Upregulation of DeltaFosB by propofol in rat nucleus accumbens

NMDA receptor within nucleus accumbens shell regulates propofol self-administration through D1R/ERK/CREB signalling pathway

Addictive properties of propofol have been demonstrated in both humans and animals. The nucleus accumbens (NAc) shell (NAsh) in the brain, along with the interactions between N-methyl-D-aspartate receptor (NMDAR) and the dopamine D1 receptor (D1R), as well as their downstream ERK/CREB signalling pathway in the NAc, are integral in regulating reward-seeking behaviour. Nevertheless, it remains unclear whether NMDARs and the NMDAR-D1R/ERK/CREB signalling pathway in the NAsh are involved in mediating propofol addiction. To investigate it, we conducted experiments with adult male Sprague-Dawley rats to establish a model of propofol self-administration behaviour. Subsequently, we microinjected D-AP5 (a competitive antagonist of NMDARs, 1.0-4.0 μg/0.3 μL/site) or vehicle into bilateral NAsh in rats that had previously self-administered propofol to examine the impact of NMDARs within the NAsh on propofol self-administration behaviour. Additionally, we examined the protein expressions of NR2A and NR2B subunits, and the D1R/ERK/CREB signalling pathways within the NAc. The results revealed that propofol administration behaviour was enhanced by D-AP5 pretreatment in NAsh, accompanied by elevated expressions of phosphorylation of NR2A (Tyr1246) and NR2B (Tyr1472) subunits. There were statistically significant increases in the expressions of D1Rs, as well as in the phosphorylated ERK1/2 (p-ERK1/2) and CREB (p-CREB). This evidence substantiates a pivotal role of NMDARs in the NAsh, with a particular emphasis on the NR2A and NR2B subunits, in mediating propofol self-administration behaviour. Furthermore, it suggests that this central reward processing mechanism may operate through the NMDAR-D1R/ERK/CREB signal transduction pathway.

Non-Opioid Anesthetics Addiction: A Review of Current Situation and Mechanism

Drug addiction is one of the major worldwide health problems, which will have serious adverse consequences on human health and significantly burden the social economy and public health. Drug abuse is more common in anesthesiologists than in the general population because of their easier access to controlled substances. Although opioids have been generally considered the most commonly abused drugs among anesthesiologists and nurse anesthetists, the abuse of non-opioid anesthetics has been increasingly severe in recent years. The purpose of this review is to provide an overview of the clinical situation and potential molecular mechanisms of non-opioid anesthetics addiction. This review incorporates the clinical and biomolecular evidence supporting the abuse potential of non-opioid anesthetics and the foreseeable mechanism causing the non-opioid anesthetics addiction phenotypes, promoting a better understanding of its pathogenesis and helping to find effective preventive and curative strategies.

Historical and Modern Evidence for the Role of Reward Circuitry in Emergence

Increasing evidence supports a role for brain reward circuitry in modulating arousal along with emergence from anesthesia. Emergence remains an important frontier for investigation, since no drug exists in clinical practice to initiate rapid and smooth emergence. This review discusses clinical and preclinical evidence indicating a role for two brain regions classically considered integral components of the mesolimbic brain reward circuitry, the ventral tegmental area and the nucleus accumbens, in emergence from propofol and volatile anesthesia. Then there is a description of modern systems neuroscience approaches to neural circuit investigations that will help span the large gap between preclinical and clinical investigation with the shared aim of developing therapies to promote rapid emergence without agitation or delirium. This article proposes that neuroscientists include models of whole-brain network activity in future studies to inform the translational value of preclinical investigations and foster productive dialogues with clinician anesthesiologists.

Subanesthetic Dose of Propofol Activates the Reward System in Rats

BACKGROUND

Propofol has addictive properties, even with a single administration, and facilitates dopamine secretion in the nucleus accumbens (NAc). Activation of the dopaminergic circuits of the midbrain reward system, including the ventral tegmental area (VTA) and NAc, plays a crucial role in addiction. However, the effects of propofol on synaptic transmission and biochemical changes in the VTA-NAc circuit remain unclear.

METHODS

We investigated the effects of subanesthetic doses of propofol on rat VTA neurons and excitatory synaptic transmission in the NAc using slice patch-clamp experiments. Using immunohistochemistry and western blot analyses, we evaluated the effects of intraperitoneal propofol administration on the expression of addiction-associated transcription factor ΔFosB (truncated form of the FBJ murine osteosarcoma viral oncogene homolog B protein) in the NAcs in 5-week-old rats.

