These studies were supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) to F.L and a Canadian Graduate Scholarship (CGSD) from NSERC to AM.L.

1. Animal Care and Housing
All experiments are approved by the Animal Care Committee of the University of Guelph, and are carried out in accordance with the recommendations of the Canadian Council on Animal Care. The current study includes 22 adult male Sprague-Dawley rats (Charles River, QC) weighing 200-225 g at the beginning of the experiment.
<ol>
	<li>Single house rats and maintain them on a reverse light/dark cycle (7:00 am OFF - 7:00 pm ON) with ad libitum access to food and water exc...

<ol>
	<li>Avena, N. M., Bocarsly, M. E., Hoebel, B. G., Gold, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Overlaps+in+the+nosology+of+substance+abuse+and+overeating:+the+translational+implications+of+&amp;#34;food+addiction&amp;#34.">Overlaps in the nosology of substance abuse and overeating: the translational implications of &amp;#34;food addiction&amp;#34.</a> Curr. Drug Abuse Rev. 4 (3), 133-139 (2011).</li><li>Ifland, J. R., Preuss, H. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Refined+food+addiction:+a+classic+substance+use+disorder.">Refined food addiction: a classic substance use disorder.</a> Med. Hyp. 72, 518-526 (2009).</li><li>Volkow, N., Wise, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+can+drug+addiction+help+us+understand+obesity.">How can drug addiction help us understand obesity.</a> Nat. Neurosci. 8 (5), 555-560 (2005).</li><li>Gearhardt, A. N., Davis, C., Kuschner, R., Brownell, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+addiction+potential+of+hyperpalatable+foods.">The addiction potential of hyperpalatable foods.</a> Curr. Drug Abuse Rev. 4 (3), 140-145 (2011).</li><li>Gearhardt, A. N., Yokum, S., Orr, P. T., Stice, E., Corbin, W. R., Brownell, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neural+correlates+of+food+addiction.">Neural correlates of food addiction.</a> Arch. Gen. Psychiatry. 68 (8), 808-816 (2011).</li><li>Volkow, N. D., Wang, G., Fowler, J. S., Telang, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Overlapping+neuronal+circuits+in+addiction+and+obesity:+evidence+of+systems+pathology.">Overlapping neuronal circuits in addiction and obesity: evidence of systems pathology.</a> Philos. Trans. Royal Soc. 363, 3191-3200 (2008).</li><li>Alsi&#246;, J., Olszewski, P. K., Levine, A. S., Schi&#246;th, H. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Feed-forward+mechanisms:+addiction-like+behavioral+and+molecular+adaptations+in+overeating.">Feed-forward mechanisms: addiction-like behavioral and molecular adaptations in overeating.</a> Front. Neuroendocrinol. 33 (2), 127-139 (2012).</li><li>Johnson, P. M., Kenny, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dopamine+D2+receptors+in+addiction-like+reward+dysfunction+and+compulsive+eating+in+obese+rats.">Dopamine D2 receptors in addiction-like reward dysfunction and compulsive eating in obese rats.</a> Nat. Neurosci. 13 (5), 635-644 (2010).</li><li>Bray, G. A., Nielsen, S. J., Popkin, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consumption+of+high-fructose+corn+syrup+in+beverages+may+play+a+role+in+the+epidemic+of+obesity.">Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity.</a> Am. J. Clin. Nutr. 79 (4), (2004).</li><li>Forshee, R. A., Storey, M. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+critical+examination+of+the+evidence+relating+high+fructose+corn+syrup+and+weight+gain.">A critical examination of the evidence relating high fructose corn syrup and weight gain.</a> Crit. Rev. Food Sci. Nutr. 47 (6), 561-582 (2007).</li><li>Moeller, S. M., Fryhofer, S. A., Osbahr, A. J., Robinowitz, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+high+fructose+corn+syrup.">The effects of high fructose corn syrup.</a> J. Am. Coll. Nutr. 28 (6), 619-626 (2009).</li><li>White, J. S., Foreyt, J. P., Melanson, K. J., Angelopoulos, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+fructose+corn+syrup:+Controversies+and+common+sense.">High fructose corn syrup: Controversies and common sense.</a> Am. J. Lifestyle Med. 4 (6), 515-520 (2010).</li><li>Grill, H. J., Norgren, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+taste+reactivity+test.+I.+Mimetic+responses+to+gustatory+stimuli+in+neurologically+normal+rats.">The taste reactivity test. I. Mimetic responses to gustatory stimuli in neurologically normal rats.</a> Brain Res. 143 (2), 263-279 (1978).</li><li>Limebeer, C. L., Vemuri, V. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inverse+agonism+of+cannabinoid+CB1+receptors+potentiates+LiCl-induced+nausea+in+the+conditioned+gaping+model+in+rats.">Inverse agonism of cannabinoid CB1 receptors potentiates LiCl-induced nausea in the conditioned gaping model in rats.</a> Br. J. Pharmacol. 161 (2), 336-349 (2010).</li><li>DeBold, R. C., Miller, N. E., Jensen, D. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+strength+of+drive+determined+by+a+new+technique+for+appetitive+classical+conditioning+of+rats.">Effect of strength of drive determined by a new technique for appetitive classical conditioning of rats.</a> J. Comp. Physiol.Psychol. 59 (1), 102-108 (1965).</li><li>Panksepp, J., Trowill, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraoral+self+injection:+I.+Effects+of+delay+of+reinforcement+on+resistance+to+extinction+and+implications+for+self-stimulation.">Intraoral self injection: I. Effects of delay of reinforcement on resistance to extinction and implications for self-stimulation.</a> Psychonomic Sci. 9 (7), 405-406 (1967).</li><li>Panksepp, J., Trowill, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraoral+self+injection:+II.+The+simulation+of+self-stimulation+phenomena+with+a+conventional+reward.">Intraoral self injection: II. The simulation of self-stimulation phenomena with a conventional reward.</a> Psychonomic Sci. 9 (7), 407-408 (1967).</li><li>Richardson, N. R., Roberts, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progressive+ratio+schedules+in+drug+self-administration+studies+in+rats:+a+method+to+evaluate+reinforcing+efficacy.">Progressive ratio schedules in drug self-administration studies in rats: a method to evaluate reinforcing efficacy.</a> J. Neurosci. Methods. 66, 1-11 (1996).