Interoception and learning: import to understanding and treating diseases and psychopathologies

Disruption of positive- and negative-feature morphine interoceptive occasion setters by dopamine receptor agonism and antagonism in male and female rats

RATIONALE

Internally perceived stimuli evoked by morphine administration can form Pavlovian associations such that they can function as occasion setters (OSs) for externally perceived reward cues in rats, coming to modulate reward-seeking behaviour. Though much research has investigated mechanisms underlying opioid-related reinforcement and analgesia, neurotransmitter systems involved in the functioning of opioids as Pavlovian interoceptive discriminative stimuli remain to be disentangled despite documented differences in the development of tolerance to analgesic versus discriminative stimulus effects.

OBJECTIVES

Dopamine has been implicated in many opioid-related behaviours, so we aimed to investigate the role of this neurotransmitter in expression of morphine occasion setting.

METHODS

Male and female rats were assigned to positive- (FP) or negative-feature (FN) groups and received an injection of morphine or saline before each training session. A 15-s white noise conditioned stimulus (CS) was presented 8 times during every training session; offset of this stimulus was followed by 4-s access to liquid sucrose on morphine, but not saline, sessions for FP rats. FN rats learned the reverse contingency. Following stable discrimination, rats began generalization testing for expression of morphine-guided sucrose seeking after systemic pretreatment with different doses of the non-selective dopamine receptor antagonist, flupenthixol, and the non-selective dopamine receptor agonist, apomorphine, combined with training doses of morphine or saline in a Latin-square design.

RESULTS

The morphine discrimination was acquired under both FP and FN contingencies by males and females. Neither flupenthixol nor apomorphine at any dose substituted for morphine, but both apomorphine and flupenthixol disrupted expression of the morphine OS. This inhibition was specific to sucrose seeking during CS presentations rather than during the period before CS onset and, in the case of apomorphine more so than flupenthixol, to trials on which access to sucrose was anticipated.

CONCLUSIONS

Our findings lend support to a mechanism of occasion setting involving gating of CS-induced dopamine release rather than by direct dopaminergic modulation by the morphine stimulus.

Generalization of a positive-feature interoceptive morphine occasion setter across the rat estrous cycle

INTRODUCTION

Interoceptive stimuli elicited by drug administration acquire conditioned modulatory properties of the induction of conditioned appetitive behaviours by exteroceptive cues. This effect may be modeled using a drug discrimination task in which the drug stimulus is trained as a positive-feature (FP) occasion setter (OS) that disambiguates the relation between an exteroceptive light conditioned stimulus (CS) and a sucrose unconditioned stimulus (US). We previously reported that females are less sensitive to generalization of a FP morphine OS than males, so we investigated the role of endogenous ovarian hormones in this difference.

METHODS

Male and female rats received intermixed injections of 3.2 mg/kg morphine or saline before each daily training session. Training consisted of 8 presentations of the CS, each followed by access to sucrose on morphine, but not saline sessions. Following acquisiton, rats were tested for generalization of the morphine stimulus to 0, 1.0, 3.2, and 5.4 mg/kg morphine. Female rats were monitored for estrous cyclicity using vaginal cytology throughout the study.

RESULTS

Both sexes acquired stable drug discrimination. A gradient of generalization was measured across morphine doses and this behaviour did not differ by sex, nor did it differ across the estrous cycle in females.

CONCLUSIONS

Morphine generalization is independent of fluctuations in levels of sex and endogenous gonadal hormones in females under these experimental conditions.

Varenicline serves as the training stimulus in the drug-discriminated goal-tracking task with rats: initial evaluation of potential neuropharmacological processes

Varenicline (Chantix) is an FDA-approved smoking cessation aid that is pharmacologically similar to nicotine, the primary addictive component found within tobacco. In support of this similarity, previous drug discrimination research in rats has reported that the internal or interoceptive stimulus effects of nicotine and varenicline share stimulus elements. Those shared elements appear to be mediated, in part, by overlapping action at alpha4beta2-containing nicotinic acetylcholine receptors (nAChRs). The research supporting this conclusion, however, has only used nicotine, and not varenicline, as the training drug. Accordingly, we used the discriminated goal tracking (DGT) task in which 1 mg/kg varenicline signaled intermittent access to sucrose. On separate intermixed saline days, sucrose was not available. Rats acquired the discrimination as measured by a differential increase in dipper entries (goal tracking) evoked by varenicline. These rats then received a series of tests with several doses of varenicline, nicotine, nornicotine (a metabolite of nicotine and tobacco alkaloid), sazetidine-A (a partial alpha4beta2 agonist), PHA-543613 (an alpha7 agonist), and bupropion (a norepinephrine and dopamine reuptake inhibitor). Control of goal tracking by varenicline was dose-dependent. Nicotine and nornicotine evoked responding comparable to the varenicline training dose indicating full substitution. Sazetidine-A partially substituted for the varenicline stimulus, whereas bupropion and PHA-543613 evoked little to no varenicline-like responding. These findings indicate that varenicline can serve as the training stimulus in the DGT task. Further, stimulus control of varenicline in the DGT task is driven by its partial agonist activity at alpha4beta2-containing nAChRs. The use of this approach could lead to a better understanding of the pharmacological action of varenicline and help guide treatment geared towards tobacco cessation through a more targeted development of novel synthetically designed, subunit-specific pharmacological interventions.

