Ad. Crocker, A NEW VIEW OF THE ROLE OF DOPAMINE-RECEPTORS IN THE REGULATION OF MUSCLE TONE, Clinical and experimental pharmacology and physiology, 22(11), 1995, pp. 846-850
1. Clinical and experimental studies support the view that nigrostriat
al dopaminergic neurons are involved in the maintenance of muscle tone
. 2. The effects of inactivating dopamine receptors in the rat substan
tia nigra on muscle tone, assessed as tonic electromyographic (EMG) ac
tivity, was investigated. 3. Dopamine receptors were inactivated by in
jections of the irreversible dopamine receptor antagonist, N-ethoxycar
bonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) into the pars reticulata of
the substantia nigra. 4. Significant increases in EMG activity were o
bserved from 2 to 24 h after EEDQ injection and were associated with a
loss of nigral dopamine receptors. 5. Increases in EMG activity were
found only when both D-1 and D-2 receptors were inactivated. 6. Inacti
vation of alpha-adrenoceptors, 5HT(2C) and muscarinic receptors had no
effect on EMG activity. 7. Injections of apomorphine did not reduce t
he increased EMG activity associated with nigral dopamine receptor los
s. 8. The results are consistent with the hypothesis that dopamine rec
eptors in the substantia nigra of the rat play an important role in th
e regulation of muscle tone.