</li><li>Berridge, K. C., Robinson, T. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Parsing+reward.">Parsing reward.</a> Trends Neurosci. 26 (11), 507-501 (2003).</li><li>Sclafani, A., Ackroff, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reinforcement+value+of+sucrose+measured+by+progressive+ratio+operant+licking+in+the+rat.">Reinforcement value of sucrose measured by progressive ratio operant licking in the rat.</a> Physiol. Behav. 79, 663-670 (2003).</li><li>Houpt, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gastrointestinal+factors+in+hunger+and+satiety.">Gastrointestinal factors in hunger and satiety.</a> Neurosci. Biobehav. Rev. 6 (2), 145-164 (1982).</li><li>Mazur, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+rate+of+reinforcement+and+rate+of+change+on+choice+behaviour+in+transition.">Effects of rate of reinforcement and rate of change on choice behaviour in transition.</a> J. Exp. Psychol. 50 (2), 111-128 (1997).</li><li>Samaha, A. N., Robinson, T. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Why+does+the+rapid+delivery+of+drugs+to+the+brain+promote+addiction.">Why does the rapid delivery of drugs to the brain promote addiction.</a> Trends Pharmacol. Sci. 26 (2), 82-87 (2005).</li><li>Berridge, K. C., Kringelbach, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Affective+neuroscience+of+pleasure:+reward+in+humans+and+animals.">Affective neuroscience of pleasure: reward in humans and animals.</a> Psychopharmacology. 199 (3), 457-480 (2008).</li><li>Kelley, A. E., Berridge, K. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+neuroscience+of+natural+rewards:+relevance+to+addictive+drugs.">The neuroscience of natural rewards: relevance to addictive drugs.</a> J. Neurosci. 22 (9), 3306-3311 (2002).</li><li>Shaham, Y., Shalev, U., Lu, L., De Wit, H., Stewart, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+reinstatement+model+of+drug+relapse:+history,+methodology+and+major+findings.">The reinstatement model of drug relapse: history, methodology and major findings.</a> Psychopharmacology. 168 (1-2), 3-20 (2003).</li><li>de Wit, H., Stewart, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drug+reinstatement+of+heroin-reinforced+responding+in+the+rat.">Drug reinstatement of heroin-reinforced responding in the rat.</a> Psychopharmacology. 79 (1), 29-31 (1983).</li><li>Schmidt, H. D., Anderson, S. M., Famous, K. R., Kumaresan, V., Pierce, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+and+pharmacology+of+cocaine+priming-induced+reinstatement+of+drug+seeking.">Anatomy and pharmacology of cocaine priming-induced reinstatement of drug seeking.</a> Eur. J. Pharmacol. 526 (1-3), 65-76 (2005).</li><li>Dunnigan, M. G., Ford, J. S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+insulin+response+to+intravenous+fructose+in+relation+to+blood+glucose+levels.">The insulin response to intravenous fructose in relation to blood glucose levels.</a> J. Clin. Endocrinol. Metab. 40 (4), 629-635 (1975).</li><li>Crapo, P. A., Kolterman, O. G., Olefsky, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+oral+fructose+in+normal,+diabetic,+and+impaired+glucose+tolerance+subjects.">Effects of oral fructose in normal, diabetic, and impaired glucose tolerance subjects.</a> Diabetes Care. 3 (5), 575-582 (1980).</li><li>L&#234;, K. A., Tappy, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolic+effects+of+fructose.">Metabolic effects of fructose.</a> Curr. Opin. Clin. Nutr. Metab. Care. 9 (4), 469-475 (2006).</li><li>Scheggi, M. E., Secci, G., Marchese, M. G., De Montis, C., Gambarana, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+palatability+on+motivation+to+operate+for+caloric+and+non-caloric+food+in+non+food-deprived+and+food-deprived+rats.">Influence of palatability on motivation to operate for caloric and non-caloric food in non food-deprived and food-deprived rats.</a> Neuroscience. 236, (2013).</li><li>Sclafani, A., Lucas, F., Ackroff, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+importance+of+taste+and+palatability+in+carbohydrate-induced+overeating+in+rats.">The importance of taste and palatability in carbohydrate-induced overeating in rats.</a> Am. J. Physiol. 270 (6), 1197-1202 (1996).</li><li>Roberts, D. C. S., Loh, E. A., Vickers, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-administration+of+cocaine+on+a+progressive+ratio+schedule+in+rats:+dose-response+relationship+and+effect+of+haloperidol+pretreatment.">Self-administration of cocaine on a progressive ratio schedule in rats: dose-response relationship and effect of haloperidol pretreatment.</a> Psychopharmacology. 97 (4), 535-538 (1989).</li><li>Reilly, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reinforcement+value+of+gustatory+stimuli+determined+by+progressive+ratio+Performance.">Reinforcement value of gustatory stimuli determined by progressive ratio Performance.</a> Pharmacol. Biochem. Behav. 63 (2), 301-311 (1999).</li><li>Zittel-Lazarini, A., Cador, M., Ahmed, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+critical+transition+in+cocaine+self-administration:+Behavioral+and+neurobiological+implications.">A critical transition in cocaine self-administration: Behavioral and neurobiological implications.</a> Psychopharmacology. 192 (3), 337-146 (2007).</li><li>Stanhope, K. L., Havel, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endocrine+and+metabolic+effects+of+consuming+beverages+sweetened+with+fructose,+glucose,+sucrose,+or+high+fructose+corn+syrup+Am.">Endocrine and metabolic effects of consuming beverages sweetened with fructose, glucose, sucrose, or high fructose corn syrup Am.</a> J. Clin. Nutr. 88 (6), 17335-17375 (2008).</li><li>Deroche-Gamonet, V., Belin, B., Piazza, P. 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The current study illustrates a novel approach for evaluating the reinforcing properties of sweet solutions by combining methods traditionally employed to study behavior motivated by drugs of abuse (intravenous operant self-administration) and to assess the palatability of tastants (taste reactivity through intraoral infusions). To this end, under very brief isoflurane-induced anesthesia, rats are implanted with an IO cannula that allows for the delivery of test solutions directly into their mouth. Following recovery fro...

