Ein Verfahren, um die Kapazität von einem Alkohol verbundenen Umweltkontextstudie zur Auslösung der Erneuerung der Alkoholsucht bei der Ratte beschrieben.
Umwelt Kontexte, in denen Drogen konsumiert werden kann Verlangen, eine subjektive Pawlowschen-konditionierte Reaktion, die Drogen-sucht Verhalten und prompte Rückfall in abstinent Drogenkonsumenten erleichtern auslösen können. Wir haben ein Verfahren, um die Verhaltens-und neuronale Prozesse, die die Auswirkungen der Kontext auf Alkohol-seeking Verhalten bei Ratten zu vermitteln studieren entwickelt. Nach Akklimatisierung an den Geschmack und die pharmakologischen Wirkungen von 15% Ethanol im Käfig, erhalten männlichen Long-Evans-Ratten Pawlow Diskriminierung Ausbildung (PDT) in Klimakammern. In jeder täglich (Mo-Fr) PDT-Sitzung, die jeweils von zwei verschiedenen 10 sec Gehöranlage Reize 16 Studien auftreten. Während eines Stimulus, der CS + 0,2 ml 15% Ethanol wird in einen Fluidanschluss für den oralen Verzehr geliefert. Der zweite Reiz, der CS, wird nicht mit Ethanol gepaart. Über die Sitzungen, Einträge in die Fluidöffnung während der CS + Zunahme, während Einträge in der CS-Stabilisierung auf einem niedrigeren Niveau, das anzeigt, dass ein Predictive Assoziation zwischen der CS + und Ethanol gewonnen. Während PDT jede Kammer mit einer bestimmten Konfiguration von visuellen, taktilen und olfaktorischen Stimuli kontextuellen ausgestattet. Nach PDT ist vom Aussterben Ausbildung in der gleichen Kammer, die jetzt mit einer anderen Konfiguration von Kontextreizen ausgestattet ist durchgeführt. Die CS + und CS sind nach wie vor präsentiert, aber Ethanol wird zurückgehalten, die einen allmählichen Rückgang in Port-Einträge während der CS + verursacht. Bei Test werden Ratten wieder in den Kontext gestellt und PDT mit dem CS + und CS nach wie vor präsentiert, aber ohne Ethanol. Diese Manipulation löst eine stabile und selektive Erhöhung der Anzahl von Eingangsports während des Alkohols prädiktiven CS +, ohne Änderung in der CS antwortet. Dieser Effekt, der als Kontext-induzierte Erneuerung genannt, veranschaulicht die leistungsstarke Kapazität von Zusammenhängen mit dem Alkoholkonsum assoziiert zu Alkohol-sucht Verhalten in Reaktion auf Alkohol Pawlow Hinweise zu stimulieren.
Rest nüchtern ist eine große Herausforderung durch Personen, die unter Alkoholmissbrauch Erkrankungen konfrontiert. Abstinenz ist eine Zeit der Anfälligkeit für den Verhaltens, psychologischen und physiologischen Auswirkungen von Umweltreizen, die routinemäßig Alkoholkonsum zu begleiten, die können, durch Pawlowschen Konditionierung, sich mit Rausch 1,2 verbunden. Exposition gegenüber Alkohol prädiktiven Cues bedingter Reaktionen wie Alkohol Begierde, die Alkohol-Rückfall der Suche nach Verhaltensweisen, die 3,4 erleichtern fördern kann zu entlocken.
Die stereotype Verhaltenssequenzen, die den Alkoholkonsum führen kann bestimmte Arten von Stimuli, routinemäßig unmittelbar vor den pharmakologischen Wirkungen von Alkoholkonsum erlebt werden. Zum Beispiel der Anblick, den Geruch und Geschmack von Alkohol sind die sensorischen Eigenschaften von Alkohol, die zuverlässig voraus Rausch. Zusätzlich zu solchen Signale, die als "diskrete" oder "proxima bezeichnet werdenl 'Cues, Umwelt Kontexte, in denen Medikamente werden regelmäßig verwendet wird, kann auch provozieren Verlangen 5,6. Exposition gegenüber physikalischen Standorten, an denen Medikamente haben bisher verwendet wurden, kann daher eine kritische Auslöser für den Rückfall 7 sein.
