Interoceptive Insular Cortex Research Articles

Spontaneous and Naloxone-Precipitated Withdrawal Behaviors From Chronic Opiates are Accompanied by Changes in N-Oleoylglycine and N-Oleoylalanine Levels in the Brain and Ameliorated by Treatment With These Mediators.

Rationale: The endocannabinoidome mediators, N-Oleoylglycine (OlGly) and N-Oleoylalanine (OlAla), have been shown to reduce acute naloxone-precipitated morphine withdrawal affective and somatic responses.Objectives: To determine the role and mechanism of action of OlGly and OlAla in withdrawal responses from chronic exposure to opiates in male Sprague-Dawley rats.Methods: Opiate withdrawal was produced: 1) spontaneously 24 h following chronic exposure to escalating doses of morphine over 14 days (Experiments 1 and 2) and steady-state exposure to heroin by minipumps for 12 days (Experiment 3), 2) by naloxone injection during steady-state heroin exposure (Experiment 4), 3) by naloxone injection during operant heroin self-administration (Experiment 5).Results: In Experiment 1, spontaneous morphine withdrawal produced somatic withdrawal reactions. The behavioral withdrawal reactions were accompanied by suppressed endogenous levels of OlGly in the nucleus accumbens, amygdala, and prefrontal cortex, N-Arachidonylglycerol and OlAla in the amygdala, 2-arachidonoylglycerol in the nucleus accumbens, amygdala and interoceptive insular cortex, and by changes in colonic microbiota composition. In Experiment 2, treatment with OlAla, but not OlGly, reduced spontaneous morphine withdrawal responses. In Experiment 3, OlAla attenuated spontaneous steady-state heroin withdrawal responses at both 5 and 20 mg/kg; OlGly only reduced withdrawal responses at the higher dose of 20 mg/kg. Experiment 4 demonstrated that naloxone-precipitated heroin withdrawal from steady-state exposure to heroin (7 mg/kg/day for 12 days) is accompanied by tissue-specific changes in brain or gut endocannabinoidome mediator, including OlGly and OlAla, levels and colonic microbiota composition, and that OlAla (5 mg/kg) attenuated behavioural withdrawal reactions, while also reversing some of the changes in brain and gut endocannabinoidome and gut microbiota induced by naloxone. Experiment 5 demonstrated that although OlAla (5 mg/kg) did not interfere with operant heroin self-administration on its own, it blocked naloxone-precipitated elevation of heroin self-administration behavior.Conclusion: These results suggest that OlAla and OlGly are two endogenous mediators whose brain concentrations respond to chronic opiate treatment and withdrawal concomitantly with changes in colon microbiota composition, and that OlAla may be more effective than OlGly in suppressing chronic opiate withdrawal responses.

Interoceptive insular cortex participates in sensory processing of gastrointestinal malaise and associated behaviors

The insular cortex plays a central role in the perception and regulation of bodily needs and emotions. Its modular arrangement, corresponding with different sensory modalities, denotes a complex organization, and reveals it to be a hub that is able to coordinate autonomic and behavioral responses to many types of stimuli. Yet, little is known about the dynamics of its electrical activity at the neuronal level. We recorded single neurons in behaving rats from the posterior insula cortex (pIC), a subdivision considered as a primary interoceptive cortex, during gastrointestinal (GI) malaise, a state akin to the emotion of disgust in humans. We found that a large proportion of pIC neurons were modulated during the rodent compensatory behaviors of lying on belly (LOB) and Pica. Furthermore, we demonstrated that LOB was correlated with low-frequency oscillations in the field potentials and spikes at the theta (8 Hz) band, and that low-frequency electrical microstimulation of pIC elicited LOB and Pica. These findings demonstrate that pIC neurons play a critical role in GI malaise perception, and that the pIC influences the expression of behaviors that alleviate GI malaise. Our model provides an accessible approach at the single cell level to study innate emotional behaviors, currently elusive in humans.

Interoceptive Insular Cortex Mediates Both Innate Fear and Contextual Threat Conditioning to Predator Odor.

