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PubMed1999

The effect of naloxone on food-motivated behavior in the obese Zucker rat.

We assessed differences in food reinforced behavior between obese and lean Zucker rats with a progressive ratio schedule 3 (PR3) in which a subject emitted three additional lever-presses each time a reinforcer was delivered. The number of responses required for a reinforcer eventually exceeded its value, termed the "break point", a sensitive measure of food motivated behavior. Break points were higher in obese rats than lean controls for grain pellets (27.5 versus 9.5, P = 0.01) but not for sweet pellets (51.6 versus 38.5, P = 0.31). We determined if naloxone (0.01-3.0 mg/kg, SC), which reduces free food intake in obese Zucker rats, affects food motivated behavior in obese Zuckers and lean controls. Naloxone reduced break points in both obese and lean rats to a similar extent when working for either grain pellets or sweet pellets. Under free-access feeding conditions, naloxone again decreased pellet intake similarly in the obese and lean Zucker rats. Naloxone appeared to decrease free-access pellet consumption to a greater extent than break point in both groups. These results show that (1) obese rats exhibit higher levels of performance for food than lean rats only when working for the less valued grain pellet, (2) naloxone reduces both break points and free-access pellet consumption independent of genotype, and (3) naloxone appears to decrease food more effectively in rats given free access to food than in rats working for food.

Animals↗
PubMed2004

["Nutrition beyond 65"--amount of usual drinking fluid and motivation to drink are interrelated in community-living, independent elderly people].

BACKGROUND: Elderly people are at increased risk of dehydration due to age-related changes in kidney function, thirst perception, body water content and homeostatic capacity. Special attitudes toward drinking may furthermore contribute to the problem. Surprisingly, little is known about usual fluid intake and the motivation to drink in community-living elderly people. Thus, the aim of the present study was the assessment of fluid intake from beverages and the motivation to drink in this population group. METHODS: From a random sample of 1200 elderly, stratified into three age-groups (65-74 y., 75-84 y., 85+ y.), 361 fulfilled the inclusion criteria (living independently in private households and mental ability to answer simple questions correctly) and took part in this cross-sectional study. Usual fluid intake of beverages and seven attitudes towards drinking were assessed in personal in-home interviews by standardized questionnaire. Drinking fluid was classified into 5 classes. The relation between drinking fluid and attitudes was checked by the chi(2) test. RESULTS: 14% of all participants (men 15%, women 14%; n.s.) reported usual drinking amounts below 1 l. This proportion was markedly higher in very-old elderly (85+ y. 27%) compared to younger participants (75-84 y. 15%, 65-74 y. 8%; p=0.001). Of all participants, 78% confirmed the statement "I am drinking because it is healthy", while 57% agreed to the statement "I am drinking because it tastes good." Subjects who stated that they pay attention to sufficient drinking amounts (63%) only rarely drank less than 1 l (7%; p<0.001). In contrast, one quarter to one third of subjects who only drink when they are thirsty (54%), who stated to drink little because of lacking thirst (30%) or to reduce the amount of drinking fluid in order to avoid micturition in general (9%) or during the night (12%) drank less than 1 l (all p<0.001). CONCLUSION: Every seventh subject aged 65 years or older and every fourth aged 85 years or older shows insufficient amounts of drinking fluid. The observed relations between usual fluid intake and attitudes towards drinking argue for the possibility to improve drinking behavior by selective educational measures.

Activities of Daily Living↗
PubMed2005

Post-circuit blues: motivations and consequences of crystal meth use among gay men in Miami.

Miami, Florida was at the vanguard of the rise of circuit parties and attendant club drug use-especially ecstasy, GHB, and ketamine-in the 1990s. Crystal methamphetamine, a drug of abuse among gay men for some years on the West coast, gradually moved east toward the end of the decade and recently became prevalent in Miami. This paper reports the results of focus group research into the motivations and consequences of crystal use among gay men in this new setting. Loneliness, fears about physical attractiveness due to aging and illness, and desires to lose sexual inhibitions were common motivations for using the drug. Continued use of crystal was often described as the cause of lost friendships, employment and long-term relationships, as well as sexual behaviors that put men at risk for HIV and other sexually transmitted infections. Implications for drug and sexual risk prevention interventions are discussed.

Adult↗
PubMed2005

Anger as a moderator of safer sex motivation among low-income urban women.