The Differential Relationship Between Self-Reported Interoceptive Accuracy and Attention With Psychopathology

Abstract. Background: Only recently has interoception been discussed as a common risk factor for psychopathology. Recent approaches distinguish between the ability to accurately perceive ( interoceptive accuracy) and the propensity to attend ( interoceptive attention) to internal signals. Objective: To examine the latent structure of self-reported interoceptive accuracy and attention and their relationships to psychopathology. Methods: We used a confirmatory factor analysis to clarify the latent structure of interoceptive accuracy and attention. Structural equation modeling was utilized to determine relationships between both abilities with internalizing and somatoform symptomatology according to the HiTOP model ( Kotov et al., 2017 ). Data from N = 619 persons from the German general population were analyzed. Results: Interoceptive attention showed significant positive relationships with all psychopathological traits ( r = .221 to r = .377), whereas interoceptive accuracy was negatively associated with internalizing symptomatology ( r = -.106). Conclusion: The present findings indicate that personal beliefs about interoceptive abilities have different influences on psychopathological developments.

The Effects of Cognitive Behavioral Therapy with Biofeedback Therapy on the Quality of Life, Anxiety, Depression and Somatic Symptoms in Patients with Dyssynergic Defecation: A Randomized Controlled Trial

Background: Dyssynergic defecation (DD) is a major cause of chronic functional constipation. Patients with DD have greater psychological distress and impaired health-related quality of life compared with the general population. This study aimed to evaluate the effectiveness of cognitive-behavioral therapy (CBT) combined with biofeedback therapy (BFT) on the quality of life, anxiety, depression and physical symptoms in patients with DD.

Methods: This randomized controlled trial (IRCT20141115019957N2) was conducted on 45DD patients who were referred to the Rehabilitation Clinic of Iran University of Medical Sciences in 2017. The convenience sampling method was used to select the participants and then they were randomly allocated into three equal groups using RANDBETWEEN function in Excel. The first group received a combination of BFT&CBT and also standard-of-care therapy (SoCT). The second group was treated with BFT and SoCT, and the third group received only SoCT. The patients were assessed by digital rectal examination and the Short Form-36, Spielberger Anxiety, Beck Depression and Constipation Scoring System questionnaires before and after the treatment.The data were analyzed by SPSS-22, ANOVA, ANCOVA and Chi-Square tests.

Results: Patients who received both CBT&BFT had significant improvement in symptoms of constipation, depression, and anxiety.Furthermore, BFT and CBT&BFT groups are valued equivalent only on the mental component of SF36 and the total SF36 questionnaire. But the physical component was significantly different, favoring CBT&BFT (p< 0.001). In CBT&BFT group,67%of patients reached the relaxed stage. In contrast, no patient reached the relaxed neither in BFT nor in SoCT.

Conclusion: According to our study, patients with unfavorable responses to BFT may become better if CBT is added to their treatment plan.

Appetitive Pavlovian conditioning of the stimulus effects of nicotine enhances later nicotine self-administration

Nicotine produces robust stimulus effects that can be conditioned to exert stimulus control over behavior through associative learning. Additionally, nicotine has weak reinforcing effects that are inconsistent with its prevalence of use and the tenacity of nicotine dependence. The present study investigated whether conditioned associations to the nicotine drug stimulus may confer additional reinforcing strength to nicotine that thereby increase its use liability, and presents a new methodological approach to investigating the interaction between the stimulus effects and reinforcing effects of drugs. Male and female Sprague-Dawley rats were divided into groups receiving intravenous infusions of either 0.03 mg/kg nicotine or 0.9% saline that were either Paired (30 s delayed) or explicitly Unpaired (4 to 6 min delayed) with sucrose deliveries over 24 daily conditioning sessions. Thereafter, recessed nosepoke response devices were installed in the chambers and infusions of their assigned drug solutions were contingently available according to a progressive ratio schedule. Rats in the Paired Nicotine condition acquired the nosepoke response, expressed active nosepoke discrimination, and self-administered significantly more infusions than rats in any of the other groups. These results demonstrate that the interoceptive stimulus effects of nicotine can form Pavlovian associations with reinforcing events that alter its reinforcement efficacy.

Understanding the stimulus effects of nicotine and bupropion in a drug-drug discriminated goal-tracking task

RATIONALE

Bupropion is a non-nicotine medication for smoking cessation that has overlapping stimulus effects with nicotine as demonstrated in drug discrimination studies. Whether these shared stimulus effects will alter acquisition or maintenance of a discrimination between nicotine and bupropion is unknown.

