Neuronal depletion in the globus pallidus of heroin addicts

Intoxications involving methoxyacetylfentanyl and U-47700: a study of 3 polydrug fatalities

Novel synthetic opioids (NSOs) represent an emerging group of novel psychoactive substances, acting as agonists at the opioid receptors. NSOs include fentanyl-related compounds, e.g. methoxyacetylfentanyl (MeACF), and non-fentanyl analogs, e.g. "U compounds" including U-47700. Here we present three cases of death involving MeACF and U-47700, with particular reference to preliminary data on pharmacokinetics and tissue distribution.After a complete post-mortem examination, general unknown screenings and analysis of drugs of abuse were performed on postmortem samples by immunoassays, gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. To quantify the analytes of interest in post-mortem blood and tissues, the standard addition method was used. A toxicological significance score (TSS), weighing the role of the NSO in each death case, was assigned.Case 1 died at the hospital after consumption of U-47700, methadone (serum levels: 2,600 ng/ml and 37 ng/ml), tilidine and benzodiazepines. In case 2, U-47700 (204 ng/ml) together with methadone (290 ng/ml), flubromazepam (480 ng/ml) and diazepam (300 ng/ml) were detected in peripheral blood. In case 3, methoxyacetylfentanyl (266 ng/ml), furanylfentanyl (4.3 ng/ml) 4-ANPP (15 ng/ml) and alprazolam (69 ng/ml) were quantified in femoral blood. In all cases, the NSO likely contributed to the death (TSS = 3).NSOs appear to be often consumed in the setting of polydrug intoxications, especially in combination with other opioids and benzodiazepines, which often exert synergistic effects. The standard addition method remains the most reliable in post-mortem analysis and toxicological results should always be evaluated together with circumstantial and autopsy data.

Inverse pattern of GABAergic system impairment in the external versus internal globus pallidus in male heroin addicts

Opioid addiction is a global problem that has been exacerbated in the USA and Europe by the COVID-19 pandemic. The globus pallidus (GP) plays a prominent neurobiological role in the regulation of behaviour as an output station of the striato-pallidal system. GABAergic large projection neurons are the main neuronal type in the external (EGP) and internal (IGP) parts of the GP, where addiction-specific molecular and functional abnormalities occur. In these neurons, glutamate decarboxylase (GAD) with isoforms GAD 65 and 67 is a key enzyme in GABA synthesis, and experimental studies suggest GAD dysregulation in the GP of heroin addicts. Our study, which was performed on paraffin-embedded brains from the Magdeburg Brain Bank, aimed to investigate abnormalities in the GABAergic function of large GP neurons by densitometric evaluation of their GAD 65/67-immunostained thick dendrites. The study revealed a bilaterally decreased fibres density in the EGP paralleled by the increase in the IGP in 11 male heroin addicts versus 11 healthy controls (significant U-test P values). The analysis of confounding variables found no interference of age, brain volume, and duration of formalin fixation with the results. Our findings suggest a dysregulation of GABAergic activity in the GP of heroin addicts, which is consistent with experimental data from animal models and plays potentially a role in the disturbed function of basal ganglia circuit in opioid addiction.

Opioid use disorder and the brain: a clinical perspective

Opioid use disorder (OUD) has gained increasing publicity and interest during recent years, with many countries describing problems of epidemic proportions with regard to opioid use and deaths related to opioids. While opioids are not themselves acutely neurotoxic, the chronic relapsing and remitting nature of this disorder means that individuals are often exposed to exogenous opioids for lengthy periods of time (either illicit or prescribed as treatment). We are increasingly characterizing the effect of such long-term opioid exposure on the brain. This narrative review aims to summarize the literature regarding OUD and the brain from a clinical perspective. Alterations of brain structure and function are discussed, as well as neurological and psychiatric disorders in OUD. Finally, we review current and new directions for assessment and treatment.

