Tachykinin-induced changes in beta-endorphin gene expression in the rat arcuate nucleus.

Previous neuroanatomical data have indicated the presence of synaptic connections between tachykinergic terminals and proopiomelanocortin (POMC) neurons in the arcuate nucleus. Consequently, tachykinins may regulate the activity of POMC neurons. To evaluate the functional signification of this regulation, the effect of intracerebroventricular injections of neurokinin A (NKA) on POMC mRNA levels was studied by using in situ hybridization. Repeated injection of NKA (40 micrograms/animal per day during 3 days) induced a 48% increase in POMC mRNA expression as compared to NaCl injected control animals. In conclusion the results of this study show an excitatory effect of tachykinin on POMC neurons and suggest a direct and/or indirect excitatory control of POMC neuronal activity by endogenous tachykinins.