Relative sensitivity to naloxone of multiple indices of opiate withdrawal: a quantitative dose-response analysis

In addition to classic somatic signs of opiate withdrawal, a number of behavioral measures are known to be sensitive, reliable indices of naloxone-precipitated opiate withdrawal in rats. It has been suggested that some behavioral indices of withdrawal may be more sensitive to precipitation by naloxone than some somatic signs of withdrawal. The purpose of the present study was to permit a quantitative assessment of the relative sensitivity to naloxone of a variety of behavioral and somatic indices of opiate withdrawal. Male Wistar rats were implanted s.c. with either two morphine (each 75 mg of base) or two placebo pellets. No sooner than 3 days after implantation, naloxone dose-response functions were determined with several behavioral paradigms and ratings of a variety of somatic withdrawal signs. In dependent rats, very low (0.004 or 0.01 mg/kg) doses of naloxone produced the following behavioral effects: 1) a reduction in spontaneous locomotor activity, 2) a disruption of schedule-controlled (fixed ratio 15) operant responding for food, 3) an elevation in intracranial self-stimulation thresholds and 4) a conditioned place aversion. These same doses of naloxone produced no significant effects in nondependent (placebo pellet-implanted) rats. The ED50 values for naloxone precipitation of all behavioral signs of withdrawal were below 0.013 mg/kg; the ED50 values for naloxone precipitation of most somatic withdrawal signs were higher. The behavioral measures used in these studies therefore represent highly sensitive indices of opiate withdrawal.     

Nociceptin fails to affect heroin self-administration in the rat

The recently isolated peptide nociceptin has a primary structure similar to that of opioid peptides. Early functional studies suggested that it may act in opposition to opioid systems. To determine whether nociceptin influences the rewarding properties of heroin, nociceptin was given intracerebroventricularly (i.c.v.) to rats trained to self-administer heroin. Rats (n = 8) were given doses of 0.01 microg, 0.1 microg, 1.0 microg and 10.0 microg in a Latin square design. None of the doses significantly affected heroin self-administration rates compared to vehicle. The highest dose of nociceptin used inhibited spontaneous locomotor activity, evidence that the peptide retained its biological activity after i.c.v. infusion. These studies suggest that nociceptin does not affect the rewarding value of heroin.     

Gene expression in wheat beer yeast strains and the synthesis of acetate esters

The synthesis of aroma compounds represents one of the most important parameters in beer production. Although it has been a historical topic of research, exactly how aroma components are formed has yet to be fully explained. Moreover, all of the research that has been published on yeast strains is focused on lagers and ales. Wheat beer yeast strains have not been the focus of aroma and flavour research. In this study, five different wheat beer yeasts were analysed to determine their capacity for producing acetate esters. In this study, the most commonly used wheat beer yeast strains for the production of German‐style wheat beer were analysed. This involved measuring the level of expression of the alcohol acetyl transferase genes ATF1, ATF2 and IAH1 over a period of 4 days (during primary fermentation) and plotting the data to observe the development of expression of the genes over time. Results confirmed their capacity to form acetate esters and showed a distinct correlation with increasing expression of the gene ATF1. However, the findings also indicated that gene expression in different yeast strains can vary considerably during fermentation. Copyright © 2016 The Institute of Brewing & Distilling     

Tail-pinch stimulation: sufficient motivation for learning

A paper clip applied to the tails of rats induced gnawing and eating, which decreased in latency and increased in duration with experience. With sustained pressure to the tail, rats learned a new habit in order to gain access to wood chips on which to gnaw. That these are also properties of behavior elicited by electrical brain stimulation suggests that both manipulations may act through the same mechanism. These results support the hypothesis that a nonspecific arousing stimulus can be a sufficient condition for establishing learned habits.     

Transition from moderate to excessive drug intake: change in hedonic set point

Differential access to cocaine self-administration produced two patterns of drug intake in rats. With 1 hour of access per session, drug intake remained low and stable. In contrast, with 6 hours of access, drug intake gradually escalated over days. After escalation, drug consumption was characterized by an increased early drug loading and an upward shift in the cocaine dose-response function, suggesting an increase in hedonic set point. After 1 month of abstinence, escalation of cocaine intake was reinstated to a higher level than before. These findings may provide an animal model for studying the development of excessive drug intake and the basis of addiction.     

Factors associated with severity of depression and high-risk sexual behavior among persons diagnosed with human immunodeficiency virus (HIV) infection.

Whereas some people appear to cope after learning that they have HIV infection, others experience depression and suicidal ideation. In this study, 142 persons with HIV infection were administered the Center for Epidemiological Studies Depression Scale. High levels of depression were predicted by lower perceived social support, attributions that health was influenced more by chance, high-risk sexual behavior practices, and greater number of HIV illness symptoms and greater duration of time knowing of one's own positive serostatus. Ongoing high-risk sexual behavior practices were predicted by higher levels of recreational drug use and of depression. These findings highlight the need for improved mental health services for persons with HIV conditions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine receptor agonists, partial agonists and psychostimulant addiction

Despite the epidemic growth of psychostimulant addiction over the past years, few pharmacological means of intervention are available to date for clinical treatment. This is of importance since the withdrawal syndrome that follows abstinence from drugs such as cocaine and the amphetamines is characterized, among other symptoms, by intense craving for the abused drug, and this is considered a critical factor leading into relapse of drug use. In this article, Luigi Pulvirenti and George Koob focus on the modulatory role shown by drugs acting at the dopamine receptor on the various phases of psychostimulant dependence in preclinical models and in human studies, and suggest that a class of compounds with partial agonist properties at the dopamine receptor may have therapeutic potential.     

Effects of 6-hydroxydopamine lesions of the nucleus accumbens septi and olfactory tubercle on feeding, locomotor activity, and amphetamine anorexia in the rat.

In Exp I with 24 male albino Wistar rats, bilateral 6-hydroxydopamine lesions of the nucleus accumbens septi (NAS) and olfactory tubercle (OT) caused enhanced intake of wet mash in 23-hr-food-deprived Ss tested in photocell activity cages during restricted 30-min sessions. This mild hyperphagia was accompanied by a significant hypoactivity in the group with NAS/OT lesions. No hyperphagia was observed during a prolonged 120-min test session or in free-feeding tests conducted in the home cage. Anorexia induced by dextroamphetamine (.5 and 1.5 mg/kg) was unaltered by the lesion, although the locomotor stimulant action of the drug was attenuated. Results of Exp II, with 36 Ss, show that the NAS/OT lesion also enhanced food intake in the photocell cages during 30-min sessions with dry food pellets but that food-associated drinking was concomitantly reduced. Results are consistent with the hypothesis that the behavioral changes caused by mesolimbic neuron destruction result in part from an inability to switch from one behavioral activity to another. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)