Behavioral and social effects of heroin self-administration and withdrawal

Opioid-driven disruption of the septal complex reveals a role for neurotensin-expressing neurons in withdrawal

Because opioid withdrawal is an intensely aversive experience, persons with opioid use disorder (OUD) often relapse to avoid it. The lateral septum (LS) is a forebrain structure that is important in aversion processing, and previous studies have linked the lateral septum (LS) to substance use disorders. It is unclear, however, which precise LS cell types might contribute to the maladaptive state of withdrawal. To address this, we used single-nucleus RNA-sequencing to interrogate cell type specific gene expression changes induced by chronic morphine and withdrawal. We discovered that morphine globally disrupted the transcriptional profile of LS cell types, but Neurotensin-expressing neurons (Nts; LS-Nts neurons) were selectively activated by naloxone. Using two-photon calcium imaging and ex vivo electrophysiology, we next demonstrate that LS-Nts neurons receive enhanced glutamatergic drive in morphine-dependent mice and remain hyperactivated during opioid withdrawal. Finally, we showed that activating and silencing LS-Nts neurons during opioid withdrawal regulates pain coping behaviors and sociability. Together, these results suggest that LS-Nts neurons are a key neural substrate involved in opioid withdrawal and establish the LS as a crucial regulator of adaptive behaviors, specifically pertaining to OUD.

Preventive effects of fixed and progressive forced exercises on memory and brain electrical activity in morphine-addicted rats

Exercise and addiction influence brain functions. The preventive effects of fixed and progressive forced exercises on both brain functions and body weight were investigated in morphine-addicted rats. Thirty-five rats were allocated to control, morphine, fixed exercise-morphine, and progressive exercise-morphine groups. Forced exercise was applied 1h/day for 21 days with morphine sulfate administered at doses of 10, 20, 30, 40, and 50 mg/kg for 5 consecutive days. The 50 mg/kg dose was repeated over the five subsequent days. Brain performance was evaluated using the passive avoidance test and EEG recordings. The passive avoidance test revealed no significant changes in brain functions (namely, latency, total dark stay time, and number of times entering the dark compartment). Compared to the control, the morphine group exhibited significantly lower alpha and beta waves but significantly higher delta and theta ones. Compared to the morphine group, the progressive and fixed exercise-morphine groups exhibited significant changes in their passive avoidance performance and only in the alpha wave of their EEG recordings. Progressive exercise improved learning, memory, and memory consolidation but reduced locomotor activity whereas fixed exercise affected EEG recordings in the addicted subjects. Clearly, different (fixed or progressive) exercise models produced different changes in brain functions.

The self-serving benefits of being a good host: A role for our micro-inhabitants in shaping opioids' function

Opioids are highly efficacious in their ability to relieve pain, but they are liable for abuse, dependence, and addiction. Risk factors to develop opioid use disorders (OUD) include chronic stress, socio-environment, and preexisting major depressive disorders (MDD) and posttraumatic stress disorders (PTSD). Additionally, opioids reduce gut motility, induce loss of gut barrier function, and alter the composition of the trillions of microbes hosted in the gastrointestinal tract, known as the gut microbiota. The microbiota are significant contributors to the reciprocal communication between the central nervous system (CNS) and the gut, termed the gut-brain axis. They have strong influences on their host behaviors, including the ability to cope with stress, sociability, affect, mood, and anxiety. Thus, they are implicated in the etiology of MDD and PTSD. Here we review the latest studies demonstrating that intestinal flora can, directly and indirectly, by affecting sociability levels, responses to stress, and mental state, alter the responses to opioids. It suggests that microbiota can potentially be used to increase the resilience to develop analgesic tolerance and OUD.

