Wilfrid Laurier University Scholars Commons @ Laurier Theses and Dissertations (Comprehensive) 2021 Sucrose Solution Access Influences Intake Value in Rats Adam Celejewski cele8580@mylaurier.ca Follow this and additional works at: https://scholars.ca/etd Recommended Citation Celejewski, Adam, "Sucrose Solution Access Influences Intake Value in Rats" (2021). Theses and Dissertations (Comprehensive).ca/etd/2346 This Thesis is brought to you for free and open access by Scholars Commons @ Laurier. It has been accepted for inclusion in Theses and Dissertations (Comprehensive) by an authorized administrator of Scholars Commons @ Laurier. For more information, please contact scholarscommons@wlu.
Sucrose Solution Access Influences Intake Value in Rats by Adam Celejewski BSc University of Toronto (2007), MSc Wilfrid Laurier (2011) THESIS/DISSERTATION Submitted to the Department/Faculty of Psychology in partial fulfillment of the requirements for Doctorate of Philosophy in Psychology Wilfrid Laurier University Adam Celejewski 2020 © SUCROSE ACCESS & VALUE 2 Abstract Previous work has shown that non-deprived rats’ intake of a 4% sucrose solution increases over 24 h access periods if it is provided every 3 or 4 days (E3D or E4D) relative to every day (ED; (Eikelboom & Hewitt, 2016). Once these access-intake differences are established, they can be enduring, even if all rats are shifted to a common access schedule. Do changes in value accompany these access-induced solution intake changes? Three approaches were applied to test for access-induced value changes. First, following extended 24 h E3D (12 exposures) or ED (36 days) access to a flavoured 4% (Experiment 1) or 12% (Experiment 2) standard sucrose solution, the standard solution was compared in a series of 24 h choice tests against ascending concentrations of a differently flavoured alternate solution on a common E2D access schedule.
Experiment 1 revealed access-induced preference increases for the standard solution after E3D relative to ED access while Experiment 2 did not, possibly due to the higher concentration of sucrose used. Second, a progressive ratio procedure was used to evaluate changes in the reinforcing efficacy of a 4% sucrose solution after an extended period of E3D or ED access. This traditional operant procedure failed to reveal access-induced changes in the breakpoint for the sucrose. The failure to reveal breakpoint differences is suggested to be due to context effects; E3D/ED sucrose solutions were provided in the home-cage while sucrose solution breakpoints were evaluated in operant chambers.
Third, in Experiments 4 and 5, palatability changes of the 4% solution were evaluated with lick microstructure analysis. Water and sucrose microstructures were compared (positive control), before comparing the microstructure of sucrose solutions during ED or E4D access periods. Both microstructure comparisons revealed a similar pattern of SUCROSE ACCESS & VALUE 3 changes, suggesting that palatability increases after E4D relative to ED access. Collectively, these results suggest that sucrose solution increases in value with E3D or E4D relative to ED access.
The results highlight that tests conducted over longer durations (24 h) may yield different results than similar tests conducted over shorter (~1 h), restricted access sessions. Experiments 1 and 2 also suggested that rats treated the two, distinctly flavoured solutions as different food sources in the preference tests, something that is not readily revealed with shorter preference tests. Similarly, the lick microstructure appeared to be different with the longer, 24 h sucrose solution access duration relative to previous shorter (~1 h), access microstructure palatability studies. Finally, Experiment 5, which also measured food intake, revealed that changes in foods provided could also profoundly affect sucrose consumption, highlighting the importance of considering the complete nutritional environment of the rat.
This work underscores the need for further study of the impact of access on value. Moreover, it encourages a holistic approach that includes monitoring the rat’s 24 intake of food and fluids as a consideration in appetitive behaviour studies. SUCROSE ACCESS & VALUE 4 Acknowledgements I wold like to thank my supervisor Rudy Eikelboom for his guidance and unyielding patience. I have learned much from him over the years.