Theoretical models suggest that both HIV knowledge and HIV risk perception inform rational decision making and, thus, predict safer sex motivation and behavior. However, the amount of variance explained by knowledge and risk perception is typically small. In this cross-sectional study, we investigated whether the predictive power of HIV knowledge and HIV risk perception on safer sex motivation is affected by trait anger. We hypothesized that anger may disrupt rational decision making, distorting the effects of both HIV knowledge and risk perception on safer sex intentions. Data from 232 low-income, urban women at risk for HIV infection were used to test a path model with past sexual risk behavior, HIV knowledge, and HIV risk perception as predictors of safer sex intentions. Moderator effects of anger on safer sex intentions were tested by simultaneous group comparisons between high-anger and low-anger women (median split). The theoretically expected "rational pattern" was found among low-anger women only, including (a) a positive effect of knowledge on safer sex intentions, and (b) buffer (inhibitor) effects of HIV knowledge and HIV risk perception on the negative path leading from past risk behavior to safer sex intentions. Among high-anger women, an "irrational pattern" emerged, with no effects of HIV knowledge and negative effects of both past risk behavior and HIV risk perception on safer sex intentions. In sum, the results suggest that rational knowledge- and risk-based decisions regarding safer sex may be limited to low-anger women.

Adolescent↗
PubMed2006

The 20-min trial of the maintenance of wakefulness test is profoundly affected by motivation.

Assessment of the ability to maintain wakefulness, although very important both for research and for clinical purposes, is still equivocal. The current gold standard is considered the Maintenance of Wakefulness Test (MWT), although there are two different potential protocols to perform it and the normal reference range has been determined on selected populations. The effect of potential "penalty" on failing the test (i.e., presenting sleepiness) has not been seriously studied. We therefore planned this study to examine the effect of motivation on the MWT results in a potentially sleepy population. We hypothesized that with the knowledge that participants may lose their driving license if they fail the test, the results would indicate significantly less sleepiness than reported for other populations. Fifty-four consecutive subjects at high risk of sleepiness referred to the sleep laboratory for evaluation of their ability to maintain wakefulness were studied. All were referred by the National Council for Driving Safety, knowing that if they failed the test, their driving license would not be renewed. Referral reasons were previously diagnosed: obstructive sleep apnea (OSA; 43%), sleep-related accident (7%), or other causes to suspect sleepiness. All underwent a full-night polysomnography (PSG) followed by MWT, five trials of 20 min each (MWT20). Of the 54 participants, 13 were treated for OSA and 28 had untreated OSA, 21 of them had severe OSA (Respiratory Disturbance Index > 30/h). Seventy-four percent of the participants had a BMI >30 kg/m2. Only 5 of the participants fell asleep in any of the MWT trials (one to five trials), which could not be predicted by severity of OSA, age, BMI, or variables derived from the previous night PSG. Of the 21 patients with severe untreated OSA, only 1 patient fell asleep during the MWT20. We conclude that motivation profoundly affects the MWT results, raising the question what should be considered normal or abnormal when sleepy results may cause penalty or other practical implications. In addition, we believe that these results suggest that for renewal of driving license purposes, the MWT20 is insufficient. We speculate that MWT40, with tighter cutoff threshold, would be a more effective tool.

Accidents, Traffic↗
PubMed1989

Effects of goal-related motivational states on the orienting of spatial attention.

Three experiments are presented indicating that motivational processes arising from incentive and feedback signals exert specific effects on the orienting of visual spatial attention. Subjects played a video game in which targets were presented in one of two peripheral locations. Pre-target cues were employed to orient attention to a location where points could be gained (positive incentive cue), to a location where points could be lost (negative incentive cue) or to neither location (neutral cue). Cost-benefit analyses were used to assess the consequences of such orienting. Although there was no evidence of general attentional biases favoring positive over negative incentives, all three experiments demonstrated an interaction between the incentive value of the current trial and the outcome of the previous trial. Following unsuccessful outcomes, attentional costs were greater for positive than negative incentives, whereas following successful outcomes, costs were larger for negative than positive cues. This pattern was evident for tasks involving detection, perceptual discrimination and memory scanning. These findings are discussed in light of contemporary models of motivation and the control of attention.

Adult↗
PubMed1994

Motivation: cause or confound in information processing/intelligence correlations?