Social housing promotes recovery of wheel running depressed by inflammatory pain and morphine withdrawal in male rats

The increased use of opioids to treat pain has led to a dramatic increase in opioid abuse. Our previous data indicate that pain may facilitate the development of opioid abuse by increasing the magnitude and duration of opioid withdrawal. The present study tested the hypothesis that social housing would facilitate recovery of activity depressed by pain and opioid withdrawal. Male Sprague Dawley rats were housed either in pairs or alone and then moved to a cage with a running wheel for 6 h daily to assess pain- and opioid withdrawal-induced depression of wheel running. Rats were implanted with two morphine (75 mg each) or placebo pellets to induce opioid dependence and were simultaneously injected with Complete Freund's Adjuvant or saline into the right hind paw to induce persistent inflammatory pain. Hind paw inflammation depressed wheel running whether rats were implanted with a morphine or placebo pellet. Pair-housed rats showed greater recovery of wheel running than individually housed rats. Spontaneous morphine withdrawal precipitated by removal of the morphine pellets caused a reduction in wheel running that was greater in rats with hind paw inflammation compared to pain free rats. Social housing facilitated recovery from withdrawal in rats with hind paw inflammation, but slowed recovery in pain free rats. These data suggest that social housing facilitates recovery by reducing pain both before and during opioid withdrawal. Our findings are consistent with previous studies showing that social buffering reduces pain-evoked responses.

The CRF1 receptor mediates social behavior deficits induced by opiate withdrawal

Poor sociability and aggressive behavior are key clinical features of opioid use disorders. The corticotropin-releasing factor (CRF) system may mediate behavioral effects of substances of abuse but its implication in substance-induced social behavior deficits and outward-directed hostility remains largely unknown. CRF signaling is mediated by two receptor types, termed CRF₁ and CRF₂ . The present study aimed at understanding the role for the CRF₁ receptor in social and aggressive behavior induced by withdrawal from repeated opiate administration. Thus, wild-type (CRF₁ +/+), CRF₁ receptor heterozygous (CRF₁ +/-), and null mutant (CRF₁ -/-) female and male mice were treated with saline or escalating doses of morphine (20-100 mg/kg, i.p.) during six consecutive days and tested in the three-chamber task for sociability (i.e., preference for an unfamiliar same-sex conspecific vs. an object) 7 days after the last administration. Moreover, aggressive biting behavior toward the unfamiliar conspecific was assessed during the three-chamber test. Opiate withdrawal disrupted sociability in CRF₁ +/+ and CRF₁ +/-, but not in CRF₁ -/-, female mice, without affecting aggressive biting behavior in any genotype. In contrast, opiate withdrawal did not affect sociability but increased aggressive biting behavior in male mice, independently of CRF₁ receptor-deficiency. Nevertheless, in opiate-withdrawn CRF₁ +/+, but not CRF₁ +/- and CRF₁ -/-, male mice, sociability directly correlated with aggressive biting behavior, suggesting a role for the CRF₁ receptor in hostility-linked social approach. These findings demonstrate the implication of the CRF₁ receptor in social behavior deficits associated with repeated opiate administration and withdrawal, revealing a new potential target for the treatment of opioid use disorders.

Long-lasting pseudo-social aggressive behavior in opiate-withdrawn mice

Poor sociability and aggressive behavior are major clinical features of opiate use disorders that may contribute to the establishment and maintenance of these harmful diseases. The present study investigated the long-term effects of chronic morphine administration and withdrawal upon social and aggressive behavior as well as the interrelationship between these two behaviors. Thus, social behavior was measured in C57BL/6J male mice 7, 21, 35 and 49 days after cessation of escalating morphine doses (20-100 mg/kg, i.p.) administered during 6 consecutive days, using the three-chamber task for sociability (i.e., preference for an unfamiliar conspecific vs. an object) and social novelty preference (i.e., preference for a novel vs. a familiar conspecific). Moreover, aggressive biting behavior towards an unfamiliar conspecific was assessed throughout the three-chamber tests. Opiate withdrawal increased both social approach and aggressive biting behavior. Moreover, in morphine-withdrawn, but not in control, mice social approach and aggressive behavior followed a similar time-course and positively correlated one with each other, suggesting that social interest was mainly driven by aggressiveness. Aggressive biting behavior was still elevated 49 days after the last morphine administration, revealing that opiate withdrawal is followed by long-lasting aggressiveness. Throughout, opiate withdrawal did not affect social novelty preference, ruling out a role for olfactory or social discrimination dysfunction in the elevated social approach and aggressive behavior. The present findings of very long-lasting aggressive behavior and aggression-driven social approach in opiate-withdrawn mice might help understanding the behavioral and brain underpinnings of poor sociability and aggressiveness commonly observed in opiate use disorders patients.