Tiermodelle wurden entwickelt, um die neuronalen Mechanismen, die die Auswirkungen der Droge verbunden Kontexte auf Drogen-sucht Verhalten 8-13 vermitteln studieren. Das hierin beschriebene Verfahren erlaubt die Untersuchung, wie Kontexte mit Alkoholkonsum kann Alkohol-sucht Verhalten, das durch eine diskrete, Alkohol prädiktiven Pavlovian Cue ausgelöst wird modulieren.
Pawlow Diskriminierung Ausbildung in einem spezifischen ökologischen Kontext, wo Ratten sind verhaltens zwischen zwei Gehöranlage Reize, eine CS +, die mit Alkohol kombiniert wird, und ein CS, die nicht zu unterscheiden geschult durchgeführt. Extinktion Einheiten werden dann in einem anderen Zusammenhang, in dem die Reaktion auf den CS durchgeführt+ Abnimmt, wenn ein Ergebnis der Alkohol zurückgehalten. Anschließend Reexposition zum Alkohol assoziiert, Pavlovian Ausbildung Kontext löst eine selektive Zunahme des Alkoholsuchverhalten der CS + hervorgerufen, ohne Änderung in Reaktion auf die CS. Dieses Ergebnis, das haben wir konsequent repliziert 9,14-16 erstreckt sich Erkenntnisse aus der instrumentellen Konditionierungsverfahren, in dem Drogen Kontexten gefunden worden, um die Erneuerung der operanten Reaktionen mit Drug-Delivery 10,13 assoziiert zu stimulieren.
Results from this procedure reveal that discrete environmental stimuli that routinely accompany alcohol delivery can acquire the capacity to drive alcohol-seeking behavior. They also demonstrate that contextual stimuli associated with the prior availability or absence of alcohol can guide conditioned behavioral responses to discrete alcohol-predictive cues.
Critical steps within the protocol
Contexts in the present task incorporate stimuli that are external to the rat. However, the interoceptive state of the rat at test can also constitute a ‘context’ that could affect renewal20. It is therefore important to habituate rats to any procedures that may occur before the renewal test and change their interoceptive state, like intracranial microinfusions or systemic injections. Moreover, habituation to microinfusions or systemic injections should be conducted prior to both extinction and PDT sessions, to prevent such procedures from becoming associated with one specific phase of the experiment.
Temporal parameters, such as CS duration, CS-US interval, and intertrial interval (ITI), have long been known to influence conditioned responding in a variety of conditioning paradigms21-26. Similarly, temporal parameters may influence the observation of the renewal effect in our procedure. Any set of parameters other than those specified in the protocol should be experimentally validated in pilot studies before proceeding to employ them in larger investigations.
Modifications and troubleshooting
Previous research has found that the amount of ethanol that rats consume in the home cage can vary as a function of the supplier from which rats are purchased17,27. Supplier is therefore an important consideration for this phase of the study. Similarly, the choice of rat strain should be considered carefully, as there are numerous reports of strain differences in ethanol consumption28-31.
Prior work in an aversive conditioning paradigm has shown that the developmental age of rats influences the observation of renewal of a Pavlovian conditioned fear response32. The lack of a renewal effect in very young rats (younger than postnatal day 20) has been suggested to be due to impaired encoding of contextual information33. The developmental age of rats to be used in the present procedure should therefore be taken into consideration.
Renewal of Pavlovian conditioned alcohol-seeking behavior has been observed when 10%9,16, 15%14, or 20%15 ethanol solutions were used during the home cage ethanol access and PDT phases of the experiment. Researchers could use any of these concentrations of ethanol for the purposes of establishing this procedure in their laboratories.
During the acquisition of Pavlovian discrimination training it is important to check fluid ports after each session to ensure that all the ethanol that was delivered has been consumed. Leaving rats in the conditioning chambers for an additional 10 – 15 min after each session may be done early in PDT to encourage consumption of any ethanol that was not consumed during the session. The number of rats leaving unconsumed ethanol in the ports should decrease as PDT progresses. If by the end of PDT rats are either (a) not consuming all the ethanol and/or (b) not responding to the CS+ then these subjects should be dropped from the study. Most rats reliably respond more to the CS+ than the CS-. However, some rats may respond at high levels to both cues, thereby not showing evidence of discrimination. Rats that show high responding to both the CS+ and CS- during PDT are not dropped from the study. In our experience, these subjects show remarkable discrimination during the first extinction session in the absence of ethanol, suggesting that their high levels of responding to the CS- during PDT are driven by the presence of ethanol in the fluid port. These subjects also tend to show robust renewal effects.
