Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration

Abstract Transition from the highest rate of lever-pressing activity during the unloading (extinction) phase of a cocaine self-administration session to an extremely low activity rate during the remission phase is in many cases gradual. This makes it difficult to assess the duration of the unloading...

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Autores principales:	Vladimir L. Tsibulsky, Andrew B. Norman
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2021
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/3784459f81b041a2bc35b55ebae92b38
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spelling	oai:doaj.org-article:3784459f81b041a2bc35b55ebae92b382021-12-02T18:37:10ZDramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration10.1038/s41598-021-98313-02045-2322https://doaj.org/article/3784459f81b041a2bc35b55ebae92b382021-10-01T00:00:00Zhttps://doi.org/10.1038/s41598-021-98313-0https://doaj.org/toc/2045-2322Abstract Transition from the highest rate of lever-pressing activity during the unloading (extinction) phase of a cocaine self-administration session to an extremely low activity rate during the remission phase is in many cases gradual. This makes it difficult to assess the duration of the unloading phase after a fixed ratio 1 (FR1) or breakpoint after a progressive-ratio (PR) self-administration session. In addition, 3–5 days of training under the PR schedule results in a dramatic and persistent increase in the rate of presses during PR sessions and in the unloading phase following FR1 self-administration sessions. The goals of this study were to find the definition of the last press demarcating the border between the unloading and remission phases of the session and to determine if this border was also affected by PR training. Rats were trained to self-administer cocaine under the FR1 schedule and then under the PR schedule of drug delivery. Distributions of inter-press intervals (IPIs) during the unloading phase in sessions before and after PR training were compared. It was found that the distribution of cocaine-induced IPIs during the unloading phase was lognormal, bimodal, and independent of previously injected cocaine unit doses. The first mode represented intervals within the short bouts of stereotypic presses and the second mode represented intervals between bouts. The two modes were approximately 0.7 s and 21 s during unloading prior to and 0.6 s and 1.5 s after PR self-administration training. The total number of presses per unloading phase increased eightfold. When the FR1 schedule was restored, the intervals between bouts remained very short for at least 7–10 days and only then started a gradual increase towards baseline levels. The last unloading press was defined as the press followed by the IPI longer than the defined criterion. PR training resulted in a substantial and long-lasting increase in lever-pressing activity during unloading. The duration of the unloading phase did not depend on the rate of lever-pressing activity.Vladimir L. TsibulskyAndrew B. NormanNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 11, Iss 1, Pp 1-10 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Vladimir L. Tsibulsky Andrew B. Norman Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration
description	Abstract Transition from the highest rate of lever-pressing activity during the unloading (extinction) phase of a cocaine self-administration session to an extremely low activity rate during the remission phase is in many cases gradual. This makes it difficult to assess the duration of the unloading phase after a fixed ratio 1 (FR1) or breakpoint after a progressive-ratio (PR) self-administration session. In addition, 3–5 days of training under the PR schedule results in a dramatic and persistent increase in the rate of presses during PR sessions and in the unloading phase following FR1 self-administration sessions. The goals of this study were to find the definition of the last press demarcating the border between the unloading and remission phases of the session and to determine if this border was also affected by PR training. Rats were trained to self-administer cocaine under the FR1 schedule and then under the PR schedule of drug delivery. Distributions of inter-press intervals (IPIs) during the unloading phase in sessions before and after PR training were compared. It was found that the distribution of cocaine-induced IPIs during the unloading phase was lognormal, bimodal, and independent of previously injected cocaine unit doses. The first mode represented intervals within the short bouts of stereotypic presses and the second mode represented intervals between bouts. The two modes were approximately 0.7 s and 21 s during unloading prior to and 0.6 s and 1.5 s after PR self-administration training. The total number of presses per unloading phase increased eightfold. When the FR1 schedule was restored, the intervals between bouts remained very short for at least 7–10 days and only then started a gradual increase towards baseline levels. The last unloading press was defined as the press followed by the IPI longer than the defined criterion. PR training resulted in a substantial and long-lasting increase in lever-pressing activity during unloading. The duration of the unloading phase did not depend on the rate of lever-pressing activity.
format	article
author	Vladimir L. Tsibulsky Andrew B. Norman
author_facet	Vladimir L. Tsibulsky Andrew B. Norman
author_sort	Vladimir L. Tsibulsky
title	Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration
title_short	Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration
title_full	Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration
title_fullStr	Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration
title_full_unstemmed	Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration
title_sort	dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration
publisher	Nature Portfolio
publishDate	2021
url	https://doaj.org/article/3784459f81b041a2bc35b55ebae92b38
work_keys_str_mv	AT vladimirltsibulsky dramaticincreaseinleverpressingactivityinratsaftertrainingontheprogressiveratioscheduleofcocaineselfadministration AT andrewbnorman dramaticincreaseinleverpressingactivityinratsaftertrainingontheprogressiveratioscheduleofcocaineselfadministration
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Dramatic increase in lever-pressing activity in rats after training on the progressive ratio schedule of cocaine self-administration

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