The aversive effects of cough suppressants on neurogenesis and emotional behaviour : chronic exposure to a common active ingredient in cough suppressants causes emotional disturbances through the suppression of adult neurogenesis, and their prevention by wolfberry polysaccharide in rats

Abstract

Cough syrup abuse is a worldwide problem with increasing prevalence, causing chronic disability to abusers. Clinical studies have revealed that abusive consumption of the cough medicine can lead to various psychiatric signs and symptoms including delusion, hallucination, anxiety and depression. These persistent psychiatric symptoms not only disturb the abusers, but are also heavy burdens to the healthcare system. However, the underlying mechanisms of these adverse effects remain elusive. In order to investigate the mechanisms as well as the possible adjunctive treatments, the objectives of the present study are: 1. To explore the effect of repeated, high-dose dextromethorphan (DXM, a common antitussive component in cough syrup) treatment on adult hippocampal neurogenesis; 2. to study the dose-response effect of DXM on neurogenesis, and 3. to investigate the potential effect of wolfberry (a traditional Chinese herb) polysaccharide on reducing emotional distress caused by repeated treatment of DXM. The results revealed that high-dose DXM treatment induced mood disturbances and suppressed neurogenesis, while wolfberry polysaccharide could reverse the undesirable effects. These findings suggest that neurogenesis may be an underlying mechanisms of emotional symptoms induced by DXM, and the result also provided insights for using wolfberry polysaccharide, an herbal component, as a possible adjunctive treatment for the rehabilitation of cough syrup abusers suffering from emotional signs and symptoms.