Numerous SP-positive pyramidal neurons in cat neocortex are glutamate-positive

An immunocytochemical technique that allows visualization of two antigens in the same neuron was used to verify the possibility that some neocortical pyramidal neurons contain both glutamate (Glu) and substance P (SP) immunoreactivity. The results show that a large fraction of SP-positive pyramidal neurons are also Glu-positive, and indicate that in a small population of cortical neurons a fast excitatory synaptic transmitter and a slow peptidic modulator coexist.