journal article
LitStream Collection
Home
Metzger, Martin; Jiang, Shucui; Wang, Jizhong; Braun, Katharina
doi: 10.1002/(SICI)1096-9861(19961202)376:1<1::AID-CNE1>3.0.CO;2-7pmid: 8946281
The mediorostral neostriatum/hyperstriatum ventrale (MNH) and neostriatum dorsocaudale (Ndc) of the domestic chick are crucially involved in auditory filial imprinting, whereas the lobus parolfactorius (LPO) seems to be involved in the emotional modulation of behavior. Because there is evidence that MNH and Ndc are akin to higher association areas in mammals, the present study evaluates the dopaminergic and thalamic input to these areas, as well as to the avian caudate/putamen homologue LPO, by using retrograde pathway tracing, together with dopamine (DA) and tyrosine hydroxylase (TH) immunohistochemistry. By combining DA immunohistochemistry with retrograde fluorescent tracing, we demonstrated that dopaminergic afferents to the MNH and Ndc arise mainly from the area ventralis, whereas the main dopaminergic input to the LPO arises from the substantia nigra. The main thalamic input to the MNH and LPO arises from the dorsal thalamic nuclei, n. dorsomedialis anterior and n. dorsolateralis anterior, whereas the thalamic input to the Ndc arises from the n. dorsolateralis posterior and n. subrotundus. Furthermore, there are reciprocal intratelencephalic connections between distinct parts of the neostriatum caudale and the mediorostral neostriatum. DA‐immunoreactive (ir) fibers are present at moderate densities in the MNH and Ndc and at high densities in the LPO. At the ultrastructural level, DA‐ and TH‐ir axon terminals in the MNH and Ndc form predominantly symmetric synaptic contacts with dendritic shafts, which are often situated in close vicinity to unstained terminals. These results indicate that the general organization of dopaminergic afferents to the chick telecephalon is similar to that of the mesotelencephalic dopaminergic subsystems in mammals such as the mesostriatal and mesolimbocortical DA system. © 1996 Wiley‐Liss, Inc.
Martínez, Albert; Lübke, Joachim; Del Río, Jose Antonio; Soriano, Eduardo; Frotscher, Michael
doi: 10.1002/(SICI)1096-9861(19961202)376:1<28::AID-CNE2>3.0.CO;2-Qpmid: 8946282
Chandelier cells are specialized cortical GABAergic neurons that establish synaptic contacts exclusively with the axon initial segments of principal neurons. They are found in all regions of the hippocampal formation. Here we describe their morphological features in the hilus and in regions CA1 and CA3 by using Golgi/electron microscopy. Attempts were also made to identify the target neurons of chandelier cells in the hilus and entorhinal cortex.
Ma, Weiya; Ribeiro‐Da‐Silva, A.; De Koninck, Y.; Radhakrishnan, V.; Henry, J.L.; Cuello, A.C.
doi: 10.1002/(SICI)1096-9861(19961202)376:1<45::AID-CNE3>3.0.CO;2-Opmid: 8946283
A quantitative analysis of substance P (SP)‐immunoreactive (IR) terminals contacting physiologically characterized dorsal horn neurons was performed. Three types of neuron were studied: nociceptive specific (NS) from lamina I (n = 3), wide dynamic range (WDR) from laminae II‐IV (n = 3), and nonnociceptive (NN) from lamina IV (n = 3). The nociceptive response of focus was a slow, prolonged depolarization to noxious stimuli, because this response was previously shown to be blocked by selective neurokinin‐1 (NK‐1) receptor antagonists.
Van Bockstaele, E.J.; Colago, E.E.O.; Moriwaki, A.; Uhl, G.R.
