In Vivo Dopamine Measurements in the Nucleus Accumbens After Nonanesthetic and Anesthetic Doses of Propofol in Rats

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.

Dopaminergic System in Promoting Recovery from General Anesthesia

Dopamine is an important neurotransmitter that plays a biological role by binding to dopamine receptors. The dopaminergic system regulates neural activities, such as reward and punishment, memory, motor control, emotion, and sleep-wake. Numerous studies have confirmed that the dopaminergic system has the function of maintaining wakefulness in the body. In recent years, there has been increasing evidence that the sleep-wake cycle in the brain has similar neurobrain network mechanisms to those associated with the loss and recovery of consciousness induced by general anesthesia. With the continuous development and innovation of neurobiological techniques, the dopaminergic system has now been proved to be involved in the emergence from general anesthesia through the modulation of neuronal activity. This article is an overview of the dopaminergic system and the research progress into its role in wakefulness and general anesthesia recovery. It provides a theoretical basis for interpreting the mechanisms regulating consciousness during general anesthesia.

Propofol exerts anti-anhedonia effects via inhibiting the dopamine transporter

Lasker's award-winning drug propofol is widely used in general anesthesia. The recreational use of propofol is reported to produce a well-rested feeling and euphoric state; yet, the neural mechanisms underlying such pleasant effects remain unelucidated. Here, we report that propofol actively and directly binds to the dopamine transporter (DAT), but not the serotonin transporter (SERT), which contributes to the rapid relief of anhedonia. Then, we predict the binding mode of propofol by molecular docking and mutation of critical binding residues on the DAT. Fiber photometry recording on awake freely moving mice and [¹⁸F] FP-CIT-PET scanning further establishes that propofol administration evokes rapid and lasting dopamine accumulation in nucleus accumbens (NAc). The enhanced dopaminergic tone drives biased activation of dopamine-receptor-1-expressing medium spiny neurons (D1-MSNs) in NAc and reverses anhedonia in chronically stressed animals. Collectively, these findings suggest the therapeutic potential of propofol against anhedonia, which warrants future clinical investigations.

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.

Effects of anesthetics on expression of dopamine and acetylcholine receptors in the rat brain in vivo

Dopamine D₂ and acetylcholine M₁ receptors might be related to post-operative cognitive dysfunction. The aim of the present study is to investigate whether several anesthetics which are used for general anesthesia and/or sedation, affect expression of dopamine D₂ and acetylcholine M₁ receptors in the rat brain. Thirty-six male rats aged 5-9 weeks old were divided into six groups (n = 6 in each group); five groups for anesthetics and one for control. The five groups were anesthetized with either dexmedetomidine 0.4 µg/kg/min, propofol 50 mg/kg/h, midazolam 25 mg/kg/h, sevoflurane 3.3%, or nitrous oxide 75% for 4 h. Then, the rats were decapitated, and the cerebral cortex, hippocampus, corpus striatum, brain stem, and cerebellum were collected from all rats. Then, real-time polymerase chain reaction was performed to examine the expression of Drd2 (cord dopamine D₂ receptor) and Chrm1 (cord acetylcholine M₁ receptor). There were no significant differences among the groups regarding Drd2 and Chrm1 mRNA expression of each region of the brain. Postsynaptic changes of dopamine D₂ and acetylcholine M₁ receptors due to administration of dexmedetomidine, propofol, midazolam, sevoflurane, and nitrous oxide are unlikely to occur at the doses of each anesthetic used in the present study.

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.

The relationship between exposure to general anesthetic agents and the risk of developing an impulse control disorder

Most studies examining the effect of extended exposure to general anesthetic agents (GAAs) have demonstrated that extended exposure induces both structural and functional changes in the central nervous system. These changes are frequently accompanied by neurobehavioral changes that include impulse control disorders that are generally characterized by deficits in behavioral inhibition and executive function. In this review, we will.

