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51.
This paper is the twentieth installment of our annual review of research concerning the opiate system. It summarizes papers published during 1997 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; eating and drinking; alcohol; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurologic disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunologic responses; and other behaviors. 相似文献
52.
Mechanisms that cause nonrandom patterns of parasite distribution among host individuals may influence the population and
evolutionary dynamics of both parasites and hosts, but are still poorly understood. We studied whether survival, reproduction,
and behavioral responses of fleas (Xenopsylla conformis) changed with the age of their rodent hosts (Meriones crassus), experimentally disentangling two possible mechanisms: (a) differential survival and/or fitness reward of parasites due
to host age, and (b) active parasite choice of a host of a particular age. To explore the first mechanism, we raised fleas
on rodents of two age groups and assessed flea survival as well as the quantity and quality of their offspring. To explore
the second mechanism, three groups of fleas that differed in their previous feeding experience (no experience, experience
on juvenile or experience on adult rodents) were given an opportunity to choose between juvenile and adult rodents in a Y-maze.
Fleas raised on juvenile rodents had higher survival and had more offspring that emerged earlier than fleas raised on adults.
However, fleas did not show any innate preference for juvenile rodents, nor were they able to learn to choose them. In contrast
to our predictions, based on a single previous exposure, fleas learned to choose adult rodents. The results suggest that two
mechanisms—differential survival and fitness reward of fleas, and associative learning by them—affect patterns of flea distribution
between juvenile and adult rodents. The former increases whereas the latter reduces flea densities on juvenile rodents. The
ability of fleas to learn to choose adult but not juvenile hosts may be due to: (a) a stronger stimulus from adults, (b) a
higher profitability of adults in terms of predictability and abundance, or (c) the evolutionary importance of recognizing
adult but not juvenile hosts as representatives of the species. 相似文献
53.
A P system and a constructive membrane-inspired DNA algorithm for solving the Maximum Clique Problem
We present a P system with replicated rewriting to solve the Maximum Clique Problem for a graph. Strings representing cliques are built gradually. This involves the use of inhibitors that control the space of all generated solutions to the problem. Calculating the maximum clique for a graph is a highly relevant issue not only on purely computational grounds, but also because of its relationship to fundamental problems in genomics. We propose to implement the designed P system by means of a DNA algorithm. This algorithm is then compared with two standard papers that addressed the same problem and its DNA implementation in the past. This comparison is carried out on the basis of a series of computational and physical parameters. Our solution features a significantly lower cost in terms of time, the number and size of strands, as well as the simplicity of the biological implementation. 相似文献
54.
Tsoularis A 《Acta biotheoretica》2007,55(3):283-295
In this paper I propose a reinforcement learning model for a predator preying upon two types of prey, the unpalatable (noxious)
models, and the palatable mimics. The latter type of prey resembles the models in appearance so as to derive some protection
from the predator who must avoid the unpalatable models. Essentially the predator is treated as a learning automaton adopting
a simple reinforcement learning strategy in order to increase its consumption of palatable prey and reduce the consumption
of unpalatable ones. The populations of both mimics and models are assumed to grow logistically. 相似文献
55.
Katsunori Motosaka Masayuki Koganezawa Satoko Narikawa Akira Furuyama Kenji Shinozaki Kunio Isono Ichiro Shimada 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2007,193(2):279-283
Acute choice behavior in ingesting two different concentrations of sucrose in Drosophila is presumed to include learning and memory. Effects on this behavior were examined for four mutations that block associative
learning (dunce, rutabaga, amnesiac, and radish). Three of these mutations cause cyclic AMP signaling defects and significantly reduced taste discrimination. The exception
was radish, which affects neither. Electrophysiological recordings confirmed that the sensitivity of taste receptors is almost indistinguishable
in all flies, whether wild type or mutant. These results suggest that food choice behavior in Drosophila involves central nervous learning and memory operating via cyclic AMP signaling pathways. 相似文献
56.
