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At least 1,657 records · Page 92Linked to original sources
PubMed2005

Lack of evidence for a role for either the in utero or suckling periods in the exaggerated salt preference of the spontaneously hypertensive rat.

When offered as a choice with drinking water in two-bottle preference tests, the spontaneously hypertensive rats (SHR) of the Okamoto strain exhibit a marked preference for saline solutions. While this behaviour is thought to be in part genetically determined, the role of environmental influences-in particular, perinatal ones-are poorly understood. In this study, we have used combined embryo transfer and cross-fostering techniques between SHR and normotensive Wistar Kyoto (WKY) rats to delineate the relative roles of the prenatal and postnatal, suckling environment on the exaggerated saline preference of male SHR and WKY offspring at 20 weeks of age. We found, using two-bottle preference tests using water and 140 mmol/l sodium chloride solution, that neither the in utero period nor the postnatal, suckling period played a role in the development of the much larger total fluid intake (water plus saline) or saline preference (proportion of the total fluid intake taken as saline) of the SHR. We thus conclude that maternal and perinatal environmental factors do not play a major role in this behaviour and that the exaggerated saline preference of the SHR is probably largely genetically determined.

Animals↗
PubMed2006

Enhanced sucrose and Polycose preference in sweet "sensitive" (C57BL/6J) and "subsensitive" (129P3/J) mice after experience with these saccharides.

Prior research with inbred mouse strains indicates that C57BL/6J (B6) mice display stronger preference and acceptance for various sweeteners than do 129P3/J (129) mice. Experiment 1 examined the extent to which this strain difference could be modified by repeated exposure to sucrose. Sucrose-naive 129 mice displayed weaker preferences than did B6 mice for 0.5% to 4% sucrose solutions during 23h/day sugar vs. water tests. Sucrose preference did not differ at 8-32% concentrations. Yet, when retested with sucrose, the 129 and B6 mice showed identical robust preferences (>90%) for 0.5-32% solutions. The strains also did not differ in sucrose preference in tests with descending sucrose concentrations (0.5-0.0625%). Sucrose-experienced 129 mice also showed enhanced preference for dilute saccharin solutions suggesting that their sweet taste responsivity was enhanced. Experiment 2 revealed that preference for dilute saccharin solutions was enhanced by prior saccharin experience in B6 but not 129 mice. Experiment 3 tested the strains with Polycose which has a palatable taste different from that of sucrose. Polycose-naive 129 mice displayed weaker preferences for dilute (0.5-4%) but not concentrated (8-32%) Polycose solutions relative to B6 mice. In the second test series Polycose preferences were nearly identical in the two strains. In Experiments 1 and 3, prior sucrose or Polycose experience also reduced or eliminated strain differences in saccharide acceptance (absolute intake) at higher but not lower concentrations. Thus, exposure to the oral and post-oral actions of sucrose and Polycose increased saccharide preference in B6 mice and even more in 129 mice so that the strain difference virtually disappeared. Whether the 129 mice responded to the taste or other properties (e.g., odor) of the dilute saccharide solutions is not certain but their gustatory sensitivity needs to be reconsidered.

Animals↗
PubMed2006

Sucrose motivation in sweet "sensitive" (C57BL/6J) and "subsensitive" (129P3/J) mice measured by progressive ratio licking.

As compared to C57BL/6J mice, 129P3/J mice show weaker preferences for and lower intakes of dilute sugar solutions. These differences have been attributed to genetic differences in their sweet taste receptor. The two mouse strains do not differ, however, in their intake of concentrated sugar solutions. The post-oral satiating effect of concentrated sugar solutions may mask strain differences in the avidity for these solutions. This hypothesis was investigated using fixed ratio (FR, low demand) and progressive ratio (PR, high demand) operant licking tests (22h/day) to measure sugar appetite. In Experiment 1, sucrose-experienced 129 mice licked less than did B6 mice for 4% but not for 16% sucrose in free access bottle tests and FR operant tests. Yet, in PR tests the 129 mice licked as much for 4% sucrose and more for 16% sucrose than did B6 mice. In Experiment 2, sucrose-naive 129 mice licked less than did B6 mice in FR and PR tests with 0.4% saccharin but the strains did not differ in PR licking in their first test with 16% sucrose. After they were given unconstrained bottle access to 16% sucrose for 3 days, the 129 mice now licked more than B6 mice in a second sucrose PR test. Thus, despite having a less sensitive sweet taste receptor, 129 mice are as much or more motivated to obtain sucrose than are B6 mice and appear to be more influenced by prior experience with sugar. This suggests that the strains differ in their central reward processing of sweet taste.