The Anesthesiologist's Armamentarium: From Recreation to Medication and Back

For millennia, mankind has sought a means of altering consciousness, often aided by naturally occurring elements. Psychotropic substances have been an integral part of spiritual, medicinal, and recreational aspects of life. The origin of anesthesiology stems directly from the use of recreational drugs; early inhaled anesthetics were first used as a means of entertainment. Hence, it is no surprise that many medications in the anesthesiologist's armamentarium are diverted for recreational use. In the 172 years following the first successful public demonstration of ether anesthesia, many drugs with abuse potential have been introduced to the practice of anesthesia. Although anesthesiologists are aware of the abuse potential of these drugs, how these drugs are obtained and used for recreational purposes is worthy of discussion. There are articles describing the historical and recreational use of specific drug classes. However, to the best of our knowledge, this is the first comprehensive review focusing on the breadth of drugs used by anesthesiologists.

Motivation, risk-taking and sensation seeking behavior in propofol anesthesia exposed peripubertal rats

Adolescent neurodevelopment confer vulnerability to the actions of treatments that produce adaptations in neurocircuitry underlying motivation, impulsivity and reward. Considering wide usage of a sedative-hypnotic agent propofol in clinical practice, we examined whether propofol is a challenging treatment for peripubertal brain. Motivation/hedonic behavior (sucrose preference test), approach/avoidance behavior (elevated plus maze test) and response to dissociative drug phencyclidine (PCP) were studied in peripubertal rats (the rodent model of periadolescence) after propofol anesthesia exposure (PAE). Neurodegeneration (Fluoro-Jade staining) and the expression of proteins (Western blot) involved in excitatory synaptic transmission and activity-dependent synaptic stabilization in the medial prefrontal cortex (mPFC) and striatum (components of motivation/reward circuitry; process both appetitive and aversive events) were examined as well. In peripubertal rats PAE produced 1) transient brain-region specific changes in the expression of N-methyl-d-aspartate (NMDA) receptor subunits NR2A and NR2B, PSD-95 and N-cadherin, without neurotoxicity, 2) hyperlocomotor response to PCP, 3) no changes in preference for palatable 1% sucrose solution and a decrease in food eaten, 4) preference for 20% sucrose solution without changes in food eaten, 5) stretch-attended postures and open arms entries in the elevated plus maze test. Overall, these novel findings show that PAE leaves transient synaptic trace recognized as early form of synaptic plasticity related to passive drug exposure in the brain systems implicated in motivation/reward, increases drug-responsiveness, favors risk-taking and preference of novel/intense stimuli repairing otherwise present motivational deficiency. These findings accentuate multifaceted response to propofol in peripuberty and the importance of environmental stability for the most favorable neurobehavioral recovery.

Comparison of propofol monotherapy and propofol combination therapy for sedation during gastrointestinal endoscopy: A systematic review and meta-analysis

BACKGROUND AND AIM

Previous randomized controlled trials have reported conflicting findings comparing propofol combination therapy (PCT) with propofol monotherapy (PMT) for sedation of patients undergoing gastrointestinal endoscopy. Therefore, a systematic review was carried out to compare the efficacy and safety of PCT and PMT in such patients.

METHODS

We searched MEDLINE, EMBASE and CENTRAL databases to identify all randomized controlled trials that compared the efficacy and safety of PCT and PMT for sedation of patients undergoing gastrointestinal endoscopy. Primary endpoints were incidence of respiratory complications, hypotension and arrhythmia, dose of propofol used, and recovery time. Procedure duration and the satisfaction of patients and doctors were also evaluated.

RESULTS

A total of 2250 patients from 22 studies were included in the final analysis. The combined analysis did not show any difference between PCT and PMT in the incidence of respiratory complications (risk ratio [RR], 0.80; 95% CI, 0.52 to 1.23; I2 = 58.34%), hypotension (RR, 1.06; 95% CI, 0.63 to 1.78; I2 = 72.13%), arrhythmia (RR,1.40; 95% CI, 0.74 to 2.64; I2 = 43.71%), recovery time (standardized mean difference [SMD], 0.16; 95% CI, -0.49 to 0.81; I2 = 95.9%), procedure duration (SMD, 0.04; 95% CI, -0.05 to 0.14; I2 = 0.0%), patient satisfaction (SMD, 0.13; 95% CI, -0.26 to 0.52; I2 = 89.63%) or doctor satisfaction (SMD, 0.01; 95% CI, -0.15 to 0.17; I2 = 0.00%). However, the dose of propofol used was significantly lower in PCT than in PMT (SMD, -1.38; 95% CI, -1.99 to -0.77; I2 = 97.70%).

