stored in liquid nitrogen for subsequent analysis. Crude synaptosomal pellets were prepared to investigate: (i) potassium‐stimulated release of preloaded [3H]glutamate and [14C]aspartate in the presence and absence of extracellular Ca2+; (ii) [3H]inositol labelling of phosphoinositides and inositol phosphates; and (iii) [14C]arachidonic acid labelling of 1,2‐diacylglycerol (1,2‐DG). Potassium‐stimulated, Ca2+‐dependent release of [3H]glutamate in synaptosomes prepared from the dentate gyrus and area CA3 was significantly greater in conditioned animals than in pseudoconditioned animals. In area CA1, K+‐stimulated, Ca2+‐dependent release of [14C]aspartate was significantly increased in conditioned animals. These results confirm in synaptosomes, and extend to a period of 24 h our previous report of an increased release of transmitter in the dentate gyrus and hippocampus associated with classical conditioning. In parallel with the increased release of amino acids, learning was associated with a significant increase in labelling of phosphoinositides and inositol phosphates by [3H]inositol and a significant increase in labelling of 1,2‐DG by [14C]arachidonic acid in the three hippocampal areas examined. It is suggested that a long‐lasting presynaptic activation of inositol lipid metabolism may contribute to the learning‐dependent increase in the capacity of hippocampal terminals to release transmitter and hence to the maintenance of a neurochemical trace which may, at least in part, underlie lasting changes in synaptic function built u

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00444.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIt has been shown that most hippocampal complex‐spike cells fire at specific locations in relation to a set of controlled spatial cues and that they continue to fire in the appropriate places when the cues are removed (O'Keefe and Conway, 1978; O'Keefe and Speakman, 1987). However, the goal remained in a constant position relative to the controlled cues throughout these experiments. It is therefore possible that the unit firing was related to the goal location and not to the controlled cues as was suggested. For example, firing in a particular location might signal the rat's intention to make a particular turn towards the goal from that location and not the location itself. There are many reasons for believing that this is an unlikely class of explanations; nevertheless a test of this hypothesis was undertaken in the present experiment. Nineteen place units were recorded from three rats as they performed the task of finding the goal location. After obtaining an accurate picture of the place fields in relation to the controlled cues and the goal, the location of the goal relative to the cues was moved and the animal retrained to the new goal. After the new goal was being consistently chosen, a second picture of the place fields of the same units was obtained. If the fields were related to the environment created by the cues then they would remain the same during the two stages of the experiment. If they were related to the goal, or to the intended movements towards the goal, then they would rotate relative to the cues. As expected, the majority of place fields remained in the same place in relation to the cues during the two stages of the experiment and were not influenced by the goal relocation. In only two cases was there any suggestion that the place fields changed their location after the goal was moved. It was concluded that the activity of place cells is related to an animal's location in an environment and that the results accord with cognitive map theory of hippocampal function (O'Keefe and Nadel, 1978

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00445.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractRats with extensive lesions of the mamillary bodies and the immediately adjoining areas exhibited a severe impairment on two spatial memory tasks. In the first task, the animals had to retrieve food from each one of eight separate locations within the daily test session. In the second task, the animals were allowed to visit a particular location and retrieve food from it and, after a variable delay, they had to select between returning to the location they had already visited and a new location that now contained the food. Rats with lesions of the mamillary region were able to perform the task with minimal delay, but their performance was impaired as the delay increased. Finally, rats with mamillary lesions were not impaired in learning a visual discrimination task or its reversal. The results show that extensive damage in the mamillary region can lead to significant and long lasting spatial memory impairments.

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1990.tb00446.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY