Apomorphine delays simple reaction time in Parkinsonian patients.
BACKGROUND
Parkinsonian patients have difficulty in the preparation and execution of movements, which translate into delayed performance of simple reaction time (SRT) paradigms.


OBJECTIVE
To examine short-term effects of an acute subcutaneous injection of the dopamine agonist apomorphine on the results of a SRT task.


METHODS
We studied a SRT paradigm in 26 non-fluctuating idiopathic Parkinsonian patients, before and 30, 60, 90 min after administration of apomorphine.


RESULTS
The reaction time (RT) was significantly delayed after apomorphine injection. We found no significant change in movement time (MT).


CONCLUSIONS
Delay of RT and the lack of response of MT to apomorphine administration may result from the sedative effects of apomorphine, overstimulation of postsynaptic dopaminergic receptors with subsequent inhibition of prefrontal cholinergic neurotransmission, and at least partial binding of apomorphine to presynaptic dopaminergic autoreceptors, which cause inhibition of locomotor activity. We suggest that future studies testing the capacity for reaction in Parkinsonian patients should consider the exact timing of the delivery of dopamine substituting drugs prior to the test.
Müller
Thomas
T
Department of Neurology, St. Josef Hospital, Ruhr University Bochum, Gudrunstrasse 56, 44791 Bochum, Germany. thomas.mueller@ruhr-uni-bochum.de
Benz
Sabine
S
Przuntek
Horst
H
D000328:Adult; D000368:Aged; D000978:Antiparkinson Agents / Q000008:administration & dosage / Q000009:adverse effects*; D001058:Apomorphine / Q000008:administration & dosage / Q000009:adverse effects*; D003071:Cognition / Q000187:drug effects; D005260:Female; D006801:Humans; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000187:drug effects*; D010300:Parkinson Disease / Q000188:drug therapy* / Q000503:physiopathology; D011930:Reaction Time / Q000187:drug effects
D000978:Antiparkinson Agents; D001058:Apomorphine