CONCLUSION

PCT showed comparable efficacy and safety to PMT with respect to respiratory complications, hypotension and arrhythmia, recovery time, procedure duration, patient satisfaction, and doctor satisfaction. However, the average dose of propofol used was higher in PMT.

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.

Glucocorticoid receptor in rat nucleus accumbens: Its roles in propofol addictions

Propofol has been demonstrated as a drug of abuse in humans. Our previous study indicated that dexamethasone, a potent agonist of glucocorticoid receptor (GR), inhibited propofol-maintained rat self-administration behaviors by systematic injection. However, the direct effect of GR in the nucleus accumbens (NAc) on propofol self-administration behavior has not been explored. The propofol-maintained self-administration was established in rats after a successive 3-h daily self-administration of propofol for 14days. On day 15, 30min prior to the last training, rats received one of three doses (0.3, 1.0, or 3.0μg/site) of dexamethasone or vehicle via intra-NAc injection. The number of active nose-poke responses, propofol injections, and inactive nose-poke responses was recorded. Dopamine D1 receptor and c-Fos expressions were detected. Plasma corticosterone level was measured by enzyme-linked immunosorbent assay. Intra-NAc administration of dexamethasone (1.0 and 3.0μg/site) facilitated the active nose-poke responses, which was accompanied by the upregulation of D1 receptor and c-Fos in the NAc. Plasma corticosterone level was not changed in dexamethasone-treated groups. This study provides crucial evidence that GR in the NAc plays an important role in regulating propofol self-administration behaviors in rats, which may be mediated by changes in D1 receptor and c-Fos expressions, and this also needs further examination with GR antagonist in the future.

Brain molecular changes and behavioral alterations induced by propofol anesthesia exposure in peripubertal rats

BACKGROUND

Propofol is commonly used in modern anesthesiology. Some findings suggest that it is highly addictive.

AIM

In this study it was examined whether propofol anesthesia exposure was able to induce behavioral alterations and brain molecular changes already described in addictive drug usage in peripubertal rats, during the onset of mid/periadolescence as a developmental period with increasing vulnerability to drug addiction.

METHODS

The expression of D1 dopamine receptor, a dopamine, and cAMP-regulated phosphoprotein with a Mr 32 000; Ca²⁺ /calmodulin-dependent protein kinase IIα; and Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog-B was examined in peripubertal rats 4, 24, and 48 hour after propofol anesthesia exposure by Western blot and immunohistochemistry. Brain regions of interest were the medial prefrontal cortex, the striatum, and the thalamus. Anxiety and behavioral cross-sensitization to d-amphetamine were examined as well.

RESULTS

Significant increase in the expression of dopamine and cAMP-regulated phosphoprotein with a Mr 32 000 phosphorylated at threonine 34, a postsynaptic marker of dopaminergic neurotransmission, and Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog-B, a marker of neuronal activity, was detected in the thalamus of experimental animals 4-24 hour after the treatment, with the accent on the paraventricular thalamic nucleus. Significant increase in the expression of Ca²⁺ /calmodulin-dependent protein kinase IIα phosphorylated at threonine 286, a sensor of synaptic activity, was observed in the prefrontal cortex and the striatum 24 hour after propofol anesthesia exposure. It was accompanied by a significant decrease in Finkel-Biskis-Jinkins murine osteosarcoma viral oncogene homolog-B expression in the striatum. Decreased behavioral inhibition in aversive environment and increased motor response to d-amphetamine in a context-independent manner were observed as well.

CONCLUSION

In peripubertal rats, propofol anesthesia exposure induces transient molecular and behavioral response that share similarities with those reported previously for addictive drugs. In the absence of additional pharmacological manipulation, all detected effects receded within 48 hour after the treatment.

Effects of propofol on conditioned place preference in male rats: Involvement of nitrergic system

BACKGROUND

Drug-induced conditioned place preference (CPP) is linked to the addictive properties of the drug used. The number of studies that have investigated the effects of propofol on CPP is limited. Research findings suggest that nitric oxide (NO) might play an important role in substance use disorders.

