bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mirror neurons responding to the observation of ingestive and communicative mouth actions in the monkey ventral premotor cortex
Authors: Ferrari Pier Francesco , Gallese Vittorio , Rizzolatti Giacomo , Fogassi Leonardo 
Published: December 2004

AbstractIn the ventral premotor cortex (area F5) of the monkey there are neurons that discharge both when the monkey performs specific motor actions and when it observes another individual performing a similar action (mirror neurons). Previous studies on mirror neurons concerned hand actions. Here, we describe the mirror responses of F5 neurons that motorically code mouth actions. The results showed that about one‐third of mouth motor neurons also discharge when the monkey observes another individual performing mouth actions. The majority of these ‘mouth mirror neurons’ become active during the execution and observation of mouth actions related to ingestive functions such as grasping, sucking or breaking food. Another population of mouth mirror neurons also discharges during the execution of ingestive actions, but the most effective visual stimuli in triggering them are communicative mouth gestures (e.g. lip smacking). Some also fire when the monkey makes communicative gestures. These findings extend the notion of mirror system from hand to mouth action and suggest that area F5, the area considered to be the homologue of human Broca's area, is also involved in communicative functions.
Effects of neonatal amygdala lesions on [125I] neurotensin binding in specific brain areas of adult rat
Authors: Bouwmeester Hans , Snapper Jolanda , Ronken Eric , Kruse Chris G. , Van Ree Jan M. 
Published: December 2004

AbstractNeurotensin has been implicated in the pathophysiology of schizophrenia. The neonatal amygdala lesion in rat has been proposed to be a neurodevelopmental model for some aspects of schizophrenia. [125I] Neurotensin binding was assessed in adult rats using in vitro autoradiography following a lesion of the basolateral amygdala at postnatal day 7 (Pd 7) or postnatal day 21 (Pd 21). The Pd 7 and Pd 21 lesions differentially affected neurotensin receptor densities in the hippocampal complex and (less pronounced) in the dopaminergic cell regions, implying a neurodevelopmental cause. These results may be of relevance for the involvement of neurotensin in the pathogenesis of schizophrenia.
Blockade of cortical muscarinic but not NMDA receptors prevents a novel taste from becoming familiar
Authors: Gutiérrez Ranier , Téllez Luis A. , Bermúdez‐Rattoni Federico 
Published: December 2004

AbstractExposure to a novel taste solution in the rat is followed by a decrease in its intake known as neophobia. This effect gradually disappears, and consumption increases from the second presentation of the taste (attenuation of neophobia), reflecting that the animal learned that it is safe to drink it. Conversely, if gastric malaise is induced after first intake, the rat will develop a long‐lasting aversion (conditioned taste aversion). Previous attempts to elucidate the physiological nature of taste memory trace stems only from procedures that require malaise to measure taste memory. Here we assess the relevance of both muscarinic and N‐methyl‐d‐aspartate receptors, known to be involved in conditioned taste aversion, on taste memory using a nonaversive procedure (attenuation of neophobia learning). Attenuation of neophobia was impaired by the muscarinic receptor antagonist, scopolamine, microinjected 20 min before, immediately after or up to 2 h after the first taste experience, suggesting that muscarinic receptors are involved in the acquisition and consolidation of attenuation of neophobia learning. However, the N‐methyl‐d‐aspartate receptor antagonist, d,l‐2‐amino‐5‐phosphonovaleric acid, did not affect attenuation of neophobia even when the same dose of the drug was able to disrupt conditioned taste aversion learning, which suggests that attenuation of neophobia learning would be independent of N‐methyl‐d‐aspartate receptors activity in the insular cortex. The neophobic response induced by strong saccharin presentation was not affected by either of the treatments given, which rules out any impairment in taste perception. These results indicate that while cortical muscarinic receptors are important in the formation and consolidation of safe memory trace, N‐methyl‐d‐aspartate receptor activity appears to be noncritical.
Protein kinase C and ERK involvement in dendritic spine plasticity in cultured rodent hippocampal neurons
Authors: Goldin Miri , Segal Menahem 
Published: December 2004

