Pharmacologic challenge in ERP research

Multiple receptors contribute to the behavioral effects of indoleamine hallucinogens

Serotonergic hallucinogens produce profound changes in perception, mood, and cognition. These drugs include phenylalkylamines such as mescaline and 2,5-dimethoxy-4-methylamphetamine (DOM), and indoleamines such as (+)-lysergic acid diethylamide (LSD) and psilocybin. Despite their differences in chemical structure, the two classes of hallucinogens produce remarkably similar subjective effects in humans, and induce cross-tolerance. The phenylalkylamine hallucinogens are selective 5-HT(2) receptor agonists, whereas the indoleamines are relatively non-selective for serotonin (5-HT) receptors. There is extensive evidence, from both animal and human studies, that the characteristic effects of hallucinogens are mediated by interactions with the 5-HT(2A) receptor. Nevertheless, there is also evidence that interactions with other receptor sites contribute to the psychopharmacological and behavioral effects of the indoleamine hallucinogens. This article reviews the evidence demonstrating that the effects of indoleamine hallucinogens in a variety of animal behavioral paradigms are mediated by both 5-HT(2) and non-5-HT(2) receptors.

Inhibitory casting decreases a vibratory inhibition index of the H-reflex in the spastic upper limb

OBJECTIVE

To test the hypothesis that application of an inhibitory cast to the spastic upper limb will decrease a vibratory inhibition index (VII) of the H-reflex in the spastic upper limb.

DESIGN

Prospective, nonrandomized, open-label trial.

SETTING

University tertiary care center.

PARTICIPANTS

Eight adults with upper limb spasticity.

INTERVENTION

Fiberglass cast application spanning the wrist to the upper arm.

MAIN OUTCOME MEASURE

The amplitude of the H-reflex with and without continuous 60Hz vibration to the tendon of the flexor carpi radialis was measured, and the VII was calculated using the formula: [H-reflex amplitude (vibrated)/H-reflex amplitude (control)] x 100%.

RESULTS

Mean VII decreased from baseline (70.7) on day 1 (67.6, p = .699), day 2 (55.9, p =.066), and day 3 (43.5, p = .033) of casting, and increased on day 4 (89.9, p = .146) after removal of the cast.

CONCLUSION

Findings lend support to the idea that during application of an inhibitory cast motor neuron excitability is decreased in the spastic upper limb.