OBJECTIVE

We sought to test this possibility using the drug discriminated goal-tracking (DGT) task and whether discrimination training history affected generalization and substitution tests.

METHODS

Sixty adult Sprague-Dawley rats (30M/30F) were equally split into three discrimination training groups: SAL-0.4NIC, 10BUP-0.4NIC, and 20BUP-0.4NIC. On nicotine days, all rats were administered subcutaneously 0.4 mg/kg nicotine and had intermittent access to liquid sucrose. On intermixed non-reinforced days, rats were administered intraperitoneally saline, 10 or 20 mg/kg bupropion. Upon completion, a range of nicotine and bupropion doses were assessed before substitution tests with varenicline and sazetidine-A were conducted.

RESULTS

The SAL-0.4NIC and 10BUP-0.4NIC groups readily discriminated by session 8, as evidenced by increased dipper entries (goal-tracking) on nicotine days. The 20BUP-0.4NIC group was slower to acquire the discrimination. Female rats, regardless of group, had higher conditioned responding evoked by the lowest dose of nicotine (0.025 mg/kg) in the dose-effect curve. The discrimination required rats to learn to withhold responding to the training dose of bupropion. This withholding of excitatory dipper entries generalized to other doses. Varenicline and sazetidine-A partially substituted for the nicotine stimulus, and this pattern did not differ with training history.

CONCLUSIONS

We are the first to study a drug-drug discrimination using the DGT task. Females appeared to have a lower discrimination threshold for nicotine that was not impacted by the learning history. Further work on the importance of sex as a biological variable and how the complex interoceptive stimulus effects of nicotine can vary with training histories is needed.

Decreased interoceptive accuracy in children with autism spectrum disorder and with comorbid attention deficit/hyperactivity disorder

Interoception refers to the awareness of internal physiological state. Several previous studies reported that people with autism spectrum disorders (ASD) and adults with attention-deficit/hyperactivity disorder (ADHD) have diverse patterns of interoception, but the extent of literature is limited and inconsistent. This study aimed to investigate the interoceptive accuracy (IA) in children with ASD, children with comorbid ASD and ADHD, and typically developing (TD) children with high and low levels of autistic traits. We administered the eye-tracking interoceptive accuracy task (EIAT) to 30 children with ASD, 20 children with comorbid ASD and ADHD, and 63 TD controls with high and low levels of autistic traits. Parent-report scales concerning ASD and ADHD symptoms were collected. ASD children with and without comorbid ADHD both exhibited lower IA than TD children. Reduced IA was also found in TD children with high-autistic traits relative to those with low-autistic traits. IA was negatively correlated with autistic and ADHD symptoms. Atypical cardiac interoception could be found in children with ASD. Difficulties in sensing and comprehending internal bodily signals in childhood may be related to both ASD and ADHD symptoms.

Changes in interoception after alcohol administration correlate with expectancies and subjective effects

Interoceptive signals give rise to subjective feeling states that can drive motivational and behavioural responses. In the context of alcohol use behaviours, interoceptive signals may shape subjective alcohol experiences and thereby support biobehavioural mechanisms of drinking behaviour change. This study examined the acute effects of alcohol on participants' interoceptive abilities and determined whether pharmacologically induced changes in heart beat detection correlate with subjective alcohol effects, craving and expectancies. Participants completed a two-session, double-blind placebo controlled experiment (n = 27). Participants consumed a beverage containing 0.4 g/kg of alcohol or a placebo. They also completed measurements of alcohol expectancies at baseline, and alcohol-induced changes in mood, craving and light-headedness. Interoceptive ability was measured using the heartbeat discrimination task prior to and following beverage administration, yielding indices of interoceptive accuracy, confidence and meta-cognition. Alcohol administration increased interoceptive accuracy compared with baseline and placebo; and those changes in interoception negatively correlated with negative alcohol expectancies. Further, changes in interoception positively correlated with perceived light-headedness and positive mood after alcohol administration, whereas null effects were found for craving. In the placebo condition, null results were obtained. Alcohol is well established to change bodily states, and here, we find that the extent to which alcohol increases participants' sensitivity to bodily states correlates with their subjective drinking experiences. This was observed in relation to mood, light-headedness and prospective alcohol expectancies. We posit that over successive alcohol experiences, changes in bodily states may feed into the development of alcohol expectancies that could in turn predict future drinking behaviours.

Interoception and alcohol: Mechanisms, networks, and implications

Interoception refers to the perception of the internal state of the body and is increasingly being recognized as an important factor in mental health disorders. Drugs of abuse produce powerful interoceptive states that are upstream of behaviors that drive and influence drug intake, and addiction pathology is impacted by interoceptive processes. The goal of the present review is to discuss interoceptive processes related to alcohol. We will cover physiological responses to alcohol, how interoceptive states can impact drinking, and the recruitment of brain networks as informed by clinical research. We also review the molecular and brain circuitry mechanisms of alcohol interoceptive effects as informed by preclinical studies. Finally, we will discuss emerging treatments with consideration of interoception processes. As our understanding of the role of interoception in drug and alcohol use grows, we suggest that the convergence of information provided by clinical and preclinical studies will be increasingly important. Given the complexity of interoceptive processing and the multitude of brain regions involved, an overarching network-based framework can provide context for how focused manipulations modulate interoceptive processing as a whole. In turn, preclinical studies can systematically determine the roles of individual nodes and their molecular underpinnings in a given network, potentially suggesting new therapeutic targets and directions. As interoceptive processing drives and influences motivation, emotion, and subsequent behavior, consideration of interoception is important for our understanding of processes that drive ongoing drinking and relapse.