OBJECTIVES

The present study sought to investigate the role of the nitrergic system on the rewarding effects of propofol by using the CPP protocol in rats.

METHODS

The experiment followed habituation, pre-conditioning, conditioning, and post conditioning sessions. Male Wistar albino rats weighing 240-290 g were divided into eight groups: control (saline), propofol (10, 20, and 40 mg/kg), the NO synthase (NOS) inhibitor N^G-nitro-L-arginine methyl ester (L-NAME) alone (30 and 60 mg/kg), and in combination with propofol (30 and 60 mg/kg L-NAME plus 40 mg/kg propofol) (n = 8 for each group). The CPP effects of propofol, L-NAME, saline, and their combinations were evaluated. All the drug and saline administrations were performed by intraperitoneal (ip) injections.

RESULTS

Propofol (10-40 mg/kg) produced CPP that was statistically significant relative to saline. Propofol-induced CPP was significantly reversed by pretreatment with L-NAME. When administered alone, L-NAME did not produce CPP and also did not produce any significant change on locomotor activity of naïve rats.

CONCLUSION

Our results suggest that propofol produces CPP effects in rats and that NO-related mechanisms may be responsible for propofol-induced CPP. Thus, propofol might have the potential to be addictive, and this possibility should be considered during clinical applications of this drug.

Propofol decreases etomidate-related myoclonus in gastroscopy

OBJECTIVE

Myoclonus, a common complication during intravenous induction with etomidate, is bothersome to both anesthesiologists and patients. This study explored the preventive effect of pretreatment with propofol on etomidate-related myoclonus.

METHODS

This was a prospective, double-blind, clinical, randomized controlled study. Totally, 363 patients who were scheduled for a short-duration, painless gastrointestinal endoscopy were divided into 5 groups. Four groups received 0 mg/kg (E group), 0.25 mg/kg (LPE group), 0.50 mg/kg (MPE group), or 0.75 mg/kg (HPE group) propofol pretreatment before etomidate anesthesia. Another group only received 1 to 2 mg/kg of propofol (P group) as anesthesia. The incidence and severity of myoclonus, patient circulation and respiratory status, and intraoperative and postoperative complications were recorded.

RESULTS

The incidence of myoclonus in the LPE group (26.8%), MPE group (16.4%), HPE group (14.9%), and P group (0) was lower than the E group (48.6%, P < .05). The incidence of grade 1, 2, and 3 of myoclonus in the LPE group, MPE group, HPE group, and P group was significantly lower than the E group, and that in the P group was lower than the LPE group (P < .05). The incidence of hypoxemia in the P group was higher than the E group, and the incidence of adverse events in the HPE group and P group was lower than the E group (P < .05).

DISCUSSION

Pretreatment with propofol was feasible for preventing etomidate-related myoclonus. Furthermore, as propofol dosage increased, its effect on reducing the incidence and severity of myoclonic movements induced by etomidate increased.

Incidence of postoperative nausea and vomiting following gynecological laparoscopy: A comparison of standard anesthetic technique and propofol infusion

OBJECTIVE

To determine the safety, efficacy, and feasibility of propofol-based anesthesia in gynecological laparoscopies in reducing incidences of postoperative nausea and vomiting compared to a standard anesthesia using thiopentone/isoflurane.

DESIGN

Randomized single-blind (for anesthesia techniques used) and double-blind (for postoperative assessment) controlled trial.

SETTING

Operation theater, postanesthesia recovery room, teaching hospital.

PATIENTS

Sixty ASA (American Society of Anesthesiologists) I and II female patients (aged 20-60 years) scheduled for gynecological laparoscopy were included in the study.

INTERVENTIONS

Patients in Group A received standard anesthesia with thiopentone for induction and maintenance with isoflurane-fentanyl, and those in Group B received propofol for induction and maintenance along with fentanyl. All patients received nitrous oxide, vecuronium, and neostigmine/glycopyrrolate. No patient received elective preemptive antiemetic, but patients did receive it after more than one episode of vomiting.

MEASUREMENTS

Assessment for incidence of postoperative nausea and vomiting as well as other recovery parameters were carried out over a period of 24 hours.

