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PubMed2002

Behavioral and electrophysiological consequences of deafferentation following chronic constriction of the infraorbital nerve in adult rats.

Deafferentation of the hind paw following sciatic nerve injury results in behavioral changes, such as autotomy, suggestive of persistent, spontaneous pain. The effects of deafferentation involving trigeminal nerves have, however, received less attention. Here, alterations in trigeminal ganglion neuronal activity and mechanically evoked and spontaneous behavior were studied in adult rats after a chronic constriction injury of the infraorbital nerve (ION). Compared to sham-operated rats, most rats with ION damage were unresponsive to mechanical stimulation of the mystacial vibrissae up to 56 days after surgery. Increased facial grooming was observed only in rats with chronic ION constriction 10 days after surgery. Free-ranging behavior was similar to that of sham-injury animals. In contrast, increases in the number of spontaneously active trigeminal ganglion neurones were observed in those rats with ION injuries at both 3 and 56 days. These data suggest that chronic constrictive injuries of the ION resulting in prolonged loss of low-threshold input from the periphery lead to only transient behavioral changes, despite the presence of spontaneous activity in trigeminal sensory neurones.

Afferent Pathways↗
PubMed2000

Skilled forelimb reaching for pasta guided by tactile input in the rat as measured by accuracy, spatial adjustments, and force.

Rats are capable of reaching for food with a single forelimb, but since they locate the target of their reach using olfaction, it is unclear how they adjust their limb movement to compensate for errors. Although it is thought that their reaching movement is ballistic and can only be adjusted by trial and error, whether they can use haptic cues to aid in locating and identifying a target has not been examined. The present study addressed this question by allowing rats to reach through a slot for rigidly held pieces of uncooked pasta of varying thickness, which could be oriented vertically or horizontally from different points around the slot and which were attached to a force transducer. The tasks required that animals not only adjust their reach and grasp to the target's location but also identify the target based on its texture. Acquisition curves were made of head orientation, limb transport trajectories, number of attempts per success, paw orientation, breaking direction and force of the grasp. A haptic discrimination test used pasta and similar sized metal rods with different tactile properties as discriminanda. The results indicated that whereas postural orientation and limb transport trajectory were not modified as a function of target orientation, paw orientation and grasp force did vary as a function of the sensory qualities of the target object, and the rats could make a haptic discriminative choice of a target object. The results show that the rat is capable of adjusting paw movements using haptic information, suggesting that somatosensory features of sensorimotor control of limb and paw movements in carnivores and primates are shared by rodents. This commonality points to a conservation of motor control in mammals, explains some of the idiosyncratic features of rat reaching behavior, and confirms that rodents provide a good model for investigating sensorimotor functions.

Animals↗
PubMed1999

Dopamine D2/D3 receptors modulate cocaine's reinforcing and discriminative stimulus effects in rhesus monkeys.

Numerous studies have suggested that dopamine (DA) D2 and D3 receptors are involved in the behavioral effects of cocaine. The present experiments evaluated the reinforcing and cocaine-like discriminative stimulus effects of several D2/D3 agonists in rhesus monkeys. In the first experiment, animals (n = 4) were trained to self-administer 0.03 mg/kg/inj cocaine under a fixed-interval (FI) 5-min schedule. When substituted for cocaine, the D2/D3 agonist quinpirole (0.003-0.03 mg/kg/inj) functioned as a reinforcer in all monkeys. In two cocaine-naive monkeys trained to respond under an FI 3-min schedule of food presentation, quinpirole maintained low rates of responding in one subject, while at the highest dose (0.03 mg/kg/inj) it functioned as a reinforcer in the second monkey. In this animal, increased activity was observed at this dose, which may have contributed to the overall rate of responding. In the second experiment, monkeys (n = 4) were trained to discriminate cocaine from saline using a two-lever, food-reinforced, drug discrimination procedure. The D2/D3 agonists quinpirole, (+/-)-7-OH-DPAT, and R-( + )-7-OH-DPAT fully substituted for cocaine. However, the time-course of substitution differed between quinpirole, which substituted for cocaine 10 min after administration, and (+/-)- and R-(+)-7-OH-DPAT, which required 60-min pretreatments. The behavioral potencies, as determined from ED50, values, correlated with previously reported in vitro binding affinity and functional activity at the D3 receptor [R-(+ )-7-OH-DPAT > (+/-)-7-OH-DPAT > quinpirole]. These results further indicate that direct-acting D2/D3 agonists can function as reinforcers and produce cocaine-like discriminative stimulus effects, and support the idea that D3 receptors should continue to be a valuable target for future behavioral studies evaluating cocaine's mechanisms of action.

