Ghrelin and Glucagon-Like Peptide-1: A Gut-Brain Axis Battle for Food Reward

Eating behaviors are influenced by the reinforcing properties of foods that can favor decisions driven by reward incentives over metabolic needs. These food reward-motivated behaviors are modulated by gut-derived peptides such as ghrelin and glucagon-like peptide-1 (GLP-1) that are well-established to promote or reduce energy intake, respectively. In this review we highlight the antagonizing actions of ghrelin and GLP-1 on various behavioral constructs related to food reward/reinforcement, including reactivity to food cues, conditioned meal anticipation, effort-based food-motivated behaviors, and flavor-nutrient preference and aversion learning. We integrate physiological and behavioral neuroscience studies conducted in both rodents and human to illustrate translational findings of interest for the treatment of obesity or metabolic impairments. Collectively, the literature discussed herein highlights a model where ghrelin and GLP-1 regulate food reward-motivated behaviors via both competing and independent neurobiological and behavioral mechanisms.     

Alcohol Use as a Function of Physical Activity and Golfing Motives in a National Sample of United States Golfers

Alcohol and physical inactivity are risk factors for a variety of cancer types. However, alcohol use often co-occurs with physical activity (PA), which could mitigate the cancer-prevention benefits of PA. Alcohol is integrated into the culture of one of the most popular physical activities for adults in the United States (U.S.), golf. This study examined how alcohol use was associated with total PA, golf-specific PA, and motives for golfing in a national sample of golfers in the U.S. Adult golfers (n = 338; 51% male, 81% White, 46 ± 14.4 years) self-reported alcohol use, golfing behavior and motives, and PA. Most (84%) golfers consumed alcohol, averaging 7.91 servings/week. Golf participation, including days/week, holes/week, and practice hours/week, was not associated with alcohol use. Golfers with stronger social motives were 60% more likely to consume alcohol. Weekly walking (incident risk ratio (IRR) = 7.30), moderate-to-vigorous PA (MVPA; IRR = 5.04), and total PA (IRR = 4.14) were associated with more alcohol servings/week. Golfers’ alcohol use may be higher than the general adult population in the U.S. and contributes 775 extra kilocalories/week, a surplus that may offset PA-related energy expenditure and cancer-protective effects. Alcohol use interventions targeting golfers may facilitate weight loss and reduce cancer risk, especially for golfers motivated by social status.     

Community care staff attitudes towards delivering a falls prevention exercise intervention to community care clients

Millions of older people world-wide receive community care services in their home to assist them to live independently. These services often include personal care, domestic assistance and social support which are delivered by non-university trained staff, and are frequently long term. Older people receiving community care services fall 50% more often than individuals of similar age not receiving services. Yet, few ongoing community care services include exercise programs to reduce falls in this population. We conducted an earlier study to examine the feasibility of community care staff delivering a falls prevention program. A critical finding was that while some of the assessment and support staff responsible for service delivery delivered the falls prevention exercise program to one or two clients, others delivered to none. Therefore, the aim of this qualitative sub-study was to understand reasons for this variation. Semi-structured interviews were conducted with 25 participating support staff and assessors from 10 community care organisations. Staff who had successfully delivered the intervention to their clients perceived themselves as capable and that it would benefit their clients. Older clients who were positive, motivated and wanted to improve were perceived to be more likely to participate. Staff who had worked at their organisation for at least 5 years were also more likely to deliver the program compared to those that had only worked up to 2 years. Staff that did not deliver the intervention to anyone were more risk averse, did not feel confident enough to deliver the program and perceived their clients as not suitable due to age and frailty. Experienced staff who are confident and have positive ageing attitudes are most likely to deliver falls prevention programs in a home care organisation.     

Effect of benzene and its homologs on unit activity in various brain structures

Department of Normal Physiology, Irkutsk Medical Institute (Presented by Academician of the Academy of Medical Sciences of the USSR K. V. Sudakov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 110, No. 7, pp. 17–19, July, 1990.     

The acceptance of SARS-CoV-2 rapid antigen self-testing: A cross-sectional study in China

Compared with the nucleic acid amplification test (NATT), the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapid antigen self-testing (RAST) has advantages in speed and convenience. However, little is known about people's acceptance and influencing factors for SARS-CoV-2 RAST. A cross-sectional study was conducted from April 21 to 30, 2022 in China. The χ² test and multivariate logistic regressions were used to identify the influencing factors. The structural equation model was used to test the extended protective motivation theory (PMT) model hypotheses. Among the total of 5107 participants, 62.5% were willing to accept the SARS-CoV-2 RAST. There were significant differences in acceptance among different residences (p < 0.001), educational level (p < 0.001), occupation (p < 0.001), monthly income (p < 0.001), travel frequency (p < 0.05), and feelings about NATT (p < 0.001). Response efficacy (β = 0.05; p = 0.025) and self-efficacy (β = 0.84; p < 0.001) had a positive effect, while response cost showed a negative effect (β = −0.07; p < 0.001). The public's major concerns about SARS-CoV-2 RAST are its reliability, testing method, price, and authority. Overall, a moderate intention to use SARS-CoV-2 RAST was found among the Chinese population. The extended PMT can be used for the prediction of intention to accept the RAST. We need to take measures to increase people's acceptance of SARS-CoV-2 RAST.     