Inflammatory Markers in Substance Use and Mood Disorders: A Neuroimaging Perspective

Chronic exposure to addictive drugs in substance use disorders and stressors in mood disorders render the brain more vulnerable to inflammation. Inflammation in the brain, or neuroinflammation, is characterized by gliosis, microglial activation, and sustained release of cytokines, chemokines, and pro-inflammatory factors compromising the permeability of the blood-brain barrier. There is increased curiosity in understanding how substance misuse and/or repeated stress exposure affect inflammation and contribute to abnormal neuronal activity, altered neuroplasticity, and impaired cognitive control, which eventually promote compulsive drug-use behaviors and worsen mood disorders. This review will emphasize human imaging studies to explore the link between brain function and peripheral markers of inflammation in substance use disorders and mood disorders.

Chronic heroin use disorder and the brain: Current evidence and future implications

The incidence of chronic heroin use disorder, including overdose deaths, has reached epidemic proportions. Here we summarise and evaluate our knowledge of the relationship between chronic heroin use disorder and the brain through a narrative review. A broad range of areas was considered including causal mechanisms, cognitive and neurological consequences of chronic heroin use and novel neuroscience-based clinical interventions. Chronic heroin use is associated with limited or very limited evidence of impairments in memory, cognitive impulsivity, non-planning impulsivity, compulsivity and decision-making. Additionally, there is some evidence for certain neurological disorders being caused by chronic heroin use, including toxic leukoencephalopathy and neurodegeneration. However, there is insufficient evidence on whether these impairments and disorders recover after abstinence. Whilst there is a high prevalence of comorbid psychiatric disorders, there is no clear evidence that chronic heroin use per se causes depression, bipolar disorder, PTSD and/or psychosis. Despite the growing burden on society from heroin use, knowledge of the long-term effects of chronic heroin use disorder on the brain remains limited. Nevertheless, there is evidence for progress in neuroscience-based interventions being made in two areas: assessment (cognitive assessment and neuroimaging) and interventions (cognitive training/remediation and neuromodulation). Longitudinal studies are needed to unravel addiction and neurotoxic mechanisms and clarify the role of pre-existing psychiatric symptoms and cognitive impairments.

Neurocognitive impairments and brain abnormalities resulting from opioid-related overdoses: A systematic review

BACKGROUND

Non-fatal opioid-related overdoses have increased significantly over the past two decades and there have been increasing reports of brain injuries and/or neurocognitive impairments following overdose events. Limited preclinical research suggests that opioid overdoses may cause brain injury; however, little is known about such injuries in humans. The purpose this systematic review is to summarize existing studies on neurocognitive impairments and/or brain abnormalities associated with an opioid-related overdose in humans.

METHODS

PubMed, Web of Science, Ovid MEDLINE and PsyINFO were searched, without year restrictions, and identified 3099 articles. An additional 24 articles were identified by reviewing references. Articles were included if they were published in English, reported study findings in humans, included individuals 18 years of age or older, and reported an objective measure of neurocognitive impairments and/or brain abnormalities resulting from an opioid-related overdose. Six domains of bias (selection, performance, attrition, detection (two dimensions) and reporting were evaluated and themes were summarized.

RESULTS

Seventy-nine journal articles, published between 1973-2020, were included in the review. More than half of the articles were case reports (n = 44) and there were 11 cohort studies, 18 case series, and 6 case-control studies. All of the studies were categorized as at-risk of bias, few controlled for confounding factors, and methodological differences made direct comparisons difficult. Less than half of the studies reported toxicology results confirming an opioid-related overdose; 64.6 % reported brain MRI results and 27.8 % reported results of neuropsychological testing. Only two studies had within subject comparative data to document changes in the brain possibly associated with an overdose. Despite these limitations, existing publications suggest that brain injuries and neurocognitive impairments are associated with opioid overdose. Additional research is needed to establish the incidence of overdose-related brain injuries and the potential impact on functioning, as well as engagement in treatment of substance use disorders.

CONCLUSIONS

Respiratory depression is a defining characteristic of opioid overdose and prolonged cerebral hypoxia may cause brain injuries and/or neurocognitive impairments. The onset, characteristics, and duration of such injuries is variable and additional research is needed to understand their clinical implications.