Atypical interoception as a common risk factor for psychopathology: A review

The inadequacy of a categorial approach to mental health diagnosis is now well-recognised, with many authors, diagnostic manuals and funding bodies advocating a dimensional, trans-diagnostic approach to mental health research. Variance in interoception, the ability to perceive one's internal bodily state, is reported across diagnostic boundaries, and is associated with atypical functioning across symptom categories. Drawing on behavioural and neuroscientific evidence, we outline current research on the contribution of interoception to numerous cognitive and affective abilities (in both typical and clinical populations), and describe the interoceptive atypicalities seen in a range of psychiatric conditions. We discuss the role that interoception may play in the development and maintenance of psychopathology, as well as the ways in which interoception may differ across clinical presentations. A number of important areas for further research on the role of interoception in psychopathology are highlighted.

Conditioned enhancement of the nicotine reinforcer

This study was designed to assess whether nicotine can acquire additional reinforcing properties through associations with other rewards. To this end, rats self-administered nicotine-alone (0.01 mg/kg) or nicotine paired with access to sucrose during the conditioning phase. In the subsequent challenge phase, we tested the effect of nicotine-sucrose pairings on the reinforcing effects of nicotine using a progressive ratio schedule of reinforcement. Using this approach, we show that (a) rats in both paired and nicotine-alone conditions self-administered similar amounts of nicotine in the initial conditioning phase of the study when intake was limited to 10 infusions per session, (b) nicotine rapidly acquired control over goal-tracking behavior in the paired condition, (c) rats that had a history of nicotine and sucrose pairings worked harder and took more nicotine as measured on a progressive ratio using a distinct response form, and (d) conditioned goal-tracking evoked by nicotine did not show extinction when sucrose was no longer paired with nicotine over the 11 days of nicotine self-administration on a progressive ratio schedule of reinforcement. Overall, our results demonstrate that in addition to the multifaceted nature of nicotine stimulus that includes primary reinforcing effects, conditioned reinforcing effects, and reward enhancing effects, nicotine can also acquire additional reinforcing properties through associations with other rewards. This ability to acquire additional reinforcing properties through associative learning may contribute to the development and perpetuation of tobacco use disorder. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Δ9-Tetrahydrocannabinol discrimination: Effects of route of administration in rats

Cannabis users typically smoke or vape cannabis or ingest it in edibles, whereas cannabinoids are typically administered via injection in rodent research. The present study examined the effects of route of administration (ROA) of Δ⁹-tetrahydrocannabinol (THC), the primary psychoactive constituent of cannabis. Adult female and male Long Evans rats were trained to discriminate intraperitoneal (i.p.) THC from vehicle in a drug discrimination procedure. Following acquisition, dose-effect curves were determined with THC using i.p., oral (p.o.), and subcutaneous (s.c.) injection in both sexes and aerosol exposure in males only, followed by a time course with one dose for each ROA. Both sexes acquired THC discrimination in a similar number of sessions, although baseline response rates were significantly lower in females than males. THC fully substituted for the 3 mg/kg i.p. training dose across all ROA. While potencies were similar for ROA involving first-pass metabolism (i.p. and p.o.), THC potency was lower with s.c. administration. During the time course analysis, aerosol administration had the shortest latency to onset of discriminative stimulus effects and the shortest duration of effect, whereas s.c. administration had the longest duration. The results of this examination of the effects of ROA on an abuse-related effect of THC provide an empirical foundation to facilitate choice of ROA for mechanistic investigation of THC's pharmacology. Further, animal models using translationally relevant ROA may facilitate more accurate predictions of their effects in humans.

Sex differences in the discriminative stimulus characteristics of a morphine occasion setter in rats

The current study investigated whether the stimulus effects of morphine can function as a positive and negative feature in a Pavlovian occasion setting drug discrimination preparation in male and female rats. Sprague-Dawley rats were assigned to a feature positive (FP) or feature negative (FN) training group and all received intermixed morphine (3.2 mg/kg, IP) or saline injections 15 min before 20-min daily training sessions. For FP rats, on morphine sessions, each of eight 15-s white noise (WN) presentations was followed by 4-s access to sucrose (0.01 ml, 26% w/v); on saline sessions, sucrose was withheld. FN rats learned the reverse contingency. FP discrimination was acquired somewhat sooner than FN discrimination, and females, but not males, became sensitized to the locomotor effects of morphine, which did not influence conditioned responding. Rats then entered dose generalization testing. There was no sex difference in dose generalization for FN groups (ED₅₀ 1.26 for males and 1.57 for females). Yet for FP rats, the dose response curve for females was shifted to the right compared to males (ED₅₀ 0.54 for males and 1.94 for females). FP females exhibited enhanced responding at a dose higher than that of their original training. These findings reveal the need to reassess our notions of drug stimuli that guide appropriate associative behaviours from the perspective of sex differences.