Sleep reductions associated with illicit opioid use and clinic-hour changes during opioid agonist treatment for opioid dependence: Measurement by electronic diary and actigraphy

Sleep problems are commonly reported during opioid agonist treatment (OAT) for opioid use disorders. Inpatient studies have found both sleep disturbances and improved sleep during OAT. Illicit opioids can also disrupt sleep, but it is unclear how they affect sleep in outpatients receiving OAT. Therefore, we used electronic diary entries and actigraphy to measure sleep duration and timing in opioid-dependent participants (n = 37) treated with methadone (n = 15) or buprenorphine (n = 22). For 16 weeks, participants were assigned to attend our clinic under different operating hours in a crossover design: Early hours (07:00-09:00) vs. Late hours (12:00-13:00) for 4 weeks each in randomized order, followed for all participants by our Standard clinic hours (07:00-11:30) for 8 weeks. Throughout, participants made daily electronic diary self-reports of their sleep upon waking; they also wore a wrist actigraph for 6 nights in each of the three clinic-hour conditions. Drug use was assessed by thrice-weekly urinalysis. In linear mixed models controlling for other sleep-relevant factors, sleep duration and timing differed by drug use and by clinic hours. Compared to when non-using, participants slept less, went to bed later, and woke later when using illicit opioids and/or both illicit opioids and cocaine. Participants slept less and woke earlier when assigned to the Early hours. These findings highlight the role OAT clinic schedules can play in structuring the sleep/wake cycles of OAT patients and clarify some of the circumstances under which OAT patients experience sleep disruption in daily life.

Not all drugs are created equal: impaired future thinking in opiate, but not alcohol, users

Episodic future thinking refers to the ability to travel forward in time to pre-experience an event. Although future thinking has been intimately linked with self and identity, to our knowledge, no prior research has compared episodic future thinking in populations with different substance use disorders. This study investigates whether there are differences in episodic future thinking between these alcohol and opiate users. The study recruited participants who were on the opiate substitution program (n = 31) and individuals who had been diagnosed with alcohol dependence (n = 21) from the Royal Prince Alfred Hospital Drug and Health Services. Healthy controls (n = 23) were recruited via Royal Prince Alfred Hospital databases and the general community. Past and future thinking was measured using four cue words. After each cue word, participants rated their phenomenological experience (e.g. emotion, reliving experience). Results indicated that alcohol-dependent individuals performed significantly higher in episodic future thinking compared to opiate users. These findings indicate that not all substance use disorder groups share similar episodic thinking capabilities. Our results suggest that the self-projection component of rehabilitation programs may have to be tailored to the different episodic construction abilities found in substance use disorder groups.

Considering the context: social factors in responses to drugs in humans

BACKGROUND

Drugs are typically used in social settings. Here, we consider two factors that may contribute to this observation: (i) the presence of other people may enhance the positive mood effects of a drug, and conversely, (ii) drugs may enhance the value of social stimuli.

METHODS

We review evidence from controlled laboratory studies with human volunteers, which investigated either of these interactions between social factors and responses to drugs. We examine the bidirectional effects of social stimuli and single doses of alcohol, stimulants, opioids, and cannabis.

RESULTS

All four classes of drugs interact with social contexts, but the nature of these interactions varies across drugs, and depends on whether the context is positive or negative.

CONCLUSIONS

Alcohol and stimulant drugs enhance the attractiveness of social stimuli and the desire to socialize, and social contexts, in turn, enhance these drugs' effects. In contrast, opioids and cannabis have subtler effects on social interactions and their effects are less influenced by the presence of others. Overall, there is stronger evidence that drugs enhance positive social contexts than that they dampen the negativity of unpleasant social settings. Controlled research is needed to understand the interactions between drugs of abuse and social contexts, to model and understand the determinants of drug use outside the laboratory.

The effects of intranasal oxytocin in opioid-dependent individuals and healthy control subjects: a pilot study

RATIONALE

There has been an explosion of research on the potential benefits of the social neuropeptide oxytocin for a number of mental disorders including substance use disorders. Recent evidence suggests that intranasal oxytocin has both direct anti-addiction effects and pro-social effects that may facilitate engagement in psychosocial treatment for substance use disorders.