Analysis of Variance↗
PubMed1979

Approach and withdrawal analysis of the effects of hypothalamic stimulation and lesions in rats.

In a paradigm in which rats would both initiate and terminate hypothalamic stimulation, "purely" rewarding lateral hypothalamic and "purely" aversive medial hypothalamic electrodes were identified. Subjects were then given a series of tests designed to assess the effects of brain stimulation on approach and withdrawal behaviors. Lateral hypothalamic stimulation facilitated approach behavior and suppressed withdrawal behaviors, whereas medial hypothalamic stimulation produced largely the opposite effects. No serious motor deficits due to stimulation were detected with either type of electrode. In a second experiment, the approach-withdrawal effects of bilateral lateral hypothalamic lesions were tested and found to suppress approach behaviors and facilitate withdrawal behaviors. Other neurological examinations revealed motor deficits, but these deficits do not account for the specific pattern of results observed on the approach-withdrawal tests. These approach-withdrawal phenomena are interpreted in terms of altering a natural balance between approach and withdrawl behavior facilitating systems in the lateral and medial hypothalamus, respectively.

Ammonia↗
PubMed1972

Enduring behavioral changes in rats with experimental phenylketonuria.

Several criticisms of past attempts to produce experimental phenylketonuria are discussed, and a model that appears to meet these criticisms is presented. This model uses inhibition in rats of phenylalanine hydroxylase (EC 1.14.3.1) by p-chlorophenylalanine and supplementation with phenylalanine to produce a high ratio of phenylalanine to tyrosine in their blood. By this method, an experimental subject is produced whose behavioral, neurological, and biochemical characteristics are similar to those of clinical patients with phenylketonuria.

Aggression↗
PubMed2004

Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite.

BACKGROUND: Total sleep deprivation in rodents and in humans has been associated with hyperphagia. Over the past 40 years, self-reported sleep duration in the United States has decreased by almost 2 hours. OBJECTIVE: To determine whether partial sleep curtailment, an increasingly prevalent behavior, alters appetite regulation. DESIGN: Randomized, 2-period, 2-condition crossover clinical study. SETTING: Clinical Research Center, University of Chicago, Chicago, Illinois. PATIENTS: 12 healthy men (mean age [+/-SD], 22 +/- 2 years; mean body mass index [+/-SD], 23.6 +/- 2.0 kg/m2). MEASUREMENTS: Daytime profiles of plasma leptin and ghrelin levels and subjective ratings of hunger and appetite. INTERVENTION: 2 days of sleep restriction and 2 days of sleep extension under controlled conditions of caloric intake and physical activity. RESULTS: Sleep restriction was associated with average reductions in the anorexigenic hormone leptin (decrease, 18%; P = 0.04), elevations in the orexigenic factor ghrelin (increase, 28%; P < 0.04), and increased hunger (increase, 24%; P < 0.01) and appetite (increase, 23%; P = 0.01), especially for calorie-dense foods with high carbohydrate content (increase, 33% to 45%; P = 0.02). LIMITATIONS: The study included only 12 young men and did not measure energy expenditure. CONCLUSIONS: Short sleep duration in young, healthy men is associated with decreased leptin levels, increased ghrelin levels, and increased hunger and appetite.