The molecular neurobiology and neuropathology of opioid use disorder

The number of people diagnosed with opioid use disorder has skyrocketed as a consequence of the opioid epidemic and the increased prescribing of opioid drugs for chronic pain relief. Opioid use disorder is characterized by loss of control of drug taking, continued drug use in the presence of adverse consequences, and repeated relapses to drug taking even after long periods of abstinence. Patients who suffer from opioid use disorder often present with cognitive deficits that are potentially secondary to structural brain abnormalities that vary according to the chemical composition of the abused opioid. This review details the neurobiological effects of oxycodone, morphine, heroin, methadone, and fentanyl on brain neurocircuitries by presenting the acute and chronic effects of these drugs on the human brain. In addition, we review results of neuroimaging in opioid use disorder patients and/or histological studies from brains of patients who had expired after acute intoxication following long-term use of these drugs. Moreover, we include relevant discussions of the neurobiological mechanisms involved in promoting abnormalities in the brains of opioid-exposed patients. Finally, we discuss how novel strategies could be used to provide pharmacological treatment against opioid use disorder.

•

Brain abnormalities caused by opioid intoxication.

•

Intoxication of opioids leads to defects in brain neurocircuitries.

•

Insight into the molecular mechanisms associated with craving in heroin addicts.

Bilateral Basal Ganglia Lesions in Patients with Heroin Overdose: A Report of Two Cases

The prevalence of opioid use has increased worldwide. Two-thirds of deaths caused by drug overdose are opioid-related. Individuals with opioid use may present with a variety of complications. The available history in unconscious patients is often insufficient, which may cause diagnostic difficulty and delayed management. We present two cases of 54-year-old and 25-year-old male patients who were brought to our emergency department after being found unconscious at home, without any known preceding event. They were in a deep coma with a Glasgow coma score of 3/15. However, their brainstem reflexes were normal. Pinpoint pupils were observed bilaterally. Brain computed tomography (CT) demonstrated the presence of bilateral basal ganglia hypodensities in both patients, in addition to multiple hypodensities scattered in the cerebral hemispheres of one patient. Toxicology screening from both patients was positive for opioids. The patients were transferred to the intensive care unit for supportive management. One patient recovered completely, whereas the other remained in a vegetative state. The presence of bilateral basal ganglia lesions in brain CT in unconscious patients should alert the physician of opioid use disorder among these patients.

Reduced volumes of the external and internal globus pallidus in male heroin addicts: a postmortem study

Deep brain stimulation (DBS) of the globus pallidus internus was recently proposed as a potential new treatment target for opioid addiction. DBS requires computer-assisted-3D planning to implant the stimulation electrode precisely. As volumes of brain regions may differ in addiction compared to healthy controls, our aim was to investigate possible volume differences in addicts compared to healthy controls. Volumes of the globus pallidus externus (PE) and internus (PI) in heroin addicts (n = 14) and healthy controls (n = 12) were assessed using morphometry of serial whole-brain sections. Total brain volume was larger in the heroin group (mean 1479 ± 62 cm³ vs. mean 1352 ± 103 cm³), as the heroin group was more than 10 years younger (p = 0.001). Despite larger mean whole brain volume, the mean relative volume of the PE and PI was smaller in addicted subjects compared to healthy controls (PE 0.658 ± 0.183 × 10^-3 vs. 0.901 ± 0.284 × 10^-3; ANOVA F(1, 24) = 6.945, p = 0.014, η² = 0.224; PI 0.253 ± 0.095 × 10^-3 vs. 0.345 ± 0.107 × 10^-3; ANOVA F(1, 24) = 5.374, p = 0.029, η² = 0.183). These findings were not significantly confounded by age, duration of autolysis, and fixation time. Our results provide further evidence for structural and not only functional deficits of the globus pallidus in addiction. In the context of previous studies, our findings support the idea of shared pathophysiological processes between comorbid depression and impulsivity in opioid addiction.

