, early research suggests.
Japanese researchers, headed by Akiyoshi Saitoh, PhD, professor in the department of pharmacy, Tokyo University of Science, compared the reactions of mice that received a classic anxiolytic agent (diazepam) to those that received disulfiram while performing a maze task and found comparable reductions in anxiety in both groups of mice.
Moreover, unlike diazepam, disulfiram caused no sedation, amnesia, or impairments in coordination.
“These results indicate that disulfiram can be used safely by elderly patients suffering from anxiety and insomnia and has the potential to become a breakthrough psychotropic drug,” Dr. Saitoh said in a press release.
The study was published online in Frontiers in Pharmacology.
Disulfiram inhibits the enzyme aldehyde dehydrogenase (ALDH), which is responsible for alcohol metabolism. Recent research suggests that disulfiram may have broader inhibitory functions.
In particular, it inhibits the cytoplasmic protein FROUNT, preventing it from interacting with two chemokine receptors (CCR2 and CCRs) that are involved in cellular signaling pathways and are associated with regulating behaviors, including anxiety, in rodents, the authors write.
“Although the functions of FROUNT-chemokines signaling in the immune system are well documented, the potential role of CNS-expressed FROUNT chemokine–related molecules as neuromodulators remains largely unknown,” they write.
The researchers had been conducting preclinical research on the secondary pharmacologic properties of disulfiram and “coincidentally discovered” its “anxiolytic-like effects.” They investigated these effects further because currently used anxiolytics – i.e., benzodiazepines – have unwanted side effects.
The researchers utilized an elevated plus-maze (EPM) test to investigate the effects of disulfiram in mice. The EPM apparatus consists of four arms set in a cross pattern and are connected to a central square. Of these, two arms are protected by vertical boundaries, while the other two have unprotected edges. Typically, mice with anxiety prefer to spend time in the closed arms. The mice also underwent other tests of coordination and the ability to navigate a Y-maze.
Some mice received disulfiram, others received a benzodiazepine, and others received merely a “vehicle,” which served as a control.
Disulfiram “significantly and dose-dependently” increased the time spent in the open arms of the EPM, compared with the vehicle-treated group, at 30 minutes after administration (F [3, 30] = 16.64; P < .0001), suggesting less anxiety. The finding was confirmed by a Bonferroni analysis that showed a significant effect of disulfiram, compared with the vehicle-treated group, at all three doses (20 mg/kg: t = 0.9894; P > .05; 40 mg/kg: t = 3.863; P < .01; 80 mg/kg: t = 6.417; P < .001).
A Student’s t-test analysis showed that diazepam likewise had a significant effect, compared to the vehicle (t = 5.038; P < .001).
Disulfiram also “significantly and dose-dependently” increased the percentage of open-arm entries (F [3, 30] = 14.24; P < .0001). The Bonferroni analysis showed this effect at all three doses (20 mg/kg: t = 0.3999; P > .05; 40 mg/kg: t = 2.693; P > .05; 80 mg/kg: t = 5.864; P < .001).
Diazepam similarly showed a significant effect, compared to the vehicle condition (t = 3.733; P < .005).
In particular, the 40 mg/kg dose of disulfiram significantly increased the percentage of time spent in the open arms at 15, 30, and 60 minutes after administration, with the peak effect occurring at 30 minutes.
The researchers examined the effect of cyanamide, another ALDH inhibitor, on the anxiety behaviors of mice and found no effect on the number of open-arm entries or percentage of time the mice spent in the open arm, compared with the vehicle condition.
In contrast to diazepam, disulfiram had no effect on the amount of spontaneous locomotor activity, time spent on the rotarod, or activity on the Y-maze test displayed by the mice, “suggesting that there were no apparent sedative effects at the dosages used.” Moreover, unlike the mice treated with diazepam, there were no increases in the number of falls the mice experienced on the rotarod.
Glutamate levels in the prelimbic-prefrontal cortex (PL-PFC) “play an important role in the development of anxiety-like behavior in mice,” the authors state. Disulfiram “significantly and completely attenuated increased extracellular glutamate levels in the PL-PFC during stress exposure” on the EPM.
“We propose that DSF inhibits FROUNT protein and the chemokine signaling pathways under its influence, which may suppress presynaptic glutamatergic transmission in the brain,” said Dr. Saitoh. “This, in turn, attenuates the levels of glutamate in the brain, reducing overall anxiety.”