Influence of fat-free mass and resting metabolic rate on increased food reinforcement after exercise training

Purpose Models of appetite control have been largely based on negative feedback from gut and adipose signaling to central appetite centers. However, contemporary models posit that fat-free mass (FFM) or the energy demand of FFM [i.e., resting metabolic rate (RMR)] may play a primary role in the motivational drive for food intake (i.e., food reinforcement). The relative reinforcing value of food (RRVfood) is associated with energy intake (EI) and increases with an acute energy deficit. Chronic exercise-induced energy deficits lead to alterations in fat mass (FM), FFM, and RMR and provide an opportunity to test whether change in (∆) FM, ∆FFM, ∆usual EI, or ∆RMR are associated with ∆RRVfood. Methods Participants (n = 29, BMI = 25–35 kg/m2) engaged in aerobic exercise expending 300 or 600 kcal, 5 days/weeks for 12 weeks. The reinforcing value of food (PMaxfood) was measured via a computer-based operant responding task and RRVfood was calculated as the reinforcing value of food relative to non-eating sedentary behaviors. RMR was determined by indirect calorimetry and body composition by DXA. Results Post-training FFM correlated with usual post-training EI (rs = 0.41, p < 0.05), PMaxfood (rs=0.52, p < 0.01), and RMR (rs = 0.85, p < 0.0001). ∆RMR negatively correlated with ∆PMaxfood (rs = − 0.38, p < 0.05) and with ∆RRVfood (rs = − 0.37, p < 0.05). ∆PMaxfood and ∆RRVfood were not associated with ∆FFM (p = 0.71, p = 0.57, respectively). Conclusions Reductions in RMR with weight loss may increase food reinforcement as means of restoring FFM and RMR to pre-weight loss amounts. Limiting reductions in RMR during weight loss may benefit weight maintenance by restricting increases in food reinforcement after weight loss.

Determination of amino acids content of the Tagetes lucida Cav. by GC/MS

Plant raw materials are widely used for the prevention and treatment providing of many diseases. The interest is the in-depth research of the flowers, leaves, and herb of Tagetes lucida. Therefore, the study aimed to determine the content of primary metabolites, namely amino acids in the raw materials of this plant. The amino acids composition and content in flowers, leaves, and herb were determined by the GC/MS method. The results of the study revealed that the raw material of Tagetes lucida contains more bound and less free amino acids. Free and bound L-proline, L-isoleucine were present in all the analyzed samples in the greatest amount (1.909 mg/g and 20.999 mg/g, 0.804 mg/g and 18.908 mg/g in the flowers; 2.721 mg/g and 18.973 mg/g, 3.459 mg/g and 28.518 mg/g in the leaves; 6.436 mg/g and 18.817 mg/g, 0.245 mg/g and 0.222 mg/g in the herb). Another free amino acid with a high content in flowers (1.321 mg/g) and herb (0.825 mg/g) of Tagetes lucida was L-aspartic acid. In addition, high content of L-phenylalanine in bound form was found in the leaves (11.843 mg/g) of the study plant. These amino acids to be considered distinguishing markers of the Tagetes lucida. This research contributes to already known information of Tagetes lucida use as herbal medicine, nutraceutical, and food reinforcement.

Acquisition of a Learned Operant and Critical Flicker-Fusion Rate in the Tuatara (Sphenodon spp.)

<p>Scientific investigation of the sensory world and behavior of the tuatara is limited. This study incorporates both ecological and psychological perspectives to test learning and visual perception using a novel operant technique and flicker-fusion rates to measure visual discrimination in tuatara. We posed four main questions: (1) can a reliable method examine learning and visual perception in tuatara?, (2) what is the critical flicker-fusion (CFF) rates for tuatara and how does it relate to motion detection ability?, (3) can stimulus control be transferred to a Y-maze from an open field arena?, and (4) what are the implications for behavioral ecology, conservation, and species welfare? Tuatara (Sphenodon punctatus) were trained using an operant conditioning procedure with food reinforcement to respond to discriminative stimuli (S+) of various flicker-fusion rates, and ignore a non-discriminative stimulus (S-). Tuatara discriminated CFF rates between 2.65-45.61 Hz, but not at 65.09 Hz. The upper threshold between 45.61-65.09 Hz is comparable to other mammalian, avian, and herpetological species. Tuatara demonstrated a learning capacity for acquisition of an operant task as well as cognitive development for learning and memory strategies. Visual discrimination is important to tuatara and may facilitate behavioral responses to many context-dependent ecological processes (i.e., predator/prey/kin recognition, mate selection, environmental discrimination, optimal foraging strategies, and communication). By understanding the importance of visual stimuli, the study provides a better perspective of the tuatara natural sensory world. Additionally, a reliable method was established that can be used for more comprehensive psychophysical experiments to further access visual perception and learning in all reptiles, with the potential to examine other sensory mechanisms such as audition, chemoreception, and tactility.</p>

Acquisition of a Learned Operant and Critical Flicker-Fusion Rate in the Tuatara (Sphenodon spp.)

