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Sandler, Robert; Smith, A. David
doi: 10.1002/cne.903030202pmid: 1672874
One 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.
Armstrong‐James, Michael; Callahan, Christopher A.; Friedman, Michael A.
doi: 10.1002/cne.903030203pmid: 1707420
The 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.
Armstrong‐James, Michael; Callahan, Christopher A.
doi: 10.1002/cne.903030204pmid: 2013636
One 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 relayed in other cortical states or serve a role in plasticity.
Perez, Julio; Hernandez, Pedro; Garcia‐Segura, Luis M.
doi: 10.1002/cne.903030205pmid: 2013637
Freeze‐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 cells.
White, Edward L.; Czeiger, David
doi: 10.1002/cne.903030206pmid: 2013638
This 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.
doi: 10.1002/cne.903030207pmid: 2013639
The 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 gregaria and Schistocerca 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 brain structure.
Hoover, J. E.; Durkovic, R. G.
doi: 10.1002/cne.903030208pmid: 1707421
To 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 results.
Thompson, Ann M.; Thompson, Glenn C.
doi: 10.1002/cne.903030209pmid: 2013640
The presence of ascending auditory inputs from the posteroventral cochlear nucleus (PVCN) to olivocochlear neurons was examined in guinea pig by using the combination Phaseolus 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 cochlea.
Luo, P. F.; Wang, B. R.; Peng, Z. Z.; Li, J. S.
doi: 10.1002/cne.903030210pmid: 2013641
In 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).
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