摘要:

AbstractOne of the links in the trisynaptic circuit of the hippocampus is the synapse between the mossy fibre terminals of dentate granule cells and CA3 pyramidal cells of Ammon's horn. This synapse has been physiologically characterized as excitatory, and there is pharmacological and immunohistochemical evidence that mossy fibre terminals utilize glutamate as a neurotransmitter. This study demonstrates the presence of GABA‐immunoreactivity in mossy fibre axons and terminals of the monkey at the electron microscopic level. We combined Golgi impregnation to identify CA3 pyramidal neurones, with postembedding immunocytochemistry to characterize the inputs to the identified cells. GABA immunoreactivity was present in mossy fibre terminals that made synaptic contact with complex embedded spines of identified Golgi‐impregnated CA3 pyramidal neurones. GABA immunoreactivity could be demonstrated in serial sections of the same mossy fibre terminals by using 3 different, antisera raised against GABA. In serial sections, the mossy fibre terminals were shown to be immunoreactive for both glutamate and GABA. In contrast, glutamate immunoreactivity but not GABA immunoreactivity was found in other terminals that did not have the morphological characteristics of mossy fibre terminals. GABA immunoreactivity in mossy fibre terminals was also demonstrated in a human surgical specimen of hippocampus.The coexistence of an “excitatory” amino acid and of an “inhibitory” amino acid in the same “excitatory” nerve terminal raises the possibility of corelease of the two transmitters, suggesting that the control of hippocampal neural activity is more complex than hit

ISSN:0092-7317    

DOI:10.1002/cne.903030202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe receptive fields of cells restricted to the D1 cortical barrel territory in the S1 cortex of the rat were examined before and after substantial lesions of the D2 barrel. We tested 131 cells (N = 62, unlesioned controls; N = 69, lesioned animals) for modal latency and response magnitude to standard vibrissal deflections of 1.14 degrees.Lesions ranged in size to encompass 22–95% of the volume of the D2 barrel hollow and 5–75% of its neighbouring septal region, as calculated from cytochrome oxidase and Nissl staining of alternate sections. Negligible loss (mean 1.1%) of other barrel hollows and their septal regions (6.3%) occurred. A mean loss of 58% of the D2 barrel hollow and 27% of its accompanying septa was paralleled by a highly significant deficit in response magnitude (57.3%) p<0.0051 of D1 barrel cells to D2 vibrissal stimulation, when compared with controls. The best‐fit relationship between deficit and volumetric loss of the D2 barrel hollow was linear (regression coefficient −0.91). In the extreme case where 95% loss of D2 barrel hollow occurred, there was a 92% deficit in response of D1 barrel cells to the D2 input. No significant loss in response magnitude to other vibrissae, including the principal D1 input, occurred. Postlesioned animals exhibited some increase in excitability to the D1 vibrissa, and to vibrissae whose principal barrel territories were undamaged (δ, γ, C1). Lesioning of the D2 barrel caused a highly significant mean increase (60%) in latency of residual responses to stimulation of the D2 vibrissal input (15.2 ms controls; 24.3 ms experimentals). No significant changes in response latency to other vibrissae compared to controls occurred. These results suggest that an intact D2 barrel is essential for the generation of responses of D1 barrel cells by the D2 vibrissa, and further imply that surround receptive fields of layer IV barrel cells are largely generated intracortically by barrel‐to‐barrel relay. The implications of these findings to cortical processing of tactile information and plasticity in the somatosensory system

