The effect of acute topiramate administration on morphine withdrawal syndrome and brain-derived neurotrophic factor in central nervous system

OBJECTIVES

Nucleus accumbens plays an important role in opioid addiction. Topiramate, increases postsynaptic gamma-aminobutyric acid receptor activity and antagonizes glutamatergic activity. Brain-derived neurotrophic factor (BDNF), which plays a key role in synaptic plasticity, is produced from proBDNF. The aim of this study is to investigate the effects of 100 µM topiramate applied into the lateral ventricle or nucleus accumbens on naloxone-induced morphine withdrawal and the BDNF/proBDNF ratio in the frontal cortex.

METHODS

In the study, 36 adult male Wistar rats weighing 250-350 g were used. Morphine dependence was created with morphine pellets following guide cannula implantations. Withdrawal findings were evaluated in naloxone-induced morphine withdrawal syndrome following topiramate administration, and locomotor activity measurements were performed simultaneously. The brains of sacrificed animals were removed for determination of BDNF/proBDNF ratio.

RESULTS

Topiramate administered by either route significantly suppressed the number of jumps in morphine withdrawal. Topiramate applied into the nucleus accumbens significantly reduced stereotypical behavior in morphine withdrawal, but did not cause any changes in other locomotor activity behaviors. Topiramate applied into the lateral ventricle significantly decreased the BDNF/proBDNF ratio, whereas administered into the nucleus accumbens significantly increased this ratio.

CONCLUSION

The findings of this study indicate that topiramate administered into the lateral ventricle and nucleus accumbens reduces naloxone-induced morphine withdrawal symptoms, stereotypical locomotor activity, and changes the BDNF/proBDNF ratio.

The discriminative stimulus effects of baclofen and gamma hydroxybutyrate in C57BL/6J mice

Baclofen and γ-hydroxybutyrate (GHB) exert γ-aminobutyric acid (GABA)B receptor agonism and have therapeutic utility but possess different pharmacological activities. We examined whether separate groups of mice could be trained to discriminate either baclofen or GHB, and the contribution of GABAB receptors to discriminative stimulus effects. Male C57BL/6J mice were trained to discriminate either baclofen (3.2 mg/kg, intraperitoneal) or GHB (178 mg/kg, intraperitoneal) from saline under a fixed-ratio 10 schedule. The GABAB antagonist 3-aminopropyl(diethoxymethyl)phosphinic acid (CGP 35348) was used to pharmacologically assess GABAB receptor involvement. The selectivity of the resulting discriminations was assessed with the opioid agonist morphine and the benzodiazepine midazolam. In baclofen-trained mice, both baclofen and GHB were readily discriminated. Baclofen produced a maximum of 86% baclofen-appropriate responding. CGP 35348 (320 mg/kg, i.p.) produced a 4.7-fold rightward shift in the dose-effect function. GHB produced a maximum of 85.8% baclofen-appropriate responding. In GHB-trained mice, both GHB and baclofen were readily discriminated. In GHB-trained mice, GHB produced a maximum of 85.3% drug-appropriate responding; CGP 35348 (320 mg/kg, i.p.) produced a 1.8-fold rightward shift in the GHB discrimination dose-effect function. Baclofen produced up to 70.0% GHB-appropriate responding. CGP 35348 (320 mg/kg, i.p.) significantly antagonized baclofen discrimination and baclofen produced up to 37% GHB-appropriate responding up to doses that disrupted operant responding. Morphine did not produce substitution for either baclofen or GHB. Midazolam produced partial substitution for both. GHB and baclofen discrimination assays in mice provide a useful approach for examining different receptor types mediating the effects of these two drugs.

Effects of linagliptin on morphine dependence in larval zebrafish (Danio rerio)

Drug addiction is a chronic, recurrent disease of the central nervous system that leads to the development of comorbidities and premature death. Despite extensive scientific research concerning addiction, no effective method of addiction pharmacotherapy has been known so far. Glucagon-like peptide 1 has been suggested to play a role in the rewarding effect of addictive drugs. Linagliptin is a selective dipeptidyl peptidase-4 inhibitor that suppresses the rapid degradation of endogenous glucagon-like peptide-1. In clinical practice, it is used as an antidiabetic drug, but recent studies have confirmed its role in the activity of the central nervous system. This pilot study was conducted to ascertain whether linagliptin might influence morphine dependence – a locomotor activity test was carried out to assess the intensity of morphine withdrawal symptom. The obtained results clearly confirmed that linagliptin (0.01 and 0.1 mM) reduced the locomotor activity in morphine-dependent larval zebrafish. The undertaken experiments clearly indicates that linagliptin is involved in the addictive effects of morphine, thus, further studies on higher organisms should be carried out.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

The Effects of Morphine, Baclofen, and Buspirone Alone and in Combination on Schedule-Controlled Responding and Hot Plate Antinociception in Rats

Better therapeutic options are needed for pain. Baclofen, buspirone, and morphine are characterized as having analgesic properties. However, little is known about potential interactions between analgesic effects of these drugs when combined. Furthermore, it is not known if the magnitude of these potential interactions will be similar for all drug effects. Thus, we tested the effects of these drugs alone and in combination for their capacity to produce thermal antinociception and to decrease food-maintained responding. Four male and four female Sprague-Dawley rats responded for food under a fixed-ratio 10 schedule; afterward they were immediately placed on a 52°C hot plate. Morphine, baclofen, and buspirone were examined alone and in 1:1 combinations, based upon ED₅₀ values. Morphine and baclofen effects were evaluated with the opioid antagonist naltrexone and the GABA_B antagonist (3-Aminopropyl)(diethoxymethyl)phosphinic acid (CGP35348), respectively. Morphine, baclofen, and buspirone dose dependently decreased operant responding, with the calculated ED₅₀ values being 7.09, 3.42, and 0.57 mg/kg, respectively. The respective antinociception ED₅₀ values were 16.15, 8.75, and 2.20 mg/kg. Analysis of 1:1 combinations showed the effects of morphine plus baclofen to decrease schedule-controlled responding and to produce thermal antinociception were synergistic. Effects of morphine plus buspirone and baclofen plus buspirone to decrease schedule-controlled responding were additive. Effects of the two combinations to produce thermal antinociception were synergistic. Naltrexone and CGP35348 antagonized the effects of morphine and baclofen, respectively. Synergistic antinociceptive effects, in conjunction with additive effects on food-maintained responding, highlight the therapeutic utility of opioid and non-opioid drug combinations.