Animals↗
PubMed2006

Conditioned partner preference in female rats for strain of male.

Female rats show conditioned place preference following paced copulation, and we have recently demonstrated that pairing almond odor with paced copulation induces a conditioned partner preference for almond-scented males. The present study examined whether cues of two different strains of male (albino and pigmented) induce a conditioned partner preference for the strain of male associated with paced copulation. Ovariectomized, hormone-primed Wistar (W) or Long-Evans (LE) female rats received 10 conditioning trials at 4-day intervals. In the Wistar-pacing group females copulated with W males in a chamber bisected by a 4-hole partition that only the female could pass through. Four days later, they copulated with LE males without the partition. The Long-Evans-pacing group received the opposite association. In the final preference test all females chose freely between two males tethered in opposite corners of an open field, one W and one LE. Regardless the strain of male, females displayed more solicitations toward the pacing-related male, and most of the females received their first ejaculation from that male. The preference was facilitated if the pacing-related male was of the same strain as the female. These results suggest that female rats have an unconditioned preference for males of the same strain, but this preference can be switched towards males of a different strain if that male is associated with the sexual reward induced by paced copulation.

Animals↗
PubMed2006

Involvement of the endocannabinoid system in drug addiction.

Recent studies have shown that the endocannabinoid system is involved in the common neurobiological mechanism underlying drug addiction. This system participates in the primary rewarding effects of cannabinoids, nicotine, alcohol and opioids, through the release of endocannabinoids in the ventral tegmental area. Endocannabinoids are also involved in the motivation to seek drugs by a dopamine-independent mechanism, demonstrated for psychostimulants and opioids. The endocannabinoid system also participates in the common mechanisms underlying relapse to drug-seeking behaviour by mediating the motivational effects of drug-related environmental stimuli and drug re-exposure. In agreement, clinical trials have suggested that the CB(1) cannabinoid antagonist rimonabant can cause smoking cessation. Thus, CB(1) cannabinoid antagonists could represent a new generation of compounds to treat drug addiction.

Animals↗
PubMed2002

Reduced 5-HT2A receptor binding after recovery from anorexia nervosa.

BACKGROUND: Several lines of evidence suggest that a disturbance of serotonin neuronal pathways may contribute to the pathogenesis of anorexia nervosa (AN). This study applied positron emission tomography (PET) to investigate the brain serotonin 2A (5HT2A) receptor, which could contribute to disturbances of appetite and behavior in AN. METHODS: To avoid the confounding effects of malnutrition, we studied 16 women recovered from AN (REC AN, >1 year normal weight, regular menstrual cycles, no bingeing or purging) compared with 23 healthy control women (CW) using [18F]altanserin, a specific 5-HT2A receptor antagonist on PET imaging. RESULTS: REC AN women had significantly reduced [18F]altanserin binding relative to CW in mesial temporal (amygdala and hippocampus), as well as cingulate cortical regions. In a subset of subjects (11 CW and 16 REC AN), statistical parametric mapping (SPM) confirmed reduced mesial temporal cortex 5HT2A receptor binding and, in addition, showed reduced occipital and parietal cortex binding. CONCLUSIONS: This study extends research suggesting that altered 5-HT neuronal system activity persists after recovery from AN and may be related to disturbances of mesial temporal lobe function. Altered 5-HT neurotransmission after recovery also supports the possibility that this may be a trait-related disturbance that contributes to the pathophysiology of AN.

Adult↗
PubMed2003

Development of levodopa-induced dyskinesias in parkinsonian monkeys may depend upon rate of symptom onset and/or duration of symptoms.

Levodopa-induced dyskinesias (LIDs) present a major problem for the long-term management of Parkinson's disease (PD) patients. Due to the interdependence of risk factors in clinical populations, it is difficult to independently examine factors that may influence the development of LIDs. Using macaque monkeys with different types of MPTP-induced parkinsonism, the current study evaluated the degree to which rate of symptom progression, symptom severity, and response to and duration of levodopa therapy may be involved in the development of LIDs. Monkeys with acute (short-term) MPTP exposure, rapid symptom onset and short symptom duration prior to initiation of levodopa therapy developed dyskinesia between 11 and 24 days of daily levodopa administration. In contrast, monkeys with long-term MPTP exposure, slow symptom progression and/or long symptom duration prior to initiation of levodopa therapy were more resistant to developing LIDs (e.g., dyskinesia developed no sooner than 146 days of chronic levodopa administration). All animals were similarly symptomatic at the start of levodopa treatment and had similar therapeutic responses to the drug. These data suggest distinct differences in the propensity to develop LIDs in monkeys with different rates of symptom progression or symptom durations prior to levodopa and demonstrate the value of these models for further studying the pathophysiology of LIDs.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1999

Noradrenaline and mixed alpha 2-adrenoceptor/imidazoline-receptor ligands: effects on sodium intake.

