Investigation of the pruritus-induced functional activity in the rat brain using manganese-enhanced MRI.

PURPOSE: To provide clear information on the activation regions of itching, we investigated the functional activity of cerebral regions in the pruritus-induced rat model using manganese-enhanced magnetic resonance imaging (MEMRI). MATERIALS AND METHODS: Itching was induced via neonatal capsaicin treatment in Sprague-Dawley rats (itching rats), and scratching behavior of the control, itching, and gabapentin (GBP)-treated itching rats was compared. Then the activated or deactivated brain regions were investigated in the control, itching, and GBP-treated itching rats using a 4.7T MRI system. RESULTS: While the itching rats engaged in vigorous scratching (121.2 ± 22.4 times), the scratching behavior was decreased in the GBP-treated itching rats (30.6 ± 8.8 times). GBP induced the attenuation of functional activity in two regions -7.10 mm from bregma, in one region -6.65 mm from bregma, and in one region -6.06 mm from bregma. The brain regions related to itching were as follows: parafascicular nucleus, thalamus, superior/inferior colliculus, periaqueductal gray, cingulate cortex, amygdala, midbrain regions, lateral habenula, and hypothalamic areas. CONCLUSION: Our MEMRI investigation indicates new functional activity of cerebral regions in rats due to the effect of itching or GBP. This information could be used to monitor the therapeutic effects of novel agents or for clinical strategies to treat pathological itch.

The association between Gabapentin or Pregabalin use and the risk of dementia: an analysis of the National Health Insurance Research Database in Taiwan.

Objective: Previous studies have shown that gabapentin or pregabalin use is associated with cognitive decline. Herein, we aimed to evaluate the association between gabapentin or pregabalin use and the risk of dementia. Methods: In this retrospective, population-based matched cohort study, all research data were collected from the 2005 Longitudinal Health Insurance Database, which contains data of 2 million people randomly selected from the National Health Insurance Research Database of Taiwan in 2005. The study extracted data from 1 January 2000, to 31 December 2017. Adult patients taking gabapentin or pregabalin were included in the exposure group, and patients not using gabapentin or pregabalin matched to exposure subjects in a 1:5 ratio by propensity scores composed of age, sex and index date were included in the non-exposure group. Results: A total of 206,802 patients were enrolled in the study. Of them, 34,467 gabapentin- or pregabalin-exposure and 172,335 non-exposure patients were used for analysis. The mean follow-up day (±standard deviation) after the index date was 1724.76 (±1282.32) and 1881.45 (±1303.69) in the exposure and non-exposure groups, respectively; the incidence rates of dementia were 980.60 and 605.48 per 100,000 person-years, respectively. The multivariate-adjusted hazard ratio of risk of dementia for gabapentin or pregabalin exposure versus the matched non-exposed group was 1.45 (95% confidence interval [CI], 1.36-1.55). The risk of dementia increased with higher cumulative defined daily doses during the follow-up period. Moreover, the stratification analysis revealed that the risk of dementia associated with gabapentin or pregabalin exposure was significant in all age subgroups; however, it was higher in younger patients (age <50) than in the older patients (hazard ratio, 3.16; 95% CI, 2.23-4.47). Conclusion: Patients treated with gabapentin or pregabalin had an increased risk of dementia. Therefore, these drugs should be used with caution, particularly in susceptible individuals.

Gabapentin Inhibits Multiple Steps in the Amyloid Beta Toxicity Cascade.

Oligomeric ß-amyloid peptide (Aß) is one of the main neurotoxic agents of Alzheimer's disease (AD). Oligomers associate to neuronal membranes, forming "pore-like" structures that cause intracellular calcium and neurotransmitter dyshomeostasis, leading to synaptic failure and death. Through molecular screening targeting the C terminal region of Aß, a region involved in the toxic properties of the peptide, we detected an FDA approved compound, gabapentin (GBP), with neuroprotective effects against Aß toxicity. At micromolar concentrations, GBP antagonized peptide aggregation over time and reduced the Aß absorbance plateau to 28% of control. In addition, GBP decreased Aß association to membranes by almost half, and the effects of Aß on intracellular calcium in hippocampal neurons were antagonized without causing effects on its own. Finally, we found that GBP was able to block the synaptotoxicity induced by Aß in hippocampal neurons, increasing post-synaptic currents from 1.7 ± 0.9 to 4.2 ± 0.7 fC and mean relative fluorescence intensity values of SV2, a synaptic protein, from 0.7 ± 0.09 to 1.00 ± 0.08. The results show that GBP can interfere with Aß-induced toxicity by blocking multiple steps, resulting in neuroprotection, which justifies advancing toward additional animal and human studies.

Involvement of l-type amino acid transporter 1 in the transport of gabapentin into human placental choriocarcinoma cells.

Gabapentin (GBP) is a widely used antiepileptic drug, with potential for use in the treatment of epilepsy in pregnant women. Although studies have examined GBP transport mechanisms across the blood-brain barrier, kidney, and intestine, the mechanism in the placenta has not been fully elucidated. We previously reported that GBP accumulates at high concentrations in human placental choriocarcinoma BeWo cells. The purpose of this study was to examine the transport mechanism of GBP in placental choriocarcinoma cells (BeWo and JEG-3), and to identify the carrier involved. High concentrations of intracellular GBP accumulations were also found in JEG-3 cells. A kinetic analysis showed that a single carrier system was involved in the uptake of GBP. Furthermore, substrates for l-type amino acid transporter (LAT) and siRNAs targeted to LAT1 significantly decreased GBP uptake. Our observations from this study suggest that LAT1 is the main contributor to GBP transport in placental choriocarcinoma cells.

Myoclonus induced by the use of gabapentin.

Myoclonus is a rare side effect of gabapentin (GBP) and has been reported in patients with preexisting myoclonus, mental retardation, chronic static encephalopathy, diffuse brain damage, impaired renal function, or end stage renal disease. We report a case of myoclonus in a patient with normal renal function and no previous disorders. A 69-year-old female underwent diskectomy and foraminotomy at the left L4-L5 level. Postoperatively, she complained of paresthesia in her left leg, which was thought to be due to root manipulation during surgery. To relieve the paresthesia, she was given tramadol, an oral opioid agonist, and GBP. One week after GBP was increased to 900 mg per day, myoclonus developed, which severely impaired her normal activity. Her symptoms resolved 2 days after discontinuation of GBP. The coadministration of tramadol and GBP may mutually enhance the myoclonic potential of each drug. The causal relationship between GBP and myoclonus was suggested by cessation of myoclonus after GBP discontinuation despite continued therapy with tramadol.

Myoclonus Induced by the Use of Gabapentin

Myoclonus is a rare side effect of gabapentin (GBP) and has been reported in patients with preexisting myoclonus, mental retardation, chronic static encephalopathy, diffuse brain damage, impaired renal function, or end stage renal disease. We report a case of myoclonus in a patient with normal renal function and no previous disorders. A 69-year-old female underwent diskectomy and foraminotomy at the left L4-L5 level. Postoperatively,she complained of paresthesia in her left leg, which was thought to be due to root manipulation during surgery. To relieve the paresthesia, she was given tramadol, an oral opioid agonist, and GBP. One week after GBP was increased to 900 mg per day, myoclonus developed, which severely impaired her normal activity. Her symptoms resolved 2 days after discontinuation of GBP. The coadministration of tramadol and GBP may mutually enhance the myoclonic potential of each drug. The causal relationship between GBP and myoclonus was suggested by cessation of myoclonus after GBP discontinuation despite continued therapy with tramadol.