Limitations of the procedure
Because the renewal test is conducted in the absence of ethanol, conditioned port entries elicited by the CS+ gradually diminish across the test session. Therefore, the overall amount of behavior generated at test, against which experimentally induced changes can be assessed, is fairly low. Because in this task responding tends to be higher at the start versus the end of the test session, it is important to examine the effects of experimental manipulations on conditioned responding on a trial-by-trial basis.
Entries into the fluid receptacle provide the main dependent measure in this task. However, an erroneous port entry might be registered if an animal is close enough to the fluid receptacle to break the infrared beam across the opening of the fluid port with its whiskers. While infrequent, erroneous responses are obvious as a dramatic increase in total port entries relative to the subject’s behavior on prior sessions. Videotaping the animals would facilitate the detection of possible erroneous responses, and allow for a more refined analysis of the behaviors exhibited by the rats throughout training and testing.
Significance of technique with respect to existing/alternative methods
Context-induced renewal of drug-seeking behavior is largely studied using an instrumental conditioning task in which the primary dependent variable is an operant response, such as a lever press8,34 or nose poke12. In the present procedure, the drug-seeking response is ‘conditioned approach’ to the fluid port that is elicited by presentations of the CS+. This response is likely acquired through Pavlovian learning, which is the learning process that mediates the formation of associations between environmental stimuli and the pharmacological effects of drugs of abuse in humans.
Future applications
This task can be used in combination with neuropharmacology, optogenetics and neurochemistry to study the neural mechanisms that are involved in context-induced renewal of Pavlovian-conditioned alcohol-seeking behavior16. In addition, behavioral and neural mechanisms that regulate the acquisition and extinction of Pavlovian-conditioned alcohol-seeking behavior can be investigated. Lastly, this task can be used to explore manipulations of extinction that might prevent renewal, an important direction for translational research aimed at reducing the impact of drug associated environmental contexts on reactivity to drug predictive cues after cue exposure therapy in human addicts.
The authors have nothing to disclose.
This work was supported by the National Institute on Alcohol Abuse and Alcoholism (RO1 AA014925 awarded to Dr. Patricia H. Janak at University of California, San Francisco, CA, USA), Fonds de recherche du Quebec – Santé (NC) and the Natural Sciences and Engineering Research Council (NC, 387224-2010). The open-access publication of this article was made possible by sponsorship from Med Associates Inc.
Name of Reagent/ Equipment | Company | Catalog Number | Comments/Description |
Heavy-duty utility cart | Rubbermaid | #4520-88 | Used to transport rats in their home cage from the colony room to the behavior room or other facilities |
Rats, Long-Evans | Harlan | – | Rats weighed 220-240g on arrival |
Ohaus scale | Fisher | #S402421 | For weighing rats; tare the bottom of a plastic container first, then put the rat in it to weigh it |
Beta-chips, aspen | Harlan | #7090A | Bedding for home cage |
Nylabone | Bio-Serv | #K3580 | Enrichment provided in the home cage |
Autoclavable rodent chow | Agribrands, Charles River | #5075 | For feeding rats |
Wire bar cage lid | Ancare | #R20SS2B | Custom made with two slots for bottles |
Cage bottom | Ancare | #R20PC | To house rats |
Stoppers | Ancare | #8.5 | Rubber stoppers to occlude opening in water bottles & graduated cylinders; goes with ball point sipper tubes |
Ball point tubes, 1.5" length | Ancare | #TD-99 | Inserted in stoppers, enables rats to drink from water bottles and graduated cylinders |
Water bottles | Ancare | #FSPC8HT | 473 ml (16 oz) capacity, needs to be occluded with stopper |