The effect of noradrenaline, and mixed ligands to alpha 2-adrenoceptors (alpha 2-AR) and imidazoline receptors (IR), injected intracerebroventricularly (i.c.v.), on sodium intake of sodium depleted rats, was tested against idazoxan, a mixed antagonist ligand to alpha 2-AR and IR. The inhibition of sodium intake induced by noradrenaline (80 nmol) was completely reversed by idazoxan (160 and 320 nmol) injected i.c.v. The inhibition of sodium intake induced by mixed ligands to alpha 2-AR and IR, UK14,304, guanabenz and moxonidine, was antagonized from 50 to 60% by idazoxan i.c.v. The results demonstrate that noradrenaline, a non-ligand for IR, acts on alpha 2-AR inhibiting sodium intake. The possibility that either alpha 2-AR or IR mediate the effect of mixed agonists on sodium intake remains an open question.

Adrenergic alpha-Agonists↗
PubMed2001

Can rhesus monkeys spontaneously subtract?

Animals, including pigeons, parrots, raccoons, ferrets, rats, New and Old World monkeys, and apes are capable of numerical computations. Much of the evidence for such capacities is based on the use of techniques that require training. Recently, however, several studies conducted under both laboratory and field conditions have employed methods that tap spontaneous numerical representations in animals, including human infants. In this paper, we present the results of 11 experiments exploring the capacity of semi-free-ranging adult rhesus monkeys to spontaneously compute (i.e. single trial, no training) the outcome of subtraction events. In the basic design, we present one quantity of objects on one stage, a second quantity on a second stage, occlude both stages, and then remove one or no objects from each stage. Having watched these events, a subject is then allowed to approach one stage and eat the food objects behind the occluder. Results show that rhesus monkeys correctly compute the outcome of subtraction events involving three or less objects on each stage, even when the identity of the objects is different. Specifically, when presented with two food quantities, rhesus monkeys select the larger quantity following subtractions of one piece of food from two or three; this preference is maintained when subjects must distinguish food from non-food subtractions, and when food is subtracted from either one or both initial quantities. Furthermore, rhesus monkeys are capable of representing zero as well as equality when two identical quantities are contrasted. Results are discussed in light of recent attempts to determine how number is represented in the brains of animals lacking language.

Animals↗
PubMed2001

Location of fruit using only airborne odor cues by a lizard.

Although squamate reptiles are known to locate conspecifics by scent-trailing and to locate and identify prey by tongue-flicking substrates, an ability to locate food using only airborne cues has previously only been suspected based on observations that dead animals can be used as bait for Komodo dragons and that some nocturnal geckos aggregate on flowers. We conducted a simple field test of the ability of the omnivorous lizard Podarcis lilfordi to find fruit hidden under opaque cups. When a board having two identical cups spaced 1 m apart, one empty and the other hiding a freshly cut piece of apricot, was placed in the habitat, lizards first contacted the cup hiding fruit at well above chance frequency. Upon contact with a cup, lizards were significantly more likely to stay next to the cup, tongue-flick at high rates, climb the cup, and attempt to bite the cup if it hid a piece of apricot. The ability to follow a concentration gradient of airborne volatile chemicals to its source is very likely mediated by olfaction, but participation by or primacy of vomerolfaction cannot be excluded.

Animals↗
PubMed1997

Bidirectional modulation of sweet and bitter taste by chlordiazepoxide and Ro 15-4513: lack of effect with GABA drugs.