57.
Substances such as acetylcholine and glutamate act as both neurotransmitters and neuromodulators. As neuromodulators, they
change neural information processing by regulating synaptic transmitter release, altering baseline membrane potential and
spiking activity, and modifying long-term synaptic plasticity. Slice physiology research has demonstrated that many neuromodulators
differentially modulate afferent, incoming information compared to intrinsic and recurrent processing in cortical structures
such as piriform cortex, neocortex, and the hippocampus. The enhancement of afferent (external) pathways versus the suppression
at recurrent (internal) pathways could cause cortical dynamics to switch between a predominant influence of external stimulation
to a predominant influence of internal recall. Modulation of afferent versus intrinsic processing could contribute to the
role of neuromodulators in regulating attention, learning, and memory effects in behavior. 相似文献
58.
Roberts PD 《Journal of computational neuroscience》2007,22(3):283-296
Dynamics of spike-timing dependent synaptic plasticity are analyzed for excitatory and inhibitory synapses onto cerebellar
Purkinje cells. The purpose of this study is to place theoretical constraints on candidate synaptic learning rules that determine
the changes in synaptic efficacy due to pairing complex spikes with presynaptic spikes in parallel fibers and inhibitory interneurons.
Constraints are derived for the timing between complex spikes and presynaptic spikes, constraints that result from the stability
of the learning dynamics of the learning rule. Potential instabilities in the parallel fiber synaptic learning rule are found
to be stabilized by synaptic plasticity at inhibitory synapses if the inhibitory learning rules are stable, and conditions
for stability of inhibitory plasticity are given. Combining excitatory with inhibitory plasticity provides a mechanism for
minimizing the overall synaptic input. Stable learning rules are shown to be able to sculpt simple-spike patterns by regulating
the excitability of neurons in the inferior olive that give rise to climbing fibers. 相似文献
59.
60.
Ruizhi Wang Hongjie Wang Ivan Carrera Shaohua Xu Madepalli K. Lakshmana 《The Journal of biological chemistry》2015,290(14):9299-9309
Brain accumulation of neurotoxic amyloid β (Aβ) peptide because of increased processing of amyloid precursor protein (APP), resulting in loss of synapses and neurodegeneration, is central to the pathogenesis of Alzheimer disease (AD). Therefore, the identification of molecules that regulate Aβ generation and those that cause synaptic damage is crucial for future therapeutic approaches for AD. We demonstrated previously that COPS5 regulates Aβ generation in neuronal cell lines in a RanBP9-dependent manner. Consistent with the data from cell lines, even by 6 months, COPS5 overexpression in APΔE9 mice (APΔE9/COPS5-Tg) significantly increased Aβ40 levels by 32% (p < 0.01) in the cortex and by 28% (p < 0.01) in the hippocampus, whereas the increases for Aβ42 were 37% (p < 0.05) and 34% (p < 0.05), respectively. By 12 months, the increase was even more robust. Aβ40 levels increased by 63% (p < 0.001) in the cortex and by 65% (p < 0.001) in the hippocampus. Similarly, Aβ42 levels were increased by 69% (p < 0.001) in the cortex and by 71% (p < 0.011) in the hippocampus. Increased Aβ levels were translated into an increased amyloid plaque burden both in the cortex (54%, p < 0.01) and hippocampus (64%, p < 0.01). Interestingly, COPS5 overexpression increased RanBP9 levels in the brain, which, in turn, led to increased amyloidogenic processing of APP, as reflected by increased levels of sAPPβ and decreased levels of sAPPα. Furthermore, COPS5 overexpression reduced spinophilin in both the cortex (19%, p < 0.05) and the hippocampus (20%, p < 0.05), leading to significant deficits in learning and memory skills. Therefore, like RanBP9, COPS5 also plays a pivotal role in amyloid pathology in vivo. 相似文献