Graduated cylinders, 100ml | Fisher | #0300741 | To contain ethanol during alcohol exposure in the home cage; spouted end needs to be cut off to enable occlusion with stoppers |
Mettler scale | Mettler Toledo | #MS6001S | For weighing water bottles and ethanol cylinders |
Polyethylene tubing, 1/32" inner diameter, 1/32" wall thickness, 3/32" outside diameter | Fisher | #14-169-1A | To connect 20 ml ethanol syringe to fluid port |
Needle, 18g, 1.5" length | Fisher | #B305199 | To connect polyethylene tubing to ethanol syringes; needs to be filed |
Syringes, 20ml, Luer-Lok non-sterile | Fisher | #1482316J | To contain ethanol on the fluid pumps; needs to be connected to the polyethylene tubing by a 18g 1 1/2 needle |
Syringes, 60ml, Luer-Lok non-sterile | Fisher | #14-820-11 | To flush polyethylene tubing after PDT sessions |
Single speed syringe pump, 3.33 rpm | Med Associates Inc. | #ENV-018MD | To hold 20 ml ethanol syringes and deliver ethanol |
Fluid port | Med Associates Inc. | #ENV-254-CB | To enable ethanol delivery during PDT sessions; connected to ethanol syringes with polyethylene tubing |
Port entry infrared detector | Med Associates Inc. | #ENV-215M | Fixed on both sides of fluid port; need 2 per fluid port |
Houselight, 28V, 100mA | Med Associates Inc. | #ENV-135M | Provides general lighting in conditioning chamber |
Clicker module | Med Associates Inc. | #ENV-225SM | Auditory stimulus for conditioning chamber |
White noise generator with speaker | Med Associates Inc. | #PHM-100 | Auditory stimulus for conditioning chamber |
Bar floor | Med Associates Inc. | #ENV-009A-GF | To go with modular test chamber |
Bench coat, absorbant | VWR | #89126-790 | Absorbant paper to put in metal tray, needs to be cut to fit the metal tray |
Polycarbonate sheet, 1/8" thick, 12-5/8"x10" | Johnston Plastics | #30102515 | To make smooth transparent floor insert used for context 1. Needs to be cut in 11.5"x12.25" pieces |
Aluminium sheet perforated, 0.063"thick, 48"x96", 0.250" holes x 0.375" centers | Anica Steel | – | To make perforated floor insert used for context 2. Needs to be cut in 11.5"x12.25" pieces |
Black cardboard, 0.053" thick, 28"x44" | Omer DeSerres | #P1909 | To construct panels covering the ceiling, door and back wall of the conditioning chamber in context 1. Needs to be cut to size. Each chamber needs three panels measuring approximately 11.5"x13.25". The panels can be joined by the narrower side using duct tape. |
All-purpose strength duct tape, 1.88"x45yd. | Duck Tape | – | Adhesive material to connect the black cardboard panels used to cover the back wall, ceiling and door in context 1. |
Modular test chamber | Med Associates Inc. | #ENV-009A | Conditioning chamber |
Sound attenuating cubicles | Med Associates Inc. | #ENV-200R3AM | Comes with installed 28V DC fan (#ENV-025F) |
Petri dish | Fisher | #08748B | Bottom only, to contain the sprayed solution that provides the odor stimulus; needs to be centered in the metal tray in conditioning chambers |
PCI interface package | Med Associates Inc. | #DIG-700P2-R2 | Connects tabletop interface cabinet to computer; includes 1 interface card, 1 Decode card, 1 ribbon cable and 1 28V DC power cable |
Large tabletop cabinet and power supply | Med Associates Inc. | #SG-6510D | Used to contain the 12 cards included in the SmartCrtrl 8 Input, 16 Output package |
SmartCtrl 8 Input, 16 Output package | Med Associates Inc. | #DIG-716P2 | Used to connect and control the devices in the conditioning chamber. The package includes all the cables, the interface module and the connection panel. |
Med PC IV software | Med Associates Inc. | #SOF-735 | Software to run programs. Needs to be installed on the computer. |
Monitor LG, 19" LCD | Concordia computer store | #W1942TQ-BF | Computer monitor; to go with computer running Med PC IV |
HP Z200 tower workstation | Concordia computer store | #BZ788US#ABA | Computer on which Med PC IV is run |
Benzaldehyde, ≥99% | Les produits chimiques OMEGA Chemical Company Inc. | #B37-50 | Dilute in tap water for almond context odor |
Lemon oil, cold pressed, California | Sigma Aldrich | #W262528-1KG-K | Dilute in tap water for lemon context odor |
Ethyl alcohol, 95% | Commercial Alcohols | – | Dilute in tap water to desired concentration |