Five rats were trained to respond for 10% sucrose and 10% sucrose/0.006% quinine in an operant procedure. Both solutions were concurrently available on independent, variable-interval 5-s schedules of reinforcement. Rats reliably responded for both solutions throughout the sessions and made approximately 68% of their total daily responses for the sucrose solution. When injected prior to the sessions with 4 mg/kg of chlordiazepoxide, rats selectively increased quinine responding; injections of the benzodiazepine inverse agonist Ro 15-4513 (9 mg/kg) led to decreased quinine responding. The effects of both chlordiazepoxide and Ro 15-4513 were reversed by the benzodiazepine antagonist flumazenil. Presession injections of flumazenil, muscimol, baclofen, or picrotoxin all resulted in no changes in responding, or a decrease in responding for both solutions. These results are discussed in terms of a bidirectional modulation of sweet-bitter taste preference by drugs acting on the benzodiazepine receptor. Moreover, the data from these experiments suggest that any changes in the oral consumption of alcohol following administration of benzodiazepine drugs must be examined in light of their effects on taste palatability.

Animals↗
PubMed1997

Calories affect zeitgeber properties of the feeding entrained circadian oscillator.

Rats with suprachiasmatic (SCN) lesions readily entrain to daily meals by increasing their activity prior to food access. Although previous experiments suggest that entrainment requires a nutritive meal, it is not yet clear what the parameters of the entraining stimulus are. The first experiment investigated the role of caloric content in resetting the feeding entrainable oscillator (FEO). Rats were entrained to 20 g chow/day until anticipatory activity was stable. The food access time was then delayed by 8 h and rats received either 0, 2, 6, or 16 g of chow for two days. Sixteen g of chow produced large delays on the next two cycles, while 0 and 2 g produced no delays. Two of 8 rats receiving 6 g showed delays, indicating that 22 kcal is near the threshold. In a second experiment, the effects of bulk were investigated. After an 8 h phase delay, rats received 0, 6, 10 or 16 g of chow mixed with cellulose for a total of 21 g for all groups. The 10 and 16 g chow groups delayed while the 0 g chow group did not. In the 6 g groups some animals phase shifted while others did not. Thus, the addition of non-nutritive bulk to the phase shifted meal had little or no effect on resetting the FEO and it appears that caloric content rather than gastric distention provides an effective zeitgeber for the FEO.

Animals↗
PubMed1999

Effects of intracerebroventricularly administered leptin on protein selection in the rat.

The effect of centrally administered rat leptin on selection of 5 and 30% protein diets was investigated in male Sprague-Dawley rats with indwelling i.c.v. cannulas. Leptin (0 vs 2.5 microg/day) was administered for 4 consecutive days, followed by an 8-day withdrawal period. Total intake was reduced to approximately 50% of that in the vehicle injected group during each day following leptin administration. Intake of both the 5 and 30% diets was reduced. Vehicle-treated rats selected a 13-15% CP diet. Diet selection in leptin-treated rats was not different during the first day, but on Days 2-4, leptin-treated rats selected a 10% CP diet. Intake began to normalize within 24-48 h after the last treatment, and was not different by Day 3 of the withdrawal period. Body weight was reduced by leptin treatment, and despite the normalization of food intake, did not recover during the withdrawal period. Rats were sacrificed at the end of the 8-day withdrawal period. Despite the reduction in body and carcass weights, liver, kidney, heart, and soleus muscle weights were not different between control and leptin-treated groups when expressed on an absolute or relative basis. However, epididymal and retroperitoneal fat pad weights were still reduced 56 and 78%, respectively, in rats that had been previously treated with leptin for 4 days and then not treated for 8 days. In addition, circulating T3 levels remained elevated in rats that had been treated with leptin. Centrally administered leptin has little effect on muscle mass, but had potent effects on intake of nonobese rats and a sustained effect on adipose tissue mass, thyroid hormone status, and body weight after withdrawal. Results from rats selecting between diets varying in protein content suggest that leptin may cause avoidance of protein.

Animals↗
PubMed1999

VMH lesions reduce excessive running under the activity-stress paradigm in the rat.

We have previously shown that excitation of certain neurons in the ventromedial nucleus of the hypothalamus (VMH) of rats induces hyperrunning activity. The present study investigated the involvement of these VMH neurons in inducing excessive running under the activity-stress paradigm. The VMH of 6-week-old male rats was bilaterally lesioned by administration of kainic acid. Control animals received saline in the VMH. They were housed in running-wheel activity cages with free access to food for 6 days of the recovering period, and then fed 1 h each day for 6 days. Control animals exhibited marked increases in both running activity and its light/dark ratio, and developed stomach ulcers. In contrast, animals with bilateral VMH lesions showed a significantly attenuated increase in running activity and no change in light/dark ratio. VMH lesions also suppressed stomach ulceration. These results suggest that VMH neurons play a crucial role in inducing excessive running and stomach ulceration during exposure to the activity-stress paradigm.

Analysis of Variance↗