In this contribution we present multi-channel microinjector arrays fabricated by a reliable three-layer SU-8 process and assembled with glutamate biosensor microprobes'. It enables local delivery of specific liquids into brain tissue for the stimulation or inhibition of neuronal activity combined with simultaneous monitoring of biochemical substances. Real-time measurements in the prefrontal cortex of the rats' brain demonstrate the successful in vivo calibration of the biosensor responding to pressure injections of small volumes of the neurotransmitter glutamate in its local vicinity.