Placebo expectation conditioning

Question 1

When the neurobiology of placebo was born?

Answer 1

The neurobiology of placebo was born when Levine et al. (1978) discovered that the opioid antagonist naloxone inhibits the placebo analgesic response.

Question 2

How placebo analgesia produced?

Answer 2

There are several lines of evidence indicating that placebos activate endogenous opioid systems, thus producing placebo analgesia. However, Gracely showed that placebo analgesia may also occur without the involvement of endogenous opioid systems and that both opioid and nonopioid components play an important role.

Question 3

Which theories state that a substance known to be nonanalgesic (e.g., saline solution) is a powerful painkiller?

Answer 3

At least two theories have been proposed to explain this phenomenon as the basis for the activation of endogenous opi- oids.
1) cognitive factors, like expectation of pain relief, are supposed to trigger the release of opioids in the CNS;
2) a classical conditioning mechanism has been proposed, in which repeated associations between active analgesics, pain relief, and therapeutic surroundings produce a conditioned placebo analgesic response; (ask)
3) the anxiety theory postulates that placebo analgesia is caused by a reduction of anxiety;
4) the response-appropriate sensation theory proposes that the global experience of pain results from a complex internal analysis of different brain states;

Question 4

Which document is known as a statement of ethical principles for medical research involving human subjects?

Answer 4

the Declaration of Helsinki

Question 5

How the pain was induced, which pain, and what was made to avoid variability among different subjects?

Answer 5

Pain was induced experimentally by means of the tourniquet technique. This test produces ischemic pain of the arm that increases over time. To avoid variability among different subjects, his or her nondominant forearm was extended, and venous blood was drained by means of an Esmarch bandage.

Question 6

How the pain tolerance was defined?

Answer 6

The pain tolerance was defined as the time from the last squeeze of the forearm to unbearable pain.

Question 7

Which drugs were administered in the experiment?

Answer 7

The conditioning drugs were morphine hydrochloride - an opioid agonist, and ketorolac tromethamine - a nonsteroid anti-inflammatory drug (NSAID) with no activity on opioid receptors.