OBJECTIVES

We aimed to assess the tolerability of intranasal oxytocin and its effects on heroin craving, implicit association with heroin and social perceptual ability in opioid-dependent patients receiving opioid replacement therapy (ORT) and healthy control participants.

METHODS

We performed a randomized, double-blind, placebo-controlled, within- and between-subjects, crossover, proof-of-concept trial to examine the effects of oxytocin (40 international units) on a cue-induced craving task (ORT patients only), an Implicit Association Task (IAT), and two social perception tasks: the Reading the Mind in the Eyes Task (RMET) and The Awareness of Social Inference Test (TASIT).

RESULTS

Oxytocin was well tolerated by patients receiving ORT but had no significant effects on craving or IAT scores. There was a significant reduction in RMET performance after oxytocin administration versus placebo in the patient group only, and a significant reduction in TASIT performance after oxytocin in both the patient and healthy control groups.

CONCLUSIONS

A single dose of intranasal oxytocin is well tolerated by patients receiving ORT, paving the way for future investigations. Despite no significant improvement in craving or IAT scores after a single dose of oxytocin and some evidence that social perception was worsened, further investigation is required to determine the role oxytocin may play in the treatment of opioid use disorder.

CLINICAL TRIAL REGISTRATION

Methadone Oxytocin Option. ClinicalTrials.gov identifier: NCT01728909.

Social stimuli enhance phencyclidine (PCP) self-administration in rhesus monkeys

Environmental factors, including social interaction, can alter the effects of drugs of abuse on behavior. The present study was conducted to examine the effects of social stimuli on oral phencyclidine (PCP) self-administration by rhesus monkeys. Ten adult rhesus monkeys (M. mulatta) were housed side by side in modular cages that could be configured to provide visual, auditory, and olfactory stimuli provided by another monkey located in the other side of a paired unit. During the first experiment, monkeys self-administered PCP (0.25 mg/ml) and water under concurrent fixed ratio (FR) 16 schedules of reinforcement with either a solid or a grid (social) partition separating each pair of monkeys. In the second experiment, a PCP concentration-response relationship was determined under concurrent progressive ratio (PR) schedules of reinforcement during both the solid and grid partition conditions. Under the concurrent FR 16 schedules, PCP and water self-administration were significantly higher during exposure to a cage mate through a grid partition than when a solid partition separated the monkeys. The relative reinforcing strength of PCP, as measured by PR break points, was greater during the grid partition condition compared to the solid partition condition indicated by an upward shift in the concentration-response curve. To determine whether the social stimuli provided by another monkey led to activation of the hypothalamic-pituitary-adrenal (HPA) axis, which may have evoked the increase of PCP self-administration during the grid partition condition, a third experiment was conducted to examine cortisol levels under the two housing conditions. A modest, but nonsignificant increase in cortisol levels was found upon switching from the solid to the grid partition condition. The results suggest that social stimulation among monkeys in adjoining cages leads to enhanced reinforcing strength of PCP.

Unlimited access to heroin self-administration: independent motivational markers of opiate dependence

The goal of the present study was to develop and validate an animal model of unlimited access to intravenous heroin self-administration combined with responding for food and water to characterize the transition to drug dependence. Male Wistar rats were allowed to lever press for heroin (60 microg/kg/0.1 ml infusion/s; fixed ratio 1; 20-s time out) and nosepoke for food and water in consecutive, daily 23-h sessions. Daily heroin intake increased over days, reaching significance by Day 14. Drug-taking increased across the circadian cycle, reflected as increases in both the nocturnal peak and diurnal nadir of heroin intake. Changes in the circadian pattern of food intake and meal patterning preceded and paralleled the changes in heroin intake. By Day 7, the circadian amplitude of feeding was blunted. Nocturnal intake decreased because rats consumed smaller and briefer meals. Diurnal intake increased due to increased meal frequency, whereas total daily food intake decreased. To control for time or experience in the self-administration boxes as a possible confound, rats with saline (no drug) tethers were tested and did not display significant changes in food intake pattern. Body weight gain slowed slightly in heroin rats relative to saline controls. Separate groups of rats revealed that significant physical dependence as measured by physical signs of opiate withdrawal following a naloxone injection (1.0 mg/kg, subcutaneous (s.c.)) was reached by Day 14. Significant increases in heroin intake could be produced using low doses of naloxone (0.003-0.03 mg/kg, s.c.) on days 28-31 of heroin access. After 6 weeks of heroin self-administration, rats injected with buprenorphine (0, 0.01, 0.04, and 0.2 mg/kg, s.c.) showed a dose-dependent reduction in heroin intake. Changes in the pattern of drug and food intake in the present unlimited heroin access model may serve as independent motivational markers for the transition to a drug-dependent state.