MAIN RESULTS

Six patients (20%) in Group A and seven patients (23.3%) in Group B experienced nausea. Two patients (6.66%) in Group B had vomiting versus 12 (40%) in Group A (p<0.05). Overall, the incidence of emesis was 60% and 30% in Groups A and B, respectively (p<0.05). All patients in Group B had significantly faster recovery compared with those in Group A. No patient had any overt cardiorespiratory complications.

CONCLUSION

Propofol-based anesthesia was associated with significantly less postoperative vomiting and faster recovery compared to standard anesthesia in patients undergoing gynecological laparoscopy.

Extracellular Signal-Regulated Kinase in Nucleus Accumbens Mediates Propofol Self-Administration in Rats

Clinical and animal studies have indicated that propofol has potential for abuse, but the specific neurobiological mechanism underlying propofol reward is not fully understood. The purpose of this study was to investigate the role of extracellular signal-regulated kinase (ERK) signal transduction pathways in the nucleus accumbens (NAc) in propofol self-administration. We tested the expression of p-ERK in the NAc following the maintenance of propofol self-administration in rats. We also assessed the effect of administration of SCH23390, an antagonist of the D1 dopamine receptor, on the expression of p-ERK in the NAc in propofol self-administering rats, and examined the effects of intra-NAc injection of U0126, an MEK inhibitor, on propofol reinforcement in rats. The results showed that the expression of p-ERK in the NAc increased significantly in rats maintained on propofol, and pre-treatment with SCH23390 inhibited the propofol self-administration and diminished the expression of p-ERK in the NAc. Moreover, intra-NAc injection of U0126 (4 µg/side) attenuated the propofol self-administration. The data suggest that ERK signal transduction pathways coupled with D1 dopamine receptors in the NAc may be involved in the maintenance of propofol self-administration and its rewarding effects.

Mild Sedation Exacerbates or Unmasks Focal Neurologic Dysfunction in Neurosurgical Patients with Supratentorial Brain Mass Lesions in a Drug-specific Manner

BACKGROUND

Sedation is commonly used in neurosurgical patients but has been reported to produce transient focal neurologic dysfunction. The authors hypothesized that in patients with frontal-parietal-temporal brain tumors, focal neurologic deficits are unmasked or exacerbated by nonspecific sedation independent of the drug used.

METHODS

This was a prospective, randomized, single-blind, self-controlled design with parallel arms. With institutional approval, patients were randomly assigned to one of the four groups: "propofol," "midazolam," "fentanyl," and "dexmedetomidine." The sedatives were titrated by ladder administration to mild sedation but fully cooperative, equivalent to Observer's Assessment of Alertness and Sedation score = 4. National Institutes of Health Stroke Scale (NIHSS) was used to evaluate the neurologic function before and after sedation. The study's primary outcome was the proportion of NIHSS-positive change in patients after sedation to Observer's Assessment of Alertness and Sedation = 4.

RESULTS

One hundred twenty-four patients were included. Ninety had no neurologic deficits at baseline. The proportion of NIHSS-positive change was midazolam 72%, propofol 52%, fentanyl 27%, and dexmedetomidine 23% (P less than 0.001 among groups). No statistical difference existed between propofol and midazolam groups (P = 0.108) or between fentanyl and dexmedetomidine groups (P = 0.542). Midazolam and propofol produced more sedative-induced focal neurologic deficits compared with fentanyl and dexmedetomidine. The neurologic function deficits were mainly limb motor weakness and ataxia. Patients with high-grade gliomas were more susceptible to the induced neurologic dysfunction regardless of the sedative.

CONCLUSIONS

Midazolam and propofol augmented or revealed neurologic dysfunction more frequently than fentanyl and dexmedetomidine at equivalent sedation levels. Patients with high-grade gliomas were more susceptible than those with low-grade gliomas.