ISSN:0092-7317    

DOI:10.1002/cne.903030203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractOne hundred and twenty‐six cells, sampled in the vicinity of the D1 barreloid in the ventroposterior medial nucleus of the thalamus, were tested for magnitude and latency of response to brief deflections (3 ms; 1.14°) of vibrissae in adult rats under controlled conditions of light urethane anaesthesia. Similar results were achieved for D1 and non‐D‐dominant cells. D1‐dominant cells (N = 76) responded to the centre‐receptive field (D1) vibrissa with a mean of 1.08 spikes per stimulus at modal latencies of 3–12 ms (inter‐quartile range 4–5 ms) and to surrounding vibrissae with a mean of 0.26 spikes per stimulus at latencies of 3–41 ms (inter‐quartile range 5–8 ms). Surround‐receptive fields showed extensive overlap but were reduced and finally eliminated by deepening anaesthesia. A cell‐by‐cell analysis showed no correlation between latency and response magnitude for responses to surround vibrissae. Response magnitudes to the surround‐ and centre‐receptive field inputs for D1‐dominant barrel cells were some 2.5‐ and 1.7‐fold greater, respectively, than for thalamic cells under identical experimental conditions. The latencies to centre‐ and surround‐receptive field inputs for D1‐dominant barrel cells were 2.5 and 10–20 ms later than for thalamus, respectively. These data on a mismatch of latencies for surround‐ and centre‐receptive fields in thalamus and cortex support the notion that surround‐receptive fields of cortical barrel cells are almost entirely constructed intracortically during light an anaesthesia (Armstrong‐James et al., '91), although it is argued that surround‐receptive fields of thalamic cells conceivably could be relaye

ISSN:0092-7317    

DOI:10.1002/cne.903030204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractFreeze‐fracture replicas of hypothalamic arcuate neurons and of Purkinje and granule cells of the cerebellar cortex from adult female rats were assessed in order to test the possible influence of estradiol on nuclear pores. Rats were ovariectomized and injected either with estradiol or with vehicle. An additional group of rats in proestrus was also studied. Pore diameter was not affected by ovariectomy or estrogen treatment. In arcuate neurons, the number of nuclear pores per nuclear membrane area, the total number of pores per nucleus, and the percentage of nuclear pores arranged in clusters were decreased by ovariectomy and increased within 30 minutes after estradiol administration to ovariectomized rats. The effect of estradiol on nuclear pores was sustained for several days; the number of pores and the percentage of pores in clusters reverted to control values by 1 month after the hormonal treatment. None of the above mentioned changes was observed in Purkinje and granule cells of the cerebellar cortex. These results indicate that estradiol may modulate the number and distribution of nuclear pores in arcuate neurons and suggest that the modification of the ultrastructure of the nuclear envelope may be one of the first effects of gonadal steroids on target cell

ISSN:0092-7317    

DOI:10.1002/cne.903030205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis is one of a series of papers aimed at identifying the synaptic output patterns of the local and distant projections of subgroups of pyramidal neurons. The subgroups are defined by the target site to which their main axon projects. Pyramidal neurons in areas 1 and 40 of mouse cerebral cortex were labeled by the retrograde transport of horseradish peroxidase (HRP) transported from severed callosal axons in the contralateral hemisphere. Terminals of the local axon collaterals of these neurons (“intrinsic” terminals) were identified in somatosensory areas 1 and 40, and their distribution and synaptic connectivity were examined. Also examined were the synaptic connections of “extrinsic” callosal axon terminals labeled by lesion induced degeneration consequent to the severing of callosal fibers. A post‐lesion survival time of 3 days was chosen because by this time the extrinsic terminals were all degenerating, whereas the intrinsic terminals were labeled by HRP.Both intrinsic and extrinsic callosal axon terminals occurred in all layers of the cortex where they formed only asymmetrical synapses. Layers II and III contained the highest concentrations of both types of callosal axon terminal. Analyses of serial thin sections through layers II and III in both areas 1 and 40 yielded similar results: 97% of the extrinsic (277 total sample) and of the intrinsic (1215 total sample) callosal axon terminals synapsed onto dendritic spines, likely those of pyramidal neurons; the remainder synapsed onto dendritic shafts of both spiny and nonspiny neurons. Thus the synaptic output patterns of intrinsic vs. extrinsic callosal axon terminals are strikingly similar. Moreover, the high proportion of axospinous synapses formed by both types of terminal contrasts with the proportion of asymmetrical, axospinous synapses that occur in the surrounding neuropil where only about 80% of the asymmetrical synapses are onto spines. This result is in accord with previous quantitative studies of the synaptic connectivities of both extrinsic and intrinsic axonal pathways in the cortex (White and Keller, 1989:Cortical Circuits: Boston: Birkhauser): in all instances, axonal pathways are highly selective for the types of elements with which the