GABRA2 rs279858-linked variants are associated with disrupted structural connectome of reward circuits in heroin abusers

The reward system plays a vital role in drug addiction. The purpose of this study is to investigate the structural connectivity characteristics and driving-control subnetwork patterns of reward circuits in heroin abusers and assess the genetic modulation on the reward network. We first defined the reward network based on systematic literature review, and built the reward network based on diffusion tensor imaging data of 78 heroin abusers (HAs) and 79 healthy controls (HCs) using structural connectomics. Then we assessed genetic factors that might modulate changes in the reward network by performing imaging-genetic screening for 22 addiction-related polymorphisms. The genetic association was validated by performing genetic associations (1032 HAs and 2863 HCs) and expanded-variant analysis. Finally, we estimated the association between these genetic variations, reward network, and clinical performance. We found that HAs had widespread deficiencies in the structural connectivity of the reward circuit (center in VTA-linked connections), which correlated with cognition deficiency. The disruptions synchronously were shown on the reward driving system and reward control system. GABRA2 rs279858-linked variants might be a key genetic modulator for heroin vulnerability by affecting the connections of reward network and cognition. The role of the reward network connections that mediates the effects of rs279858 on cognition would be disrupted by heroin addiction. These findings provide new insights into the neurocircuitry and genetic mechanisms of addiction.

Increased densities of nitric oxide synthase expressing neurons in the temporal cortex and the hypothalamic paraventricular nucleus of polytoxicomanic heroin overdose victims: possible implications for heroin neurotoxicity

Heroin is one of the most dangerous drugs of abuse, which may exert various neurotoxic actions on the brain (such as gray matter loss, neuronal apoptosis, mitochondrial dysfunction, synaptic defects, depression of adult neurogenensis, as well as development of spongiform leucoencephalopathy). Some of these toxic effects are probably mediated by the gas nitric oxide (NO). We studied by morphometric analysis the numerical density of neurons expressing neuronal nitric oxide synthase (nNOS) in cortical and hypothalamic areas of eight heroin overdose victims and nine matched controls. Heroin addicts showed significantly increased numerical densities of nNOS immunoreactive cells in the right temporal cortex and the left paraventricular nucleus. Remarkably, in heroin abusers, but not in controls, we observed not only immunostained interneurons, but also cortical pyramidal cells. Given that increased cellular expression of nNOS was accompanied by elevated NO generation in brains of heroin addicts, these elevated levels of NO might have contributed to some of the known toxic effects of heroin (for example, reduced adult neurogenesis, mitochondrial pathology or disturbances in synaptic functioning).

Bilateral acute necrosis of the globi pallidi and rhabdomyolysis due to combined methadone and benzodiazepine toxicity

Methadone continues to be a widely used maintenance therapy for opiate dependence. However, methadone-related deaths have been reported frequently for over 4 decades now. Anoxic brain injury with pulmonary edema secondary to respiratory depression is the recognized mechanism of methadone death, although pathological intracranial findings are rarely described in methadone deaths. A selective area of brain injury has never been reported with methadone use. We present a case of a 23-year-old man who had acute necrosis of the bilateral globi pallidi in the brain and systemic rhabdomyolysis after ingesting methadone and nasally insufflating alprazolam. We also present a review of the literature on deaths following opioid use and associated brain injury.

Hippocampal damage impairs recognition memory broadly, affecting both parameters in two prominent models of memory

Declarative memory is thought to rely on two processes: recollection and familiarity. Recollection involves remembering specific details about the episode in which an item was encountered, and familiarity involves simply knowing that an item was presented even when no information can be recalled about the episode itself. There has been debate whether the hippocampus supports only recollection or whether it supports both processes. We approached this issue in a relatively theory-neutral way by fitting two prominent models that have been used to describe recognition memory: dual process signal detection and unequal variance signal detection. Both models yield two parameters of interest when fit to recognition memory data. The dual process signal detection model yields estimates of recollection (r) and familiarity (d'). The unequal variance signal detection model yields estimates of the ratio of the variance of target and foil memory strength distributions (σtarget/σfoil) and the difference in the means of the two distributions (d). We asked how the two parameters of each model were affected by hippocampal damage. We tested five patients with well-characterized bilateral lesions thought to be limited to the hippocampus and age-matched controls. The patients exhibited a broad memory deficit that markedly reduced the value of both parameters in both models. In addition, the pattern of results exhibited by the patients was recapitulated in healthy controls as the delay between learning and testing was extended. Thus, hippocampal damage impairs both component processes of recognition memory.