Adult↗
PubMed1984

Together intracranial angiotensin and systemic mineralocorticoid produce avidity for salt in the rat.

Rats that have no need for sodium will run to small rewards of 3% NaCl solution in a runway after they have been treated with both a mineralocorticoid and angiotensin II. When given alone at the low doses used here, neither the mineralocorticoid nor the angiotensin produce the behavior. This result encourages the idea that it is a synergy of the hormones of sodium conservation, angiotensin and aldosterone, that apprises the brain of the need for salt and generates the appetite for the taste of salt.

Angiotensin II↗
PubMed1992

Prostaglandins do not mediate interferon-alpha effects on mouse behavior.

Interferons play an important role in cell function as well as host defense against virus infection. Interferon-alpha stimulates cyclooxygenase-catalyzed prostaglandin synthesis. Therefore, a cyclooxygenase inhibitor was used to determine whether the behavioral effects of mouse interferon-alpha in mice are mediated by increased prostaglandin synthesis. Male DBA/2J mice were exposed to 1600 U/g mouse interferon-alpha, the buffer in which the interferon was diluted, 5 mg/kg of a cyclooxygenase inhibitor, indomethacin, or 5 mg/kg indomethacin plus 1600 U/g mouse interferon-alpha. As in previous studies, interferon decreased activity and food pellets obtained in the first 4 hours after administration. Indomethacin had no effect on this effect of interferon; therefore, we conclude that the behavioral effects of interferon are not mediated by the fever or anorectic effects of prostaglandins.

Animals↗
PubMed2001

Leptin reverses sucrose-conditioned place preference in food-restricted rats.

Previous studies have suggested that food restriction can modify performance in the conditioned place preference (CPP) paradigm. In the present study, we tested the hypotheses that food restriction would enhance the development of a CPP to low-calorie sucrose pellets and that peripheral leptin replacement in food-restricted animals would reverse this effect. Using a range of 45-mg sucrose pellets (0-15 pellets) as a reward, we observed that a significant place preference was conditioned in food-restricted, but not ad libitum-fed rats. This CPP was reversed either by treatment of food-restricted rats with the dopamine receptor antagonist alpha-flupenthixol (200 microg/kg ip) during the training protocol or by chronic subcutaneous replacement of leptin (125 microg/kg/day) that attenuated the food restriction-induced decrease of circulating leptin. We conclude that dopaminergic signaling and the fall of plasma leptin concentrations contribute to the CPP of food-restricted rats. This finding suggests that in addition to metabolic adaptations, hypoleptinemia results in behavioral adaptations during states of energy deprivation.

Animals↗
PubMed1990

Cue exposure during a period of abstinence reduces the resumption of operant behavior for oral ethanol reinforcement.

The present study examined the prediction made by learning theories of drug addiction that systematic cue exposure (extinction) procedures should reduce ethanol (EtOH) consumption. In 3 experiments, male rats were trained on a variable-interval schedule to press a bar for a sweetened EtOH solution. These procedures established associations between a variety of cues (contextual, response feedback, visual, taste) and EtOH consumption. After performance had stabilized, a period of abstinence was imposed during which no EtOH was available. Groups of rats differed only in the number of EtOH-associated cues experienced during this period. The level of EtOH consumption after abstinence was reduced in proportion to the degree of cue exposure. These findings support the learning hypothesis that drug-associated cues contribute to the resumption of drug-taking behavior and further suggest that extinction procedures may be valuable in preventing relapse.

Alcohol Drinking↗
PubMed1995

Functional differences between the prelimbic and anterior cingulate regions of the rat prefrontal cortex.