Glucocorticoid receptor mediated the propofol self-administration by dopamine D1 receptor in nucleus accumbens

Propofol, a widely used anesthetic, can cause addictive behaviors in both human and experimental animals. In the present study, we examined the involvement of glucocorticoid receptor (GR) signaling in the molecular process by which propofol may cause addiction. The propofol self-administration model was established by a fixed ratio 1 (FR1) schedule of reinforced dosing over successive 14days in rats. On day 15, the rats were treated with dexamethasone, a GR agonist (10-100μg/kg), or RU486, a GR antagonist (10-100μg/kg) at 1h prior to the last training. The animal behaviors were recorded automatically by the computer. The expression of dopamine D1 receptor in the nucleus accumbens (NAc) was examined by Western blot and the concentrations of plasma corticosterone were measured by enzyme-linked immunosorbent assay (ELISA). To further examine the specificity of GR in the process, mineralocorticoid receptor (MR) antagonist, spironolactone, and dexamethasone plus MR agonist, aldosterone, were also tested. Administration of dexamethasone (100μg/kg) or RU486 (⩾10mg/kg) significantly attenuated the rate of propofol maintained active nose-poke responses and infusions, which were accompanied by reductions in both plasma corticosterone level and the expression of D1 receptor in the NAc. Neither spironolactone alone nor dexamethasone combined with aldosterone affected the propofol-maintaining self-administrative behavior, indicating GR, but not MR, modulates the propofol reward in rats. In addition, neither the food-maintaining sucrose responses under FR1 schedule nor the locomotor activity was affected by any doses of dexamethasone or RU486 tested. These findings provide evidence that GR signaling may play an important role in propofol reward.

Clinical and psychological characteristics of propofol abusers in Korea: a survey of propofol abuse in 38, non-healthcare professionals

BACKGROUND

The aim of this study is to investigate the characteristics of propofol abuse based on the results of a survey analysis of abusers among non-healthcare professionals in Korea.

METHODS

Thirty-eight propofol abusers were questioned between October and December 2010, and were enrolled and voluntarily participated in a structured survey consisting of an interview and completing a previously prepared questionnaire. The questionnaire was divided into three distinct parts: part 1 dealt with the history of propofol abuse; part 2 highlighted the problems caused by propofol abuse; and part 3 enquired regarding demographics of abusers.

RESULTS

Thirty-one (81.6%) of the 38 interviewees abused propofol for more than one year. During the last 12 months, 34 (89.0%) received propofol at two or three times a week. The minimum and maximum amounts of propofol (median, range) administered each time were 500 (100, 1000) and 2000 (500, 4000) mg, respectively. Stress relief and the maintenance of a sense of well-being were quoted the most important reasons for the first-time administration of propofol and its subsequent abuse, respectively. The majority of abusers (36.0, 97.3%) reported a sense of pleasure or euphoria at the time of their propofol injection. Withdrawal symptoms occurred in five abusers (13.2%). Thirteen (36.1%) reported disruptions in their work life. None of the respondents had previously admitted to and or reported abuse of any other controlled substances.

CONCLUSIONS

These results provided reference data for the regulation of propofol in Korea as a controlled substance and may also be of interest to international agencies in other countries.

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.

Locomotor stimulation by acute propofol administration in rats: Role of the nitrergic system

BACKGROUND

The addictive potential of propofol has been scientifically discussed. Drugs' psychostimulant properties that can be assessed via measurements of locomotor activity are linked to their addictive properties. No studies that have investigated the effects of propofol on locomotor activity have been reported to date. The present study sought to investigate the effects and possible mechanisms of action of propofol on locomotor activity in rats.

METHODS

Adult male albino Wistar rats (250-330g) were used as subjects. The locomotor activities of the rats were recorded for 30min immediately following intraperitoneal administration of propofol (20 and 40mg/kg), saline or vehicle (n=8 for each group). NG-nitro arginine methyl ester (l-NAME, 15-60mg/kg), a nitric oxide (NO) synthase inhibitor, and haloperidol (0.125-5mg/kg), a non-specific dopamine receptor antagonist, were also administered to other groups of rats 30min prior to the propofol (40mg/kg) injections, and locomotor activity was recorded for 30min immediately after propofol administration (n=8 for each group).

