Morehead State University

Poster Title

Behavioral Measures Provide Further Evidence for an Amphetamine-Induced Acute Withdrawal State

Presenter Information

Ian Smith, Morehead State University

Institution

Morehead State University

Abstract

Twenty hours after receiving a moderate dose of the psycho-stimulant amphetamine, rats appear to be in an acute withdrawal state. Our studies used different behavioral procedures to seek further evidence for this phenomenon. Study 1 employed a conditioned place procedure. Twenty hours after saline treatment, animals were placed for 45 min in one distinctive context, and 20 hours after amphetamine treatment they were placed in a second. Following this training phase, animals were allowed free access to both contexts, and the amount of time they spent in each was quantified. Rats exhibited an aversion for the context that had been preceded by amphetamine administration, suggesting that the amphetamine-induced state present at hour 20 post-treatment had aversive characteristics. Study 2 employed a progressive ratio procedure. In this procedure, the number of responses required to receive successive small rewards is increased after each reward. The response was pressing a lever, and the reward was sugar solution. The highest number of lever presses the animal is willing to make to procure the reward is called the “breakpoint.” Progressive ratio breakpoint was assessed at different times following saline or amphetamine administration. Breakpoint was lower around hour 20 post-amphetamine treatment, suggesting that the amphetamine-induced state present at that time rendered animals less willing to work for reward. Amphetamine elicits multiple indicators of acute withdrawal. Different indicators seem to have a similar time course, raising the possibility that they may be mediated by a similar mechanism. Understanding the nature of acute withdrawal should aid the effort to prevent and treat the adverse effects produced by psycho-stimulants.

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Behavioral Measures Provide Further Evidence for an Amphetamine-Induced Acute Withdrawal State

Twenty hours after receiving a moderate dose of the psycho-stimulant amphetamine, rats appear to be in an acute withdrawal state. Our studies used different behavioral procedures to seek further evidence for this phenomenon. Study 1 employed a conditioned place procedure. Twenty hours after saline treatment, animals were placed for 45 min in one distinctive context, and 20 hours after amphetamine treatment they were placed in a second. Following this training phase, animals were allowed free access to both contexts, and the amount of time they spent in each was quantified. Rats exhibited an aversion for the context that had been preceded by amphetamine administration, suggesting that the amphetamine-induced state present at hour 20 post-treatment had aversive characteristics. Study 2 employed a progressive ratio procedure. In this procedure, the number of responses required to receive successive small rewards is increased after each reward. The response was pressing a lever, and the reward was sugar solution. The highest number of lever presses the animal is willing to make to procure the reward is called the “breakpoint.” Progressive ratio breakpoint was assessed at different times following saline or amphetamine administration. Breakpoint was lower around hour 20 post-amphetamine treatment, suggesting that the amphetamine-induced state present at that time rendered animals less willing to work for reward. Amphetamine elicits multiple indicators of acute withdrawal. Different indicators seem to have a similar time course, raising the possibility that they may be mediated by a similar mechanism. Understanding the nature of acute withdrawal should aid the effort to prevent and treat the adverse effects produced by psycho-stimulants.