The effects of reversible lidocaine-induced lesions of 2 subregions of the rat medial prefrontal cortex (mPFC) were examined on a series of cognitively based foraging behaviors on a radial-arm maze. Lesions of the prelimbic (PL) or anterior cingulate (AC) cortex prior to the retention phase of a delayed-foraging task disrupted performance differentially; rats with PL lesions visited arms in a random manner, whereas rats with AC lesions revisited previously baited arms preferentially. Rats with AC lesions were also impaired on a single-trial foraging task; they made numerous revisits to previously baited arms. PL lesions had no effect on performance of this task in well-trained rats. However, rats trained on the 2-phase task did not adapt to a new foraging strategy after a PL lesions, when they were switched unexpectedly to the single-trial foraging task. These data demonstrate functional heterogeneity within the rat mPFC and suggest that the PL is involved in processes through which recently acquired information is used to organize and modify foraging behavior, whereas the AC may play an important role in response flexibility.

Animals↗
PubMed1998

Prenatal cocaine alters social competition of infant, adolescent, and adult rats.

This series of experiments examined whether gestational cocaine exposure alters later social behavior exhibited during competition for biologically relevant stimuli. Rat offspring were derived from dams that received subcutaneous injections of 40 mg/kg/3cc cocaine HCl daily on gestational Days 8-20, pair-fed dams injected with saline, or nontreated control dams. Offspring competed with peers for access to a nipple in infancy, and to water in adolescence or adulthood. Prenatal cocaine exposure resulted in a decreased ability of cocaine-exposed infant rats to compete successfully for a nipple. Although adolescent and adult cocaine-exposed rats were no less successful than controls when competing for water, they exhibited a notable increase in aggression toward competitors during testing. Data provide evidence of alterations in social behavior and social competition as a result of prenatal cocaine exposure.

Aggression↗
PubMed1988

Biological correlates of behavioral development in the ant, Novomessor albisetosus (Mayr).

Physical changes are associated with temporal polyethism, the division of labor according to age. The period of developing ovaries corresponds with the age when workers are found with the brood and queen. Resorption of ovaries occurs at a time when workers no longer tend brood and queen. Two bursts of exoskeleton hardening and growth of the poison gland apparatus corresponds with a transitional period in the behavioral development of workers and finally with their development into nest defenders and foragers.

Age Factors↗
PubMed2004

Cooperation between Drosophila flies in searching behavior.

In Drosophila melanogaster food search behaviour, groups of flies swarm around and aggregate on patches of food. We wondered whether flies explore their environment in a cooperative way as interactions between individual flies within a population might influence the flies' ability to locate food sources. We have shown that the food search behavior in the fruit fly Drosophila is a two-step process. Firstly, 'primer' flies search the environment and randomly land on different food patches. Secondly, the remaining group of flies move to the most favorable food source and aggregate there. We call this a 'search-aggregation' cycle. Our data demonstrate that flies do not individually assess all available food resources. Rather, social interactions between flies appear to affect their choice of a specific food patch. A genetic analysis of this 'search-aggregation' behavior shows that flies carrying mutations in specific genes (for example, the dunce (dnc) gene which codes for a phosphodiesterase) were defective in this search-aggregation behavior when compared to normal flies. Future investigations of the neuronal signaling involved in this behavior will help us to understand the complexities of this aspect of Drosophila social behaviour.

Animals↗
PubMed2001

Phase transition between disordered and ordered foraging in Pharaoh's ants.

The complex collective behavior seen in many insect societies strongly suggests that a minimum number of workers are required for these societies to function effectively. Here we investigated the transition between disordered and ordered foraging in the Pharaoh's ant. We show that small colonies forage in a disorganized manner, with a transition to organized pheromone-based foraging in larger colonies. We also show that when food sources are difficult to locate through independent searching, this transition is first-order and exhibits hysteresis, comparable to a first-order phase transition found in many physical systems. To our knowledge, this is the first experimental evidence of a behavioral phase transition between a maladaptive (disorganized) and an adaptive (organized) state.

Animals↗
PubMed1978

Blood meal size as a factor affecting continued host-seeking by Aedes aegypti (L.).

