Second messenger and protein phosphorylation mechanisms underlying possible genetic vulnerability to alcoholism

Neurological correlates of brain reward circuitry linked to opioid use disorder (OUD): Do homo sapiens acquire or have a reward deficiency syndrome?

The extant literature confirms that an array of polymorphic genes related to- neurotransmitters and second messengers govern the net release of dopamine in the Nucleus Accumbens (NAc) in the mesolimbic region of the brain. They are linked predominantly to motivation, anti-stress, incentive salience (wanting), and wellbeing. Notably, in 2000 the Nobel Prize was awarded to Carlsson, Greengard, and Kandel for their work on the molecular and cellular function of dopaminergic activity at neurons. This historical psychopharmacological work involved neurotransmission of serotonin, endorphins, glutamate, and dopamine, and the seminal work of Blum, Gold, Volkow, Nestler, and others related to neurotransmitter function and related behaviors. Currently, Americans are facing their second and worst opioid epidemic, prescribed opioids, and easy access drive this epidemic of overdoses, and opioid use disorders (OUDs). Presently the clinical consensus is to treat OUD, as if it were an opioid deficiency syndrome, with long-term to life-long opioid substitution therapy. Opioid agonist administration is seen as necessary to replace missing opioids, treat OUD, and prevent overdoses, like insulin is used to treat diabetes. Treatment of OUD and addiction, in general, is similar to the endocrinopathy conceptualization in that it views opioid agonist MATs as an essential core to therapy. Is this approach logical? Other than as harm reduction, is using opioids to treat OUD therapeutic or harmful in the long term? This historical Trieste provides a molecular framework to understand the current underpinnings of endorphinergic/dopaminergic mechanisms related to opioid deficiency syndrome and generalized reward processing depletion. WC 249.

Review : Molecular Basis of Addictive States

Drug addiction can be viewed as a form of neural plasticity—drug—induced neural plasticity. This is because most features of addiction develop gradually and progressively in response to repeated exposure to a drug of abuse and can persist for a long time, perhaps even a lifetime, after discontinuation of drug administration. Within this context of neural plasticity, studies of drug addiction offer a unique opportunity to establish the biological basis of a complex and clinically relevant behavioral abnormality. This derives from the fact that many aspects of addiction can be reproduced with increasing accuracy in laboratory animals. The availability of animal models, in turn, has made it possible to identify specific regions of the brain that mediate behavioral aspects of addiction. Identification of these discrete brain regions has made it possible to begin the process of identifying the molecular and cellular basis of addiction mediated via these regions. This situation for drug addiction contrasts markedly with that for most other model systems of neural plasticity, for which behavioral, let alone clinical, correlates are not readily apparent. It also contrasts with many other neuropsychiatric abnormalities, for example, schizophrenia and depression, for which animal models are much less straight forward and much more difficult to interpret. Advances made in the field of drug addiction have the potential of providing insight into the types of mechanisms underlying other forms of neural plasticity and even, per haps, other neuropsychiatric abnormalities. The goal of this review is to describe recent progress in under standing the molecular basis of addictive states. The Neuroscientist 1:212-220, 1995

The paradox of drug taking: the role of the aversive effects of drugs

In 1991, Woods described the paradoxical nature of eating, specifically, that it produced aversive and negative effects. He noted in this analysis the multiple physiological and behavior adaptations, both learned and unlearned, that were aimed at regulating food intake and reducing its aversive, disruptive effects. From this position, he argued that consumption reflected a balance of the positive and aversive effects of eating. The present review extends this analysis to drug use and abuse, i.e., that drug taking itself also is a balance of reward and aversion. Although traditionally the analysis of drug use and abuse has focused on a drug's positive and negative rewarding effects, the present review highlights the aversive effects of these same drugs, e.g., cocaine, morphine, alcohol, and describes such effects as protective in nature. This balance and the manner by which it can be impacted by subject and experiential factors are described with a focus on genetic models of drug abuse using the Lewis and Fischer inbred rat strains.

The effect of acute and chronic exposure to ethanol on the developing encephalon: a review

OBJECTIVES: to compare the acute and chronic effects of ethanol on the neural development, by analysis of the ontogenetic neural structure of mammals. METHODS: searches were performed in the following electronic databases: MEDLINE, SciElo, PubMed, LILACS, CAPES periodical, and the Open Journal System. The descriptors used were: "chronic ethanol toxicity", "chronic alcohol toxicity", "acute ethanol toxicity", "acute alcohol", "neural ontogenic development", "neuronal migration disturbances", "neural structure". The following inclusion criteria were used: articles published between 2003 and 2007, some classic articles in the field and an important neuropsychology textbook. RESULTS: the analysis of papers revealed that, although several studies of the chronic effects of ethanol exposure on the mammalian nervous system have been conducted, only a few have investigated the acute effects of ethanol on specific days of gestation, and these studies have revealed important disorders relating to the cerebral tissue. CONCLUSIONS: it should be recommended that women refrain from the consumption of ethanol during gestational phase to protect the fetus' health. Furthermore, the acute consumption of ethanol by women nearing the eighth or ninth week of gestation has been shown to be potentially harmful to the nervous tissue of the fetus.

