NK1 receptor expression by cholinergic interneurones in human striatum

Neurokinin-1 (NK1) receptor expression in human striatum was analysed using the polymerase chain reaction. To determine whether cholinergic interneurones express this receptor, in situ hybridization histochemistry was then applied to caudate nucleus and putamen. Radioactive oligonucleotide probes specific for choline acetyltransferase (ChAT) and NK1 receptor mRNA were used on adjacent cryostat sections. All of the 160 identified neurones positive for ChAT were also labelled for NK1 receptor. Moreover, in the caudate nucleus, NK1 receptor mRNA was detected in a population of large neurones that were not cholinergic. These results are consistent with the hypothesis that NK1 receptor-mediated mechanisms are involved in the function of cholinergic interneurones. This might be relevant to pharmacological or pathophysiological situations where substance P inputs are modified.