The study of the neurobiological and behavioral basis of addiction to food relies on the observations that, similarly to drugs of abuse, excessive consumption of palatable foods promotes behavioral dependence1-4 and induces alterations in brain reward circuits in both humans5-6 and laboratory animals7-8. But, while there are several protocols and procedures for studying the addictive properties of drugs of abuse in laboratory rats, adapting these methods to assess &#34;addictive&#34; behaviors induced by food presents unique challenges. The goal of the current study was to apply principles of operant intravenous (IV) drug self-administration to the investigation of operant self-administration of sweet solutions delivered by intraoral (IO) infusion. The sweet employed was high fructose corn syrup (HFCS) because, although controversial, there is evidence that HFCS may be linked to the modern epidemic of obesity9-12.
Traditionally, IO infusions are delivered to study the palatability of tastants in taste reactivity experiments13. Briefly, an IO cannula is surgically implanted into the cheek of rats and IO infusions of various solutions are passively delivered14. The objective is to study orofacial reactions of the animals to the tastants. However, IO cannulas have also been implanted chronically in the palate of rats to determine whether they would learn to press a lever to self-infuse solutions directly into their oral cavity; hence the term IO self-injection15-17. In the current study, we describe a procedure that utilizes minor surgery&#160;and that allows long term operant self-administration testing. This procedure has several significant advantages over traditional procedures that involve drinking a solution from a spout (a), or operant responding for solid pellets (b), or operant responding for drops of fluid delivered in a receptacle (c).
In comparison to (a), IO self-administration involves an operant response (i.e.&#160;pressing a lever) and therefore it is possible to modify the schedule regulating the relationship between response requirements and delivery of IO infusions. For example, by employing a progressive ratio (PR) schedule, whereby responses required for successive infusions increase exponentially within a session18, it is possible to assess how much an animal &#34;wants&#34; the next infusion19. This important aspect of &#34;seeking&#34; behavior cannot be assessed when animals drink a solution from a spout, unless a special apparatus that controls fluid delivery and monitors responses is employed20. Moreover, IO self-administration provides a mean to compare behaviors motivated by different reinforcing stimuli. That is, it is possible to compare operant responding maintained by sweets and other reinforcers such as drugs of abuse in so called &#34;substitution studies.&#34;
In comparison to (b), IO self-administration allows testing of any concentration and any volume of any water-soluble food additive. This is critical to study behavior motivated by sweets such as HFCS because, to the best of our knowledge, there are no commercially available solid pellets of fructose, or fructose-glucose combinations at different ratios, that would be suitable for operant chambers. Also, the importance of controlling and manipulating concentration/volume ratios is mandatory in experiments where intake can be modulated both by the caloric value of a solution (leading to nutrient-specific satiety) and by how much of that solution can be consumed within a given period of time (i.e.&#160;fullness)21. IO self-administration also shortens the delay between the operant response and the delivery of the primary reinforcer, a factor that plays an important role in the acquisition and maintenance of operant behavior16,22-23.
Finally, in comparison to (c), IO self-administration allows the delivery of passive IO infusions of controlled quantities of the test solution, and this makes it possible to measure orofacial responses of &#34;liking&#34; (objective hedonic reaction such as tongue protrusions24-25) and whether these responses change during IO self-administration. Furthermore, the ability to administer passive IO infusions has significant applications for the study of relapse to food-seeking. That is, in studies of IV drug self-administration, following periods of extinction, drug primes (i.e.&#160;administration of a small dose of the drug26) can &#34;reinstate&#34; responding27-28. Therefore, the ability to deliver IO infusions without any action on the part of the animal can be used to study &#34;food&#34; primed reinstatement, as well as potential cross reinstatement between food and drugs of abuse.
IO self-administration of sweet solutions is also preferable to IV and intra-gastric self-administration. In fact, although IV infusions of fructose in both humans and laboratory animals produce physiological consequences similar to those observed following oral consumption29-31, this is a poor model of how sweets are normally consumed (i.e.&#160;orally). Moreover, gustatory signals produced by mastication confer important information about the palatability of food, and when this stage of the digestive process is omitted, the development of maladaptive behaviors such as overeating is reduced32-33.