The importance of acquisition learning on nicotine and varenicline drug substitution in a drug-discriminated goal-tracking task

Nicotine and varenicline (Chantix®; the leading non-nicotine cessation pharmacotherapy) can come to control appetitive behaviors such as goal-tracking. We tested rats (N = 48) in a drug-discriminated goal-tracking (DGT) task where each rat received daily subcutaneous injections of either nicotine (0.4 mg/kg) or saline (0.9% [w/v]) interspersed across the acquisition phase (Phase 1). On saline days, sucrose was intermittently available. On nicotine days, sucrose was withheld. All rats acquired the discrimination with increased goal-tracking rates on saline days relative to nicotine days. Following acquisition, rats were separated into four groups to assess drug-substitution and discrimination reversal in Phase 2. The first group maintained the stimulus-reinforcer relation from acquisition (NIC-). The reversal group was now given access to sucrose on nicotine days (NIC+). The substitution group replaced nicotine with varenicline (1 mg/kg) while maintaining the acquisition stimulus-reinforcer relation (VAR-). The substitution and reversal group had nicotine replaced by varenicline and the stimulus-reinforcer relation reversed (VAR+). Rats in all groups learned or maintained their Phase 1 discriminations. For Phase 2, the reversal groups (+ conditions) acquired their discriminations within 10 sessions. The VAR- group displayed a pattern of disrupted discrimination at the outset of Phase 2 but was reestablished after continued training. In substitution testing, VAR groups received nicotine and NIC groups received varenicline. The NIC- and VAR- groups displayed full substitution of the test stimulus whereas the NIC+ and VAR+ groups displayed partial substitution of the test stimulus. Rats underwent nicotine extinction in Phase 3. Initial responding for each group mimicked Phase 2 training (i.e., higher responding by the reversal groups). All rats maintained similarly low levels of responding after six sessions. In conclusion, initial learning history with nicotine (i.e., + or -) influenced drug-stimulus substitution and the rate at which new learning (e.g., reversal) occurs with the varenicline and nicotine interoceptive stimuli.

Continuous High Frequency Deep Brain Stimulation of the Rat Anterior Insula Attenuates the Relapse Post Withdrawal and Strengthens the Extinction of Morphine Seeking

Deep brain stimulation (DBS) modulates the neuronal activity in specific brain circuits and has been recently considered as a promising intervention for refractory addiction. The insula cortex is the hub of interoception and is known to be involved in different aspects of substance use disorder. In the present study, we investigate the effects of continuous high frequency DBS in the anterior insula (AI) on drug-seeking behaviors and examined the molecular mechanisms of DBS action in morphine-addicted rats. Sprague-Dawley rats were trained to the morphine-conditioned place preference (CPP, day 1-8) followed by bilaterally implanted with DBS electrodes in the AI (Day 10) and recovery (Day 10-15). Continuous high-frequency (HF) -DBS (130 Hz, 150 μA, 90 μs) was applied during withdrawal (Day 16-30) or extinction sessions. CPP tests were conducted on days 16, 30, 40 during withdrawal session and several rats were used for proteomic analysis on day 30. Following the complete extinction, morphine-CPP was reinstated by a priming dose of morphine infusion (2 mg/kg). The open field and novel objective recognition tests were also performed to evaluate the DBS side effect on the locomotion and recognition memory. Continuous HF-DBS in the AI attenuated the expression of morphine-CPP post-withdrawal (Day 30), but morphine addictive behavior relapsed 10 days after the cessation of DBS (Day 40). Continuous HF-DBS reduced the period to full extinction of morphine-CPP and blocked morphine priming-induced recurrence of morphine addiction. HF-DBS in the AI had no obvious effect on the locomotor activity and novel objective recognition and did not cause anxiety-like behavior. In addition, our proteomic analysis identified eight morphine-regulated proteins in the AI and their expression levels were reversely changed by HF-DBS. Continuous HF-DBS in the bilateral anterior insula prevents the relapse of morphine place preference after withdrawal, facilitates its extinction, blocks the reinstatement induced by morphine priming and reverses the expression of morphine-regulated proteins. Our findings suggest that manipulation of insular activity by DBS could be a potential intervention to treat substance use disorder, although future research is warranted.