The insular cortex (IC), among other brain regions, becomes active when humans experience fear or anxiety. However, few experimental studies in rats have implicated the IC in threat responses. We have recently reported that inactivation of the primary interoceptive cortex (pIC) during pre-training, or the intra-pIC blockade of protein synthesis immediately after training, impaired the consolidation of auditory fear conditioning. The present study was designed to investigate the role of the pIC in innate and learned defensive responses to predator odor. Freezing behavior was elicited by single or repetitive exposures to a collar that had been worn by a domestic cat. Sessions were video-recorded and later scored by video observation. We found that muscimol inactivation of the pIC reduced the expression of freezing reaction in response to a single or repeated exposure to cat odor. We also found that pIC inactivation with muscimol impaired conditioning of fear to the context in which rats were exposed to cat odor. Furthermore, neosaxitoxin inactivation of the pIC resulted in a prolonged and robust reduction in freezing response in subsequent re-exposures to cat odor. In addition, freezing behavior significantly correlated with the neural activity of the IC. The present results suggest that the IC is involved in the expression of both innate and learned fear responses to predator odor.

Oleoyl glycine: interference with the aversive effects of acute naloxone-precipitated MWD, but not morphine reward, in male Sprague-Dawley rats.

Oleoyl glycine (OlGly), a recently discovered fatty acid amide that is structurally similar to N- acylethanolamines, which include the endocannabinoid, anandamide (AEA), as well as endogenous peroxisome proliferator-activated receptor alpha (PPARα) agonists oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), has been shown to interfere with nicotine reward and dependence in mice. Behavioral and molecular techniques were used to investigate the ability of OlGly to interfere with the affective properties of morphine and morphine withdrawal (MWD) in male Sprague-Dawley rats. Synthetic OlGly (1-30 mg/kg, intraperitoneal [ip]) produced neither a place preference nor aversion on its own; however, at doses of 1 and 5 mg/kg, ip, it blocked the aversive effects of MWD in a place aversion paradigm. This effect was reversed by the cannabinoid 1 (CB1) receptor antagonist, AM251 (1 mg/kg, ip), but not the PPARα antagonist, MK886 (1 mg/kg, ip). OlGly (5 or 30 mg/kg, ip) did not interfere with a morphine-induced place preference or reinstatement of a previously extinguished morphine-induced place preference. Ex vivo analysis of tissue (nucleus accumbens, amygdala, prefrontal cortex, and interoceptive insular cortex) collected from rats experiencing naloxone-precipitated MWD revealed that OlGly was selectively elevated in the nucleus accumbens. MWD did not modify levels of the endocannabinoids 2-AG and AEA, nor those of the PPARα ligands, OEA and PEA, in any region evaluated. Here, we show that OlGly interferes with the aversive properties of acute naloxone-precipitated morphine withdrawal in rats. These results suggest that OlGly may reduce the impact of MWD and may possess efficacy in treating opiate withdrawal.

Conditioned gaping produced by high dose Δ9-tetrahydracannabinol: Dysregulation of the hypothalamic endocannabinoid system

Δ9-tetrahydracannabinol (THC) is recognized as an effective treatment for nausea and vomiting via its action on the cannabinoid 1 (CB1) receptor. Paradoxically, there is evidence that THC can also produce nausea and vomiting. Using the conditioned gaping model of nausea in rats, we evaluated the ability of several doses of THC (0.0, 0.5, 5 and 10 mg/kg, i.p.) to produced conditioned gaping reactions. We then investigated the ability of the CB1 receptor antagonist, rimonabant, to block the establishment of THC-induced conditioned gaping. Real-time polymerase chain reaction (RT-PCR) was then used to investigate changes in endocannabinoid related genes in various brain regions in rats chronically treated with vehicle (VEH), 0.5 or 10 mg/kg THC. THC produced dose-dependent gaping, with 5 and 10 mg/kg producing significantly more gaping reactions than VEH or 0.5 mg/kg THC, a dose known to have anti-emetic properties. Pre-treatment with rimonabant reversed this effect, indicating that THC-induced conditioned gaping was CB1 receptor mediated. The RT-PCR analysis revealed an upregulation of genes for the degrading enzyme, monoacylglycerol lipase (MAGL), of the endocannabinoid, 2-arachidolyl glycerol (2-AG), in the hypothalamus of rats treated with 10 mg/kg THC. No changes in the expression of relevant genes were found in nausea (interoceptive insular cortex) or vomiting (dorsal vagal complex) related brain regions. These findings support the hypothesis that THC-induced nausea is a result of a dysregulated hypothalamic-pituitary-adrenal axis leading to an overactive stress response.

The activity of discrete sets of neurons in the posterior insula correlates with the behavioral expression and extinction of conditioned fear.