doi: 10.1002/(SICI)1096-9861(19961202)376:1<65::AID-CNE4>3.0.CO;2-Mpmid: 8946284
We have recently shown, by using immunoelectron microscopy, that the mu‐opioid receptor (μOR) is prominently distributed within noradrenergic perikarya and dendrites of the nucleus locus coeruleus (LC), many of which receive excitatory‐type (i.e., asymmetric) synaptic contacts from unlabeled axon terminals. To characterize further the neurotransmitter present in these afferent terminals, we examined in the present study the ultrastructural localization of an antipeptide sequence unique to the μOR in sections that were also dually labeled for the opioid peptide leucine‐enkephalin (L‐ENK). Immunogold‐silver labeling for μOR was localized to extrasynaptic portions of the plasma membranes of perikarya and dendrites. The μOR‐labeled dendrites were usually postsynaptic to axon terminals containing heterogeneous types of synaptic vesicles and forming asymmetric synaptic specializations characteristic of excitatory‐type synapses. The majority of these were immunolabeled for the endogenous opioid peptide L‐ENK. Some μOR‐labeled dendrites received synaptic contacts from unlabeled axon terminals in fields containing L‐ENK immunoreactivity. In such cases, the μOR‐labeled dendrites were in proximity to L‐ENK axon terminals that contained intense peroxidase labeling within large dense core vesicles along the perimeter of the axoplasm. These results indicate that L‐ENK may be released by exocytosis from the dense core vesicles and diffuse within the extracellular space to reach μOR sites on the postsynaptic dendrite or dendrites of other neighboring neurons. The present study also reveals that unlabeled terminals apposed to μOR‐labeled dendrites may contain other opioid peptides, such as methionine‐enkephalin. These data demonstrate several sites where endogenous opioid peptides may interact with μOR receptive sites in the LC and may provide an anatomical substrate for the LC's involvement in mechanisms of opiate dependence and withdrawal. © 1996 Wiley‐Liss, Inc.
Verwer, R.W.H.; Van Vulpen, E.H.S.; Van Uum, J.F.M.
doi: 10.1002/(SICI)1096-9861(19961202)376:1<75::AID-CNE5>3.0.CO;2-Lpmid: 8946285
The prefrontal cortex (PFC) and the amygdala are involved in a number of common functions, such as emotional and social behavior, stress, visceral functions, ingestive behavior, self‐stimulation, and certain aspects of learning and memory. The amygdala massively projects to the PFC and may play a role in the developmental plasticity reported for several of these functions. We have studied the normal postnatal development of the amygdaloid projections to the rat prefrontal cortex by using the retrogradely transported fluorescent dye fast blue and the anterograde tracer Phaseolus vulgaris‐leucoagglutinin (PHA‐L). Shortly after birth some fibers were observed in the frontal pole of the rat brain. These fibers were scattered throughout all prefrontal cortical areas. The majority of the amygdaloid cells contributing to this pattern at that stage of development were located in the anterior and ventral basolateral nuclei, whereas a minority were located in the posterior basolateral nucleus. The transition from a diffuse fiber distribution to a characteristic bilaminar pattern occurred around postnatal day 12 in the lateral and rostral medial PFC. The PHA‐L injections confirmed the existence of a topographical organization of the amygdalo‐prefrontocortical projections. Our observations suggest that the development of amygdala innervation of the PFC parallels the emergence of PFC cytoarchitectural organization. © 1996 Wiley‐Liss, Inc.
Tobet, Stuart A.; Chickering, Troy W.; Sower, Stacia A.
doi: 10.1002/(SICI)1096-9861(19961202)376:1<97::AID-CNE6>3.0.CO;2-Jpmid: 8946286
Gonadotropin releasing‐hormone (GnRH) regulates the hypothalamo‐pituitary‐gonadal axis in vertebrates. The regulation of GnRH is intimately related to information from the olfactory system. Additionally, GnRH neurons are thought to be derived from progenitor cells in medial olfactory placodes. The present experiments were conducted to characterize the earliest development of GnRH neurons in lamprey and to determine their relationship to cells and fibers derived from the olfactory system. Eggs from fertile adult sea lamprey were fertilized in the laboratory, and larvae were maintained for up to 100 days. GnRH neurons were visualized within the lamprey preoptic area and hypothalamus as soon as GnRH was detectable (22 days after fertilization). The number of neurons increased with age through day 100. GnRH neurons were never seen within the olfactory system. The cells and fibers of the olfactory system were identified using the lectin, Grifonia Simplicifolia‐1 (GS‐1). Overlap between the olfactory and GnRH systems were at the level of fiber projections. GS‐1 reactive cells of apparent placodal origin did not enter the region of the preoptic area or hypothalamus that contained GnRH neurons. Recently divided cells were labeled with the thymidine analog, bromodeoxyuridine (BrdU). The positions of BrdU‐labeled cells after different survival times suggest a predominant medial‐lateral radial neuron migration with a small number in positions suggestive of migration between the olfactory epithelium and the telencephalic lobes. Regardless of survival time, these cells were always found close to their entry point into the brain, suggesting minimal rostral‐caudal migration. Based on these results, we hypothesize that GnRH neurons in developing lamprey originate within proliferative zones of the diencephalon and not in the olfactory system. Based on the overlap of olfactory‐ and GnRH‐containing fibers from prolarval stages to metamorphosis, olfactory stimuli may play a major role in the regulation of GnRH secretion in lamprey. © 1996 Wiley‐Liss, Inc.