RESULTS

In the current-clamp mode, a subanesthetic dose (0.5-5 µmol/L) of propofol increased the action potential frequency in about half the VTA neurons (excited neurons: control: 9.4 ± 3.0 Hz, propofol 0.5 µmol/L: 21.5 ± 6.0 Hz, propofol 5 µmol/L: 14.6 ± 5.3 Hz, wash: 2.0 ± 0.7 Hz, n = 14/27 cells; unchanged/suppressed neurons: control: 1.68 ± 0.94 Hz, propofol 0.5 µmol/L: 1.0 ± 0.67 Hz, propofol 5 µmol/L: 0.89 ± 0.87 Hz, wash: 0.16 ± 0.11 Hz, n = 13/27 cells). In the voltage-clamp mode, about half the VTA principal neurons showed inward currents with 5 µmol/L of propofol (inward current neurons: control: -20.5 ± 10.0 pA, propofol 0.5 µmol/L: -62.6 ± 14.4 pA, propofol 5 µmol/L: -85.2 ± 18.3 pA, propofol 50 µmol/L: -17.1 ± 39.2 pA, washout: +30.5 ± 33.9 pA, n = 6/11 cells; outward current neurons: control: -33.9 ± 14.6 pA, propofol 0.5 µmol/L: -29.5 ± 16.0 pA, propofol 5 µmol/L: -0.5 ± 20.9 pA, propofol 50 µmol/L: +38.9 ± 18.5 pA, washout: +40.8 ± 32.1 pA, n = 5/11 cells). Moreover, 0.5 µmol/L propofol increased the amplitudes of evoked excitatory synaptic currents in the NAc, whereas >5 µmol/L propofol decreased them (control: 100.0 ± 2.0%, propofol 0.5 µmol/L: 118.4 ± 4.3%, propofol 5 µmol/L: 98.3 ± 3.3%, wash [within 10 min]: 70.7 ± 3.3%, wash [30 minutes later]: 89.9 ± 2.5%, n = 13 cells, P < .001, Dunnett's test comparing control and propofol 0.5 µmol/L). Intraperitoneally administered subanesthetic dose of propofol increased ΔFosB expression in the NAc, but not in VTA, 2 and 24 hours after administration, compared with the Intralipid control group (propofol 2 hours: 0.94 ± 0.15, 24 hours: 0.68 ± 0.07; Intralipid 2 hours: 0.40 ± 0.03, 24 hours: 0.37 ± 0.06, P = .0002 for drug in the 2-way analysis of variance).

CONCLUSIONS

Even a single administration of a subanesthetic dose of propofol may cause rewarding change in the central nervous system. Thus, there is a potential propofol rewarding effect among patients receiving anesthesia or sedation with propofol, as well as among health care providers exposed to propofol.

Acute and chronic neurobehavioral effects of the designer drug and bath salt constituent 3,4-methylenedioxypyrovalerone in the rat

BACKGROUND

The substantial increase in use of 3,4-methylenedioxypyrovalerone (MDPV), a popular recreational synthetic cathinone, has raised legitimate questions about its behavioral consequences and abuse liability.

AIMS

The aim of this study was to study MDPV-induced neurobehavioral effects in the rat, using different paradigms traditionally developed to study drug-attributed addictive properties.

METHODS

Different patterns of intraperitoneal 3 mg/kg MDPV administration were investigated. Consequences on rat horizontal locomotion and behavior of acute, intermittent (once daily dosing over 10 days), and binge (three-time daily dosing for 3 days) MDPV administration as well as challenge after 10 day MDPV withdrawal were studied. The dopamine receptor-D1 antagonist, SCH23390, was bilaterally infused in the nucleus accumbens to determine the role of D1-receptors in MDPV-related effects on the associative memory recall using the conditioned place preference paradigm. In addition, in a separate experience using western blot, we investigated the effects of chronic MDPV administration (four injections during 24 h) on ΔFosB expression in the nucleus accumbens, caudate putamen, and prefrontal cortex.