The interoceptive insular cortex is known to be involved in the perception of bodily states and emotions. Increasing evidence points to an additional role for the insula in the storage of fear memories. However, the activity of the insula during fear expression has not been studied. We addressed this issue by recording single units from the posterior insular cortex (pIC) of awake behaving rats expressing conditioned fear during its extinction. We found a set of pIC units showing either significant increase or decrease in activity during high fear expression to the auditory cue ("freezing units"). Firing rate of freezing units showed high correlation with freezing and outlasted the duration of the auditory cue. In turn, a different set of units showed either significant increase or decrease in activity during low fear state ("extinction units"). These findings show that expression of conditioned freezing is accompanied with changes in pIC neural activity and suggest that the pIC is important to regulate the behavioral expression of fear memory. NEW & NOTEWORTHY Here, we show novel single-unit data from the interoceptive insula underlying the behavioral expression of fear. We show that different populations of neurons in the insula codify expression and extinction of conditioned fear. Our data add further support for the insula as an important player in the regulation of emotions.

Nausea-Induced 5-HT Release in the Interoceptive Insular Cortex and Regulation by Monoacylglycerol Lipase (MAGL) Inhibition and Cannabidiol.

Using the rat conditioned gaping model of nausea, the interoceptive insular cortex (IIC) has been identified as a critical site for the regulation of lithium chloride (LiCl)-induced nausea. Indirect evidence supports a model where serotonin (5-HT) acts on postsynaptic 5-HT3 receptors and its release is suppressed by elevating 2-arachidonylglycerol (2-AG) by monoacylglycerol lipase (MAGL) inhibition to suppress nausea. Here, we directly test the hypothesis that systemic LiCl elevates 5-HT in the IIC, and this is prevented by pretreatments that reduce 5-HT release. Using male Sprague Dawley rats, LiCl (but not saline), elevated 5-HT selectively in the IIC, for 20 min after LiCl administration (127.2 mg/kg, i.p.). Systemic pretreatment with the MAGL inhibitor, MJN110, prevented the LiCl-induced elevation of 5-HT in the IIC. Systemic cannabidiol (CBD), which reduces LiCl-induced nausea by acting at 5-HT1A somatodendritic autoreceptors, also prevented LiCl-induced elevation of 5-HT in the IIC. Since 5-HT3 receptor agonists delivered to the IIC produce nausea, we tested and confirmed the hypothesis that the intra-IIC administration of 5-HT3 receptor antagonist, ondansetron, but not MJN110, would prevent LiCl-induced conditioned gaping reactions produced by intra-IIC administration of the 5-HT3 receptor agonist, m-chlorophenylbiguanide (mCPBG). Finally, we demonstrate that exposure to a LiCl-paired flavor (but not a saline-paired flavor) produces elevated 5-HT release in the IIC, while rats display conditioned gaping reactions. These results confirm that LiCl-induced nausea is triggered by elevated 5-HT release in the IIC and is attenuated by treatments that reduce 5-HT availability in this region.

CB₁ receptor antagonism in the bed nucleus of the stria terminalis interferes with affective opioid withdrawal in rats.

The bed nucleus of the stria terminalis (BNST) is a region of the extended amygdala that is implicated in addiction, anxiety, and stress related behaviors. This region has been identified in mediating the aversive state of naloxone-precipitated morphine withdrawal (MWD) and cannabinoid Type I (CB1) receptors have been found to modulate neurotransmission within this region. Previous findings suggest that the CB1 antagonist/inverse agonist, AM251, administered systemically or by infusion into the central nucleus of the amygdala (CeA) prevented the aversive affective properties of MWD as measured by conditioned place aversion learning. As well, when administered systemically or by infusion into the basolateral nucleus of the amygdala (BLA) or the interoceptive insular cortex, the monoaclyglycerol lipase (MAGL) inhibitor, MJN110 (which elevates 2-arachidonlyglycerol), also prevented a naloxone-precipitated MWD induced place aversion. Given the connectivity of these regions and the BNST, the present study sought to determine whether cannabinoid modulation of the BNST would also prevent the affective properties of naloxone precipitated MWD-induced place aversion learning. Prior to conditioning trials, rats received intra-BNST infusions of AM251, in Experiment 1, or MJN110 in Experiment 2. AM251, but not MJN110, prevented the establishment of the MWD-induced place aversion. The current findings emphasize an important role for the BNST in opioid withdrawal and suggest that the ameliorative effects of systemically administered CB1 antagonists are mediated, in part, by their actions within this region. (PsycINFO Database Record

Double Dissociation of Monoacylglycerol Lipase Inhibition and CB1 Antagonism in the Central Amygdala, Basolateral Amygdala, and the Interoceptive Insular Cortex on the Affective Properties of Acute Naloxone-Precipitated Morphine Withdrawal in Rats.

