Adolescent Methylone Exposure and its Effects on Behavioural Development in Adulthood

Abstract

Originally developed as an anti-depressant and later available as a ‘party-pill’ in New Zealand, methylone is currently classed as an illegal drug. This is due to findings of its similarity in chemical structure to that of Ecstasy (MDMA). Methylone is a relatively new drug into which little research has been conducted. Consequently, no known study has investigated the long-term effects on behavioural development arising from exposure during adolescence. The present thesis therefore aimed to identify long-term effects of chronic adolescent exposure to methylone on adult anxiety-like behaviours. This was achieved by the use of 80 rats (40 males: 40 females) and exposing them to either a methylone or saline treatment for ten consecutive days. Two different treatment age groups (early versus late adolescence) were examined and to ensure adequate comparisons could be made, two control groups were utilised. All rats were tested during adulthood in four specifically selected anxiety-measure tests; the open-field, preference for the light side of a light-dark box, acoustic startle and responsiveness to the novel arm of a Y-maze. The results suggested methylone-exposed rats displayed more anxiolytic behaviours than saline-treated rats. In the open field methylone exposed rats exhibited less ambulation than controls and those treated in early adolescence defecated more while rats treated in late adolescence occupied the corners of the apparatus more exhibiting higher anxiety-like behaviours. Exploratory behaviours in the Y-maze were decreased in methylone-treated rats, and those exposed in early adolescence entered the novel arm less often. However, acoustic startle results suggested methylone-exposed rats were less anxious as evidenced by a lower startle amplitude than controls. Overall, the results suggested differences in anxiety-like behaviours between methylone-exposed rats and controls. It did not appear that being exposed to methylone in early adolescence resulted in vast differences in anxiety-like behaviours than if exposure began in late adolescence.