Quantitative analysis of astrogliosis in drug-dependent humans

Drug addiction is a chronic, relapsing disease caused by neurochemical and molecular changes in the brain. In this human autopsy study qualitative and quantitative changes of glial fibrillary acidic protein (GFAP)-positive astrocytes in the hippocampus of 26 lethally intoxicated drug addicts and 35 matched controls are described. The morphological characterization of these cells reflected alterations representative for astrogliosis. But, neither quantification of GFAP-positive cells nor the Western blot analysis indicated statistical significant differences between drug fatalities versus controls. However, by semi-quantitative scoring a significant shift towards higher numbers of activated astrocytes in the drug group was detected. To assess morphological changes quantitatively, graph-based representations of astrocyte morphology were obtained from single cell images captured by confocal laser scanning microscopy. Their underlying structures were used to quantify changes in astroglial fibers in an automated fashion. This morphometric analysis yielded significant differences between the investigated groups for four different measures of fiber characteristics (Euclidean distance, graph distance, number of graph elements, fiber skeleton distance), indicating that, e.g., astrocytes in drug addicts on average exhibit significant elongation of fiber structures as well as two-fold increase in GFAP-positive fibers as compared with those in controls. In conclusion, the present data show characteristic differences in morphology of hippocampal astrocytes in drug addicts versus controls and further supports the involvement of astrocytes in human pathophysiology of drug addiction. The automated quantification of astrocyte morphologies provides a novel, testable way to assess the fiber structures in a quantitative manner as opposed to standard, qualitative descriptions.

Association of PTPRB gene polymorphism with drug addiction

Several lines of evidence support the involvement of protein tyrosine phosphatase receptor type beta (PTPRB) in addiction. Generally, PTPs interact with both neuronal receptors and cell adhesion molecules, and appear to play roles in neurite growth and neuronal differentiation. We previously identified a role of the cell adhesion molecule NrCAM in polysubstance abuse vulnerability in humans, as well as in the rewarding effects of abused drugs in animals. Furthermore, we have identified genomic regions containing several cell adhesion molecules as polysubstance abuse vulnerability loci by whole-genome association study. The present study of human chromosome 12 loci revealed that the Ser127Gly polymorphism in PTPRB is associated with substance abuse vulnerability in three independent case-control samples (European-American from COGA families, USA, n = 177, P = 0.047; European-American from Maryland, USA, n = 650, P = 0.018; and African-American from Maryland, USA, n = 331, P = 0.009). However, this polymorphism was not associated with alcoholism in Japanese subjects (n = 1,599, P = 0.37). To confirm the importance of PTPRB in responses to drugs of abuse the expression of Ptprb in mouse brain was examined after chronic morphine treatment and found to be up-regulated in some brain regions. Thus, PTPRB is an addiction-associated and drug-regulated gene whose variants may affect substance abuse vulnerability.

Cellular and molecular mechanisms involved in the neurotoxicity of opioid and psychostimulant drugs

Substance abuse and addiction are the most costly of all the neuropsychiatric disorders. In the last decades, much progress has been achieved in understanding the effects of the drugs of abuse in the brain. However, efficient treatments that prevent relapse have not been developed. Drug addiction is now considered a brain disease, because the abuse of drugs affects several brain functions. Neurological impairments observed in drug addicts may reflect drug-induced neuronal dysfunction and neurotoxicity. The drugs of abuse directly or indirectly affect neurotransmitter systems, particularly dopaminergic and glutamatergic neurons. This review explores the literature reporting cellular and molecular alterations reflecting the cytotoxicity induced by amphetamines, cocaine and opiates in neuronal systems. The neurotoxic effects of drugs of abuse are often associated with oxidative stress, mitochondrial dysfunction, apoptosis and inhibition of neurogenesis, among other mechanisms. Understanding the mechanisms that underlie brain dysfunction observed in drug-addicted individuals may contribute to improve the treatment of drug addiction, which may have social and economic consequences.

