Assessment of the Reinforcing Properties of Orally Administered MDMA ('Ecstasy') in Rats

The so-called “party drug” 3,4-Methylenedioxymethamphetamine (MDMA, or ecstasy) may share many of the addictive properties common to other CNS stimulants. In humans MDMA is primarily consumed orally in one more pills per session. However, animal research has mostly focused on examining the effects of MDMA as a function of other routes of administration. Route of administration can have profound effects on the subjective and reinforcing properties of drugs of abuse. This thesis assessed the locomotor-activating and reinforcing properties of MDMA when delivered orally. MDMA-induced hyperlocomotion was used to examine magnitude of response and onset of action as a function of ip, sc and oral administration. Significant route-dependant effects were found with ip producing higher locomotor activity than sc and oral respectively. Onset of action was slower for subcutaneous administration compared with both ip and oral administration. The reinforcing properties of MDMA were examined by use of the self-administration procedure. Oral MDMA self-administration was firstly examined using simple schedules of reinforcement as a function of two different vehicle substrates, water (under water deprivation) and saccharin. Oral MDMA maintained responding and reliable dose-response curves were obtained under both water and saccharin vehicle conditions. However, both saccharin and water vehicle conditions also acted as strong reinforcers in these studies. Further studies utilising a behavioural economic approach were conducted in order to delineate the reinforcing effects of MDMA from that of its parent vehicle. In addition, demand-curve analysis using both the Linear-Elasticity model (Hursh et al., 1988, 1989) and the Exponential Model of Demand (Hursh & Silberberg, 2008) were compared in order to evaluate each model and assess the relative reinforcing efficacy of oral MDMA. Demand curves for the oral self-administration of MDMA revealed that responding for MDMA was more elastic (lower Pmax) than responding for saccharin-alone indicating that saccharin functioned as stronger reinforcer than did MDMA+saccharin. The results of these studies provide evidence for the positive-reinforcing effects of MDMA when it is delivered via the oral route of administration, however, the relative reinforcing efficacy of orally delivered MDMA appears to be low

Slot Machine Near Wins: Effects on Pause and Sensitivity to Win Ratios

When a near-win outcome occurs on a slot machine, stimuli presented resemble those presented when money is won, but no money is won. Research has shown that gamblers prefer and play for longer on slot machines that present near wins. One explanation for this is that near wins are conditioned reinforcers. If so, near wins would produce longer latencies to the next response than clear losses. Another explanation is that near wins produce frustration; if so, then near wins would produce shorter response latencies. The two current experiments manipulated win ratio across two concurrently available slot machines and also manipulated near win frequency. Latencies were longer following near wins, consistent with near wins functioning as conditioned reinforcers. We also explored the effects of near wins on sensitivity to relative win rate and found that higher rates of near wins were associated with greater sensitivity to relative win frequency, an effect also consistent with near wins as conditioned reinforcers

Assessment of the Reinforcing Properties of Orally Administered MDMA ('Ecstasy') in Rats

The so-called “party drug” 3,4-Methylenedioxymethamphetamine (MDMA, or ecstasy) may share many of the addictive properties common to other CNS stimulants. In humans MDMA is primarily consumed orally in one more pills per session. However, animal research has mostly focused on examining the effects of MDMA as a function of other routes of administration. Route of administration can have profound effects on the subjective and reinforcing properties of drugs of abuse. This thesis assessed the locomotor-activating and reinforcing properties of MDMA when delivered orally. MDMA-induced hyperlocomotion was used to examine magnitude of response and onset of action as a function of ip, sc and oral administration. Significant route-dependant effects were found with ip producing higher locomotor activity than sc and oral respectively. Onset of action was slower for subcutaneous administration compared with both ip and oral administration. The reinforcing properties of MDMA were examined by use of the self-administration procedure. Oral MDMA self-administration was firstly examined using simple schedules of reinforcement as a function of two different vehicle substrates, water (under water deprivation) and saccharin. Oral MDMA maintained responding and reliable dose-response curves were obtained under both water and saccharin vehicle conditions. However, both saccharin and water vehicle conditions also acted as strong reinforcers in these studies. Further studies utilising a behavioural economic approach were conducted in order to delineate the reinforcing effects of MDMA from that of its parent vehicle. In addition, demand-curve analysis using both the Linear-Elasticity model (Hursh et al., 1988, 1989) and the Exponential Model of Demand (Hursh & Silberberg, 2008) were compared in order to evaluate each model and assess the relative reinforcing efficacy of oral MDMA. Demand curves for the oral self-administration of MDMA revealed that responding for MDMA was more elastic (lower Pmax) than responding for saccharin-alone indicating that saccharin functioned as stronger reinforcer than did MDMA+saccharin. The results of these studies provide evidence for the positive-reinforcing effects of MDMA when it is delivered via the oral route of administration, however, the relative reinforcing efficacy of orally delivered MDMA appears to be low

Assessment of the Reinforcing Properties of Orally Administered MDMA ('Ecstasy') in Rats

The so-called “party drug” 3,4-Methylenedioxymethamphetamine (MDMA, or ecstasy) may share many of the addictive properties common to other CNS stimulants. In humans MDMA is primarily consumed orally in one more pills per session. However, animal research has mostly focused on examining the effects of MDMA as a function of other routes of administration. Route of administration can have profound effects on the subjective and reinforcing properties of drugs of abuse. This thesis assessed the locomotor-activating and reinforcing properties of MDMA when delivered orally. MDMA-induced hyperlocomotion was used to examine magnitude of response and onset of action as a function of ip, sc and oral administration. Significant route-dependant effects were found with ip producing higher locomotor activity than sc and oral respectively. Onset of action was slower for subcutaneous administration compared with both ip and oral administration. The reinforcing properties of MDMA were examined by use of the self-administration procedure. Oral MDMA self-administration was firstly examined using simple schedules of reinforcement as a function of two different vehicle substrates, water (under water deprivation) and saccharin. Oral MDMA maintained responding and reliable dose-response curves were obtained under both water and saccharin vehicle conditions. However, both saccharin and water vehicle conditions also acted as strong reinforcers in these studies. Further studies utilising a behavioural economic approach were conducted in order to delineate the reinforcing effects of MDMA from that of its parent vehicle. In addition, demand-curve analysis using both the Linear-Elasticity model (Hursh et al., 1988, 1989) and the Exponential Model of Demand (Hursh & Silberberg, 2008) were compared in order to evaluate each model and assess the relative reinforcing efficacy of oral MDMA. Demand curves for the oral self-administration of MDMA revealed that responding for MDMA was more elastic (lower Pmax) than responding for saccharin-alone indicating that saccharin functioned as stronger reinforcer than did MDMA+saccharin. The results of these studies provide evidence for the positive-reinforcing effects of MDMA when it is delivered via the oral route of administration, however, the relative reinforcing efficacy of orally delivered MDMA appears to be low.</p