Chronic nicotine treatment changes the axonal distribution of 68 kDa neurofilaments in the rat ventral tegmental area

Region-specific decreases of neurofilament proteins (NF) were described in the ventral tegmental area (VTA) of rats treated chronically with morphine, cocaine or alcohol. In a previous study, we demonstrated that NF levels were also changed in the VTA after chronic treatment with nicotine. The aim of this study was to clarify the submicroscopic basis of decreased immunoreactivity for NF-68, NF-160 and NF-200, as determined by using NR4, BF10 and RT97 antibodies, respectively. Microdensitometric analysis of brain sections showed that immunoreactivity for all NF was reduced in the VTA of animals exposed chronically to nicotine (0.4 mg/kg per day, 6 days of treatment), when compared to rats exposed to saline. Reduction in immunoreactivity was significant for NF-68 (P < 0.05), NF-160 (P < 0.01) and NF-200 (P < 0.05), showing a relative reduction of 34%, 42% and 38%, respectively, when compared to saline-treated rats. No difference was observed for any of the NF under study when immunoreactivity measurements in the substantia nigra were compared. Ultrastructural analysis was applied to evaluate changes in NF-68, NF-160 and NF-200 immunoreactivity in regions of the VTA that contain dopaminergic neurons following chronic nicotine treatment. At the electron microscopic level, no degenerative changes were found in neurons or glial cells of the VTA. With ultrastructural immunohistochemistry, evaluation of the homogeneity parameter of NF distribution showed a loss of homogeneity for NF-68 linked to the nicotine treatment. In areas in which NF organization appeared well preserved, analysis of the numerical density of NF revealed no significant difference for NF-68 (897/ micro m2 vs. 990/ micro m2), NF-160 (970/ micro m2 vs. 820/ micro m2) and NF-200 (1107/ micro m2 vs. 905/ micro m2) in nicotine-treated rats when compared to saline-treated rats. These results confirm that nicotine shares the same properties with cocaine and morphine in reducing NF in the VTA, a key brain structure of the rewards system, and that chronic nicotine treatment changes the axonal distribution of 68 kDa neurofilaments in the rat VTA.

Internalization of mu-opioid receptors produced by etorphine in the rat locus coeruleus

Chronic administration of mu-opioid receptor agonists is known to produce adaptive changes within noradrenergic neurons of the locus coeruleus. Although mu-opioid receptors are densely expressed by locus coeruleus neurons, the effects of acute and chronic administration of agonists on the subcellular distribution of mu-opioid receptors remain poorly understood. Therefore, we examined the ultrastructural distribution of mu-opioid receptor immunoreactivity in the locus coeruleus of rats subjected to either acute morphine, or etorphine, or chronic morphine treatment. In the locus coeruleus of control rats receiving acute saline injections or placebo pellet implants, immunogold-silver labeling for mu-opioid receptors was localized to parasynaptic and extrasynaptic portions of the plasma membranes of perikarya and dendrites. Only 8% of the gold-silver particles analyzed were distributed within the cytoplasm of dendrites and perikarya in vehicle-treated rats. Immunolabeling for mu-opioid receptors was distributed along portions of the plasma membrane that were often apposed by astroglial sheaths. After acute injections of etorphine, there was a dramatic internalization of mu-opioid receptors to intracellular compartments. Quantitative analysis of gold-silver particles indicative of mu-opioid receptors showed that a substantial number of gold particles shifted from the plasma membrane to early endosomes in dendrites from etorphine-treated rats. In dendrites sampled from etorphine-treated rats, 85% of the gold-silver grains indicative of mu-opioid receptor labeling were located in intracellular compartments as compared to 15% that were distributed along the plasma membrane. In animals that received either acute morphine injections or chronic morphine via pellet implantation, no change in the subcellular distribution of immunogold particles indicative of mu-opioid receptors was detected when compared to matched control animals. These results provide the first ultrastructural evidence that mu-opioid receptors are internalized by agonists such as etorphine, but not the partial agonist morphine, in the locus coeruleus.

Chronic nicotine treatment decreases neurofilament immunoreactivity in the rat ventral tegmental area

Region-specific decreases of neurofilament proteins have been described in the ventral tegmental area of rats chronically treated with either morphine or cocaine. The aim of the present study was to assess if the levels of neurofilament proteins are changed in the ventral tegmental area by chronic treatment with nicotine. Immunoreactivity for NF-68, NF-160 and NF-200 was determined using NR4, BF10 and RT97 antibodies, respectively. Measurements were performed using computer-assisted microdensitometry of brain sections from rats exposed to chronic nicotine treatment (0.4 mg/kg/dayx6 days) or to saline. Chronic nicotine treatment reduced NF-160 and NF-200 immunoreactivity by 44.5% (P<0.01) and 22.5% (P<0. 05), respectively, in the ventral tegmental area but not in the substantia nigra. A trend towards reduction was observed for NF-68 immunoreactivity in the ventral tegmental area. These preliminary results suggest that nicotine shares the same properties with cocaine and morphine to reduce neurofilament proteins in the ventral tegmental area, a key brain structure of the reward system.

No allelic association of an exon 13 polymorphism of the Gsα gene to alcohol and/or drug dependence

The adenylyl cyclase signal transduction system, a ubiquitous second messenger system, has been identified as a potential marker for genetic risk of alcohol and drug dependence. Using the polymerase chain reaction (PCR) to amplify exon 13 of the Gsα gene, two alleles were distinguished by denaturing gradient gel electrophoresis. One allele, designed A, contained the previously published C in the codon for asparagine 371, while the second allele, designated A, contains a C-T transition that conserves the asparagine residue at codon 371. The neutral polymorphism eliminates a Fok I restriction enzyme cleavage site, allowing use of restriction fragment length polymorphisms of PCR products to determine allelic frequency in 235 subjects with alcohol and/or drug dependence and in 85 control subjects. Since allele frequencies differ significantly by race, comparisons between affected individuals and controls were conducted separately for white and black groups. Within race, there were no significant differences in the frequency of the A allele among alcoholics, subjects dependent on cocaine or opioids, subjects dependent on these drugs and alcohol, and controls. We conclude that there is no association between alcohol and/or drug dependence and alleles of an exon 13 polymorphism of the Gsα gene in either black or white individuals.