RESULTS

Propofol produced significant increases in the locomotor activities of the rats in the first 5min of the observation period [F(2,21)=9.052; p<0.001]. l-NAME [F(4,35)=3.112; p=0.02] but not haloperidol [F(4,35)=2.440; p=0.067] pretreatment blocked the propofol-induced locomotor hyperactivity. l-NAME did not cause any significant change in locomotor activity in naïve rats [F(2,21)=0.569; p=0.57].

CONCLUSIONS

Our results suggest that propofol might cause a short-term induction of locomotor activity in rats and that this effect might be related to nitrergic but not dopaminergic mechanisms.

Prescribing patterns of the four most commonly used sedatives in endoscopic examination in Korea: propofol, midazolam, diazepam, and lorazepam

As the sedative use increases due to the effectiveness and relatively safe profile, the abuse potential is also increasing. This study was conducted to examine the usage of four sedative agents in endoscopic examination and to compare the propofol use with the other three sedatives. Using National Health Insurance claims data from 2008 to 2012, we identified the number of cases of conscious sedation during endoscopy using one or more of the following agents: propofol, midazolam, diazepam, and lorazepam. The general characteristics of patients and medical service providers were analyzed, and the regional and annual distributions of frequency of use were compared. We also identified patient cases with excessive number of endoscopic examinations. Among the total of 3,156,231 sedatives users, midazolam was the most commonly used agent (n=2,845,250, 90.1%). However, the largest increase in patient number, which increased from 11,410 in 2008 to 28,170 in 2012, was observed with propofol. While the majority of patients received an annual endoscopy, we identified several suspected abuse cases of patients receiving endoscopies repetitively as many as 114 times in five years. The rise of sedative use in endoscopic examinations and several patient cases of repeated sedative administration suggest a potential risk for abuse. Medical service providers should be cautious when using sedatives and carefully review each patient's medical history prior to the procedure.

[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.

Abuse potential of propofol used for sedation in gastric endoscopy and its correlation with subject characteristics

Background

Propofol has been widely used for an induction and/or maintenance of general anesthesia, or for sedation for various procedures. Although it has many ideal aspects, there have been several cases of drug abuse and addiction. The authors investigated whether there are abuse liable groups among the general population.

Methods

We surveyed 169 patients after gastric endoscopic examination, which used propofol as a sedative, with the Addiction Research Center Inventory (ARCI) questionnaire. Other characteristics of the patients, such as past history, smoking habits, depression, anxiety, alcohol abuse liability and sleep disturbance, were recorded by history taking and several questionnaires before the exam.

Results

Propofol had a high Morphine-Benzedrine Group (MBG) score (representative value for euphoria) of 6.3, which is higher than marijuana, and a Pentobarbital-Chlorpromazine-Alcohol Group (PCAG) score (representative value of sedation) of 8.1, which is lower than most opioids. The MBG score showed no statistically significant correlation between any of the characteristics of the groups. In females, the PCAG score showed a correlation with age, and in males, it showed a correlation with a sleeping problem.

Conclusions

Propofol had relatively high euphoria and low residual sedative effects. It had a more potent sedative effect in the female group who were young, and in the male group who had a low sleep quality index. There were differences in the abuse liability from a single exposure to propofol in the general population. Further study is needed to evaluate the abuse liability of repeated exposure.

Dependence potential of propofol: behavioral pharmacology in rodents

Propofol is an anesthetic commonly used to provide sedation or to induce and maintain an anesthetic stated. However, there are reports which indicate propofol may cause psychological dependence or be abused. In the present study, we used various behavioral tests including climbing test, jumping test, conditioned place preference, and self-administration test to assess the dependence potential and abuse liability of propofol compared to a positive control (methamphetamine) or a negative control (saline or intralipid). Among the tests, the conditioned place preference test was conducted with a biased method, and the selfadministration test was performed under a fixed ratio (FR) 1 schedule, 1 h per session. No difference was found in the climbing test and jumping test, but propofol (30 mg/kg, i.p.) increased the rewarding effect in the conditioned place preference test, and it showed a positive reinforcing effect compared to the vehicle. These results indicate that propofol tends to show psychological dependence rather than physical dependence, and it seems not to be related with dopaminergic system.

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.

Differential involvement of GABAA and GABAB receptors in propofol self-administration in rats

AIM

Propofol has shown abuse potential. The aim of the present study is to investigate the effects of GABA(A) antagonist and GABA(B) agonist on propofol reinforcement.

