Lecture Outline #10: Endorphins, Aerobic Exercise, and Fertility

“mens sana in corpore sano” (healthy minds are in healthy bodies) – JUVENAL

I. THE DISCOVERY OF ENDOGENOUS OPIATES

1. First discovered there are specific cell receptors for opioids in CNS of vertebrates.

2. These receptors are in the brain (hypothalamus), spinal cord, ileum, vas deferens, etc.

3. This meant the mammalian body probably has natural opiates.

4. A search led to the discovery of the endorphins (Scotland & Sweden in 1974/1975).

II. THE ENDORPHINS (endorphin = endogenous-morphine)

1. First discovered was met-enkephalin (tyr-gly-gly-phe-met) and leu-enkephalin.

2. These compounds are metabolized very rapidly.

3. The most potent, stable form is a pre-hormone called b-endorphin (31 AA's).

4. b-endorphin is expressed in the anterior pituitary, hypothalamus, and some CNS cells.

5. b-endorphin comes especially from pituitary, in the form of POMC.

6. Met-enkephalin may be released from adrenal medulla along with catecholamines.

III. EFFECT OF ENDORPHINS ON BEHAVIOR

1. Endorphins have an analgesic effect (i.e., insensibility to pain without loss of consciousness).

2. In addition, these endogenous morphines have a variety of general effects on the body.

IV. VARIOUS ROLES AND ACTIONS OF ENDORPHINS

1. Endorphins may not be released during short exposure to painful stimuli, but are released during longer painful, stressful experiences. ("reward transmitters" for difficult tasks???)

2. Endorphins may be higher in obese, drug-free humans, causing. . . .:

3. Coffee may exert its stimulatory effect by caffeine antagonizing opioid receptors.

4. Endorphins reduce total acid output and volume of gastric secretions.

5. Endorphins increase in many (not all) postoperative patients about 48 hours after surgery.

6. Reduction in endorphin receptors may be related to migraine headaches.

7. Endorphins have been used to reduce the pain in cancer patients.

8. Endorphins may be related to chronic alcoholism:

9. b-endorphin increases significantly in the brain of mammals (humans) during pregnancy and labor.

10. Aerobic exercise increases blood levels of endorphins: b-endorphin & enkephalins.

V. EXERCISE THERAPY

1. “State anxiety” versus “trait anxiety” (anxiety = painful, or apprehensive, uneasiness of mind)

2. State anxiety increases during the first half of exercise, plateaus during the second half, and then drops below baseline within 10 min after exercise ceases.

3. Trait anxiety is significantly reduced by exercise 3 times per week.

4. College jogging classes improve physical and mental fitness (and self-confidence).

5. 15 minutes of brisk walking may have a greater effect than one dose of meprobamate.

6. Running is good for depression, and one can be virtually symptom-free within 3 weeks.

7. The “runner’s high” is typically experienced only by well-conditioned runners.

8. 45-60 minutes of exercise at 70% of aerobic capacity may be best.

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