Dopamine/glutamate interaction as studied by combining turning behaviour and c-Fos expression

Dopamine (DA) and glutamate N-methyl- d-aspartate (NMDA) receptors extensively interact in the mediation of motor behaviours originated in basal ganglia. In unilaterally 6-hydroxydopamine (6-OHDA) lesioned rats, this interaction is of a different sign depending on whether D 1 or D 2 receptors are stimulated. Contralateral turning behaviour induced by D 1 agonists is potentiated by the NMDA antagonist MK 801, while turning behaviour induced by D 2 agonists is decreased. NMDA receptors not only modulate the acute turning behaviour induced by DA agonists but also the long-term effects induced by stimulation of DA receptors. MK 801, in fact, prevents the sensitization (priming) of D 1-mediated turning behaviour induced by a single exposure to a DA agonist. Prevention of priming by MK 801, also appears to be different depending on whether D 1 or D 1 D 2 receptors are stimulated. Studies on c-fos expression induced by DA D 1 agonists in the 6-OHDA lesioned striatum show that detection of Fos-like immunoreactivity correlates to the long-term but not the acute effects induced by DA receptor stimulation and NMDA receptor blockade.