Topiramate evokes pharmacological activity via a blockade of voltage-dependent sodium channels, reduction in glutamate release, inhibition of AMPA receptors and kainate receptors, and potentiation of GABAergic neurotransmission. Therefore, it is used not only as an antiseizure drug but is also effective in migraine prophylaxis, cluster headaches, neuropathic pain, and alcohol dependence. The aim of this study was to investigate the effect of topiramate in morphine dependence in mice, particularly in terms of morphine tolerance, morphine withdrawal signs, and morphine sensitization. In these experiments, topiramate was administered both acutely and chronically. Topiramate significantly reduced the morphine tolerance in the hot-plate test and attenuated naloxone-induced morphine withdrawal signs. Its effect on morphine sensitization to the locomotor activity of mice was poor. The obtained results showed that topiramate might be an effective drug for reducing the physical symptoms of morphine dependence.

Background: Linagliptin, a potent and highly selective dipeptidyl peptidase-4 (DPP-4) inhibitor approved for the treatment of type 2 diabetes, enhances glucagon-like peptide-1 (GLP-1) signaling. Because GLP-1 receptors are widely expressed in the brain, DPP-4 inhibitors have emerged as potential modulators of central nervous system function. The present study investigated the effects of linagliptin (10 and 20 mg/kg, i.p.) on ketamine- (10 mg/kg, i.p.) and diazepam-induced (2 mg/kg, i.p.) deficits in passive avoidance performance in mice. Behavioral effects were assessed using the passive avoidance test, and brain-derived neurotrophic factor (BDNF) levels in the prefrontal cortex and hippocampus were determined by enzyme-linked immunosorbent assay (ELISA). Linagliptin attenuated ketamine- and diazepam-induced deficits in passive avoidance performance. In addition, both acute and chronic administration of linagliptin increased BDNF levels in the prefrontal cortex but not in the hippocampus. These findings provide preliminary evidence that linagliptin modulates passive avoidance performance in mice and is associated with increased BDNF levels in the prefrontal cortex. Further studies employing complementary behavioral paradigms and additional molecular approaches are required to clarify the neuropharmacological mechanisms underlying these effects.