The goal of the present study was to determine whether correlations between information processing scores and intelligence can be explained in terms of between-subject motivational differences. One hundred and nine male and female volunteer college students were tested on a battery of microcomputerized cognitive tests. One hundred of these subjects returned for a second session in which they were randomly assigned to an incentive or no-incentive condition and then retested. The effort expended on the tests was measured via heart rate, skin conductance, and a self-report questionnaire. Criterion measures, including the Advanced Otis-Lennon Test of Mental Abilities and Advanced Raven Progressive Matrices were also taken. The findings revealed that incentives had relatively modest effects on performance. In no case, however, did incentives affect the overall IQ-performance correlation for the tests used in the battery. These results support the view that correlations between information processing scores and intelligence reflect common mental capacities, rather than some affective variable such as motivation.

Adolescent↗
PubMed1991

Microinjection of the dopamine antagonist cis-flupenthixol into the MPOA impairs copulation, penile reflexes and sexual motivation in male rats.

Microinjection of the dopamine antagonist cis-flupenthixol into the medial preoptic area was previously shown to impair male rat copulatory behavior. The present experiments provide further evidence of cis-flupenthixol's inhibitory effects on male sexual behavior. Following microinjections of moderate to high doses of cis-flupenthixol, males exhibited slower copulatory rates and fewer ejaculations in copula, fewer ex copula erections and penile movements, and reduced sexual motivation in an X-maze. Locomotion in the X-maze was not significantly affected. Microinjections of the inactive isomer trans-flupenthixol produced no change in any behavioral measure, indicating that cis-flupenthixol's effects were receptor mediated. We suggest that dopamine receptors in the MPOA influence copulation primarily by regulating reflexive and motivational factors, but not locomotion.

Animals↗
PubMed1993

Socio-sexual behavior in male rats after lesions of the medial preoptic area: evidence for reduced sexual motivation.

Different hypotheses have been put forward trying to explain the mechanisms associated with the disruption of male sexual behavior after lesions of the medial preoptic area (MPOA). It has been suggested that sexual motivation, motor execution or both are affected by MPOA lesions. In the present experiment, the socio-sexual behavior of male rats bearing extensive MPOA lesions, that abolished sexual behavior, was compared with that of sham-lesioned animals and to prelesion levels. The socio-sexual interactions were recorded for 10 min in one prelesion and two postlesion tests. The frequency and duration of the following behaviors were recorded: rearing, sniffing, self-grooming, grooming partner, genital exploration, pursuit and resting. The analysis of the socio-sexual interactions showed that the frequency and duration of pursuit was reduced in the first and second tests after the lesion in comparison to both prelesion levels and to a sham-lesioned group. There is strong evidence that pursuit is the only precopulatory behavior that can consistently predict the appearance of sexual behavior. When pursuit is reduced the transition from the precopulatory to the copulatory phase is made more difficult. Therefore, it appears that the MPOA lesions reduce the subject's motivation to engage in sexual behavior.

Animals↗
PubMed1992

The NMDA antagonist dizocilpine (MK801) attenuates motivational as well as somatic aspects of naloxone precipitated opioid withdrawal.

The non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine has recently been reported to antagonize certain overt withdrawal signs in morphine dependent rats. The purpose of the present study was to reassess this response and examine the effect of this drug in a model presumably reflective of the motivational impact of withdrawal using the place conditioning technique. Rats were made opiate dependent by the subcutaneous implantation of a 75 mg morphine pellet. Three-4 days later withdrawal was precipitated by naloxone 0.5 mg/kg. Dizocilpine (0.1-0.5 mg/kg) attenuated many of the subsequent behaviours elicited by naloxone, notably diarrhoea, mouth movements, paw shakes and ptosis. In a separate group of morphine dependent rats, naloxone (0.05 mg/kg) precipitated withdrawal produced a clear place aversion. This place aversion was blocked by dizocilpine (0.02-0.1 mg/kg) pre-treatment prior to conditioning. Therefore dizocilpine may modify both motivational and somatic aspects of opioid withdrawal.

Animals↗
PubMed1993

The antinociceptive and motivational effects of intranigral injection of opioid agonists.

The antinociceptive potency of morphine and the morphine metabolite morphine-6-glucuronide (M6G) was examined after injection into the substantia nigra and periaqueductal gray (PAG) of rats. Both drugs produced antinociception in both sites. The antinociceptive potency of M6G was significantly greater than morphine in the nigra. There was no difference in the antinociceptive potency of M6G in the nigra and PAG. M6G and other opioids were also examined for motivational effects after intranigral injection. A high dose of intranigral morphine (10.0 nmol) produced a conditioned place preference. No significant motivational effects were produced by 1.0 nmol of M6G, D-Ala2, N-Me-Phe4,Gly5-ol-enkephalin (DAGO), D-Pen2,D-Pen5-enkephalin (DPDPE), or U-50,488H. It is concluded that the substantia nigra plays an important role in opioid antinociception. The role of the nigra in opioid reward is questionable.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1979

Dorsal bundle extinction effect: motivation or attention?