Behavioral significance of phasic changes in mesolimbic dopamine-dependent electrochemical signal associated with heroin self-injections

Summary High-speed chronoamperometry with monoamine-selective carbon fiber electrodes was used in rats to monitor, during 5–6 consecutive daily sessions, changes in DA-dependent electrochemical signal in the nucleus accumbens (NAcc) during intravenous heroin (0.1 mg/kg) self-administration (SA) behavior and passive repeated drug injections performed with a temporal scheme similar to that in the SA experiment. In trained animals, biphasic signal fluctuations time-locked to the individual lever-presses were found to accompany all but the first daily SAs. The signal gradually increased by 30–40 nM for the 10 minutes preceding the SA, reached a peak at the moment of lever-press and decreased abruptly by 40 nM for 3–4 min after heroin SA. The cycle then repeated, reaching a new peak at the moment of the next lever-press. Rapid bi-directional fluctuations in signal associated with individual heroin SAs were superimposed on substantial tonic increase in signal baseline (400–500 nM). This increase quickly developed after presentation of heroin-related light cue and the first SA, was relatively stable during all subsequent SAs and decreased towards the baseline after the last SA of a session. Changes in signal baseline induced by repeated heroin SAs depended strongly upon the signal's basal level (r=– 0.787); that signal preferentially increased when its basal values were low (0–300 nM), and decreased when signal was tonically elevated (> 600 nM). Repeated passive heroin injections also induced biphasic signal fluctuations and a similar tonic increase in signal baseline. Although a transient signal decrease (25 nM for 2–4 minutes) followed by a prolonged signal increase occurred after each but not the first passive injection, the gradual pre-injection signal acceleration was absent.Although DOPAC, a principal DA metabolite, may significantly contribute to the tonic increase in electrochemical signal seen during SA session, the changes in extracellular DA may be the main contributor to both the rapid signal increases preceding drug-taking and the transient signal decreases following heroin SA. If so, the present findings suggest that activation of mesolimbic DA cells and increase in DA transmission may be involved in the mediation of motivational and/or activational components of drug-seeking and drug-taking behavior. An acute termination of previous drug- and behavior-associated DA activation with a transient inhibition of DA release, immediately following heroin SA may correlate with the drug's rewarding action, representing a part of a mechanism regulating drug-taking behavior.     

Relationship between achievement goal orientations and perceived motivational climate on intrinsic motivation

This study examines first the relationship of perceived motivational climate and goal orientation to indices of intrinsic, extrinsic motivation and amotivation, and second their respective role in predicting these indices of motivation. A total of 160 students enrolled in physical activity classes volunteered to participate. Results of Pearson correlation analyses indicated that students who perceived their class climate as emphasizing mastery were more likely to feel self-determined. Hierarchical regression analyses revealed that perceived motivational climate was a better predictor of all indices of motivation than goal orientations. Results, discussed according to the achievement goal perspective and the hierarchical model of intrinsic and extrinsic motivation, highlight a possible motivational process explaining how the motivational climate overrides goal orientations.     

Psychomotor retardation and anhedonia in depression

Anhedonia, the inability to experience pleasure, and observed changes in psychomotor performance are frequent psychopathological phenomena in major depression with possible common neurobiological mechanisms. Interest, pleasure and reactivity to pleasurable stimuli contribute to movement generation and observable behaviour. Therefore the relationship between anhedonia and psychomotor retardation was studied in 48 depressed patients. Subjectively experienced anhedonia correlated with self-rated but not with observer-rated global severity of depression. There was a significant correlation between anhedonia and psychomotor retardation assessed with the Widlöcher Retardation Scale. The results suggest the existence of an empirical relationship between reduced ability to experience pleasure and observable psychomotor retardation in depression. Specific measures of psychomotor phenomena may provide further insights into the relationship between observable behaviour and self-experienced symptoms in depression.     

Modulation of feeding-induced activation of mesolimbic dopamine transmission by appetitive stimuli and its relation to motivational state

We have previously shown in non-deprived rats that feeding of an unfamiliar palatable food (Fonzies(R)) phasically stimulates in vivo dopamine (DA) transmission in the medial nucleus accumbens (NAc) and this effect undergoes habituation after a previous (24 h) Fonzies meal (Bassareo & Di Chiara 1997, J. Neurosci., 17, 851-861). The present study shows that an unfamiliar food (Kinder(R)) with a taste and composition (milk chocolate) different from that of Fonzies, also induces a release of DA in the NAc subjected to one-trial habituation. Habituation was taste specific as no cross-habituation was observed between Fonzies and Kinder. In undeprived rats, a 40-min exposure to an intrinsic appetitive stimulus (food smell arising from a Fonzies-filled plastic box) also prevented the increase in dialysate DA associated with Fonzies feeding, and this effect was partially reversed by food deprivation. Food deprivation also prevented habituation of Fonzies-induced increase of dialysate DA in the NAc. Predictive association of an empty plastic box to Fonzies feeding resulted in the acquisition of appetitive properties by the box and in facilitation (rather than inhibition) of the phasic responsiveness of DA transmission to Fonzies feeding. A 10-min pre-exposure to appetitive olfactory stimuli intrinsic to Fonzies still prevented, like a 40-min pre-exposure, the NAc DA response to Fonzies feeding; however, a 5-min pre-exposure to these appetitive stimuli did not prevent the DA response in the NAc. These results show that the phasic responsiveness of NAc DA transmission to an unfamiliar palatable food is under strong modulatory control by primary (consummatory) and secondary (appetitive) stimuli, and that the sign and extent of this control depends on the nature of the appetitive stimulus, delay of reward and motivational state (deprivation).