ISSN:0092-7317    

DOI:10.1002/cne.903030206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe central complex is a prominent structure in the insect brain, yet its anatomical organization and functional role is still poorly understood. To facilitate investigations on the physiology of the central complex, this study describes its anatomical organization in the brain of locusts (Schistocerca gregariaandSchistocerca americana) based on an investigation of serotonin immunocytochemistry. Most subdivisions of the central complex including the protocerebral bridge, several layers in the upper division of the central body, and the noduli of the central body are innervated by serotonin‐immunoreactive neurons, while the lower division of the central body does not exhibit serotonin‐like immunoreactivity. Several types of serotonin‐immunoreactive neurons can be distinguished. A system of about 60 columnar neurons innervates the protocerebral bridge, layer III of the upper division of the central body, and the noduli. A group of 15–20 bilateral pairs of serotonin‐immunoreactive neurons connects the posterior optic tubercles with the protocerebral bridge. About ten pairs of neurons with somata in the inferior protocerebrum innervate layer la of the upper division of the central body. In addition, large‐field neurons arborize in layers Ia and Ib of the upper division of the central body and in the lateral accessory lobes. The detailed mapping of serotonin immunoreactivity provides further insight into the anatomical organization of the central complex and suggests that serotonin is a major neuroactive substance within this brai

ISSN:0092-7317    

DOI:10.1002/cne.903030207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractTo determine the morphological relationships among extensor digitorum longus (EDL), tibialis anterior (TA), and semitendinosus (St) motor nuclei in the spinal cord of the cat, these nuclei were retrogradely labeled with three different fluorescent tracers. The fluorochromes‐bisbenzimide, nuclear yellow, and propidium iodide‐were applied by intramuscular injection or soaking the muscle nerve. The positions of the labeled motor nuclei were bilaterally symmetrical The EDL and TA motoneurons were located in close proximity to one another, in the lateral regions of lamina IX in spinal segments L6 and L7. Although the boundaries of each nucleus were tightly opposed, the EDL and TA motor nuclei overlapped minimally, with the somata of EDL motoneurons positioned dorsal to those of TA. The St motor nucleus was located ventromedial to that of EDL and extended from the caudal portion of L6 through S1. Supplemental studies of the reflex effects evoked in EDL, TA, and St muscles by cutaneous nerve stimulation provided physiological observations that maybe related to these anatomical resu

ISSN:0092-7317    

DOI:10.1002/cne.903030208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe presence of ascending auditory inputs from the posteroventral cochlear nucleus (PVCN) to olivocochlear neurons was examined in guinea pig by using the combinationPhaseolus vulgaris‐leucoagglutinin (PHA‐L) anterograde and horseradish peroxidase (HRP) retrograde tract‐tracing technique. By labeling the somata of olivocochlear neurons after injection of HRP into the cochlea and simultaneously labeling terminal endings of PVCN efferent neurons after injection of PHA‐L into PVCN, we observed neuronal connections between these two elements within all regions of the superior olivary Complex known to contain olivocochlear neurons. These regions include the superior paraolivary nucleus, medial nucleus of the trapezoid body, lateral superior olive, and periolivary regions. All possible projection patterns regarding side of input and output of both large (four combinations) and small (two combinations) olivocochlear neurons were observed. However, the most frequently observed pattern was the PVCN projection to a contralaterally located and contralaterally projecting, large olivocochlear neuron. Thus the most prevalent pattern demonstrated a feedback pathway that crossed the brainstem twice. Additional patterns demonstrated pathways that fed back to the same cochlea as well as pathways that fed forward to the opposite

