Modulation of pyramidal neurons excitability by dopamine in the mouse frontal cortex

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

Buenos Aires

Congreso; XIV International Biophysics Congress; 2002

Frontal cortex is densely innervated by mesencephalic dopaminergic fibers. Dopamine (DA) could either increase or decrease action potential threshold of rat frontal pyramidal neurons. The mechanisms for this DA modulation remain controversial. We examined here the actions of DA on the excitability of pyramidal cells in the layer V of mice frontal cortex using whole-cell patch-clamp recordings. In agreement with previous evidences, we found a dual effect of DA on neuronal firing properties: DA increased action potential threshold in 50% of the recorded cells (n=9), and showed the opposite effect on the other 50% (n=9). To test if the dual nature of DA effects was related to changes in monoamine basal levels, we performed recordings in slices from frontal lobe of monoamine depleted animals (treated with a-methyl-p-tyrosine 200mg/Kg+ reserpine 5mg/Kg or 50mg/Kg i.p). Preliminary results showed that at the lower concentration of reserpine DA applications produced similar results to controls. In sharp contrast to these, when the higher concentration of reserpine was used, DA consistently produced an inhibitory effect on cell firing.