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At least 793 records · Page 44Linked to original sources
PubMed1979

Effects of lithium chloride injections on rank-related fighting, maternal aggression and locust-killing responses in naive and experienced 'TO' strain mice.

Three experiments investigated lithium chloride's (LiCl) effects on three forms of aggression in male 'TO' strain mice. Models of aggression investigated, included attack by preisolated males on male conspecifics (rank-related or intermale fighting), attack by lactating females on male intruders (maternal aggression) and the locust-killing response (a form of predatory aggression?) In the first study, injections of naive male mice with 0.2 and 0.4 mEq of LiCl resulted in marked declines in rank-related fighting. The effects of this treatment on locust killing could not be assessed, as this activity was already at a low incidennce in controls. In a second experiment, LiCl injection had little influence on the locust-killing response in selected, experienced male killer mice. As in Experiment 1, rank-related fighting was suppressed by this treatment. The third experiment revealed that LiCl injections did not influence either maternal aggression or locust killing in naive females and predatory aggression in experienced-killer females. These results provide further support for the contention that these three behaviors have very different physiological bases. The data suggests that one should be cautious when extrapolating between different models of aggression even within the same species.

Aggression↗
PubMed1993

A triple dissociation of memory systems: hippocampus, amygdala, and dorsal striatum.

This study investigated the respective roles of the hippocampus, the amygdala, and the dorsal striatum in learning and memory. A standard set of experimental conditions for studying the effects of lesions to the three brain areas using an 8-arm radial maze was used: a win-shift version, a conditioned cue preference (CCP) version, and a win-stay version. Damage to the hippocampal system impaired acquisition of the win-shift task but not the CCP or win-stay tasks. Damage to the lateral amygdala impaired acquisition of the CCP task but not the win-shift or win-stay tasks. Damage to the dorsal striatum impaired acquisition of the win-stay task but not the win-shift or CCP tasks. These results are consistent with the hypothesis that the mammalian brain may be capable of acquiring different kinds of information with different, more-or-less independent neural systems. A neural system that includes the hippocampus may acquire information about the relationships among stimuli and events. A neural system that includes the amygdala may mediate the rapid acquisition of behaviors based on biologically significant events with affective properties. A neural system that includes the dorsal striatum may mediate the formation of reinforced stimulus-response associations.

Amygdala↗
PubMed1994

Endogenous regulation of the attraction of Aedes aegypti mosquitoes.

Even when host attractants are present, there are times when endogenous physiological mechanisms prevent female mosquitoes from responding to them and engaging in host-seeking behavior. These times include a brief postemergence period, periods of the day determined by a circadian clock, and following a blood meal before and after eggs develop, which are controlled by nervous and humoral mechanisms. Other factors such as age, nutrition, and mating status can further modulate host-seeking behavior. The interplay of these factors affects the frequency at which mosquitoes will approach a host and feed on its blood, thus affecting the rates of parasite acquisition and transmission.

Aedes↗
PubMed1999

Dopamine denervation of specific striatal subregions differentially affects preparation and execution of a delayed response task in the rat.

In the present study, the effects of unilateral or bilateral dopamine denervation of either the dorsal or ventral striatum on the preparation and execution of a delayed response task in the rat were investigated. Animals were instructed to hold a lever pressed down by the presentation of a visual and/or acoustic signal, and were required to hold the lever until a trigger stimulus occurred after an unpredictable delay ranging from 2 to 4 s. The trigger stimulus required animals to release the lever and to press a second lever for food reinforcement. The time between instruction and trigger signal represented the preparation phase preceding movement. The motor performance was evaluated by using reaction and movement times in addition to correct responses in each session. Dopaminergic denervation of either the dorsal or ventral striatum ipsilaterally to the side in which the second lever to be pressed was located did not significantly change reaction and movement times, although it reduced the percentage of correct trials. A significant increase of both reaction and movement times was recorded only after bilateral denervation of the ventral striatum. The analysis of incorrect responses indicated that dopaminergic innervation of the two striatal subregions had different functions in the correct execution of the behavioral paradigm. In the group of animals with dorsal lesions the most frequent incorrect response was represented by a lack of the conditioned response to the presentation of the instruction stimulus starting the trial. If the animals reacted properly to this signal, the performance thereafter was correct in the majority of trials. Conversely, animals with ventral lesions exhibited a large repertoire of incorrect responses throughout the paradigm, including premature release or delayed press of levers, and omission of the second lever press. Histological verification of brain coronal sections by tyrosine-hydroxylase immunoreactivity showed that the lesions were confined in either the dorsal or ventral striatum, sparing the lateral region. The data support the hypothesis that dopaminergic innervation enables the two striatal regions to differently participate in the preparation and execution of complex delayed sensorimotor tasks. Indeed, the dorsal striatum seems to be involved in the correct utilization of external sensory information for the initiation of conditioned behavior, whereas, the ventral striatum appears to be mainly concerned with the temporal expectation of impending stimuli that trigger reward-reinforced movements.