Mild hypoxia disrupts recollection, not familiarity

Yonelinas et al. (2002) found that hypoxic patients exhibited deficits in recollection that left familiarity relatively unaffected. In contrast, Manns, Hopkins, Reed, Kitchener, and Squire (2003) studied a group of hypoxic patients who suffered severe and equivalent deficits in recollection and familiarity. We reexamine those studies and argue that the discrepancy in results is likely due to differences in the hypoxic groups that were tested (i.e., differences in amnestic severity, subject sampling methods, and patient etiology). Yonelinas et al. examined memory in 56 cardiac arrest patients who suffered a brief hypoxic event, whereas Manns et al. examined a group of severely amnesic patients that consisted of 2 cardiac arrest patients, 2 heroin overdose patients, 1 carbon monoxide poisoning patient, and 2 patients with unknown etiologies. We also consider an alternative explanation proposed by Wixted and Squire (2004), who argued that the two patient groups suffered similar deficits, but that statistical or methodological artifacts distorted the results of each of Yonelinas et al.'s experiments. A consideration of those results, however, indicates that such an explanation does not account for the existing data. All of the existing evidence indicates that recollection, but not familiarity, is disrupted in mild hypoxic patients. In more severe cases of hypoxia, or those with more complex etiologies such as heroin overdose, more profound deficits may be observed.

Chronic morphine modulates the contents of the endocannabinoid, 2-arachidonoyl glycerol, in rat brain

Opioids and cannabinoids are among the most widely consumed drugs of abuse in humans and the phenomena of cross-tolerance or mutual potentiation have been demonstrated between the two drugs. Several authors have suggested that both drugs share common links in their molecular mechanisms of action, although this has been a matter of controversy. Furthermore, no data exist on the possible adaptive changes in the contents of arachidonoylethanolamide (anandamide, AEA) and 2-arachidonoylglycerol (2-AG), the two major endogenous ligands for cannabinoid receptors, in morphine-tolerant rats. In the present work, we investigated the alterations in cannabinoid receptor functionality and endocannabinoid levels in rats chronically treated with morphine (5 mg/kg, s.c., twice a day for 5 days). Autoradiographic-binding studies using [(3)H]CP-55 940 revealed a slight but significant reduction in cannabinoid receptor level in the cerebellum and hippocampus of morphine-tolerant rats, while CP-55 940-stimulated [(35)S]GTPgammaS binding showed a strong decrease (40%) in receptor/G protein coupling in the limbic area of these animals. Moreover, in the same brain regions we measured, by isotope-dilution gas chromatography/mass spectrometry, the contents of AEA and 2-AG. Chronic morphine exposure produced a strong reduction in 2-AG contents without changes in AEA levels in several brain regions (ie striatum, cortex, hippocampus, limbic area, and hypothalamus). These findings clearly demonstrate that prolonged activation of opioid receptors could alter the cannabinoid system, in terms of both receptor functionality and endocannabinoid levels, and suggest the involvement of this system, alone or in combination with other mediators, in the phenomenon of morphine tolerance.

New aspects in the treatment of heroin dependence with special reference to neurobiological aspects

The Swiss trials on medical prescription of injectable diacetylmorphine (pharmaceutical heroin) for "severe" heroin dependence provoked very controversial commentaries. Despite methodological shortcomings, the evaluation of the Swiss heroin trials yielded some interesting findings. Study participants showed substantial improvements in health and well-being and noticeable declines in illicit drug use and criminal activities. Heroin prescription may thus be helpful for some of those who continue to regularly use illicit heroin while maintained on methadone or who refuse other available treatment options. However, research-based evidence suggests that the intravenous (IV) application of heroin under medical supervision may have untoward side effects. Recent studies have shown that heroin injections produce transient, but significant decreases in systemic and cortical oxygenation most likely secondary to respiratory depression. Among others, these effects are the subject of ongoing studies.