ISSN:0092-7317    

DOI:10.1002/cne.903030209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractIn order to study the morphological characteristics and terminating patterns of the neurons of the trigeminal mesencephalic nucleus (Vme),55 masseteric neurons in Vme in the rat were stained by intracellular injection of horseradish peroxidase (HRP). Labeled cells were distributed throughout the nucleus. These neurons were divided into three types: uni‐ or pseudounipolar (type A, n = 43), bipolar (type B, n = 5), and multipolar cells (type C, n = 7). Each type was further divided into two subtypes according to the largest diameter of the perikarya (type a ≥ 30 μm, type b<30 μm).The central processes of type Aaneurons projected to the following three groups of target nuclei: (1) nuclei functioning as interneurons, including supratrigeminal nucleus (Vsup), intertrigeminal nucleus (Vint), juxta‐trigeminal region (Vjux), and parvicellular nucleus of the pontomedullary reticular formation (PcRF); (2) motor nuclei, including the trigeminal motor nucleus (Vmo), accessory facial nucleus (NVIIacs), accessory abducens nucleus (NVIacs), and a small number of labeled axons in the oculomotor nucleus and trochlear nucleus; (3) sensory nuclei, including the dorsomedial part of the principal trigeminal sensory nucleus (Vpdm) and the dorsomedial part of subnucleus oralis of the trigeminal spinal nucleus (Vodm). Labeled processes were dense in the Vsup, Vmo, and Vpdm.The proprioceptive pathway of the fifth nerve is discussed. Direct projections from type Aaneurons of Vme to the Vpdm and dorsolateral part of the Vsup contribute to conduction of the proprioceptive information from spindles of masticatory muscle to the contralateral thalamus in the rat.Different axon morphology, distribution, terminal branch density, and terminating patterns of type Aaneurons were noted in different functional groups of the projecting nuclei, especially in the Vsup, Vmo, and Vpdm. The highest terminal branching density, the most extensive distribution, and two different types of branching patterns (claw‐like and comb‐like) were observed in Vsup. Selective distribution and single‐beaded or “Y”‐shaped terminal branches were observed in Vmo. In the Vpdm the axtinal branches were sparser than in the Vsup or Vmo, and had an arrangement like the branches of a weeping willow tree. These characteristics of anatomical organization might be related to the function of each

ISSN:0092-7317    

DOI:10.1002/cne.903030210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractOlivocochlear neurons have somata in the superior olivary complex and provide an efferent innervation to the cochlea. One subgroup of olivocochlear neurons, medial olivocochlear neurons, sends fibers to innervate the cochlear outer hair cells. En route to the cochlea, medial olivocochlear fibers give off branches to the ventral cochlear nucleus, the first auditory center of the brain. This study examines the cochlear‐nucleus branches of medial olivocochlear fibers, comparing those from fibers that innervate the cochlear base with those from fibers that innervate the cochlear apex. Basal fibers give off dorsal branches to the granule cell lamina and ventral branches to the auditory nerve root. Apical fibers give off few dorsal branches but many ventral branches that terminate rostrally to the nerve root. This cochleotopic mapping of medial olivocochlear branches corresponds in a general way to that of afferent fibers. Unlike afferent fibers, however, the branches terminate primarily along the edges of the cochlear nucleus. In the mouse, the particular edges of termination are (1) the medial border of the ventral cochlear nucleus where it meets the underlying vestibular nerve root, and (2) the border between the ventral cochlear nucleus and the granule cell lamina. Neurons and dendrites of these border regions may thus integrate efferent and afferent information in a frequency‐specific man

ISSN:0092-7317    

DOI:10.1002/cne.903030211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY