Dopamine modulation of pyramidal neurons of the mouse frontal cortex in vitro

WEDEMEYER , C; POMATA, PE; RUBINSTEIN, M; CALVO, DJ

Vaquerias- La Falda - Prov. de Cordoba

Taller; IV Taller Argentino de Neurociencias; 2002

Taller Argentino de Neurociencias

The mouse frontal cortex is densely innervated by dopaminergic fibers originated in the mesencephalic ventral tegmental area. Intracellular recordings showed that dopamine (DA)  could elicit  excitatory as well inhibitory effects by increasing or decreasing the action potential threshold of rat frontal pyramidal neurons. The mechanisms of this DA modulation of the cortical neuron activity remain controversial. We examined the actions of DA on the excitability of pyramidal cells of the layer V in mice frontal cortex using whole cell patch clamp recording. In agreement with previous evidences, we found a dual effect of DA on neuronal firing properties: DA increased the action potential threshold in 50% of the recorded cells, and showed the opposite effect on the other 50%. To test if the dual nature of DA effect was related to changes in monoamine basal levels, we performed recording in slices of monoamine depleted animals treated with a-methyl-p-tyrosine 200 mg/Kg + reserpine (Res) 5 mg/Kg or 50 mg/Kg i.p. Preliminary results showed that, at lower concentration doses of Res, DA applications produced similar results to controls. In sharp contrast to these, when higher doses of Res were used for depleted, DA consistently produced inhibitory effect on cell firing.