Male albino Wistar rats were injected bilaterally with 4 micrograms of 6-hydroxydopamine into the dorsal noradrenergic bundle to deplete forebrain noradrenaline to less than 5% of control values. Acquisition learning of a fixed interval schedule or a continuously reinforced schedule was not altered but resistance to extinction was seen after food reinforced training on either schedule but not after water reinforced training. A possible increase in food motivation was tested by the use of preloading with free food prior to a fixed interval session but both control and lesioned rats reacted similarly to this manipulation thus appearing to exclude an increase in food motivation. An attentional explanation is proposed and tested by the demonstration that resistance to extinction does not occur after a partially (variable ratio 4), as opposed to a continuously, reinforced schedule. Further evidence in favour of an attentional mechanism comes from the finding that on both a fixed interval and a continuously reinforced schedule the lesion has to be present during the acquisition phase to result in subsequent resistance to extinction. Intact animals trained on either schedule and subsequently subjected to the lesion failed to show an increased resistance to extinction.

Animals↗
PubMed1984

An empirical study of the structure of the patrol/marking motivational system in the rat.

The existence and structure of an hypothesized motivational system of patrol/marking was supported and elucidated by a behavioral study on untrained highly inbred laboratory rats. One rat (the "runner") was placed into a test chamber containing a wire-mesh running wheel flanked by two chambers, one of which contained another rat (the "target"). Four conditions of runners (socially-isolated males, socially-housed males, non-estrous females, and estrous females) were exposed to four types of targets (socially-housed males, non-estrous females, estrous females, and blank targets consisting of any empty target chamber). Also placed in the chamber was a Petri dish containing scent-markings of the target rat. The experiment was designed in a counterbalanced way with 10 replications and repeated two times in two separate years. As predicted from the hypothesis, scent-marking, sniffing the dish, locomotion (number of wheel revolutions), and approach (differential running towards the target) were all correlated with each other and varied in the same way as a function of the hormonal and experiential condition of the runner and the type of target. They were interpreted to reflect motor patterns of a single unitary patrol/marking motivational system. Grooming, on the other hand, did not correlate with the other behaviors and facial gland secretion was, therefore, rejected as a motor pattern of patrol/marking.

Animals↗
PubMed1988

A simple device for estimating some behavioral and electrophysiological features of shelter-seeking motivation in the rat.

Motivational-emotional mechanisms were analyzed both by behavioral and electrophysiological methods. Rats were required to run along a straight runway alley (200 cm long) from a small, illuminated "starting plate" on one end to a dimly lit box on the other. The animal was hand-carried from the box to the starting plate and then it returned to the box without any additional reinforcement. Such locomotor reaction was acquired very quickly and could subsequently be evoked over several months. The behavioral effects of isolated changes in the experimental design were tested. The typical picture of the hippocampal RSA, during such motivational reactions was recorded.

Animals↗
PubMed1989

Level searching: a new assay of sexual motivation in the male rat.

Mendelson and Gorzalka recently described a bilevel chamber for the evaluation of rodent sexual behavior. In initial studies it was observed that during 5 min adaptation periods prior to the introduction of a sexually receptive female rat, male rats with prior sexual experience in these chambers would move from level to level in apparent search for the female rat. In Experiment 1, we examined the acquisition of this level searching behavior in male rats. Sexually active male rats were given access to either sexually receptive or nonreceptive female rats following a 5 min period alone in the bilevel chamber. Only male rats that pursued and copulated to ejaculation with sexually receptive females in the bilevel chamber significantly increased the number of their level to level movements in subsequent tests during the 5 min periods prior to the introduction of the female rat. In Experiment 2, male rats that had acquired asymptotic rates of level searching showed a significant attenuation of this behavior when the presentation of a female rat into the chamber was discontinued. These findings lead us to conclude that the increase in level to level movement by the male rat represents a sexually motivated search for the female rat. We suggest that the analysis of the acquisition, maintenance, and extinction of level searching behavior might serve as a simple assay of sexual motivation in the male rat.

