Regulation of Substance P Immunoreactivity in GABA Neurons of Monkey Visual Cortex by Sensory Deprivation

Until recently it has generally been considered that sub stance P (SP) immunoreactive neurons were absent from the mammalian cerebral cortex. There have now been three reports of the existence of SP-like immunoreactivity in the cerebral cortices of rats [1] and monkeys [2,3]. One problem in all these studies, however, was that the antisera used were directed against the C-terminal sequence of the peptide, a sequence that is conserved in the other mammalian tachykinins [4]. In the present report, we provide evidence for the presence of SP-like immunoreactivity in cortical cells, based upon immunocytochemistry using an antiserum directed against other sequences of SP. In addition, we show that there are two populations of putative SP cortical neurons. In one, SP immunoreactivity is colocalized with that for gamma aminobutyric acid (GABA), in the other with immunoreactivity for neuropeptide Y (NPY) and somatostatin (SRIF). Furthermore, in the monkey visual cortex, SP and GABA levels are regulated by visual experience [5].