mise à jour du
23 octobre 2005
J Psychopharmacol
1986; 89; 4; S32
The syndrome of sedation and yawning behaviour in the rat is dependent on postsynaptic dopamine d-2 receptors
Scheel-Krüger J.
Psychopharmacological Research Laboratory,
Sct. Hans Hospital, DK-4000 Roskilde


Previous studies have suggested that the syndrome of sedation and yawning behaviour in the rat is dependent on stimulation of dopamine autoreceptors - mainly because the syndrome is produced by dopamine D-2 agonists given systemically in low doses known to suppress the release of endogenous dopamine.
However, exactly the same syndrome was found after the local intracerebral injection of high doses of dopamine agonists into the anterodorsal region of the striatum, i.e. the D-2 agonist LV 171555 (5-10 ug), -NPA (1-2.5 µg), N,N-propyl-5,6-ADTN (1-2.5 µg) and apomorphine (10 µg), whereas the D-1 agonist SKF 38393 (5-10 ) was inactive. The systemic injection of the D-2 antagonists sulpiride and haloperidol produced total antagonism of the sedation, yawning syndrome induced by LV 171555 injected into the striatum, whereas the D-1 antagonist SCM 23390 produced no inhibition.
In support for the role of postsynaptic D-2 receptors, it was found that the depletion of endogenous dopamine by the local injection of 6-OH-DA or systemic injection by reserpine + cr-MT produced no inhibition of 10 µg LV 171555 injected into the striatum. The local injection of sulpiride (50-100 ng) did not per se induce the sedative/yasning syndrome.
Furthermore, a modulatory role of dopamine D-l receptors iras found since the systemic injection of SCM 23390 antagonized the stereotyped behavioural stimulation by -NPA or N,N-propyl-5,6-ADTN given systemically or locally into intermediate ventromedial region of striatum and changed the behaviour of the rets into sedation and yenning activity.