Apomorphine (Apo), a short acting
dopamine (DA) receptor agonist, stimulates
growth hormone (GH) secretion, decreases
prolactin secretion, induces yawning, penile
erections and other physiological effects in
man. An effect on behavior, movement disorders
and alcoholism has also been described.
Apo-mediated responses are used to evaluate
DA function in psychiatric and neurological
disorders. Many of the studies in schizophrenia
using the GH response to Apo as an index of
central DA function are difficult to interpret
because of failure to control for key
variables.
The GH response to Apo is a useful system to
evaluate the effects of various drugs including
peptides which may not cross the blood brain
barrier on DA function in man.
Apo is a potent sedative. Specific
antimanic, antischizophrenic, and anticraving
effects in alcoholics have not been convincingly
demonstrated. Side effects of Apo and failure to
use active placebo make double-blind studies
difficult.
Apo improves parkinsonian symptoms and
certain forms of reflex epilepsy but beneficial
effects in other involuntary movement disorders
requires further documentation.
Apo may be a useful agent to evaluate DA
function in impotent patients and predict a
therapeutic response to long-acting dopaminergic
agents.
Impairment of DA function may play a role in
diabetic impotence.
The development of a simple polygraphic
method to monitor the yawning response to Apo
may facilitate clinical studies on the basic
physiology of yawning in man and the use of the
yawning response as a measure of central DA
function in schizophrenia and other clinical
disorders.
The use of Apo with 18F-fluorodeoxyglucose
positron emission tomography to examine regional
DA function in man opens up a promising area of
research.
Though long-acting orally active aporphine
DA agonists and antagonists have been developed
the problem of tolerance may limit their
therapeutic potential.
-Lal S,
Grassino A, Thavundayil YX, Bubrovsky B A
simple method for study of yawning in man
induced by the dopamine receptor agonist,
apomorphine. Progr Neuropsychopharmacol Biol
Psychiatry 1987; 11; 223-228
-Lal S, Y
Tesfaye et al Apomorphine: clinical studies
on erectile impotence and yawning. Prog
Neuropsychopharmacol Biol Psychiatry (1989)
13(3-4): 329-39
-Tesfaye Y,
Lal S Hazard of yawning Canadian Med Assoc J
1990;142;1;p15 - 1991;145;12;p1560