<table border="1">
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 <td>Reagents</td>
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 <td>Meloxicam</td>
 <td>Boehringer Ingelheim Canada Ltd.</td>
 <td></td>
 <td>From the Ontario Veterinary College pharmacy</td>
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 <td>Procaine Penicillin G</td>
 <td>Pen Aqueous, Wyeth Animal Health</td>
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 <td>From the Ontario Veterinary College pharmacy</td>
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 <td>Lidocaine HCl 2%</td>
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 <td></td>
 <td>From the Ontario Veterinary College pharmacy</td>
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 <td>Marcaine 0.5 %</td>
 <td></td>
 <td></td>
 <td>From the Ontario Veterinary College pharmacy</td>
 </tr>
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 <td>Lubricating eye ointment</td>
 <td></td>
 <td></td>
 <td>Product can be bought at any pharmacy</td>
 </tr>
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 <td>2% Lidocaine Viscous Oral (Topical Anesthetic)</td>
 <td>Pharmascience Inc.</td>
 <td>CDMV # 14705</td>
 <td>100 ml bottle</td>
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 <td>Isoflurane USP</td>
 <td>Pharmaceutical Partners of Canada</td>
 <td>CDMV # 108737</td>
 <td>250 ml bottle</td>
 </tr>
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 <td>Bacti-Stat</td>
 <td>Merck Sante Animale</td>
 <td>CDMV # 6449</td>
 <td>3.785 L bottle</td>
 </tr>
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 <td>Isopropyl alcohol (70%)</td>
 <td>Perdu Pharma</td>
 <td>Fisher # MPX18404</td>
 <td>4 L bottle</td>
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 <td>Betadine 10%</td>
 <td>McKesson Canada</td>
 <td>CDMV # 104826</td>
 <td>500 ml bottle</td>
 </tr>
 <tr>
 <td>Super Germiphene</td>
 <td>Ceva Animal Health</td>
 <td>CDMV # 103629</td>
 <td>454 ml bottle</td>
 </tr>
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 <td>Chlorhexidene(Novadent)</td>
 <td>Zoetis</td>
 <td>CDMV # 8908</td>
 <td>236 ml bottle</td>
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 <td>High Fructose Corn Syrup</td>
 <td>Natures Flavours</td>
 <td>HFCS-55</td>
 <td>1 Gallon bottle</td>
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 <td>Materials</td>
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 <td>PE90 tubing</td>
 <td>Becton Dickinson and Company</td>
 <td>VWR # CA-63019-080A</td>
 <td>100 ft/coil</td>
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 <td>PE160 tubing</td>
 <td>Becton Dickinson and Company</td>
 <td>VWR # CA-63018-747</td>
 <td>100 ft/coil</td>
 </tr>
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 <td>Polypropylene Mesh</td>
 <td>Small Parts Inc.</td>
 <td>CMP-0297-D</td>
 <td></td>
 </tr>
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 <td>Soldering iron</td>
 <td></td>
 <td></td>
 <td>Product can be bought at any hardware store</td>
 </tr>
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 <td># 64 Elastic bands</td>
 <td>Staples Office supplies</td>
 <td>Item # 13556</td>
 <td>Product can be bought at any office supply store</td>
 </tr>
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 <td>15 G thin-walled 3.5 inch needles</td>
 <td></td>
 <td>VWR # CABD1108</td>
 <td>12 needles per pack</td>
 </tr>
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 <td>Electric razor (1/2 in wide blade)</td>
 <td></td>
 <td></td>
 <td>Product can be bought at any pet supply store</td>
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 <tr>
 <td>Percision Glide Needles 20 G needles (1 &frac12; in)</td>
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a novel procedure for evaluating the reinforcing properties of tastants in laboratory rats: operant intraoral self-administration