Acoustic Stimulation↗
PubMed2001

Why do female Aedes aegypti (Diptera: Culicidae) feed preferentially and frequently on human blood?

Adult female Aedes aegypti (L.), the vector of dengue and yellow fever viruses, have an affinity for feeding on human blood and a tendency to forego feeding on sugar. This observation challenges two tenets of mosquito biology: (1) mosquitoes imbibe plant carbohydrates for synthesis of energy reserves and blood for reproduction and (2) egg production is reduced when mosquitoes feed on human blood compared with blood from other species. Sub-optimal amounts of the amino acid isoleucine in human blood (particularly free isoleucine in plasma) are thought to be responsible for lowered egg production when human blood is ingested. We tested the hypothesis that feeding on human blood is associated with a selective advantage for Ae. aegypti and is an underlying reason for this mosquito's intimate and epidemiologically important relationship with human beings. Our five experiments examined the effects of different isoleucine concentrations on accumulated energy reserves, frequency of host contact, survival, and egg production. When mosquitoes imbibed blood meals over a 7- to 10-d period and were not fed sugar, increased isoleucine concentration decreased energy reserves and did not increase egg production. Aedes aegypti took smaller but more frequent blood meals when feeding on a low-isoleucine human host daily compared with a high-isoleucine mouse host. Previous reports that isoleucine enhances egg production were confirmed only when females were fed sugar, an unusual behavior for most domestic Ae. aegypti populations. Females fed human blood and water had greater age-specific survival (l(x)), reproductive output (m(x)), and cumulative net replacement (R0) than cohorts fed human blood plus sugar or isoleucine-rich mouse blood with or without access to sugar. The unique isoleucine concentration of human blood is associated with Ae. aegypti's unusual propensity to feed preferentially and frequently on humans--a behavior that increases this mosquito's fitness, synthesis of energy reserves, and contact with human hosts, making it an especially effective disseminator of human pathogens.

Aedes↗
PubMed2001

Accumulation of hippocampal place fields at the goal location in an annular watermaze task.

To explore the plastic representation of information in spatially selective hippocampal pyramidal neurons, we made multiple single-unit recordings in rats trained to find a hidden platform at a constant location in a hippocampal-dependent annular watermaze task. Hippocampal pyramidal cells exhibited place-related firing in the watermaze. Place fields tended to accumulate near the platform, even in probe trials without immediate escape. The percentage of cells with peak activity around the hidden platform was more than twice the percentage firing in equally large areas elsewhere in the arena. The effect was independent of the actual position of the platform in the room frame. It was dissociable from ongoing motor behavior and was not related to linear or angular speed, swim direction, or variation in hippocampal theta activity. There was no accumulation of firing in any particular region in rats that were trained with a variable platform location. These training-dependent effects suggest that regions of particular behavioral significance may be over-represented in the hippocampal spatial map, even when these regions are completely unmarked.

Action Potentials↗
PubMed1988

Behavioral effects of angiotensin II and angiotensin II-(4-8)-pentapeptide in rats.

One nM of angiotensin II (AII) or angiotensin II-(4-8)-pentapeptide [AII(4-8)] given intracerebroventricularly did not affect locomotor and exploratory behavior of rats in open field. AII significantly increased and AII(4-8) did not affect vertical activity of animals in electromagnetic motimeter. Neither of the peptides influenced horizontal activity in the motimeter. Both peptides intensified stereotypy produced by apomorphine and amphetamine. AII significantly improved, while AII(4-8) did not affect, consolidation of memory of the correct way to food in T-maze. Similarly, AII increased and AII(4-8) did not change the rate of acquisition of conditioned avoidance responses in a shuttle-box. Of the two examined peptides only AII significantly improved retrieval of memory of the passive avoidance behavior. The results show that AII(4-8) influences central dopaminergic system but, unlike its parent peptide AII, has no apparent effect on memory.