Hof, Patrick R.; Ungerleider, Leslie G.; Webster, Maree J.; Gattass, Ricardo; Adams, Michelle M.; Sailstad, Cynthia A.; Morrison, John H.
doi: 10.1002/(SICI)1096-9861(19961202)376:1<112::AID-CNE7>3.0.CO;2-6pmid: 8946287
Previous studies of the primate cerebral cortex have shown that neurofilament protein is present in pyramidal neuron subpopulations displaying specific regional and laminar distribution patterns. In order to characterize further the neurochemical phenotype of the neurons furnishing feedforward and feedback pathways in the visual cortex of the macaque monkey, we performed an analysis of the distribution of neurofilament protein in corticocortical projection neurons in areas V1, V2, V3, V3A, V4, and MT. Injections of the retrogradely transported dyes Fast Blue and Diamidino Yellow were placed within areas V4 and MT, or in areas V1 and V2, in 14 adult rhesus monkeys, and the brains of these animals were processed for immunohistochemistry with an antibody to nonphosphorylated epitopes of the medium and heavy molecular weight subunits of the neurofilament protein. Overall, there was a higher proportion of neurons projecting from areas V1, V2, V3, and V3A to area MT that were neurofilament protein‐immunoreactive (57–100%), than to area V4 (25–36%). In contrast, feedback projections from areas MT, V4, and V3 exhibited a more consistent proportion of neurofilament protein‐containing neurons (70–80%), regardless of their target areas (V1 or V2). In addition, the vast majority of feedback neurons projecting to areas V1 and V2 were located in layers V and VI in areas V4 and MT, while they were observed in both supragranular and infragranular layers in area V3. The laminar distribution of feedforward projecting neurons was heterogeneous. In area V1, Meynert and layer IVB cells were found to project to area MT, while neurons projecting to area V4 were particularly dense in layer III within the foveal representation. In area V2, almost all neurons projecting to areas MT or V4 were located in layer III, whereas they were found in both layers II–III and V–VI in areas V3 and V3A. These results suggest that neurofilament protein identifies particular subpopulations of corticocortically projecting neurons with distinct regional and laminar distribution in the monkey visual system. It is possible that the preferential distribution of neurofilament protein within feedforward connections to area MT and all feedback projections is related to other distinctive properties of these corticocortical projection neurons. © 1996 Wiley‐Liss, Inc.
Hale, Irene L.; Fisher, Steven K.; Matsumoto, Brian
doi: 10.1002/(SICI)1096-9861(19961202)376:1<128::AID-CNE8>3.0.CO;2-5pmid: 8946288
Cytochalasin D (CD) interferes with the morphogenesis of outer segment disc membrane in photoreceptors. Disruption of either the actin network in the ciliary stalk, where membrane evagination is initiated, or the actin core of the calycal processes, whose position could define the disc perimeter, could be responsible. We have attempted to determine which of these local F‐actin populations is involved in membrane morphogenesis and what step in the process is actin‐dependent. Biocytin accumulation in nascent discs, detected by fluorescent avidin and laser scanning confocal microscopy (LSCM), provided a means of labeling abnormal discs and a measure of disc membrane addition. F‐actin content and distribution were assessed using fluorescent phalloidin and LSCM. First, we examined the effects of a range of CD dosages (0.1, 1.0, or 10.0 μM) on rod photoreceptors in Xenopus laevis eyecup cultures. Ectopic outgrowth of discs, evaluated by LSCM and transmission electron microscopy (TEM), occurred at each concentration. Phalloidin labeling intensified in the ciliary stalk with increasing CD concentration, indicating F‐actin aggregation. In contrast, it diminished in the calycal processes, indicating dispersal; TEM showed that calycal process collapse ensued. Disruption was evident at a lower concentration in the ciliary stalk (0.1 μM) than in the calycal processes (1.0 μM). TEM confirmed that the calycal processes remained intact at 0.1 μM. Thus, CD's action on the ciliary stalk network is sufficient to disrupt disc morphogenesis. Second, we examined the effect of CD on temperature‐induced acceleration of the rate of disc formation. In the absence of CD, a 10°C temperature shift increased the disc formation rate nearly three‐fold. CD (5 μM) caused a 94% inhibition (P < 0.025) of this response; yet, the rate of membrane addition to ectopically growing discs exhibited the expected three‐fold increase. Thus, CD's action interferes with the generation of new discs. © 1996 Wiley‐Liss, Inc.
Showing 1 to 10 of 11 Articles