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Behavioral economic assessment of price and cocaine consumption following self-administration histories that produce escalation of either final ratios or intake.

Oleson EB, Roberts DC - Neuropsychopharmacology (2008)

Bottom Line: It was found that a history of LgA training produced an increase in cocaine consumption; whereas a history of PR training produced an increase in the maximal price (P(max)) expended for cocaine.Importantly, the concepts of consumption and price were found to be dissociable.That is, LgA training produced an increase in consumption but a decrease in P(max), whereas PR training produced an increase in P(max) without increasing consumption.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.

ABSTRACT
Various self-administration procedures are being developed to model specific aspects of the addiction process. For example, 'increased cocaine intake over time' has been modeled by providing long access (LgA) to cocaine during daily self-administration sessions under a fixed-ratio (FR1) reinforcement schedule. In addition, 'increased time and energy devoted to acquire cocaine' has been modeled by providing access to cocaine during daily self-administration sessions under a progressive-ratio (PR) schedule. To investigate the distinctiveness of these models, the behavioral economics variables of consumption and price were applied to cocaine self-administration data. To assess changes in consumption and price, cocaine self-administration was tested across a descending series of doses (0.237-0.001 mg per injection) under an FR1 reinforcement schedule to measure drug intake in the high dose range and thresholds in the low range. Cocaine consumption remained relatively stable across doses until a threshold was reached, at which maximal responding was observed. It was found that a history of LgA training produced an increase in cocaine consumption; whereas a history of PR training produced an increase in the maximal price (P(max)) expended for cocaine. Importantly, the concepts of consumption and price were found to be dissociable. That is, LgA training produced an increase in consumption but a decrease in P(max), whereas PR training produced an increase in P(max) without increasing consumption. These results suggest that distinct aspects of the addiction process can be parsed using self-administration models, thereby facilitating the investigation of specific neurobiological adaptations that occur through the addiction process.

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Dose-effect and price-effect relationships derived from self-administration data using a threshold procedure. (A) Dose-response relationship from a group of animals (n=8) tested through a descending series of unit injection doses of cocaine during daily 2 h sessions. The dose of cocaine was reduced each day by adjusting the pump duration (top x-axis); the corresponding unit injection dose is shown on the bottom x-axis. Data are expressed as mean (±SEM) responses on an FR1 schedule. (B) The dose-intake relationship demonstrates that a relatively stable level of cocaine intake is maintained at the high end of the dose range. Data are expressed as mean (±SEM) daily intake. (C) An individual animal’s Pmax (maximal price) is graphically determined. The animal’s daily responses (right y-axis) and intake (left y-axis) are both plotted as a function of unit-price (FR1/unit-dose). The unit-price at which maximal responding occurs (Pmax), which is graphically distinguishable as the apex of the price-response function (white circles), coincides with the point before which daily intake (black triangles) rapidly declines in response to an increase in price.
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Figure 1: Dose-effect and price-effect relationships derived from self-administration data using a threshold procedure. (A) Dose-response relationship from a group of animals (n=8) tested through a descending series of unit injection doses of cocaine during daily 2 h sessions. The dose of cocaine was reduced each day by adjusting the pump duration (top x-axis); the corresponding unit injection dose is shown on the bottom x-axis. Data are expressed as mean (±SEM) responses on an FR1 schedule. (B) The dose-intake relationship demonstrates that a relatively stable level of cocaine intake is maintained at the high end of the dose range. Data are expressed as mean (±SEM) daily intake. (C) An individual animal’s Pmax (maximal price) is graphically determined. The animal’s daily responses (right y-axis) and intake (left y-axis) are both plotted as a function of unit-price (FR1/unit-dose). The unit-price at which maximal responding occurs (Pmax), which is graphically distinguishable as the apex of the price-response function (white circles), coincides with the point before which daily intake (black triangles) rapidly declines in response to an increase in price.

Mentions: Pmax, defined as the unit-price at which maximal responding occurs (Hursh 1991), can be determined two ways. A common method used to determine Pmax involves calculating the unit-price at which maximal responding occurs on a demand curve (Hursh, 1991; Campbell, et al 1999; Cosgrove and Carroll, 2002). Individual demand curves were obtained by graphing daily intake (total drug in mg per 2 hr session) as a function of unit-price (FR1/unit dose). Pmax values were first calculated by analyzing the point at which the slope of a demand curve became elastic, which theoretically represents the point at which maximal responding occurs (Hursh, 1991). Calculated Pmax values and representative demand curves that were curve-fitted using equations described in greater detail by Hursh and Silberberg (2008) are demonstrated in the Supplementary Information (S2). Pmax can also be determined graphically by measuring the unit-price at which maximal responding occurs by plotting daily responding as a function of unit-price (Greenwald and Hursh, 2006; Lenoir and Ahmed, 2007). The apex of the price-response function (white-circles; Figure 1C) was used to determine Pmax. The relationship between Pmax values calculated using a demand curve analysis and Pmax values that were graphically determined is demonstrated in the Supplemental Information (S2) and further described in the results section. All Pmax values reported in the current study were determined graphically from individual animals, as demonstrated in Figure 1C.


