Manipulating the Sensory Properties of Food Enhances Food Intake in Rats Under Simulated Microgravity: a Demonstration of Sensory Specific Satiety with the Hindlimb Unloaded Model Project Leader: Tyler Stinnett Funded by NASA’s South Carolina Space Grant Consortium Research Experience for Undergraduates Grant

Observation: Astronauts are not eating enough Cephalic Fluid Shift Space Adaptation Syndrome Dizziness Nausea Loss of appetite Reduction of smell and taste Decreased food intake = Insufficient energy intake = Decrease in mission productivity

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 (Morey-Holton and Globus, 2002) However, we are unaware of any previous attempts to manipulate feeding behaviors

Is there an animal model of increased eating? Yes! Sensory Specific Satiety (Rolls, et al, Brain Research, 1986; 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 Unloaded Model

Our Modifications to the Hindlimb Unloading Apparatus Need for more affordable and space saving cage –Collapsible –2 sides with rollers are taller for rats over 500g –Disposable bedding tray –Easy angle adjuster

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 minutes Rat Chow Meal Minutes Rat Chow or Froot Loops ® (same caloric densities) - Counterbalanced Experiment Returned to standard cages Day 7 Day 0: Transferred to experimental cage Day 1: hr food deprivation begins Day 0-1 Experiment Day 2 Continuation of tail suspension Days hr food deprivation begins Day 6 Food deprivation

How SSS was measured... Cumulative 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 post hoc test *p<0.05 Latency to Eat in Meal 2 (minutes): Latency- the time between access to and consuming the first bite of food

Three Components of Sensory Specific Satiety #1: Satiated Animal Satiated- does not consume available food.

~50% * * Meal 1 Food Intake at 60 and 90 Minutes

Three Components of Sensory Specific Satiety #1: Satiated Animal #2: Decreased Latency to feed on a more palatable second meal

Latency to Eat Meal 2 * * * * Reminder: Latency is the time between food presentation and the first bite.

Three Components of Sensory Specific Satiety #1: Satiated animal #2: Decreased latency to feed on a more palatable second meal #3: Increased intake of a more palatable second meal

Meal 2 Food Intake at 30 minutes * * * * * ~40% *

Summary: Rats in the Hindlimb Unloaded model exhibit Sensory Specific Satiety by consuming more Froot Loops ® than rat chow. Rats in the Hindlimb Unloaded model eat significantly less than their horizontal counterparts.

Conclusions: Rats in simulated microgravity show decreased food intake, however, intake can be augmented by manipulating sensory properties of food.

Future Directions: What Part(s) of the Brain Regulates Overeating During Sensory Specific Satiety? Neural Activity (action potentials/ sec) Repeated offerings of 50 ml portions of glucose rejects glucose Taken from Rolls et al, 1986 Neural Activity in the Lateral Hypothalamus (LH)

Manipulating the Sensory Properties of Food Enhances Food Intake in Rats Under Simulated Microgravity: a Demonstration of Sensory Specific Satiety with the Hindlimb Unloaded Model Project Leader: Tyler Stinnett Funded by NASA’s South Carolina Space Grant Consortium Research Experience for Undergraduates Grant