Effects of d-amphetamine on choice of social versus monetary reinforcement: a discrete-trial test

Two mutually exclusive options were concurrently available to eight volunteers during 60-min experimental sessions. Subjects chose every three minutes between conversing with another same-sex volunteer and providing speech monologues for monetary reinforcement. d-Amphetamine (12.5 and 25 mg/70 kg) significantly increased choice of social over monetary reinforcement. Drug-produced increases in choice of the social option were associated with increases in total seconds of speech and the rate of social conversation. d-Amphetamine also increased subject ratings of effects indicative of greater sociability such as friendliness, elation and energetic. These results suggest that d-amphetamine can increase the relative reinforcing effects of social interaction.

Time allocation in a concurrent schedule of social interaction and monetary reinforcement: effects of d-amphetamine

Two mutually exclusive options (socializing versus monetary reinforcement) were concurrently available to two normal volunteers during 60-min experimental sessions under controlled laboratory conditions. The amount of money available in the monetary option was adjusted for individual subjects during baseline conditions until subjects divided their time approximately evenly between a social option in which they could converse with another same-sex volunteer or a monetary option in which money was earned for sitting quietly in a private room. In both subjects studied, d-amphetamine (5-25 mg) increased the percent of time allocated to the social option and total seconds of speech. This effect occurred even though increases in the time allocated to the social option necessarily resulted in a forfeiture of monetary reinforcement. The present results provide the first empirical evidence, to our knowledge, that d-amphetamine can increase the relative reinforcing effects of social interaction.

Biological mechanisms in posttraumatic stress disorder. Relevance for substance abuse

Recent studies suggest a significant biological contribution to posttraumatic stress disorder (PTSD). In particular, central catecholamine and endogenous opioid systems have been implicated both in this syndrome and in substance abuse. We review relevant animal and human studies that support these hypotheses and suggest that this overlap may contribute to the incidence of substance abuse in PTSD. The animal studies have primarily employed the learned helpless and conditioned emotional response models and have included assessments of brain catecholamines, locus ceruleus activity, and behavioral correlates in rodents and nonhuman primates. Human studies have used only indirect measures to assess these variables. However, both therapeutic approaches and attempts at self-medication for PTSD have supported this hypothesis.

Acute marijuana effects on social conversation

The present study assessed the acute effects of smoked marijuana on social conversation. Speech quantity was recorded continuously in seven moderate marijuana users during separate 1 h experimental sessions following the paced smoking of 0, 1.01, 1.84, and 2.84% THC marijuana cigarettes. Subjects engaged in conversation with undrugged partners who smoked placebo marijuana cigarettes. The active marijuana produced significant decreases in speech quantity, increases in heart rate, and increases in self-reports of "high" and sedation. Partners showed no effects in speech quantity or self-reports of drug effects that were systematically related to the doses administered to the subject pair members. The effects on speech quantity observed in the present study after acute dosing are similar to the effects on social conversation reported previously during chronic marijuana dosing. Marijuana appears to be an exception to the general rule that drugs of abuse increase verbal interaction.

The abstinence phobias: links between substance abuse and anxiety

This paper presents a new model to explain the observed relationship between anxiety and substance abuse. Specifically, the concept of "abstinence phobias," common across psychoactive substances, is developed. The evidence needed to support this concept is outlined, and relevant data from studies of opiate, alcohol, and tobacco dependences are reviewed. Parallel data obtained from the treatment of obesity are discussed. It is concluded that the abstinence phobia merits further study; clinical implications are also considered.