The effect of ingested blood on the host-seeking response of two strains of Aedes aegypti was examined. Using an olfactometer, females fed partial blood meals were scored for host-seeking behavior within 1 h, and their blood meal sizes were measured chemically immediately afterwards. The suppression of host-seeking within 1 h after a blood meal appears to be caused by abdominal distention from ingested blood. Mosquitoes of either strain were attracted to a host when the blood meal size was less than 2.5 microliter; above this threshold there was a sharp decline in the tendency to respond. Small mosquitoes resulting from a low larval diet had a lower threshold, and were more likely to cease host-seeking after a small blood meal. Multiple feeding within a single gonotrophic cycle may result if mosquitoes take small blood meals which are insufficient to terminate host-seeking. Partial meals and reduced feeding success of mosquitoes can result from defensive host behavior, which in the laboratory rat was shown to increase at high mosquito densities.

Aedes↗
PubMed2001

On the behavioral significance of head direction cells: neural and behavioral dynamics during spatial memory tasks.

Current theories assume that rats use the directional information reflected by head direction (HD) cells when performing spatial tasks. This assumption was assessed by monitoring anterior thalamic HD cell activity and relating it to the subject's behavioral response on 2 spatial memory tasks that tested either reference memory or working memory. In both tasks, there was a significant number of trials where there was not a tight coupling between the preferred firing direction of HD cells and the direction of the behavioral response. In addition, it was possible to intentionally change the preferred direction of HD cells without affecting performance accuracy. An additional experiment showed that manipulations that affected internal, but not external, cues impaired performance on the reference memory task. These findings suggest that HD cell activity was not consistently guiding the subjects' behavior on these 2 spatial tasks.

Animals↗
PubMed2000

Salt appetite in salt-replete rats: involvement of mesolimbic structures in deoxycorticosterone-induced salt craving behavior.

Chronic administration of the mineralocorticoid deoxycorticosterone acetate (DOCA) induces a steady and robust increase in salt appetite and plasma Na(+) over the course of treatment. Interestingly, salt appetite behavior persists in rats even with elevated plasma Na(+) levels. Since there is evidence that the pathways normally associated with salt and water homeostasis are relatively unaffected in the DOCA-treated rat, we hypothesized that other regulatory systems may be hyperactive giving rise to this dysfunctional condition. The mesolimbic dopaminergic system has long been associated with orienting and reward-seeking behaviors such as those observed in reproduction, drug abuse, and appetite. Furthermore, we have previously shown that chronic DOCA administration results in an increase in mRNA levels of the endogenous opiate enkephalin in male rats given 24-hour access to tap water and 2% NaCl (two-bottle choice). Thus, in the present study, we tested the hypothesis that the mesolimbic dopaminergic system is dysfunctionally sensitized to the presence of a salt stimulus in DOCA-treated animals. Four groups of rats were injected with DOCA (5 mg/rat/day, 11 days) and one with vehicle (all were given access to water but access to salt was regulated). Two DOCA groups were given 2 h of 2% NaCl access/day and on the last day, one group was not given access (2hX). One of the two remaining DOCA groups was given 24-hour access to salt (24h) and the other no access at all (24hX). Consistent with our hypothesis, in the shell of the nucleus accumbens (AcbSh) we found relatively higher enkephalin- and tachykinin-mRNA abundance in the 2h vs. 2hX and dynorphin-mRNA in the 24h vs. 24hX groups. In addition, there were decreases in dopamine transporter binding in the AcbSh and decreases in tyrosine hydroxylase immunoreactivity throughout the striatum in the 24h vs. 24hX group. Furthermore, rats denied access to salt (2hX and 24hX) had higher cholecystokinin-mRNA levels in the ventral tegmental area compared to the 2h and 24h groups, respectively. These results suggest that basal ganglia structures associated with reward and goal-seeking behavior may be activated to elicit salt craving behavior in the DOCA-induced salt-appetitive rat.

Animals↗