AbstractThe roles of protein kinase C and the MAP‐kinase extracellular receptor kinase in structural changes associated with long‐term potentiation of network activity were examined in cultured hippocampal neurons. A brief exposure to a conditioning medium that favours activation of the N‐methyl‐d‐aspartate receptor caused a rapid and specific increase in staining of neurons for the phosphorylated form of extracellular receptor kinase as well as of cyclic AMP response element binding protein. Exposure of the cultures to the conditioning medium was followed by a protein synthesis‐dependent formation of novel dendritic spines. An extracellular receptor kinase antagonist PD98059 blocked the phosphorylated form of extracellular receptor kinase response and the formation of novel spines. A selective protein kinase C agonist, phorbol 12‐myristate 13‐acetate, caused activation of extracellular receptor kinase and formation of novel spines. The protein kinase C antagonist GF109203x blocked the phosphorylated form of extracellular receptor kinase response and the subsequent spine formation by phorbol 12‐myristate 13‐acetate. Both the conditioning medium and phorbol 12‐myristate 13‐acetate caused a delayed increase in mean amplitude of miniature excitatory postsynaptic currents recorded in the hippocampal neurons. These results indicate that activation of extracellular receptor kinase mediates the effect of a conditioning protocol on the formation of dendritic spines. The formation of novel spines was associated with long‐term increase in network activity and functional synaptic connectivity among the cultured neurons.
High level of mGluR7 in the presynaptic active zones of select populations of GABAergic terminals innervating interneurons in the rat hippocampus
Authors: Somogyi Peter , Dalezios Yannis , Luján Rafael , Roberts J. David B. , Watanabe Masahiko , Shigemoto Ryuichi 
Published: December 2004

AbstractThe release of neurotransmitters is modulated by presynaptic metabotropic glutamate receptors (mGluRs), which show a highly selective expression and subcellular location in glutamatergic terminals in the hippocampus. Using immunocytochemistry, we investigated whether one of the receptors, mGluR7, whose level of expression is governed by the postsynaptic target, was present in GABAergic terminals and whether such terminals targeted particular cells. A total of 165 interneuron dendritic profiles receiving 466 synapses (82% mGluR7a‐positive) were analysed. The presynaptic active zones of most GAD‐(77%) or GABA‐positive (94%) synaptic boutons on interneurons innervated by mGluR7a‐enriched glutamatergic terminals (mGluR7a‐decorated) were immunopositive for mGluR7a. GABAergic terminals on pyramidal cells and most other interneurons in str. oriens were mGluR7a‐immunonegative. The mGluR7a‐decorated cells were mostly somatostatin‐ and mGluR1α‐immunopositive neurons in str. oriens and the alveus. Their GABAergic input mainly originated from VIP‐positive terminals, 90% of which expressed high levels of mGluR7a in the presynaptic active zone. Parvalbumin‐positive synaptic terminals were rare on mGluR7a‐decorated cells, but on these neurons 73% of them were mGluR7a‐immunopositive. Some type II synapses innervating interneurons were immunopositive for mGluR7b, as were some type I synapses. Because not all target cells of VIP‐positive neurons are known it has not been possible to determine whether mGluR7 is expressed in a target‐cell‐specific manner in the terminals of single GABAergic cells. The activation of mGluR7 may decrease GABA release to mGluR7‐decorated cells at times of high pyramidal cell activity, which elevates extracellular glutamate levels. Alternatively, the presynaptic receptor may be activated by as yet unidentified endogenous ligands released by the GABAergic terminals or the postsynaptic dendrites.
Glutamatergic input governs periodicity and synchronization of bursting activity in oxytocin neurons in hypothalamic organotypic cultures
Authors: Israel Jean‐Marc , Le Masson Gwendal , Theodosis Dionysia T. , Poulain Dominique A. 
Published: December 2004

