Hunger and the Fat Rat

This activity provides a simulated experiment on weight regulation in rats.

The Hypothalamus
* What are the two techniques used to study hypothalamic dysfunction? How do they differ?

The two techniques used to study hypothalamic dysfunction are stimulation and destruction. To simulate the hypothalamus a small wire probe is inserted into the hypothalamus and a weak but constant current is passed through its insulated tip. Generally, simulation makes the controlling region preform its function until the current is stopped, but this method requires the subject to be continuously connected during the entire duration of the experiment and its affects are usually not permanent. Whereas destruction is performed with the same probe but it is performed at a much higher current and it stops the region from preforming its function by causing lesions on the affected area. This only needs to be performed once but causes permanent damage Experimental Simulation

What conclusions were you able to draw about the effects of the following procedures on the experimental rats:

* Stimulation of the lateral hypothalamus (LH)?

Upon stimulation of the lateral hypothalamus a 5-10 gram increase in daily food consumption and a weight gain of almost 175 grams was noted over a 90 day period.

* Destruction of the LH?

Upon destruction of the lateral hypothalamus a 15-20 gram decrease in daily food consumption and a weight loss of almost 175 grams was noted over a 90 day period.

* Stimulation of the ventromedial hypothalamus (VMH)?

Upon stimulation of the ventromedial hypothalamus a 10-20 gram decrease in daily food consumption and a weight loss of almost 50 grams was noted over a 90 day period.

* Destruction of the VMH?

Upon destruction of the ventromedial hypothalamus a 10-20 gram increase in daily food consumption and a weight gain of almost 200 grams was noted over a 90 day period.

* What did you learn from this experiment about these two regions of the hypothalamus?

After preforming the above tests on both the lateral and ventromedial hypothalamus I have found that they are essentially the “on / off” switch for the hunger drive. “On” being the lateral and “off” being the ventromedial.

Some Cautions
* What are the two problems with a simple conclusion to this research question?

1. This test is not practical or ethical to perform on humans. 2. There is no way to know if humans would respond the same to this type of testing as rats. I.E. Is a rat’s brains comparable to a human’s?