Thanks also to Paul Mallet who shared some of his equipment, especially the operant chambers. And thanks to my lab mates Gehan Senthinathan and Angela Mastroianni who helped with some the experimental work, and who’s company was always appreciated. Finally I would like to thank Aula Al Muslim, my partner for always being by my side. SUCROSE ACCESS & VALUE 5 Table of Contents Abstract.4 Table of Figures.14 List of Abbreviations.22 Intermittent and Continuous Sweet Solutions Access.29 Intermittent Access to Fluids and Foods.34 Monday, Wednesday and Friday Access.35 Daily 12 h Sugar Solution Access.38 Measuring Sugar Solution Intake.40 Intake by Volume or Calories Consumed.40 Intake by Preference.41 Short Term Intake Tests.43 Non-Nutritive Sweeteners.44 Measuring the Value of Food and Drink.44 The Problem with Consumption or Response/Reinforcement Rate Value Measures.45 Choice as a Measure of Reward.46 Choice as a Measure of E(3, 4)D/ED Access-Induced Value Differences.49 SUCROSE ACCESS & VALUE 6 Progressive Ratio Measure of Reward Value.50 Progressive Ratio as a Measure of E(3, 4)D/ED Access-Induced Value Differences.53 Microstructure of Sucrose Solution Intake.53 Organization of the Microstructure of Drinking.54 What is an Optimal Episode Pause Criterion?.56 Lick Microstructure Over Shorter Recording Sessions, 60 Min or Less.56 Lick Microstructure Over Longer Recording Sessions, 24 h or More.59 Microstructure Sucrose Solution Intake Under E4D/ED Access Conditions.63 Summary and Dissertation Direction.70 General Procedures and Materials.78 Solution Intake By Weight.78 SUCROSE ACCESS & VALUE 7 Half-maximal Standard Solution Intake.79 Combined Standard and Alternate Solution Intake by Weight.79 Preference for the Standard by Weight.80 Solution Intake by Calories.80 Combined Alternate and Standard Solution Intake by Calories.81 Preference for Standard Solution Calories.82 Access-Induced Intake Differences.83 Access-Induced Choice Difference.88 Experiment 2: Choice II.94 Combined Standard and Alternate Solution Intake by Weight.94 Preference for Standard Solution by Weight.95 SUCROSE ACCESS & VALUE 8 Solution Intake by Calories.95 Combined Standard an Alternate Solution Intake by Calories.95 Preference for the Standard Solution by Calories.96 Experimental Parameter Considerations for Experiments 1 and 2.100 Experiment 3: Progressive Ratio.108 Phase II: E3D/ED Home-cage 4% Sucrose Solution Access.108 Phase III: PR Test.108 Phase IV: E2D Home-cage 4% Sucrose Solution Access.109 Phase I: PR Baseline.110 Phase II: E3D/ED Home-cage 4% Sucrose Solution Access.110 SUCROSE ACCESS & VALUE 9 Phase III: PR Test.111 Phase IV: E2D Home-cage 4% Sucrose Solution Access.111 Experiment 4: Lick Microstructure I.125 Solution Intake, Licks and Microstructure.125 Initial Lick Rate.126 EPC Duration and Episode Size and Number.127 Distribution of Licking Over 24 h.127 Episode as Proportion of Total Licks.127 Water Versus Sucrose Intake and Intake Microstructure (Days 7, 8, 9, & 10).128 Fluid Intake and Licks.128 Correlation Between Licks and Consumption.129 Water and Sucrose Solution Episodes.130 Sucrose Intake and Intake Microstructure with E4D/ED Access (Days 9, 10, 26 & 30).131 Sucrose Solution Intake and Licks.132 Correlation Between Licks and Consumption.132 SUCROSE ACCESS & VALUE 10 Lick Microstructure.132 E4D and ED Access Sucrose Solution Episodes.133 Initial Lick Rate.134 Standard Housing Sucrose Solution Intake.135 Fluid Intake and Lick Number.137 Water Versus Sucrose Intake Microstructure.