AbstractDuring suckling, oxytocin (OT) neurons display a bursting electrical activity, consisting of a brief burst of action potentials which is synchronized throughout the OT neuron population and which periodically occurs just before each milk ejection in the lactating rat. To investigate the basis of such synchronization, we performed simultaneous intracellular recordings from pairs of OT neurons identified retrospectively by intracellular fluorescent labelling and immunocytochemistry in organotypic slice cultures derived from postnatal rat hypothalamus. A spontaneous bursting activity was recorded in 65% of OT neurons; the remaining showed only a slow, irregular activity. Application of OT triggered bursts in nonbursting neurons and accelerated bursting activity in spontaneously bursting cells. These cultures included rare vasopressinergic neurons showing no bursting activity and no reaction to OT. Bursts occurred simultaneously in all pairs of bursting OT neurons but, as in vivo, there were differences in burst onset, amplitude and duration. Coordination of firing was not due to electrotonic coupling because depolarizing one neuron in a pair had no effect on the membrane potential of its partner and halothane and proprionate did not desynchronize activity. On the other hand, bursting activity was superimposed on volleys of excitatory postsynaptic potentials (EPSPs) which occurred simultaneously in pairs of neurons. EPSPs, and consequently action potentials, were reversibly blocked by the non‐NMDA glutamatergic receptor antagonist CNQX. Taken together, these data, obtained from organotypic cultures, strongly suggest that a local hypothalamic network governs synchronization of bursting firing in OT neurons through synchronous afferent volleys of EPSPs originating from intrahypothalamic glutamatergic inputs.
Selective modifications in GAD67 mRNA levels in striatonigral and striatopallidal pathways correlate to dopamine agonist priming in 6‐hydroxydopamine‐lesioned rats
Authors: Carta A.R. , Fenu S. , Pala P. , Tronci E. , Morelli M. 
Published: December 2004

AbstractThe present study investigated long‐term alterations in striatal gene expression after single exposure of unilaterally 6‐hydroxydopamine‐lesioned rats to different dopamine agonists (priming). Rats were primed with the D1 agonist SKF38393 (10 mg/kg), the D2/D3 agonist quinpirole (0.2 mg/kg), the dopamine precursor L‐DOPA (50 mg/kg) or with vehicle (drug‐naive), and GAD67, dynorphin and enkephalin mRNAs were evaluated in the striatum by in situ hybridization, 3 days after priming. To evaluate GAD67 mRNA in striatonigral and striatopallidal neurons, identified as enkephalin (−) and (+) neurons, double‐labelling in situ hybridization was used. Drug‐naive lesioned rats showed an increase in GAD67 mRNA in enkephalin (−) and (+) neurons, an increase in enkephalin and a decrease in dynorphin mRNAs. Priming with either SKF38393 or quinpirole further increased GAD67 mRNA in enkephalin (−) and (+) neurons, however, while SKF38393 produced a high and unbalanced activation toward enkephalin (−) neurons, after quinpirole the increase was of low intensity and similar in the two pathways. Dynorphin mRNA was increased by SKF38393 but not by quinpirole, whereas enkephalin mRNA was not changed by either priming. L‐DOPA produced a high and similar increase in GAD67 mRNA in enkephalin (−) and (+) neurons. Priming differentially affected peptides and GAD67 mRNA in striatopallidal and striatonigral neurons depending on the dopamine agonist used. The degree of enduring overactivity of the striatopallidal and striatonigral pathways may be related to the ability of L‐DOPA and D1 or D2/D3 receptor agonists to prime motor behavioural responses and to produce dyskinetic side‐effects.
The opposite effects of stress on dendritic spines in male vs. female rats are NMDA receptor‐dependent
Authors: Shors T. J. , Falduto J. , Leuner B. 
Published: December 2004