Angiotensins↗
PubMed1991

Sex-specific impairment in sexual and ingestive behaviors of monosodium glutamate-treated rats.

L-monosodium glutamate (MSG) (4 mg/g b.wt.) was injected subcutaneously to pups on days 1 and 3. At age 3.5 months, sexual and ingestive behaviors were observed. Neonatal MSG treatment resulted in severe and widespread neuron destruction in the basomedial hypothalamus of both sexes, but only super-chiasmatic nucleus in male rats. A decline in sexual behavior was also observed. Serum levels of testosterone and dihydrotestosterone in male rats as well as serum level of progesterone in female rats were decreased. Ovariectomized MSG-treated female rats injected with estradiol benzoate followed by progesterone showed a dramatic improvement in sexual behavior, whereas castrated MSG-treated male rats injected with testosterone propionate did not meliorate the decline of sexual behavior. Neonatal MSG treatment also induced reductions of body weight in male rats, higher diurnal percentages of food and water intake in male rats than in female rats, and a decline of water-to-food ratio. These observations suggest that neonatal male rats show higher susceptibility to glutamate-induced dysfunction of sexual and ingestive behaviors than females. Our findings also suggest a sex difference in the mechanism of dysfunction of sexual behavior, i.e., decreased copulatory activity in male rats is mainly due to CNS damage, in contrast to decreased blood progesterone level in female rats.

Animals↗
PubMed1990

Conditioned responses to a taste conditioned stimulus paired with lithium chloride administration.

The present experiments examined whether behavioral conditioned responses (CRs) develop to lithium chloride (LiCl)-paired tastes and whether these CRs are similar to the behaviors that follow administration of the drug. Rats were exposed to a saccharin solution via intraoral infusions before being injected with either LiCl or saline. CRs were assessed after conditioning when the saccharin conditioned stimulus was delivered alone. The unconditioned response to LiCl delivery is a very distinctive posture that has been termed "lying-on-belly." The present study indicates that this behavior pattern also occurs after the delivery of a LiCl-paired taste solution. The similarity between these unconditioned and conditioned behaviors is consistent with the hypothesis that responses are conditioned during taste aversion acquisition and that CRs are similar to those that are generated by the drugs used in conditioning.

Animals↗
PubMed2006

Operant behavior of rats under fixed-interval reinforcement schedules: a dynamical analysis via the extended return map.

The extended-return-map was employed to analyze the inter-response time data of operant experiments using fixed-interval schedules and food reinforcement. After intensive training over numerous sessions, rats gradually developed several types of temporal patterns of lever pressing behaviors, which were visualized through different patterns of data point distributions in the extended-return-map. Analyses with randomly shuffled data sets confirmed that these patterns depended on the sequential order of the inter-response time data, indicating that they reflected dynamics of the behavior. A procedure was developed to quantify the difference between patterns in the extended-return-maps, thus, enabling the comparison between sessions, and between animals. Simulations suggested that, in addition to the two-state break-and-burst responding, both multiple switches of behavioral states during the inter-reinforcement periods and the acceleration of lever pressing rate should be taken into consideration for the dynamics found in the data.

Animals↗
PubMed2005

Glucocorticoids dose-dependently remodel energy stores and amplify incentive relativity effects.

To test whether glucocorticoids amplify incentive motivation, three groups of rats were adrenalectomized and replaced subcutaneously with pellets of corticosterone (B), containing 0, 30, or 80% B and cholesterol. A fourth group of sham adrenalectomized rats received cholesterol pellets. Animals were placed on a four-arm maze baited with 32% sucrose for 5-min daily sessions. After 7 days of minimal drinking on the maze at free-feeding weights, their body weights were gradually reduced to 90% of their free-feeding weights for the next 12 days (pre-shift phase). The sucrose concentration was reduced to 4% for the next 2 days (post-shift phase). B dose-dependently increased 32% sucrose intake, insulin secretion, and relative fat depots. Intake was reduced similarly in all groups following the shift to 4%, resulting in a relative B-dependent intake suppression following the shift to 4%. Videoscoring of locomotor activity indicated that search behaviors were not different between groups prior to the shift to 4%, whereas the increase in search behavior following the shift to 4% sucrose was entirely B-dependent. These data were predicted by a new model of chronic stress positing two regulatory axes on brain by glucocorticoids: one indirect axis by which glucocorticoids remodel energy stores to provide metabolic feedback and a direct axis whereby glucocorticoids act directly on brain to remodel appetitive structure.

