Comparison of the Distributions of Neuropeptide Y-, Tyrosine Hydroxylase-, and Tryptophan Hydroxylase-Expressing Neurons in the Hypothalamic Arcuate Nucleus

Abstract

Several levels of interactions between serotonin and neuropeptide Y (NPY) have been proposed in the hypothalamic control of food intake. This study aimed at elucidating the anatomical relationship between the NPY-expressing neurons and the newly characterized neuronal population of tryptophan hydroxylase (TpH)-expressing (serotonin synthesizing enzyme) neurons in the hypothalamic arcuate nucleus. In addition, their distribution was compared to that of tyrosine hydroxylase (TH), the dopamine synthesizing enzyme. No co-localization of NPY and TpH, or NPY and TH was found in the arcuate nucleus either in intact or in colchicine-treated animals. These results suggest that there is likely no functional co-transmission between these transmitter systems in an intact arcuate nucleus.

Keywords:

• Serotonin
• Neuropeptide Y
• Tyrosine hydroxylase
• Tryptophan hydroxylase
• Hypothalamus
• Arcuate nucleus