The Effects of Simulated Microgravity on Sensory Specific

Satiety in Rats Using the Hindlimb Unloading Model

Bio 250 and 450 classes

Presenters: Elizabeth Gowan, Casey Skinner, and Tyler Stinnett Funded by NASA’s South Carolina Space Grant Consortium Research Experience for Undergraduates Grant

Observation: Astronauts get sick in space

• Cephalic Fluid Shift

• Space Adaptation Syndrome

• Dizziness

• Nausea

• Loss of appetite

• Loss of smell and taste

Decreased food intake = insufficient energy intake

Why does this matter?

• Renewed interest in space exploration

• Difficulties reduce productivity

• Cost effectiveness in NASA spending

How can we increase astronauts’ food consumption?

Study humans in simulated microgravity

Difficult and cost-prohibitive

Animal model of simulated microgravity?

•Yes! >800 papers published using this animal model

•None have attempted to manipulate feeding behaviors

Is there an animal model of increased eating?

Sensory Specific Satiety (Ahn and Phillips, 1999)

A hungry rat fed until satiated on rat chow WILL NOT eat more rat chow

A hungry rat fed until satiated on rat chow WILL eat Froot Loops ®

Purpose:

• To combine an existing model of simulated microgravity with an existing model of increased eating

Hypothesis:

• Rats exhibit sensory specific satiety under conditions of simulated microgravity.

Methods• 7 Male Sprague-Dawley Rats

• Fed Rat Chow ad-libitum except on experimental days

• Used NASA Hindlimb Unloading Model

•Institutional Animal Care and Use Committee Approved

What is the Hindlimb Unloading Model?

• Simulates microgravity (Morey-Holton & Globus, 2002.)

– Cephalic Fluid Shift– Symptoms of Space Adaptation Syndrome

2 week

recovery period

Horizontal

Week 1

body weight & food intake measured twice daily

Experimental Time Line

1 week recovery period

1 week recovery period

HU

Week 3

HU

Week 6

Horizontal

Week 8

Weekly Procedures

Meal 1 - 90 minutesRat Chow

Meal 2 - 30 MinutesRat Chow or Froot Loops(same caloric densities)

- Counterbalanced

• Experiment• Returned to standard cages

Day 7

• Transferred to experimental cage• 14-18 hr food deprivation begins

Day 0-1

• Experiment

Day 2

• Hanging out in the

experimental cage!

Days 3-5

• 14-18 hr food deprivation begins

Day 6

Food deprivation

How SSS was measured...• Food Intake (grams):

• Meal 1 at 60 and 90 minutes• Meal 2 at 30 minutes

Statistical Analysis• Two Way Repeated Measures ANOVA

•Student-Newman-Keuls Test *p<0.05

• Latency to Eat (minutes):• Meal 2

Treatment

Horiz D2 HU D2 Horiz D7 HU D7

Cu

mu

lati

ve F

oo

d In

take

(g

ram

s)

0

1

2

3

4

5

6

7

8

~50%

*~50%

*

Meal 1 Food Intake at 60 and 90 Minutes

Treatment

Horiz D2 HU D2 Horiz D7 HU D7

La

ten

cy

to

fe

ed

(m

in)

0

10

20

30

40 Rat chow/Rat chowRat chow/Froot loops

Latency to Eat Meal 2

**

*

*

Treatment

Horiz D2 HU D2 Horiz D7 HU D7

Cu

mu

lati

ve F

oo

d In

take

(g

ram

s)

0

1

2

3

4 Rat chow/Rat chowRat chow/ Froot Loops

Meal 2 Food Intake at 30 minutes

*

*

*

**

~40%

~40%

*

Conclusions:

• Rats in Hindlimb Unloading model exhibit Sensory Specific Satiety.

• Rats in Hindlimb Unloading model eat significantly less than their horizontal counterparts.

Relevance:

• How does this relate to astronauts?

• Future Directions:– Promote increased energy intake

• Manipulate sensory properties• Increase caloric density

Acknowledgements:

• Funded by a grant awarded to Drs. Davis and Hettes from NASA’s South Carolina Space Grant Consortium.

The Effects of Simulated Microgravity on Sensory Specific

Satiety in Rats Using the Hindlimb Unloading Model

Bio 250 and 450 classes

Presenters: Elizabeth Gowan, Casey Skinner, and Tyler Stinnett Funded by NASA’s South Carolina Space Grant Consortium Research Experience for Undergraduates Grant

Latency to Feed Meal 1

Overnight Food Intake