Effect of the hypnotic flurazepam on the sleep of pentazocine and heroin addicts during withdrawal

Fourteen male heroin addicts being detoxified on methadone and 14 male pentazocine addicts being detoxified drug-free were observed over a 24-hour period for 2 weeks in their sleeping patterns to assess the effects of flurazepam upon sleep during withdrawal. Results of objective and subjective measures find that flurazepam use is associated with more objective nighttime arousals and less total sleep for the heroin group compared to the pentazocine group. Heroin patients felt they had a poorer quality of sleep and took flurazepam more frequently than did the pentazocine patients. Heroin patients' assessments of their sleep and number of arousals correlated poorly with observations.

The effects of methadone on the social behavior and activity of the rat

Pairs of 80-day-old female rats were given SC injections of either 0, 1, 2.5, or 4 mg/kg of methadone hydrochloride on each of 6 days. Both animals of the pair received the same dose. One hour postinjection, each pair was observed in a circular arena for a five minute period during which the following dependent measures were recorded: total time in contact, latency to initial contact, frequency of aggressive grooms, and locomotor activity. The results indicated that the rats treated with methadone spent less time in contact, took longer to contact, and aggressively groomed each other less frequently than rats treated with a saline vehicle. Also, the results suggested that the disruption of social behavior produced by methadone was not a reflection of decreased activity levels.

Opiates, catecholamines, behavior, and mood

Indirect evidence has linked opioid reinforcement with changes in noradrenergic metabolism secondary to drug administration. Methodological precedents for biobehavioral correlations in depressive illness have suggested an important association between changes in mood and biogenic amine excretion patterns in the urines of patients during depression and recovery. This paper presents preliminary data on the possible relationship between changes in catecholamine excretion that were observed and the changes in behavior, mood, psychiatric status, and cardiorespiratory physiology secondary to heroin administration and methadone-assisted withdrawal. This study focuses on the urinary excretion of MHPG, since an appreciable fraction of this metabolite is probably derived from norepinephrine originating in the brain. The subjective changes in mood associated with heroin use, the decrease in respiratory rate, and the behavioral and mental status effects associated with opiate intoxication were observed only in the individuals whose MHPG excretion increased during the period of opiate administration.

Drug-produced changes in human social behavior: facilitation by d-amphetamine

The effects of oral d-amphetamine 5-30 mg on human social and verbal behavior were studied using repeated observations within subjects under a time-sampling observation procedure in a residential research ward. d-Amphetamine increased socializing in all three subjects studied, but only increased standing in one of the subjects. In the second experiment throat microphones and voice-operated relays were used to measure automatically quantitative aspects of dyadic verbal interactions during 1-hr daily sessions. Total speaking time showed dose-related increases in 5 of the 7 subjects receiving d-amphetamine. Adjective checklist self-report scores indicating stimulant drug effects were as sensitive and reliable as the speaking measure to the effects of d-amphetamine in these subjects. Speaking time also increased in 2 of the 8 partners who received placebo when the subjects with whom they were paired received d-amphetamine. This represents a socially mediated indirect drug effect. Adjective checklist scores of the partners receiving placebo were not changed when the paired subjects received d-amphetamine. Under controlled experimental conditions the naturalistic human behaviors of socializing and speaking are sensitive dependent variables for behavioral pharmacology research.

Effects of response requirement upon human sedative self-administration and drug-seeking behavior

Five male volunteers with histories of sedative drug abuse were given the opportunity to self-administer up to 20 oral doses per day of either diazepam (10 mg per dose) or sodium pentobarbital (30 mg per dose). Each dose was purchased with tokens earned by exercising on a stationary exercise bicycle. Each two minutes of exercise earned one token. In a mixed order across days the number of tokens required to purchase each dose was varied among 1, 3, 5, 8 and 10. Drug intake decreased as a function of increased response requirement for purchasing the drug. Response output for drug tended to be an inverted-U shaped function of the response requirement. Thus, the cost of drug doses act as a powerful environmental influence upon both of these aspects of drug abuse behavior - amount of drug consumed and amount of drug-seeking behavior.

Interpersonal behavior in a small group setting during the heroin addiction cycle

In a study of social interaction during an experimental addiction cycle, male narcotic addicts expressed more hostility after higher doses of heroin. No consistent role variations were observed in dominance, friendliness, or therapeutic-orientation.