<p>Scientific investigation of the sensory world and behavior of the tuatara is limited. This study incorporates both ecological and psychological perspectives to test learning and visual perception using a novel operant technique and flicker-fusion rates to measure visual discrimination in tuatara. We posed four main questions: (1) can a reliable method examine learning and visual perception in tuatara?, (2) what is the critical flicker-fusion (CFF) rates for tuatara and how does it relate to motion detection ability?, (3) can stimulus control be transferred to a Y-maze from an open field arena?, and (4) what are the implications for behavioral ecology, conservation, and species welfare? Tuatara (Sphenodon punctatus) were trained using an operant conditioning procedure with food reinforcement to respond to discriminative stimuli (S+) of various flicker-fusion rates, and ignore a non-discriminative stimulus (S-). Tuatara discriminated CFF rates between 2.65-45.61 Hz, but not at 65.09 Hz. The upper threshold between 45.61-65.09 Hz is comparable to other mammalian, avian, and herpetological species. Tuatara demonstrated a learning capacity for acquisition of an operant task as well as cognitive development for learning and memory strategies. Visual discrimination is important to tuatara and may facilitate behavioral responses to many context-dependent ecological processes (i.e., predator/prey/kin recognition, mate selection, environmental discrimination, optimal foraging strategies, and communication). By understanding the importance of visual stimuli, the study provides a better perspective of the tuatara natural sensory world. Additionally, a reliable method was established that can be used for more comprehensive psychophysical experiments to further access visual perception and learning in all reptiles, with the potential to examine other sensory mechanisms such as audition, chemoreception, and tactility.</p>

A common limiter circuit for opioid choice and relapse identified in a rodent addiction model

Activity in numerous brain regions drives heroin seeking, but no circuits that limit heroin seeking have been identified. Furthermore, the neural circuits controlling opioid choice are unknown. In this study, we examined the role of the infralimbic cortex (IL) to nucleus accumbens shell (NAshell) pathway during heroin choice and relapse. This model yielded subpopulations of heroin versus food preferring rats during choice, and choice was unrelated to subsequent relapse rates to heroin versus food cues, suggesting that choice and relapse are distinct behavioral constructs. Supporting this, inactivation of the IL with muscimol produced differential effects on opioid choice versus relapse. A pathway-specific chemogenetic approach revealed, however, that the IL-NAshell pathway acts as a common limiter of opioid choice and relapse. Furthermore, dendritic spines in IL-NAshell neurons encode distinct aspects of heroin versus food reinforcement. Thus, opioid choice and relapse share a common addiction-limiting circuit in the IL-NAshell pathway.

Impact of Fluoxetine on Behavioral Invigoration of Appetitive and Aversively Motivated Responses: Interaction With Dopamine Depletion

Impaired behavioral activation and effort-related motivational dysfunctions like fatigue and anergia are debilitating treatment-resistant symptoms of depression. Depressed people show a bias towards the selection of low effort activities. To determine if the broadly used antidepressant fluoxetine can improve behavioral activation and reverse dopamine (DA) depletion-induced anergia, male CD1 mice were evaluated for vigorous escape behaviors in an aversive context (forced swim test, FST), and also with an exercise preference choice task [running wheel (RW)-T-maze choice task]. In the FST, fluoxetine increased active behaviors (swimming, climbing) while reducing passive ones (immobility). However, fluoxetine was not effective at reducing anergia induced by the DA-depleting agent tetrabenazine, further decreasing vigorous climbing and increasing immobility. In the T-maze, fluoxetine alone produced the same pattern of effects as tetrabenazine. Moreover, fluoxetine did not reverse tetrabenazine-induced suppression of RW time but it reduced sucrose intake duration. This pattern of effects produced by fluoxetine in DA-depleted mice was dissimilar from devaluing food reinforcement by pre-feeding or making the food bitter since in both cases sucrose intake time was reduced but animals compensated by increasing time in the RW. Thus, fluoxetine improved escape in an aversive context but decreased relative preference for active reinforcement. Moreover, fluoxetine did not reverse the anergic effects of DA depletion. These results have implications for the use of fluoxetine for treating motivational symptoms such as anergia in depressed patients.