METHODS

Sprague-Dawley rats were trained to self-administer propofol at a dose of 1.7 mg/kg per infusion under a fixed ratio (FR1) schedule of reinforcement for 14 d. In a separate set of experiments, food-maintained self-administration under a fixed ratio (FR5) schedule and locomotor activities of Sprague-Dawley rats were examined.

RESULTS

GABA(A) receptor antagonist bicuculline (0.25 mg/kg, ip) significantly increased the number of injections and active responses. Pretreatment with GABA(B) receptor agonist baclofen (3 mg/kg, ip) significantly decreased the number of active responses and total infusions of propofol during the training session. Moreover, microinjection of baclofen (50 and 100 ng/side) into the ventral tegmental area (VTA) significantly decreased the number of active responses and total infusions of propofol. Neither baclofen (1-3 mg/kg, ip) nor bicuculline (0.25-1 mg/kg, ip) affected food-maintained responses or motor activities.

CONCLUSION

Propofol maintains its reward properties partially through GABA(A) receptor activation. Stimulation of GABA(B) receptors in VTA may counteract the reinforcing properties of propofol.

Upregulation of DeltaFosB by propofol in rat nucleus accumbens

BACKGROUND

It is well established that all drugs of abuse converge onto common circuitry and induce chronic addiction by modulating the addictive signaling molecules such as DeltaFosB in the mesocorticolimbic system. Recent case reports suggest that propofol may have abuse potential. However, there is no direct evidence showing that propofol has an effect on the key addictive signaling molecules in the mesocorticolimbic system. In this study, we determined the effect of propofol on the expression of DeltaFosB in rat nucleus accumbens (NAc) and the potential mechanism involved.

METHODS

To determine the effect of propofol on the expression of DeltaFosB in rat NAc, 2 well-known addictive agents, ethanol and nicotine, were used as positive controls. Experiments were conducted on 36 male Sprague-Dawley rats (150 to 200 g). These animals were divided into 4 treatment groups: vehicle (saline), propofol (10 mg/kg), ethanol (1 g/kg), and nicotine (0.5 mg/kg). All drugs were administered by intraperitoneal injection twice per day for 7 days. The animals were then killed and their NAc were isolated for DeltaFosB measurements.

RESULTS

As expected, both ethanol and nicotine significantly increased DeltaFosB expression. Intriguingly, propofol elicited a robust increase in DeltaFosB expression similar to that of ethanol and nicotine. Moreover, the dopamine receptor D1, an upstream molecule of DeltaFosB, was also significantly upregulated by propofol.

CONCLUSIONS

In the current study, we have identified, for the first time, that propofol is able to induce the addictive signaling molecule DeltaFosB in NAc via dopamine receptor D1. This new evidence at the molecular level suggests that propofol may have abuse potential.

A Survey of Propofol Abuse in Academic Anesthesia Programs

BACKGROUND

Although propofol has not traditionally been considered a drug of abuse, subanesthetic doses may have an abuse potential. We used this survey to assess prevalence and outcome of propofol abuse in academic anesthesiology programs.

METHODS

E-mail surveys were sent to the 126 academic anesthesiology training programs in the United States.

RESULTS

The survey response rate was 100%. One or more incidents of propofol abuse or diversion in the past 10 yr were reported by 18% of departments. The observed incidence of propofol abuse was 10 per 10,000 anesthesia providers per decade, a fivefold increase from previous surveys of propofol abuse (P = 0.005). Of the 25 reported individuals abusing propofol, 7 died as a result of the propofol abuse (28%), 6 of whom were residents. There was no established system to control or monitor propofol as is done with opioids at 71% of programs. There was an association between lack of control of propofol (e.g., pharmacy accounting) at the time of abuse and incidence of abuse at the program (P = 0.048).

CONCLUSIONS

Propofol abuse in academic anesthesiology likely has increased over the last 10 yr. Much of the mortality is in residents. Most programs have no pharmacy accounting or control of propofol stocks. This may be of concern, given that all programs reporting deaths from propofol abuse were centers in which there was no pharmacy accounting for the drug.