Animals↗
PubMed1994

The abnormal quinine drinking aversion in the Brattleboro rat with diabetes insipidus is reversed by the vasopressin agonist DDAVP: a possible role for vasopressin in the motivation to drink.

The Brattleboro rat with hypothalamic diabetes insipidus (BDI) has an abnormal aversion to drinking quinine-adulterated water compared with normal rats of the parent Long Evans (LE) strain. This BDI animal tolerates marked hypovolemia and decreased body weight in preference to drinking the quinine-adulterated fluid, indicative of a reduced motivation to drink. Acute or chronic treatment of BDI rats with desamino-8D arginine vasopressin (DDAVP) restored to normal their drinking response to quinine solution. Partial restoration of fluid turnover in BDI rats with hydrochlorothiazide, which has an antidiuretic effect in diabetes insipidus (when vasopressin is absent), failed to abolish the abnormal drinking response to quinine-adulterated solution in 8 out of 12 animals. In contrast, induction of diabetes mellitus in LE rats, which resulted in a marked polydipsia and polyuria even though vasopressin was still present, did not impair the drinking response to quinine solutions. These results suggest that the abnormal drinking response to quinine-adulterated fluid in BDI rats is reversed by treatment with the vasopressin V2-receptor agonist DDAVP but is unlikely to be a consequence of the restoration of fluid turnover to normal levels by a renal action. A possible central action involving vasopressin and the motivation to drink is discussed.

Animals↗
PubMed1986

Behavioral deficits induced by low doses of apomorphine in rats: evidence for a motivational and cognitive dysfunction which discriminates among neuroleptic drugs.

In order to further assess the alterations (motor, motivational or cognitive) that might underlie animal behavioral deficits associated with a reduced dopamine transmission, the effects of apomorphine at doses thought to stimulate dopaminergic autoreceptors were studied on rat operant behavior. Apomorphine (30 micrograms/kg SC) decreased the number of food rewards obtained, when rats trained on a continuous reinforced schedule were shifted to schedules of fixed ratio higher than 2:FR3, FR4, and FR8. In rats shifted to a FR4 schedule, apomorphine (7.5, 15, 30, 60 micrograms/kg SC) dose-relatedly reduced the number of rewards obtained. In rats subjected to previous extinction sessions, apomorphine (30 micrograms/kg) did not affect lever pressing reinstated on presentation of primary reinforcers but inhibited responding renewed on presentation of secondary reinforcers. Under a FR(3 + 1) schedule where the last (rewarded) response was distinct from the initial (non-rewarded) responses, the detrimental effect of apomorphine on response rates was considerably weaker than under a conventional FR4 schedule. The reward deficits caused by apomorphine under the FR4 schedule were dose-dependently and completely reversed by amisulpride (0.125, 0.25, 0.5, 1 and 2 mg/kg), pimozide (0.125 mg/kg), sulpiride (8, 16, 32 and 64 mg/kg), but not by conventional neuroleptics (namely chlorpromazine, fluphenazine, haloperidol, metoclopramide and thioridazine). It is suggested that behavioral deficits associated with a reduced dopamine transmission such as that caused by low doses of apomorphine involve motivational and cognitive dysfunctions rather than motor impairments. In account of its differential sensitivity to neuroleptic drugs, apomorphine-induced deficit might have some relevance for a further delineation of the mechanisms of action of these compounds.

Animals↗
PubMed1994

Effects of alcohol on the sexual motivation of the male rat.

Previous research measuring the effects of alcohol on sexual behavior has primarily focused on its effects on copulation. The present experiment was designed to investigate the effects of alcohol on the sexual motivation of the male rat by requiring operant responding to gain access to a sexually receptive female. A novel apparatus was used that allowed both visual and olfactory cues from an estrous female to reach the male. Lever presses resulted in the opening of a door that permitted the male rat to enter an adjacent chamber where a receptive female was located. Treatment with low to moderate doses of alcohol (0.5 g/kg and 1.0 g/kg) resulted in increased latencies to emit the first response of the males working for access to females, but did not affect response rate or subsequent mount or ejaculation latencies, when these males were allowed access to the receptive female. Furthermore, alcohol failed to show any response-reinstating or disinhibitory effects when tested following a period of nonreinforced extinction trials. An additional experiment, in which rats received equivalent doses of alcohol, revealed no decrease in spontaneous locomotion. Taken together, these data suggest that the response-reducing effects of alcohol are probably not a result of general drug-induced reductions in activity, but rather an attenuating action of the drug on sexual motivation.

Animals↗