ED Access Sucrose Intake Microstructure.141 Initial Lick Rate.144 Experiment 5: Lick Microstructure II.150 Licking and Feeding Recordings.150 Baseline and Habituation.152 Food Calories and Sucrose Solution Consumed.152 Licks , Initial Lick Rate, and Episodes of Licking.153 EPC Duration and Episode Size and Number.154 SUCROSE ACCESS & VALUE 11 Food Calories.154 Baseline Food Kilocalories (Day 7, 8, 13, 14).155 Food Calories: Chamber/Home-cage Access I.155 Food Calories: Home-cage Access.156 Food Calories: Chamber/Home-cage Access II.156 Food Calories: Summary.156 Fluid Intake, Licks and Intake Microstructure.157 Distribution of Licking Over 24 h.157 Episodes as a Proportion of Total Licks.157 Water Versus Sucrose Intake and Intake Microstructure (Days 13 & 22).158 Correlation Between Water Licks and Consumption.158 Water and Sucrose Episodes.159 Sucrose Intake and Intake Microstructure with E4D/ED Access.160 Solution Intake: Chamber/Home-cage Access I.160 Solution Intake: Home-cage Access.161 Solution Intake: Chamber/Home-cage Access II.162 Correlation Between Sucrose Solution Licks and Consumption.162 SUCROSE ACCESS & VALUE 12 Lick Microstructure.162 E4D and ED Access Sucrose Solution Episodes.164 Initial Lick Rate.175 Limited Access Versus 24 h Choice Tests.178 Standard and Alternate Solutions Were Treated as Distinct Food Sources.180 Influence of Familiarity on Preference.185 Lick Microstructure Analyses.189 Evidence for Access-Induced Changes in Palatability.190 Limited Access Versus All Day Microstructure Recordings.193 Sucrose Solution and Water Comparisons are Valid.199 Does Postingestive Experience Influence Lick Microstructure?.201 Lick Microstructure Summary.201 Conclusions and Significance.203 E(3, 4)D/ED Access Changes Sucrose Solution Value.203 Longer Daily Access is Different from Short Access Sessions.207 SUCROSE ACCESS & VALUE 13 Changes in the Availability of Calorie Containing Resources In Longer Daily Sessions.210 Future Direction and Broader Implications.286 SUCROSE ACCESS & VALUE 14 Table of Figures Figure 1: Intake of a 4% sucrose solution with continuous or intermittent access.218 Figure 2: Temporal representation sample lick data (4% sucrose solution) grouped across the EPC duration range.219 Figure 3: Mean (±SEM) intake of a 16% sucrose solution with E3D or ED access in Phase I and of a 4% sucrose solution with E2D access in Phase II.220 Figure 4, Experiment 1: Phase I mean (± SEM) 4% Standard sucrose solution intake consumed with E3D or ED access.221 Figure 5, Experiment 1: Phase II mean (± SEM) 4% Standard and Alternate solution intake following a period of E3D or ED Standard solution access.222 Figure 6, Experiment 1: Phase II mean (± SEM) combined solution consumed following a period of E3D or ED 4% Standard solution access.223 Figure 7, Experiment 1: Phase II mean preference (± SEM) for the Standard solution following a period of E3D or ED 4% Standard solution access.224 Figure 8, Experiment 1: Phase II mean (± SEM) calorie intake from the 4% Standard and Alternate solutions following a period of E3D or ED Standard solution access.225 Figure 9, Experiment 1: Phase II mean (± SEM) combined solution calorie intake following a period of E3D or ED 4% Standard solution access.226 Figure 10, Experiment 1: Phase II mean preference (± SEM) for 4% Standard solution calories following a period of E3D or ED Standard solution access.227 SUCROSE ACCESS & VALUE 15 Figure 11, Experiment 1: Phase III mean (± SEM) 4% Standard sucrose solution consumed with E2D access following different E3D/ED access experience.228 Figure 12, Experiment 2: Phase I mean (± SEM) 12% Standard sucrose solution intake with E3D or ED access.229 Figure 13, Experiment 2: Phase II mean (± SEM) 12% Standard and Alternate solution intake following a period of E3D or ED Standard solution access.230 Figure 14, Experiment 2: Phase II mean (± SEM) solution intake by Test Number and Alternate solution concentration.231 Figure 15, Experiment 2: Phase II mean (± SEM) combined solution consumed following a period of E3D or ED Standard (12%) solution access.232 Figure 16, Experiment 2: Phase II mean preference (± SEM) for the Standard (12%) solution following a period of E3D or ED Standard solution access.233 Figure 17, Experiment 2: Phase II mean (± SEM) calorie intake from Standard (12%) and Alternate solutions following a period of E3D or ED Standard solution access.234 Figure 18, Experiment 2: Phase II mean overall solution calorie intake (± SEM) following a period of E3D or ED Standard (12%) solution access.235 Figure 19, Experiment 2: Phase II mean preference (± SEM) for the Standard (12%) solution calories following a period of Standard solution E3D or ED access.236 Figure 20, Experiment 2: Phase III mean Standard 12% sucrose solution intake (± SEM) with E2D access.237 Figure 21, Experiment 3: Mean (± SEM) breakpoint over 9 consecutive PR baseline session.238 SUCROSE ACCESS & VALUE 16 Figure 22, Experiment 3: Mean (± SEM) 24 h 4% sucrose solution intake before and after PR baseline and testing.239 Figure 23, Experiment 3: Mean (± SEM) breakpoint over 6 PR test sessions following extended E3D/ED 4% sucrose access experience.240 Figure 24, Experiment 4: Licks for water (Days 5 – 8 ) and 4 % sucrose solution (Days 9 – 30) over the dark/light cycle from representative rats with E4D access and ED access.241 Figure 25, Experiment 4: Mean (± SEM) intake of (A) and licks for (B) water (Days 5 – 8 ), or 4% sucrose solution with E4D/ED access (Days 9 – 33).