Behavioral economic assessment of price and cocaine consumption following self-administration histories that produce escalation of either final ratios or intake.

Oleson EB, Roberts DC - Neuropsychopharmacology (2008)

Dose-effect and price-effect relationships derived from self-administration data using a threshold procedure. (A) Dose-response relationship from a group of animals (n=8) tested through a descending series of unit injection doses of cocaine during daily 2 h sessions. The dose of cocaine was reduced each day by adjusting the pump duration (top x-axis); the corresponding unit injection dose is shown on the bottom x-axis. Data are expressed as mean (±SEM) responses on an FR1 schedule. (B) The dose-intake relationship demonstrates that a relatively stable level of cocaine intake is maintained at the high end of the dose range. Data are expressed as mean (±SEM) daily intake. (C) An individual animal’s Pmax (maximal price) is graphically determined. The animal’s daily responses (right y-axis) and intake (left y-axis) are both plotted as a function of unit-price (FR1/unit-dose). The unit-price at which maximal responding occurs (Pmax), which is graphically distinguishable as the apex of the price-response function (white circles), coincides with the point before which daily intake (black triangles) rapidly declines in response to an increase in price.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2626138&req=5

Figure 1: Dose-effect and price-effect relationships derived from self-administration data using a threshold procedure. (A) Dose-response relationship from a group of animals (n=8) tested through a descending series of unit injection doses of cocaine during daily 2 h sessions. The dose of cocaine was reduced each day by adjusting the pump duration (top x-axis); the corresponding unit injection dose is shown on the bottom x-axis. Data are expressed as mean (±SEM) responses on an FR1 schedule. (B) The dose-intake relationship demonstrates that a relatively stable level of cocaine intake is maintained at the high end of the dose range. Data are expressed as mean (±SEM) daily intake. (C) An individual animal’s Pmax (maximal price) is graphically determined. The animal’s daily responses (right y-axis) and intake (left y-axis) are both plotted as a function of unit-price (FR1/unit-dose). The unit-price at which maximal responding occurs (Pmax), which is graphically distinguishable as the apex of the price-response function (white circles), coincides with the point before which daily intake (black triangles) rapidly declines in response to an increase in price.
Mentions: Pmax, defined as the unit-price at which maximal responding occurs (Hursh 1991), can be determined two ways. A common method used to determine Pmax involves calculating the unit-price at which maximal responding occurs on a demand curve (Hursh, 1991; Campbell, et al 1999; Cosgrove and Carroll, 2002). Individual demand curves were obtained by graphing daily intake (total drug in mg per 2 hr session) as a function of unit-price (FR1/unit dose). Pmax values were first calculated by analyzing the point at which the slope of a demand curve became elastic, which theoretically represents the point at which maximal responding occurs (Hursh, 1991). Calculated Pmax values and representative demand curves that were curve-fitted using equations described in greater detail by Hursh and Silberberg (2008) are demonstrated in the Supplementary Information (S2). Pmax can also be determined graphically by measuring the unit-price at which maximal responding occurs by plotting daily responding as a function of unit-price (Greenwald and Hursh, 2006; Lenoir and Ahmed, 2007). The apex of the price-response function (white-circles; Figure 1C) was used to determine Pmax. The relationship between Pmax values calculated using a demand curve analysis and Pmax values that were graphically determined is demonstrated in the Supplemental Information (S2) and further described in the results section. All Pmax values reported in the current study were determined graphically from individual animals, as demonstrated in Figure 1C.

Bottom Line: It was found that a history of LgA training produced an increase in cocaine consumption; whereas a history of PR training produced an increase in the maximal price (P(max)) expended for cocaine.Importantly, the concepts of consumption and price were found to be dissociable.That is, LgA training produced an increase in consumption but a decrease in P(max), whereas PR training produced an increase in P(max) without increasing consumption.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.

ABSTRACT
Various self-administration procedures are being developed to model specific aspects of the addiction process. For example, 'increased cocaine intake over time' has been modeled by providing long access (LgA) to cocaine during daily self-administration sessions under a fixed-ratio (FR1) reinforcement schedule. In addition, 'increased time and energy devoted to acquire cocaine' has been modeled by providing access to cocaine during daily self-administration sessions under a progressive-ratio (PR) schedule. To investigate the distinctiveness of these models, the behavioral economics variables of consumption and price were applied to cocaine self-administration data. To assess changes in consumption and price, cocaine self-administration was tested across a descending series of doses (0.237-0.001 mg per injection) under an FR1 reinforcement schedule to measure drug intake in the high dose range and thresholds in the low range. Cocaine consumption remained relatively stable across doses until a threshold was reached, at which maximal responding was observed. It was found that a history of LgA training produced an increase in cocaine consumption; whereas a history of PR training produced an increase in the maximal price (P(max)) expended for cocaine. Importantly, the concepts of consumption and price were found to be dissociable. That is, LgA training produced an increase in consumption but a decrease in P(max), whereas PR training produced an increase in P(max) without increasing consumption. These results suggest that distinct aspects of the addiction process can be parsed using self-administration models, thereby facilitating the investigation of specific neurobiological adaptations that occur through the addiction process.

Show MeSH
Related in: MedlinePlus