En Pointe: Dancers Report Their Pain Less Variably Than Do Controls

The subjective nature of pain and the lack of a gold standard for objective measurement hinders effective assessment, diagnosis, and treatment. Some individuals, such as professional dancers, are better in assessing and reporting bodily sensations. This observational study aimed to assess whether dancers report their pain less variably, than other people do. After consenting, subjects completed the focused analgesia selection test (FAST), which assesses subjects' variability of pain reports. FAST outcomes, ICC and R² reflect the magnitude of variability of pain reports observed. In addition, subjects underwent a taste task, which similarly assesses variability of tastes (salty and sweet) intensity reports and completed the Multidimensional Assessment of Interoceptive Awareness questionnaire. Thirty-three professional dancers and 33 healthy aged-matched controls were recruited. The dancers exhibited less variability of pain reports then controls (P = .013), but not in case of tastes-reports. Years of practice was positively correlated with pain reporting variability (r = .447, P = .009, and r = .380, P = .029; for FAST ICC and R², respectively). Multidimensional Assessment of Interoceptive Awareness subscores correlated with pain reporting variability: R² and ICC with emotional awareness (r = .260, P = .040, and r = .274, P = .030, respectively), and R² with trusting [r = .254, P = .044]). PERSPECTIVE: The difference between dancers and controls in the magnitude of variability of pain reports is probably due to the dancers' extensive training, which focuses on attention to body signals. Our results suggest that training can improve subjective pain reports, which are essential for quality clinical care.

Role of mPFC and nucleus accumbens circuitry in modulation of a nicotine plus alcohol compound drug state

Combined use of nicotine and alcohol constitute a significant public health risk. An important aspect of drug use and dependence are the various cues, both external (contextual) and internal (interoceptive) that influence drug-seeking and drug-taking behavior. The present experiments employed the use of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) and complementary Pavlovian drug discrimination procedures (feature-positive and feature-negative training conditions) in order to examine whether medial prefrontal cortex (prelimbic; mPFC-PL) projections to the nucleus accumbens core (AcbC) modulate sensitivity to a nicotine + alcohol (N + A) interoceptive cue. First, we show neuronal activation in mPFC-PL and AcbC following treatment with N + A. Next, we demonstrate that chemogenetic silencing of projections from mPFC-PL to nucleus accumbens core decrease sensitivity to the N + A interoceptive cue, while enhancing sensitivity to the individual components, suggesting an important role for this specific projection. Furthermore, we demonstrate that clozapine-N-oxide (CNO), the ligand used to activate the DREADDs, had no effect in parallel mCherry controls. These findings contribute important information regarding our understanding of the cortical-striatal circuitry that regulates sensitivity to the interoceptive effects of a compound N + A cue.

Considering Drug-Associated Contexts in Substance Use Disorders and Treatment Development

Environmental contexts that are reliably associated with the use of pharmacologically active substances are hypothesized to contribute to substance use disorders. In this review, we provide an updated summary of parallel preclinical and human studies that support this hypothesis. Research conducted in rats shows that environmental contexts that are reliably paired with drug use can renew extinguished drug-seeking behavior and amplify responding elicited by discrete, drug-predictive cues. Akin to drug-associated contexts, interoceptive drug stimuli produced by the psychopharmacological effects of drugs can also influence learning and memory processes that play a role in substance use disorders. Findings from human laboratory studies show that drug-associated contexts, including social stimuli, can have profound effects on cue reactivity, drug use, and drug-related cognitive expectancies. This translationally relevant research supports the idea that treatments for substance use disorders could be improved by considering drug-associated contexts as a factor in treatment interventions. We conclude this review with ideas for how to integrate drug-associated contexts into treatment-oriented research based on 4 approaches: pharmacology, brain stimulation, mindfulness-based relapse prevention, and cognitive behavioral group therapy. Throughout, we focus on alcohol- and tobacco-related research, which are two of the most prevalent and commonly misused drugs worldwide for which there are known treatments.

Evidence for incentive salience sensitization as a pathway to alcohol use disorder

The incentive salience sensitization (ISS) theory of addiction holds that addictive behavior stems from the ability of drugs to progressively sensitize the brain circuitry that mediates attribution of incentive salience (IS) to reward-predictive cues and its behavioral manifestations. In this article, we establish the plausibility of ISS as an etiological pathway to alcohol use disorder (AUD). We provide a comprehensive and critical review of evidence for: (1) the ability of alcohol to sensitize the brain circuitry of IS attribution and expression; and (2) attribution of IS to alcohol-predictive cues and its sensitization in humans and non-human animals. We point out gaps in the literature and how these might be addressed. We also highlight how individuals with different alcohol subjective response phenotypes may differ in susceptibility to ISS as a pathway to AUD. Finally, we discuss important implications of this neuropsychological mechanism in AUD for psychological and pharmacological interventions attempting to attenuate alcohol craving and cue reactivity.