This paper describes a novel method for studying the bio-behavioral basis of addiction to food. This method combines the surgical component of taste reactivity with the behavioral aspects of operant self-administration of drugs. Under very brief general anaesthesia, rats are implanted with an intraoral (IO) cannula that allows delivery of test solutions directly in the oral cavity. Animals are then tested in operant self-administration chambers whereby they can press a lever to receive IO infusions of test solutions. IO self-administration has several advantages over experimental procedures that involve drinking a solution from a spout&#160;or operant responding for solid pellets or solutions delivered in a receptacle. Here, we show that IO self-administration can be employed to study self-administration of high fructose corn syrup (HFCS). Rats were first tested for self-administration on a progressive ratio (PR) schedule, which assesses the maximum amount of operant behavior that will be emitted for different concentrations of HFCS (i.e.&#160;8%, 25%, and 50%). Following this test, rats self-administered these concentrations on a continuous schedule of reinforcement (i.e.&#160;one infusion for each lever press) for 10 consecutive days (1 session/day; each lasting 3 hr), and then they were retested on the PR schedule. On the continuous reinforcement schedule, rats took fewer infusions of higher concentrations, although the lowest concentration of HFCS (8%) maintained more variable self-administration. Furthermore, the PR tests revealed that 8% had lower reinforcing value than 25% and 50%. These results indicate that IO self-administration can be employed to study acquisition and maintenance of responding for sweet solutions. The sensitivity of the operant response to differences in concentration and schedule of reinforcement makes IO self-administration an ideal procedure to investigate the neurobiology of voluntary intake of sweets.

