The behavioural pharmacology of mephedrone (“bath salts”) and its effects on anxiety-related behaviours in male and female hooded rats
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The current generation of designer drugs of abuse are synthetic analogues of the stimulant cathinone. Popularly known as ‘bath salts’, these drugs are marketed as safer (and often legal) alternatives to known psychoactive drugs like methamphetamine, cocaine, and ecstasy. There is emerging literature on the pharmacology and toxicology of these ‘bath salts’, though to date few scientific studies have specifically examined the behavioural sequelae. The current study therefore sought to assess some of the behavioural effects of mephedrone, one of the most common primary active ingredients of ‘bath salts’. Male and female hooded rats were used in three experiments examining anxiety-like behaviours in a number of established behavioural testing paradigms. Experiment 1 examined the dose-response relationship and found that mephedrone produced more anxiety-like behaviours as dose increased, though interestingly only for female rats (males instead displayed an inverted ‘U’ shaped doseresponse curve). A large number of stereotyped behaviours were observed at high doses so this was examined in Experiment 2. It was found that as mephedrone dose increased, so too did the frequency of stereotyped behaviours, though this finding also differed across the sexes in its presentation (males tended to exhibit more non-ambulatory behaviours such as head swaying whereas females tended to display more locomotor stereotypies). Experiment 3 examined the adolescent behavioural teratology of mephedrone by chronically treating rats during adolescence, and then later testing them in adulthood. Results showed that adolescent mephedrone use increased anxiety-like behaviours later in life, though there was some evidence that this effect could be mitigated by environmental enrichment. Taken together, the findings of this study suggest that mephedrone is a powerful anxiogenic compound capable of producing behavioural changes following both acute and chronic administration. Of particular interest and concern is the different presentation of effects noted in male and female subjects.