ORIGINAL PAPER The Selective Inhibition of the D 1 Dopamine Receptor Results in an Increase of Metabolized Dopamine in the Rat Striatum A. Bueno-Nava • R. Gonzalez-Pina • A. Alfaro-Rodriguez • A. Avila-Luna • E. Arch-Tirado • M. Alonso-Spilsbury Received: 1 December 2011 / Revised: 14 April 2012 / Accepted: 27 April 2012 / Published online: 10 May 2012 Ó Springer Science+Business Media, LLC 2012 Abstract Our aim was to study the specific role of the postsynaptic D 1 receptors on dopaminergic response and analyze the metabolized dopamine (DA) in the rat striatum. We used male Wistar rats to evaluate the effects of different doses of a D 1 agonist (SKF-38393) and a D 1 antagonist (SCH-23390), and their co-administration. The levels of DA and L-3, 4-dihydroxyphenylacetic acid (DOPAC) were measured using high performance liquid chromatography. The systemic injection of SKF-38393 alone at 1, 5 and 10 mg/kg did not alter the DA and DOPAC levels or the DOPAC/DA ratio. In contrast, injection of SCH-23390 alone at 0.25, 0.5 and 1 mg/kg significantly increased the DA and DOPAC levels, as well as the DOPAC/DA ratio, compared with the respective control groups. The co-administration of SCH-23390?SKF-38393 did not alter the DA or DOPAC levels, but it did significantly inhibit the SCH-23390- induced increase of the DA and DOPAC levels. The SCH-23390?SKF-38393 and the SCH-23390-only groups showed an increase in the DOPAC/DA ratio. The co-administration of SCH-23390?PARGYLINE significantly decreased the DOPAC levels and the DOPAC/DA ratio com- pared with the control and SCH-23390 groups. Taken together, our results showed that selective inhibition with SCH-23390 produced an increase in metabolized DA via striatal monoamine oxidase. These findings also contribute to the understanding of the role of postsynaptic D 1 receptors in the long-loop negative feedback system in the rat striatum. Keywords Dopamine Á Dopaminergic system Á Monoamine oxidase Á Striatum Á Rat Introduction The basal ganglia are associated with motor control [1]. Alterations in basal ganglia circuit function are manifested by unwanted movements [2]. The basal ganglia includes the striatum and the substantia nigra pars compacta (SNc). The striatum receives afferent input from the SNc [3]. Previous studies have indicated that D 2 receptors, but not A. Bueno-Nava Doctorate Program in Biological Sciences, Universidad Auto ´noma Metropolitana Iztapalapa-Xochimilco, Calzada del Hueso 1100, Col Villa Quietud D.F. 04960, Mexico A. Bueno-Nava (&) Laboratorio de Cromatografı ´a y Microdia ´lisis, Departamento de Neurorrehabilitacio ´n, Instituto Nacional de Rehabilitacio ´n, SSA, Calz. Me ´xico-Xochimilco 289, Col. Arenal de Guadalupe Deleg. Tlalpan, Mexico City C.P. 14389, Mexico e-mail: abueno@inr.gob.mx A. Bueno-Nava Á A. Alfaro-Rodriguez Á A. Avila-Luna Laboratorio de Neuroquı ´mica, Departamento de Neurorrehabilitacio ´n, Instituto Nacional de Rehabilitacio ´n, SSA, Mexico city, Mexico R. Gonzalez-Pina Laboratorio de Neuroplasticidad, Departamento de Neurorrehabilitacio ´n, Instituto Nacional de Rehabilitacio ´n, SSA, Mexico city, Mexico E. Arch-Tirado Laboratorio de Bioacu ´stica, Departamento de Neurorrehabilitacio ´n, Instituto Nacional de Rehabilitacio ´n, SSA, Mexico city, Mexico M. Alonso-Spilsbury Departamento de Produccio ´n Agrı ´cola y Animal, Universidad Auto ´noma Metropolitana-Xochimilco, Calzada del Hueso 1100, Col. Villa Quietud D.F. 04960, Mexico 123 Neurochem Res (2012) 37:1783–1789 DOI 10.1007/s11064-012-0790-5