Acquisition of IO self-administration
Figure 3 represents operant responding on the active and inactive levers during self-administration of 8%, 25%, or 50% HFCS for 10 consecutive sessions. Rats acquire IO self-administration of HFCS within the first three sessions and maintain stable active lever responding (as described above) for the remainder of acquisition. Concentration-dependent differences in active lever responses are also evident: compared to 25%, responding i...

Watch this Scientific Journal Video about A Novel Procedure for Evaluating the Reinforcing Properties of Tastants in Laboratory Rats: Operant Intraoral Self-administration at JoVE.com

A Novel Procedure for Evaluating the Reinforcing Properties of Tastants in Laboratory Rats: Operant Intraoral Self-administration

The current study evaluates a novel procedure for assessing the reinforcing effects of palatable solutions in laboratory rats: intraoral self-administration. To this end, operant responding (i.e.&#160;lever pressing) for intraoral infusions of sweet solutions at different concentrations was measured on continuous and progressive ratios schedules of reinforcement.

This paper describes a novel method for studying the bio-behavioral basis of addiction to food. This method combines the surgical component of taste ...

a-novel-procedure-for-evaluating-reinforcing-properties-tastants

Research

JoVE Journal

Behavior

12.6K Views.  University of Guelph.  L'attuale studio valuta una nuova procedura per la valutazione degli effetti di rinforzo delle soluzioni appetibili in topi di laboratorio: intraorale auto-amministrazione. A tal fine, rispondendo operante (cioè leva pressione) per gli infusi endorali di soluzioni dolci a diverse concentrazioni è stata misurata sui rapporti continui e progressivi orari di rinforzo. 