Exploring the interoceptive stimulus effects of nicotine and varenicline

Learning processes associated with nicotine influence the development of addiction to tobacco products. In the present report, we are interested in the interoceptive stimulus effects of nicotine acquiring control over appetitive behaviors - specifically, reward seeking. Also of interest is the current smoking cessation drug, varenicline (Chantix®). Varenicline, with its nicotine-like stimulus effects, can decrease withdrawal and cravings for a subset of individuals addicted to nicotine, though relapse is still common. We trained rats (N = 48) with nicotine (0.4 mg/kg, SC) as an excitatory stimulus (i.e., paired with sucrose) in a drug-discriminated goal-tracking (DGT) task. There was no access to sucrose on interspersed saline days. After acquisition of the initial nicotine-saline discrimination, rats were separated into four groups to test discrimination reversal and drug substitution. The control group maintained nicotine as the excitatory stimulus (NIC+). The substitution group had varenicline (1 mg/kg) replace nicotine as the stimulus paired with sucrose (VAR+). One reversal group had nicotine signal the absence of sucrose (i.e., now available on intermixed saline sessions; NIC-). The last group was similar to the NIC- group except varenicline replaced nicotine on non-reinforced sessions (VAR-). We found that varenicline fully substituted as the training stimulus when the drug-sucrose relation remained in place (VAR+). Both reversal groups acquired the new discrimination, albeit slowly and more variable for the VAR- group in comparison to NIC-. There was an effect of group during substitution testing. Specifically, nicotine fully substituted for varenicline regardless of condition. However, varenicline only partially substituted for the nicotine stimulus. At the start of extinction, responding mimicked that of the rats training condition. However, by extinction session 12, all groups maintained similarly low levels of responding. These findings show nicotine and varenicline share stimulus elements, yet the conclusion of partial to full substitution depends on the nature of the testing protocol.

Effects of nicotine conditioning history on alcohol and methamphetamine self-administration in rats

BACKGROUND

Smoking constitutes a significant public health risk. Alcohol and methamphetamine use disorders are also highly co-morbid with smoking, further increasing negative health outcomes. An important question in determining the underlying neurobiology of nicotine poly-drug use is understanding whether having a positive history with nicotine effects alters later drug-taking behavior.

METHODS

The current experiments sought to elucidate whether having an appetitive nicotine conditioning history would affect later alcohol or methamphetamine self-administration. Adult male and female Long-Evans rats were first trained on a discriminated goal-tracking task in which the interoceptive effects of nicotine predicted sucrose reinforcement. As a control, pseudo-conditioned groups were included that had equated nicotine and sucrose experience. Rats were then shifted to either alcohol self-administration or methamphetamine self-administration.

RESULTS

Nicotine conditioning history had no effect on acquisition or maintenance of alcohol self-administration in males or females. In contrast, an appetitive nicotine conditioning history decreased methamphetamine self-administration in female rats, but not males.

CONCLUSIONS

In female, but not male, rats, an appetitive conditioning history with nicotine decreases methamphetamine, but not alcohol, self-administration. This dissociation suggests that the effects may be due to a specific increase in the reinforcing value of methamphetamine. This may have implications for better understanding the progression of drug use from nicotine to methamphetamine.

Neural hypersensitivity to pleasant touch in women remitted from anorexia nervosa

Interoception, or the sensing and integration of bodily state signals, has been implicated in anorexia nervosa (AN), given that the hallmark symptoms involve food restriction and body image disturbance. Here we focus on brain response to the anticipation and experience of affective interoceptive stimuli. Women remitted from AN (RAN; N = 18) and healthy comparison women (CW; N = 26) underwent a pleasant affective touch paradigm consisting of gentle strokes with a soft brush administered to the forearm or palm during functional neuroimaging. RAN had a lower brain response relative to CW during anticipation of touch, but a greater response when experiencing touch in the right ventral mid-insula. In RAN, this reduced anticipatory response was associated with higher levels of harm avoidance. Exploratory analyses in RAN also suggested that lower response during touch anticipation was associated with greater body dissatisfaction and higher perceived touch intensity ratings. This reduced responsivity to the anticipation of pleasant affective interoceptive stimuli in association with higher harm avoidance, along with an elevated response to the experience of touch, suggests an impaired ability in AN to predict and interpret incoming physiological stimuli. Impaired interoception may thus impact one's sense of self, thereby supporting observations of disturbed body image and avoidance of affective and social stimuli. Therapeutic approaches that help AN to better anticipate and interpret salient affective stimuli or improve tolerance of interoceptive experiences may be an important addition to current interventions.

Experimental analysis of behavior and tobacco regulatory research on nicotine reduction

With the signing of H.R. 1256, the Family Smoking Prevention and Tobacco Control Act, the United States Food and Drug Administration (FDA) gained regulatory authority over the tobacco industry. A notable clause in this Act permits the FDA to regulate nicotine yields. However, they cannot completely remove this addictive constituent from tobacco products. This restriction has prompted the FDA to seek research on the threshold dose of nicotine that does not support dependence. This idea of threshold dose has led to an interesting reframing of scientific questions. For example, some researchers studying nicotine from this regulatory perspective translated the notion of an addiction threshold to a construct thought to play a role in addiction but which can be more readily operationalized. Examples include reinforcement threshold, discrimination threshold, and reinforcer-enhancement threshold. In this Perspective Paper, we highlight the importance of behavioral pharmacology and, specifically, the experimental analysis of behavior to help establish a scientific basis for policy decisions regarding nicotine yields. Recent research, including exemplars provided herein, note vast individual differences in the effects of nicotine at a known dose. Unfortunately, the behavioral and biological factors that contribute to such individual variations remain to be understood. We believe that behavior analysts are uniquely well-positioned to contribute to this understanding.