Both CB1 receptor antagonism and agonism, in particular by 2-arachidonyl glycerol (2-AG), have been shown to reduce somatic symptoms of morphine withdrawal (MWD). Here we evaluated the effects of both systemic pretreatment with the monoacylglycerol lipase (MAGL) inhibitor MJN110 (which selectively elevates 2-AG) and central administration of both MJN110 and the CB1 antagonist (AM251) on the affective properties of MWD. Acute MWD induced place aversion occurs when naloxone is administered 24 h following a single exposure to a high dose of morphine. Systemic pretreatment with the MAGL inhibitor, MJN110, prevented the aversive effects of acute MWD by a CB1 receptor-dependent mechanism. Furthermore, in a double dissociation, AM251 infusions into the central amygdala, but MJN110 infusions into the basolateral amygdala, interfered with the naloxone-precipitated MWD induced place aversion. As well, MJN110, but not AM251, infusions into the interoceptive insular cortex (a region known to be activated in acute MWD) also prevented the establishment of the place aversion by a CB1 mechanism of action. These findings reveal the respective sites of action of systemically administered MJN110 and AM251 in regulating the aversive effects of MWD.

A role for the interoceptive insular cortex in the consolidation of learned fear

A growing body of evidence suggests that learned fear may be related to the function of the interoceptive insular cortex. Using an auditory fear conditioning paradigm in rats, we show that the inactivation of the posterior insular cortex (pIC), the target of the interoceptive thalamus, prior to training produced a marked reduction in fear expression tested 24h later. Accordingly, post-training anisomycin infused immediately, but not 6h after, also reduced fear expression tested the following day, supporting a role for the pIC in consolidation of fear memory. The long-term (ca. a week) and reversible inactivation of the pIC with the sodium channel blocker neosaxitoxin, immediately after fear memory reactivation induced a progressive decrease in the behavioral expression of conditioned fear. In turn, we observed that fear memory reactivation is accompanied by an enhanced expression of Fos and Zif268, early genes involved in neural activity and plasticity. Taken together these data indicate that the pIC is involved in the regulation of fear memories.

Cannabinoids suppress acute and anticipatory nausea in preclinical rat models of conditioned gaping.

The sensation of nausea is one of the most debilitating human experiences. Current antiemetic therapies are effective in reducing vomiting, but are less effective in reducing acute and delayed nausea and are completely ineffective in reducing anticipatory nausea. Recent preclinical evidence using a selective rat model of nausea (conditioned gaping reactions) has revealed that cannabinoids have great promise as treatments for nausea and that their antinausea effects may be mediated by the interoceptive insular cortex.

A Role for the Insular Cortex in Long-Term Memory for Context-Evoked Drug Craving in Rats

Drug craving critically depends on the function of the interoceptive insular cortex, and may be triggered by contextual cues. However, the role of the insula in the long-term memory linking context with drug craving remains unknown. Such a memory trace probably resides in some neocortical region, much like other declarative memories. Studies in humans and rats suggest that the insula may include such a region. Rats chronically implanted with bilateral injection cannulae into the high-order rostral agranular insular cortex (RAIC) or the primary interoceptive posterior insula (pIC) were conditioned to prefer the initially aversive compartment of a 2-compartment place preference apparatus by repeatedly pairing it to amphetamine. We found a reversible but long-lasting loss (ca. 24 days) of amphetamine-conditioned place preference (CPP) and a decreased expression in the insula of zif268, a crucial protein in memory reconsolidation, when anisomycin (ANI) was microinjected into the RAIC immediately after the reactivation of the conditioned amphetamine/context memory. ANI infusion into the RAIC without reactivation did not change CPP, whereas ANI infusion into pIC plus caused a 15 days loss of CPP. We also found a 24 days loss of CPP when we reversibly inactivated pIC during extinction trials. We interpret these findings as evidence that the insular cortex, including the RAIC, is involved in a context/drug effect association. These results add a drug-related memory function to the insular cortex to the previously found role of the pIC in the perception of craving or malaise.