AbstractDendritic spines in the hippocampus are sources of synaptic contact that may be involved in processes of learning and memory [Moser (1999) Cell. Mol. Life Sci., 55, 593–600]. These structures are sensitive to sex differences as females in proestrus possess a greater density than males and females in other stages of the estrous cycle [Woolley et al.. (1990) J. Neurosci., 10, 4035–4039]. Moreover, exposure to an acute stressful event increases spine density in the male hippocampus but decreases spine density in the female hippocampus [Shors et al.. (2001) J. Neurosci., 21, 6292–6297]. Here we demonstrate that antagonism of N‐methyl‐d‐aspartate (NMDA) receptors prevents the increase in spine density as females transition from diestrus 2 to proestrus, when estrogen levels are rising. Antagonism of NMDA receptors during exposure to the stressful event also prevented the changes in spine density in males and females, despite differences in the direction of these effects. Thus, the stress‐induced increase in spine density was prevented in the male hippocampus as was the stress‐induced decrease in spine density in the female hippocampus. NMDA receptor antagonism during exposure to the stressful event did not alter corticosterone levels or the corticosterone response to stress. These data suggest that both increases and decreases in spine density can be dependent on NMDA receptor activation.
Pre‐ and postsynaptic contributions of voltage‐dependent Ca2+ channels to nociceptive transmission in rat spinal lamina I neurons
Authors: Heinke B. , Balzer E. , Sandkühler J. 
Published: December 2004

AbstractActivation of voltage‐dependent Ca2+ channels (VDCCs) is critical for neurotransmitter release, neuronal excitability and postsynaptic Ca2+ signalling. Antagonists of VDCCs can be antinociceptive in different animal pain models. Neurons in lamina I of the spinal dorsal horn play a pivotal role in the processing of pain‐related information, but the role of VDCCs to the activity‐dependent Ca2+ increase in lamina I neurons and to the synaptic transmission between nociceptive afferents and second order neurons in lamina I is not known. This has now been investigated in a lumbar spinal cord slice preparation from young Sprague–Dawley rats. Microfluorometric Ca2+ measurements with fura‐2 have been used to analyse the Ca2+ increase in lamina I neurons after depolarization of the cells, resulting in a distinct and transient increase of the cytosolic Ca2+ concentration. This Ca2+ peak was reduced by the T‐type channel blocker, Ni2+, by the L‐type channel blockers, nifedipine and verapamil, and by the N‐type channel blocker, ω‐conotoxin GVIA. The P/Q‐type channel antagonist, ω‐agatoxin TK, had no effect on postsynaptic [Ca2+]i. The NMDA receptor channel blocker D‐AP5 reduced the Ca2+ peak, whereas the AMPA receptor channel blocker CNQX had no effect. Postsynaptic currents, monosynaptically evoked by electrical stimulation of the attached dorsal roots with C‐fibre and Aδ‐fibre intensity, respectively, were reduced by N‐type channel blocker ω‐conotoxin GVIA and to a much lesser extent, by P/Q‐type channel antagonist ω‐agatoxin TK, and the L‐type channel blockers verapamil, respectively. No difference was found between unidentified neurons and neurons projecting to the periaqueductal grey matter. This is the first quantitative description of the relative contribution of voltage‐dependent Ca2+ channels to the synaptic transmission in lamina I of the spinal dorsal horn, which is essential in the processing of pain‐related information in the central nervous system.
Diversity beyond variance: modulation of firing rates and network coherence by GABAergic subpopulations
Authors: Földy Csaba , Aradi Ildiko , Howard Allyson , Soltesz Ivan 
Published: December 2004

AbstractComputational modelling studies have revealed that heterogeneity in interneuronal networks can powerfully modulate firing rates, responses to excitatory inputs, theta‐gamma oscillations and network synchrony. In these previous studies, heterogeneity was represented by the degree of variance in various interneuronal synaptic and cellular parameters. However, a major characteristic of gamma‐amino‐butyric‐acid‐ergic (GABAergic) synaptic and interneuronal populations is the presence of distinct subgroups, which variance‐based approaches cannot fully address. Here we apply an information theory‐based measure of diversity, the Shannon–Wiener diversity index (equivalent to entropy), which takes into account both the number and relative abundance of categories within a population. Computational modelling data and experimental dynamic clamp results show that increasing the diversity index in the somatically injected inhibitory post synaptic currents (IPSC) peak conductances modulates the firing rates of CA1 pyramidal cells in a predictable manner that depends on both the mean and variance of the IPSC conductance. Furthermore, increases in the diversity index in interneuronal populations strongly decreased network coherence, even when population variance, the previously applied measure of heterogeneity, remained unchanged. These modelling and experimental results reveal a new approach to the study of interneuronal heterogeneity, and demonstrate the modulation of principal cell firing rates and interneuronal network coherence by parameter clustering at both the synaptic and cellular levels.
Host mortality, predation and the evolution of parasite virulence
Authors: Choo Karen , Williams Paul D. , Day Troy 
Published: December 2004