Double dissociation of the anterior and posterior dorsomedial caudate-putamen in the acquisition and expression of associative learning with the nicotine stimulus

Tobacco use is the leading cause of preventable deaths worldwide. This habit is not only debilitating to individual users but also to those around them (second-hand smoking). Nicotine is the main addictive component of tobacco products and is a moderate stimulant and a mild reinforcer. Importantly, besides its unconditional effects, nicotine also has conditioned stimulus effects that may contribute to the tenacity of the smoking habit. Because the neurobiological substrates underlying these processes are virtually unexplored, the present study investigated the functional involvement of the dorsomedial caudate putamen (dmCPu) in learning processes with nicotine as an interoceptive stimulus. Rats were trained using the discriminated goal-tracking task where nicotine injections (0.4 mg/kg; SC), on some days, were paired with intermittent (36 per session) sucrose deliveries; sucrose was not available on interspersed saline days. Pre-training excitotoxic or post-training transient lesions of anterior or posterior dmCPu were used to elucidate the role of these areas in acquisition or expression of associative learning with nicotine stimulus. Pre-training lesion of p-dmCPu inhibited acquisition while post-training lesions of p-dmCPu attenuated the expression of associative learning with the nicotine stimulus. On the other hand, post-training lesions of a-dmCPu evoked nicotine-like responding following saline treatment indicating the role of this area in disinhibition of learned motor behaviors. These results, for the first time, show functionally distinct involvement of a- and p-dmCPu in various stages of associative learning using nicotine stimulus and provide an initial account of neural plasticity underlying these learning processes.

Modulation of sensitivity to alcohol by cortical and thalamic brain regions

The nucleus accumbens core (AcbC) is a key brain region known to regulate the discriminative stimulus/interoceptive effects of alcohol. As such, the goal of the present work was to identify AcbC projection regions that may also modulate sensitivity to alcohol. Accordingly, AcbC afferent projections were identified in behaviorally naïve rats using a retrograde tracer which led to the focus on the medial prefrontal cortex (mPFC), insular cortex (IC) and rhomboid thalamic nucleus (Rh). Next, to examine the possible role of these brain regions in modulating sensitivity to alcohol, neuronal response to alcohol in rats trained to discriminate alcohol (1 g/kg, intragastric [IG]) vs. water was examined using a two-lever drug discrimination task. As such, rats were administered water or alcohol (1 g/kg, IG) and brain tissue was processed for c-Fos immunoreactivity (IR), a marker of neuronal activity. Alcohol decreased c-Fos IR in the mPFC, IC, Rh and AcbC. Lastly, site-specific pharmacological inactivation with muscimol + baclofen (GABA_A agonist + GABA_B agonist) was used to determine the functional role of the mPFC, IC and Rh in modulating the interoceptive effects of alcohol in rats trained to discriminate alcohol (1 g/kg, IG) vs. water. mPFC inactivation resulted in full substitution for the alcohol training dose, and IC and Rh inactivation produced partial alcohol-like effects, demonstrating the importance of these regions, with known projections to the AcbC, in modulating sensitivity to alcohol. Together, these data demonstrate a site of action of alcohol and the recruitment of cortical/thalamic regions in modulating sensitivity to the interoceptive effects of alcohol.

On the Origin of Interoception

Over the course of a century, the meaning of interoception has changed from the restrictive to the inclusive. In its inclusive sense, it bears relevance to every individual via its link to emotion, decision making, time-perception, health, pain, and various other areas of life. While the label for the perception of the body state changes over time, the need for an overarching concept remains. Many aspects can make any particular interoceptive sensation unique and distinct from any other interoceptive sensation. This can range from the sense of agency, to the physical cause of a sensation, the ontogenetic origin, the efferent innervation, and afferent pathways of the tissue involved amongst others. In its overarching meaning, interoception primarily is a product of the central nervous system, a construct based on an integration of various sources, not per se including afferent information. This paper proposes a definition of interoception as based on subjective experience, and pleas for the use of specific vocabulary in addressing the many aspects that contribute to it.

Sensation within the skin

This Viewpoint emphasizes interoceptive discriminative stimulus modulation of voluntary operant behavior (a la B. F. Skinner), rather than elicitation of Pavlovian conditioned reflexes. In doing so, I will restate how the operant drug discrimination paradigm may not only elucidate smoking and other addictive behaviors but also anxiety (Troisi, J. R., II. (2003) Spontaneous recovery during, but not following, extinction of the discriminative stimulus effects of nicotine in rats: Reinstatement of stimulus control. Psychol. Rec. 53, 579-592).