Endocrine/Sex Lab

Introduction

As we have learned, pheromones are chemicals produced by one individual that influences the behavior of another individual. The use of pheromones is utilized by many organisms, apart from birds. Mammals can use pheromones to mark territory, communicate emotions, and to signal when they are ready to mate. In this lab, behavioral response to chemicals will be observed in male and female rabbits.

Intraspecific competition is when animals of the same species compete. In some instances, this competition is for mates. Males may mitigate this competition through mate-guarding. This is when a male stays in very close proximity to a female during fertile days or after copulation. This can ensure that the female only mates with him or increases the chance that his sperm will be the sperm that fertilizes the female. For this experiment, mate-guarding will be prompted for rice fish.

Sex hormones may play a role in pain perception. There are contradicting studies that claim that estrogen and testosterone influence pain. Some studies claim that estrogen, in higher levels, can increase pain tolerance by the release of endorphins that bind to brain cell receptors. These endorphins regulate how the pain is managed. Other studies say that testosterone dulls pain by stifling excitatory brain pathways, whereas estrogen blocks inhibitory pathways that can lessen pain sensing. Emotional response from these hormones may also have an impact on how humans react to pain.

Pain, for this lab, will be simulated by measuring heart rate through exposure to ice water and to spice. Temperatures within the range of under 15°C to over 43°C can invoke feelings of pain. Response to temperatures are regulated by the activation of transient receptor potential channels (TRP channels). TRPA1 is activated in more extreme cold to indicate potentially dangerous temperatures. Capsaicin, the chemical in peppers responsible for the feeling of spiciness, increases membrane permeability and activates TRPV1, which detects heat. Capsaicin is interpreted as extreme heat, which is why it can cause feelings of pain.

Materials

• Male rabbits
• Female rabbits
• Urine from both rabbits
• 6 stuffed rabbits
• Testosterone
• Human pheromones
• Enclosures for rabbits
• 20 rice fish
• Large tank
• 3 small tanks
• Dividers for the small tanks
• Pulse oximeters
• Plain corn chips
• Franks Red Hot
• Tabasco
• Cholula
• Sriracha
• Topatío
• Mild Pace Salsa
• Plastic tubs
• Ice
• Water

Pre-Lab Questions

1. What organ is frequently used to detect pheromones and where is it typically located?

2. Give an example of mate-guarding in a species other than rice fish. Why might this be advantageous for that species?

3. What are induced ovulators?

4. Will the number of action potentials increase or decrease with increasing spice?

5. Explain what is happening to membrane potential in response to capsaicin.

Activity 1

Stuffed bunnies will be treated separately with nothing, pregnant rabbit urine, female urine, male urine, testosterone, and human pheromone.

One at a time, the male and female rabbits will be allowed to interact with the stuffed bunnies.

Record the behavior of each rabbit in response to each of the stuffed bunnies.

Sex of rabbit	Stuffed bunny treatment	Observations
Male	Control
	Pregnant urine
	Female urine
	Male urine
	Testosterone
	Human Phero
Male	Control
	Pregnant urine
	Female urine
	Male urine
	Testosterone
	Human Phero
Female	Control
	Pregnant urine
	Female urine
	Male urine
	Testosterone
	Human Phero
Female	Control
	Pregnant urine
	Female urine
	Male urine
	Testosterone
	Human Phero
Female (pregnant)	Control
	Pregnant urine
	Female urine
	Male urine
	Testosterone
	Human Phero

Activity 2

Each of 4 tanks will have different combinations of males and females. On one end, 4 quadrants will be drawn. For 10 minutes, observe the behavior of the fish in each tank. Pay special attention to which quadrants the fish spend time in.

Tank 1: Female in Section 1, males in the middle and Section 3.

Sex/placement of rice fish	Behavior observations
Middle male
Section 3 male
Female

Tank 2: All female fish

Placement of rice fish	Behavior observations
Middle
Section 1
Section 3

Tank 3: All male fish

Placement of rice fish	Behavior observations
Middle
Section 1
Section 3

Tank 4: Male in Section 1, females in the middle and Section 3

Sex/placement of rice fish	Behavior observations
Middle male
Section 1 female
Section 3 female

Activity 3 

1. In groups of 2-3, fill a tub with ice water. Each person will submerge a hand in the ice water until it becomes too uncomfortable. Do not exceed 5 minutes. (This is not a competition, please be mindful of your body, and do not hurt yourself for the sake of our lab). Heart rate should be measured every 30 seconds until the person removes their hand. The final heart rate will be recorded.

Recording interval	Heart rate:
Resting:
Interval 1:
Interval 2:
Interval 3:
Interval 4:
Interval 5:
Interval 6:
Interval 7:
Interval 8:
Interval 9:
Interval 10:
Removal Time:

2. Eat a chip dipped in each of the hot sauces. Each hot sauce has a different Scoville unit. Begin with the lowest unit and work your way up. Record your heart rate before you eat it, as you eat it, and after. Give yourself some recovery time between each tasting.

Hot sauce and Scoville unit	Heart rates
Pace Salsa 25-50 SHU	Before: During: After:
Frank’s Red Hot 450 SHU	Before: During: After:
Tabasco 700 SHU	Before: During: After:
Cholula 1,000 SHU	Before: During: After:
Sriracha 2,200 SHU	Before: During: After:
Topatío 3,000 SHU	Before: During: After:

Post-Lab Questions

1. Which of the stuffed bunnies were the male rabbits more interested in and why? What about the females?

 

2. Which group of rice fish exhibited mate-guarding? What actions were observed that showed this behavior?

 

3. Did heart rate increase as discomfort increased?

 

4. Was there a difference in time of hand removal or heart rate for males vs. females in the pain activities? Do you think this was due to an emotional or hormonal response?

 

5. Draw and label a sensory neuron.