AbstractOne of the most accepted views in the theoretical literature on virulence evolution is that a parasite's virulence will evolve to higher levels when its host's background mortality rate increases. Surprisingly, however, although many sources of background mortality involve predation, there has not yet been any theoretical research that explicitly considers how the dynamics of this important ecological interaction affects virulence evolution. Here, we consider how predation affects virulence evolution by explicitly introducing a predator into a classical susceptible–infected–susceptible epidemiological model. We find that, contrary to previous predictions, different sources of host mortality affect virulence evolution in different ways. Moreover, the way in which virulence evolution is affected depends on how tightly coupled the predator's dynamics are to the host population, and this can result in somewhat counterintuitive results. For example, indirect ecological effects can cause elevated host mortality to result in the evolution of lower parasite virulence, even if this elevated mortality arises from factors unrelated to predation.
Invasive aliens and sampling bias
Authors: Simons Andrew M. 
Published: December 2004

AbstractTwo hypotheses have been proposed to explain the observation of increased vigour of invasive alien plants in their nonindigenous ranges: phenotypic plasticity, and the post‐invasion evolution of increased competitive ability (EICA). Here I specify how a general pattern of increased vigour may result from sampling bias. Ignoring failed invasions can account for the illusion of increased vigour over a broad range of assumptions. Plasticity and EICA need not be viewed as explanations for a general pattern of increased vigour even if they are the mechanisms underlying every occurrence.
Spatial heterogeneity reduces temporal variability in stream insect communities
Authors: Brown Bryan L. 
Published: December 2004

AbstractAlthough all natural systems are heterogeneous, the direct influence of spatial heterogeneity on most ecological variables is unknown. In many systems, spatial heterogeneity is positively correlated with both microhabitat refugia and species richness. Both an increased number of microhabitat refugia and the effects of statistical averaging via increased species richness should lead to an inverse relationship between spatial heterogeneity and variability in community composition. To test this prediction, I measured diversity and temporal variability of invertebrate communities in a northern New Hampshire stream along a natural gradient of spatial heterogeneity formed by variation in stream substrates. On average, there was a 42% decrease in community variability along a gradient of increasing heterogeneity. This pattern was robust to changes in metrics of both heterogeneity and community variability. There was also a significant positive relationship between taxon richness and spatial heterogeneity with predicted taxon richness increasing c. 1.5× along the heterogeneity gradient. By resampling community abundance data, I estimated that statistical averaging accounted for only 4% of the observed decrease in community variability in this study. I concluded that the remaining decrease was very likely explained by a greater number of refugia from predation and/or flooding in high‐heterogeneity habitats. The results of this study suggest that maximizing heterogeneity in ecological restoration programmes may promote temporally stable and diverse communities and may aid in responsible management of aquatic resources.
Mechanisms of coexistence of a bacteria and a bacteriophage in a spatially homogeneous environment
Authors: Lythgoe K. A. , Chao L. 
Published: December 2004

AbstractWhen bacteriophage are added to laboratory bacteria populations, bacteria mutants that are resistant to the phage quickly dominate the population. The phage will only persist in the long‐term if there are sufficient bacteria in the population that show susceptibility to the phage. We investigated the mechanisms allowing for coexistence by adding the virulent bacteriophage φ6 to cultures of the bacterium Pseudomonas syringae pv. phaseolicola in a spatially homogeneous environment. We saw large differences between replicate cultures, in particular when one or both of the species persisted. These differences can be explained by variation in the timing of the appearance of various resistant phenotypes in the bacteria populations before the phage were added, which determines their relative frequencies within the populations. Although these resistant phenotypes have similar fitnesses in the presence and in the absence of the phage, they have a profound effect on the persistence of the phage. Our results give a clearer understanding of the ecological mechanisms that lead to the coexistence of bacteria and virulent phage in environments where there are no spatial refuges available to the bacteria population.