Effects of thyrotropin-releasing hormone on catecholamine concentration in various structures of the rat brain

In an attempt to identify the site of TRH-action in the central nervous system (CNS), we have measured catecholamine levels in discrete brain regions of rats after an intravenous administration of TRH or a long-term intraventricular administration of TRH using Alzet's osmotic minipump. An intravenous administration of 50 micrograms TRH caused a rapid increase in dopamine (DA) concentration in the septal nucleus and then returned to the basal level at 30 min after injection. The concentration of DA in the septal nucleus after the long-term TRH intraventricular administration was also significantly higher than that in the controls. These results indicate that a long-term intraventricular administration of TRH as well as a bolus intravenous injection of TRH may affect the release or metabolism of DA in the septal nucleus.