Adaptation, Physiological↗
PubMed1986

Enhancement of optokinetic responses by lateral hypothalamic areas associated with attack in cats.

Stimulation of lateral hypothalamic sites associated with predatory attack and known to modify trigeminal reflex systems enhanced efficiency of visual following over a wide range of target velocities. Furthermore, lateral hypothalamic stimulation reversed reflex habituation seen after continuous and after repeated optokinetic stimulation. These findings support the hypothesis that the lateral hypothalamus directs behavioral responses relevant to orienting to and capturing prey, at least in part, by regulation of reflex mechanisms in different sensory modalities. Possible neural substrates for the observed effects are discussed.

Animals↗
PubMed1977

Behavioral and biochemical effects of knife cuts that preferentially interrupt principal afferent and efferent connections of the striatum in the rat.

Knife cuts were made that preferentially interrupted (a) the nigrostriatal pathway; (b) pallidofugal projections to the lower brainstem; (c) caudate-pallidal interconnections; and (d) fibers entering or leaving the striatum ventrally. The effects of these cuts on conditioned (shuttle box) avoidance, passive avoidance, swimming escape, sucrose-rewarded alley running, locomotor activity, and various measures of sensory-motor function were examined. The norepinephrine, dopamine and serotonin content of the striatum, residual forebrain and hypothalamus were determined following the completion of behavioral testing. The pattern of results suggests that striatal functions which are significantly influenced by several afferent and efferent connections are essential for the acquisition and, perhaps, execution of complex behavior in appetitive as well as aversive test paradigms. A special role for the dopaminergic afferents to the striatum was not established in these tests.

Animals↗
PubMed2005

Manipulations of serotonin function in the nucleus accumbens core produce differential effects on ethanol and sucrose seeking and intake.

OBJECTIVE: Behaviorally relevant stimuli, including alcohol, are processed through the nucleus accumbens/ventral tegmental area (VTA)/prefrontal cortex circuit. It is hypothesized that serotonin affects ethanol-directed behaviors by interacting with this system via projections from the dorsal raphe to the nucleus accumbens and VTA. The current studies utilized two different operant paradigms, one focusing on reinforcer seeking and one focusing on reinforcer self-administration (both with an ethanol and a sucrose solution as the reinforcer) to elucidate serotonin-specific regulation of these behaviors. METHODS: The present experiments assessed the effects of microinjections of a serotonin1B agonist (CGS12066B) and a serotonin1A agonist (8-OH-DPAT) in the nucleus accumbens core on ethanol- and sucrose-reinforced seeking and intake. In four separate experiments, male Long-Evans rats were trained to complete a single response requirement that resulted in access to 10% ethanol or 2% sucrose for a 20-min drinking period. RESULTS: Before microinjections, ethanol-reinforced subjects were consuming an average of 0.5-0.95 g/kg ethanol and making 50-100 responses during intermittent nonreinforced sham (no drug) sessions (sucrose groups had similar baseline response levels). In summary, findings from the four experiments showed the following: (1) manipulations of serotonin function that had effects on ethanol-reinforced responding had either no effect or less pronounced effects on sucrose-reinforced responding; (2) administration of the serotonin1B agonist decreased seeking behaviors to a greater degree than drinking behaviors; and (3) administration of the serotonin1A agonist decreased ethanol intake but not seeking with no impact at all on sucrose-reinforced behaviors. CONCLUSIONS: Manipulations of serotonin activity in the nucleus accumbens core had little effect on sucrose-reinforced behaviors and differential effects on ethanol seeking versus intake, suggesting that this area may play a complex but selective role in the stimulus processing of external and internal alcohol-associated cues.

Alcohol Drinking↗
PubMed1985

Aquatic prey capture in ambystomatid salamanders: patterns of variation in muscle activity.

Functional morphologists commonly study feeding behavior in vertebrates by recording electrical activity from head muscles during unrestrained prey capture. Rarely are experiments designed to permit a partitioning variation in muscle electrical activity patterns. Analysis of muscle activity during aquatic prey capture in two morphologically distinct species of salamanders, Ambystoma dumerilii and A. mexicanum, is conducted to assess variation at four levels: between species, among individuals within species, among experiments conducted on different days, and among feedings. The results show that 1) mean correlations among the 11 electromyographic variables measured for each feeding are low and vary considerably among individuals, 2) many of the variables show significant differences among experimental days, 3) only one variable, the difference in timing between the depressor mandibulae and sternohyoideus muscles, showed significant variation between species, and 4) seven of the 11 variables showed significant variation among individuals within species. Overall, the variation between feedings (trials) was high, and there was some variation between days on which the experiments were conducted. Neither electrode position within the muscle nor satiation contributed to the high trial variance. The results suggest that functional analyses of feeding behavior should include an assessment of variation due to individuals, days, and trials, because the amount of variation at these levels may render differences between species nonsignificant.

