INTERACTION BETWEEN NEUROTENSIN AND NEURONAL SODIUM/POTASSIUM-ATPase. MODULATION BY ANTIPSYCHOTIC AGENTS

G. RODRÍGUEZ DE LORES ARNAIZ; C. G. ROSIN ; M. G. LÓPEZ ORDIERES

St. Louis, Missouri

Congreso; XXXXII Congreso de la Sociedad Americana de Neuroquímica (ASN); 2011

Sociedad Americana de Neuroquímica (ASN)

Interaction between neurotensin and neuronal sodium/potassium-ATPase. Modulation by antipsychotic agents Rodríguez de Lores Arnaiz, G.1,2, Rosin, C.1,2, López Ordieres, M.G.1,2 1 Inst Biol Cel y Neuroc “Prof. E. De Robertis”, CONICET-UBA, Fac Med, Universidad de    Buenos Aires, Buenos Aires, Argentina 2 Cátedra de Farmacol, Fac Farm y Bioq, UBA. Paraguay 2155, 1121-Buenos Aires, Argentina Diverse evidences indicate the relationship between neurotensinergic and dopaminergic systems. Neurotensin inhibits synaptosomal membrane sodium/potassium-ATPase activity, an effect blocked by SR 48692, antagonist of neurotensin receptor NTS1 type. Assays of high affinity [3H]-ouabain binding (to analyze potassium site of sodium/potassium-ATPase) showed that in vitro addition of neurotensin decreases binding. Administration of typical antipsychotic haloperidol (antagonist for D2 dopaminergic receptor), prevents neurotensin inhibitory action on the enzyme. Herein  potential interaction between high affinity neurotensin receptor (NTS1), D2 dopaminegic and sodium/potassium-ATPase activitywas studied. Wistar rats were administered with neurotensin (3, 10 y 30 µg, i.c.v.) and 60 min later, animals were sacrificed, cerebral cortices harvested and processed to obtain membrane fraccions for [3H]-ouabain binding assays. Results showed a statistically significant decrease in binding with the 30 µg neurotensin dose. To analyze the participation of D2 dopaminegic receptors in [3H]-ouabain binding inhibition by neurotensin, rats were administered i.p. with antipsychotic drugs haloperidol (2 mg/kg) and clozapine (3,10 and 30 mg/kg). Animals were sacrificed 18 hours later, cerebral cortices harvested, membrane fractions prepared and [3H]-ouabain binding assayed in the absence and presence of neurotensin at 10 micromolar concentration. No differences versus controls for basal binding or for binding inhibition by neurotensin were recorded. To analyze the interaction between dopaminergic D2 and NTS1 receptors, [3H]-neurotensin binding to cortical membranes from rat injected with haloperidol (2 mg / kg, i.p) was assayed. Saturation curves and Scatchard transformation showed an increase (roughly five times) in both Bmax and Kd. Taking into account that sodium/potassium-ATPase activity is modified by catecholamines, assays were carried out in the presence of dopamine and / or SR 48692. Results confirmed 32% enzyme inhibition with dopamine at micromolar concentration. This effect remained unaltered by SR 48692, indicating that NTS1 was not involved. It is postulated that D2 dopaminegic receptors are involved in neurotensin binding to its NTS1 receptor but not in peptide effect on potassium site of sodium/potassium-ATPase.