RESULTS

Acute MDPV administration increased stereotypies and open arm entries in the elevated plus maze while SCH23390 abolished MDPV-induced enhancing effects on memory consolidation. Intermittent MDPV administration resulted in sensitization of MDPV-induced locomotor effects and tolerance during the following challenge. With binge MDPV administration, locomotor activity was not altered despite tolerance onset after challenge. SCH23390 abolished MDPV-induced conditioned place preference. Chronic MDPV administration induced ΔFosB accumulation in the nucleus accumbens, caudate putamen, and prefrontal cortex.

CONCLUSIONS

Our findings clearly show that MDPV produces profound behavioral alterations mediated by the activation of the dopaminergic system similarly to other amphetamines.

Presence of Inhibitory Glycinergic Transmission in Medium Spiny Neurons in the Nucleus Accumbens

It is believed that the rewarding actions of drugs are mediated by dysregulation of the mesolimbic dopaminergic system leading to increased levels of dopamine in the nucleus accumbens (nAc). It is widely recognized that GABAergic transmission is critical for neuronal inhibition within nAc. However, it is currently unknown if medium spiny neurons (MSNs) also receive inhibition by means of glycinergic synaptic inputs. We used a combination of proteomic and electrophysiology studies to characterize the presence of glycinergic input into MSNs from nAc demonstrating the presence of glycine transmission into nAc. In D1 MSNs, we found low frequency glycinergic miniature inhibitory postsynaptic currents (mIPSCs) which were blocked by 1 μM strychnine (STN), insensitive to low (10, 50 mM) and high (100 mM) ethanol (EtOH) concentrations, but sensitive to 30 μM propofol. Optogenetic experiments confirmed the existence of STN-sensitive glycinergic IPSCs and suggest a contribution of GABA and glycine neurotransmitters to the IPSCs in nAc. The study reveals the presence of glycinergic transmission in a non-spinal region and opens the possibility of a novel mechanism for the regulation of the reward pathway.

Neurobiology of Propofol Addiction and Supportive Evidence: What Is the New Development?

Propofol is a short-acting intravenous anesthetic agent suitable for induction and maintenance of general anesthesia as well as for procedural and intensive care unit sedation. As such it has become an unparalleled anesthetic agent of choice in many institutional and office practices. However, in addition to its idealistic properties as an anesthetic agent, there is accumulating evidence suggesting its potential for abuse. Clinical and experimental evidence has revealed that not only does propofol have the potential to be abused, but also that addiction to propofol shows a high mortality rate. Based on this evidence, different researchers have shown interest in determining the probability of propofol to be an addictive agent by comparing it with other drugs of abuse and depicting a functional similitude that involves the mesocorticolimbic pathway of addiction. In light of this, the Drug Enforcement Agency and the American Society of Anesthesiologists have put forth certain safety recommendations for the use of propofol. Despite this, the abuse potential of propofol has been challenged at different levels and therefore the preeminent focus will be to further validate the linkage from medicinal and occasional use of propofol to its addiction, as well as to explore the cellular and molecular targets involved in establishing this linkage, so as to curb the harm arising out of it. This review incorporates the clinical and biomolecular evidence supporting the abuse potential of propofol and brings forth the promising targets and the foreseeable mechanism causing the propofol addiction phenotypes, which can be called upon for future developments in this field.

Can the dopaminergic-related effects of general anesthetics be linked to mechanisms involved in drug abuse and addiction?

BACKGROUND

General anesthetics (GA) are well known for the ability to induce a state of reversible loss of consciousness and unresponsiveness to painful stimuli. However, evidence from animal models and clinical studies show that GA exposure may induce behavioral changes beyond acute effects. Most research and concerns are focused on changes in cognition and memory.

METHODS

We will look at effects of GA on behavior that is mediated by the dopaminergic system.

RESULTS

Pharmacological resemblance of GA with drugs of abuse, and the complexity and importance of dopaminergic systems in both reward seeking and addictive illnesses make us believe that it deserves an overview about what is already known and what matters to us as healthcare workers and specifically as anesthesiologists.

CONCLUSION

A review of available evidence strongly suggests that there may be a link between the effects of GA on the brain and substance abuse, partly explained by their influence on the dopaminergic system.

Molecular neurobiology of addiction: what's all the (Δ)FosB about?

