Electrochemical detection of excitatory neurotransmitters (NTs) such as glutamate (GLU) and dopamine (DA) have generated much interest in the field of chemical neuroscience. These NTs have several important functions in mammalian brain, e.g. activating “reward-mechanism” center in the brain, learning and memory. DA deficiency causes depression, ADHD and Parkinson’s disease. Abnormal GLU levels are associated with Epilepsy, Alzheimer’s disease, dementia, insomnia and insufficient adrenaline function. New electrode materials (e.g. carbon nanotubes, boron-doped nanocrystalline diamond, platinized platinum) and probe designs (e.g. high density arrays) are much needed to better understand the neurological disorders that costs at least $100B annually in US alone. The probes are expected to near simultaneously measure multiple NTs in real-time with high spatial-temporal resolution. In our experiments, we use a commercial platinum (Pt) microelectrode array with eight individually addressable sites. Pt is well-known for its high selectivity towards hydrogen peroxide, a common by-product of enzyme-based GLU biosensor. The Pt microelectrodes are suitably modified with multi-walled carbon nanotubes (CNTs) for DA and enzymes for GLU detection and nafion for improved selectivity. Fast scan cyclic voltammetry and amperometry techniques are used to detect the NTs. We report increase in sensitivities of GLU and DA and their suitability for long-term in vitro measurements. The development of electrochemical models to explain the progression of surface fouling and sensor performance using impedance techniques will be elucidated in some detail.