The neuropathology of heroin abuse

A broad spectrum of neuropathologic changes are encountered in the brains of heroin abusers. The main findings are due to infections, either due to bacterial spread from bacterial endocarditis, mycoses, or from HIV-1 infection. Other complications include hypoxic-ischemic changes with cerebral edema, ischemic neuronal damage and neuronal loss, which are assumed to occur under conditions of prolonged heroin-induced respiratory depression, stroke due to, for example, thromboembolism, vasculitis, septic emboli, hypotension, and positional vascular compression. Myelopathy is believed to be the result of an isolated vascular accident within the spinal cord due to an as yet unknown mechanism. A distinct entity, spongiform leukoencephalopathy, has been described mainly after inhalation of pre-heated heroin. A lipophilic toxin-induced process was considered to be due to contaminants and to be induced or enhanced by cerebral hypoxia, but a definite toxin could not be identified. At the cellular level, abnormalities in signal transduction systems and changes of various receptor densities have been reported. The exact etiology of the different neuropathological alterations associated with heroin abuse is still unclear, but may also be related to additional substances used as adulterants.

EEG power spectra and behavioral correlates in rats given chronic morphine. Lack of residual long-term EEG and neuronal changes

The short-term (during tolerance to behavioural effects and withdrawal) and long-term (3, 6, 9 and 12 months after treatment) effects of morphine on mean total electroencephalographic spectral power (analysed by means of fast Fourier transform) and band distribution (delta, theta, alpha, beta) were studied in freely moving young rats implanted with chronic cortical bilateral recording electrodes. Morphine was administered i.p. daily for 1 month at weekly increasing doses of 20, 50, 100 and 200 mg kg-1, and the electroencephalogram was evaluated for 2 h at every change of dose. Treatment with 20, 50 and 100 mg kg-1 led to a significant increase in mean total spectral power 30-60 min from treatment. However, the dose of 100 mg kg-1 led to a smaller increase than that obtained with 50 mg kg-1 and no change was shown with the highest dose, suggesting the progressive development of tolerance. The modification observed for 100 mg kg-1 was accompanied by a relative increase in the delta and decrease in the theta and alpha power spectra. Between the last day of morphine and the first 3 days of abstinence, a progressive decrease in mean total spectral power accompanied by a significant increase in delta and beta and a decrease in theta and alpha frequency was observed. Long-term EEG activity and the counting of the pyramidal cells of the hippocampus failed to reveal any pathological findings after 3, 6, 9 and 12 months.

Heroin prolongs survival time and retards tumor growth in mice with neuroblastoma

The effect of heroin on tumor growth and survival time was studied in mice with neuroblastoma. Daily SC injections of either 3, 6, 10, 15 mg/kg heroin were initiated either 2 weeks prior to tumor cell inoculations (pre-treated groups) of 10(6) S20Y cells or one week after tumor transplantation (post-treated groups); control animals received saline injections prior to tumor cell inoculation (saline-tumor group). Heroin administration that began prior to tumor cell inoculation was effective in inhibiting tumor growth and prolonging life-span at all dosages utilized, but a dose-related response was not observed. A prolongation in mean survival time of 32-39% and median survival time of 8-50% was found in tumor-bearing animals of the pre-treated groups in comparison to mice in the saline-tumor group. Tumor growth was retarded in mice pre-treated with heroin, but mean tumor size of these animals was comparable to controls on the day of death. Only one post-treated group, 6 mg/kg, was observed to have alterations in tumor growth and survival time. Heroin's action in retarding tumor growth and prolonging life-span was blocked by concomitant of an opiate antagonist (naloxone, 10 mg/kg). These results suggest that, in addition to heroin's analgesic and behavioral properties, this opiate may have an even greater biologic significance by modulating neoplasia.