The transcription factor ΔFosB is upregulated in numerous brain regions following repeated drug exposure. This induction is likely to, at least in part, be responsible for the mechanisms underlying addiction, a disorder in which the regulation of gene expression is thought to be essential. In this review, we describe and discuss the proposed role of ΔFosB as well as the implications of recent findings. The expression of ΔFosB displays variability dependent on the administered substance, showing region-specificity for different drug stimuli. This transcription factor is understood to act via interaction with Jun family proteins and the formation of activator protein-1 (AP-1) complexes. Once AP-1 complexes are formed, a multitude of molecular pathways are initiated, causing genetic, molecular and structural alterations. Many of these molecular changes identified are now directly linked to the physiological and behavioral changes observed following chronic drug exposure. In addition, ΔFosB induction is being considered as a biomarker for the evaluation of potential therapeutic interventions for addiction.

[Life-threatening fentanyl and propofol addiction: interview with a survivor]

Anesthesiologists have a well-known increased risk of substance abuse including the intravenous administration of opioids and propofol. However, katamnestic reports from the point of view of propofol-addicted anesthesiologists themselves are missing which would aid a better understanding of the dynamics and progress of addiction. This article presents an interview with a formerly addicted female anesthesiologist who after long-term abuse with oral tilidine combined with naloxone switched to intravenous administration of fentanyl and later on propofol. Several life-threatening incidents occurred but after some severe setbacks occupational rehabilitation outside the field of anesthesiology was successful following inpatient treatment. This case shows exemplarily in accordance with the current literature that warning signs in addicted physicians are often ignored by colleagues and supervisors and rehabilitation is possible under professional therapy and continuous surveillance. Additionally, this case emphasizes the necessity of controlling the distribution of propofol to reduce the life-threatening professional risk to anesthesiologists.

MicroRNA expression profile and functional analysis reveal that miR-382 is a critical novel gene of alcohol addiction

Alcohol addiction is a major social and health concern. Here, we determined the expression profile of microRNAs (miRNAs) in the nucleus accumbens (NAc) of rats treated with alcohol. The results suggest that multiple miRNAs were aberrantly expressed in rat NAc after alcohol injection. Among them, miR-382 was down-regulated in alcohol-treated rats. In both cultured neuronal cells in vitro and in the NAc in vivo, we identified that the dopamine receptor D1 (Drd1) is a direct target gene of miR-382. Via this target gene, miR-382 strongly modulated the expression of DeltaFosB. Moreover, overexpression of miR-382 significantly attenuated alcohol-induced up-regulation of DRD1 and DeltaFosB, decreased voluntary intake of and preference for alcohol and inhibited the DRD1-induced action potential responses. The results indicated that miRNAs are involved in and may represent novel therapeutic targets for alcoholism.

Self-administration of propofol is mediated by dopamine D1 receptors in nucleus accumbens in rats

As a widely used intravenous short-acting anesthetic, propofol is recently indicated by clinical and animal studies for its abuse potential, but the mechanism underlying propofol abuse is largely unknown. This study examined the contribution of dopamine receptor subtype (D1 and D2 receptors) and neuroanatomical locus (i.e. nuclear accumbens) in the maintenance of propofol self-administration in rats. After the acquisition and maintenance of self-administration of propofol (1.7 mg/kg/infusion) under a fixed ratio (FR1) schedule of reinforcement over 14 days, rats were treated by either intraperitoneal injection or intra-nucleus accumbens (NAc) injection of D1 receptor antagonist (SCH23390) or D2 receptor antagonists (spiperone and eticlopride) 10 min prior to the subsequent propofol self-administration. We demonstrated (i) systemic administration of SCH23390 (10, 30, 100 μg/kg, i.p.) dose-dependently decreased the rate of propofol-maintained self-administration, suggesting a critical role of the D1 receptor in mediating propofol self-administration; (ii) the blockade of the propofol self-administration by SCH23390 was specific since spiperone and eticlopride did not affect propofol self-administration and SCH23390 at these doses did not affect food-maintained responding under an FR5 schedule; (iii) intra-accumbenal injection of SCH23390 (2.5 μg/site) but not eticopride (3.0 μg/site) attenuated the propofol self-administration, localizing nuclear accumbal D1 receptors as a critical locus in the reinforcement of propofol. Together, these findings provide the first direct evidence that D1 receptors in nuclear accumbens play an important role in the maintenance of propofol self-administration.