Activity Cycles↗
PubMed1988

Stimulus-specific long-term habituation of visually guided orienting behavior toward prey in toads: a 14C-2DG study.

The regional distribution of cerebral glucose utilization, revealed by the 14C-2DG technique, was compared between (i) toads after stimulus-specific long-term habituation of the orienting response toward a repeatedly presented prey dummy ('habituation group') and (ii) non-habituated toads, readily orienting toward the repetitively presented prey stimulus ('naive group'). In the 'habituation group', the ventral medial pallium (vMP), a certain portion of the preoptic area (PO), and the dorsal hypothalamus (dHYP) showed a statistically significant increase in 14C-2DG-uptake; decrease was observed in the ventral layers of the optic tectum (vOT), a portion of the tegmental reticular formation (RET), the ventral cerebellum (vCB), and the striatum (STR). The results suggest that stimulus-specific long-term habituation of prey-catching affects both, components of the stimulus-response mediating circuit (e.g., involving OT), and structures extrinsic to it, (e.g., vMP, PO, dHYP), which may belong to a modulatory circuitry. Bilateral lesions to vMP strongly delay habituation. Our results are suggesting that damping of the adequate behavioral motor response during habituation involves active inhibitory processes of a modulatory system that develops in strength during stimulus repetition so as to suppress response output, which basically supports Sokolov's hypothesis (1975).

Animals↗
PubMed1993

Two types of motivation revealed by ibotenic acid nucleus accumbens lesions: dissociation of food carrying and hoarding and the role of primary and incentive motivation.

Rats with dopamine-depleting lesions of the nucleus accumbens (NAcc) no longer carry food and leave it in a refuge (carry-to-leave or hoard). The present study replicates this finding and extends it to rats with ibotenic acid lesions. The same rats, however, were found to carry food to a refuge to eat it (carry-to-eat). Thus, within a test session, control rats would first carry food to eat it, and when sated, carry the remaining food to leave it in the refuge. NAcc food-deprived rats carried food to eat it but when sated engaged mainly in exploratory behavior. When carrying-to-eat, NAcc rats modulated responses normally to food size and eating time, their movement speed and motor patterns were normal, and their eating times were normal. Nevertheless, they were slower to return for food after eating, and they did not show normal slowing of eating times with successively presented food pellets. The failure of NAcc rats to carry-to-leave when sated was not related to general inactivity. In activity tests, they were as active in the light, more active in the dark, and did not differ from control rats under amphetamine (1.25 and 2.5 mg/kg). Their impairments were also not related to damage to other forebrain related structures, as they displayed normal neocortical and hippocampal atropine-sensitive and atropine-resistant electroencephalograms (EEG). The finding that NAcc rats carry-to-eat when hungry but do not carry-to-leave when sated suggests two separate conclusions. First, food carrying can be dissociated into two separate actions with respect to neural control, carrying-to-eat and carrying-to-leave. Second, the selective involvement of the NAcc in only carrying-to-leave suggests that it is associated with recruiting actions in response to the secondary incentive features of food but is not required for behaviors associated with food consumption. Other structures are presumably activated by the primary drive-reducing features of food. The results are discussed in relation to two-factor theories of motivation.

Animals↗
PubMed1985

A neural model of interactions subserving prey-predator discrimination and size preference in anuran amphibia.

The model described is an extension of a previous model of the optic tectum (Arbib & Lara, 1982; Lara, Arbib & Cromarty, 1982; Lara & Arbib, 1982) and takes into consideration anatomical, physiological and behavioral studies in anurans, as well as earlier modelling efforts (Ewert & Von Seelen, 1974; Didday, 1976). Computer simulations were conducted to analyze how interactions among retina, optic tectum and pretectum may give frogs and toads the ability to discriminate between prey and predator stimuli. Results from simulations have allowed us to reproduce empirical observations, to suggest new experiments, and to postulate what neural mechanisms might be involved in some phenomena related to prey-catching orienting behavior, with direction invariance of prey-predator recognition being a consequence of tectal architecture, and size preference and response latency depending on the motivational state of the animal.

Animals↗