title: Multidrug-resistance gene 1-type p-glycoprotein (MDR1 p-gp) inhibition by tariquidar impacts on neuroendocrine and behavioral processing of stress.
abstract: The multidrug-resistance gene 1-type p-glycoprotein (MDR1 p-gp) is a major gate-keeper at the blood-brain barrier (BBB), protecting the central nervous system from accumulation of toxic xenobiotics and drugs. In addition, MDR1 p-gp has been found to control the intracerebral access of glucocorticoid hormones and thus to modulate the activity of the hypothalamic-pituitary-adrenocortical (HPA) system. In view of the implication of glucocorticoids in the control of behavior, we examined how acute pharmacological inhibition of MDR1 p-gp at the BBB by tariquidar (XR9576; 12 mg/kg, PO) impacts the neuroendocrine and behavioral processing of stress in C57BL/6JIcoHim inbred mice. Inhibition of MDR1 p-gp at the BBB did not alter emotional behavior at baseline. However, mice that were sensitized by water-avoidance stress, a mild psychological stressor, displayed significantly reduced anxiety-related behavior in the elevated plus-maze test when treated with tariquidar. Tariquidar, however, had no effect on stress-coping performance assessed in the forced swim test. Investigating the impact of acute MDR1 p-gp inhibition on the glucocorticoid system, we observed a significant attenuation of the mild stress-induced increase of plasma corticosterone after tariquidar administration. In order to examine whether the anti-anxiety effect of tariquidar in sensitized animals is mediated by glucocorticoids, the animals were treated with corticosterone (1mg/kg, SC) immediately after exposure to water-avoidance stress. Corticosterone caused a significant anxiolytic-like effect in this stress-related anxiety protocol, whereas tariquidar could not further enhance corticosterone's anti-anxiety effects. The current data show for the first time that pharmacological inhibition of MDR1 p-gp at the murine BBB by tariquidar alters emotional behavior and HPA axis activity. By facilitating the entry of corticosterone into the brain, tariquidar enhances feedback inhibition of the HPA system and in this way improves anxiety-related stress processing. These findings highlight a novel approach to the treatment of stress-related affective disorders in humans.
authors: Research Unit of Translational Neurogastroenterology, Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz 8010, Austria. thoeringer@mpipsykl.mpg.de
authors: Christoph K
authors: CK
authors: Thoeringer
authors: Thomas
authors: T
authors: Wultsch
authors: Anaid
authors: A
authors: Shahbazian
authors: Evelin
authors: E
authors: Painsipp
authors: Peter
authors: P
authors: Holzer
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors*; D000223:Adaptation, Psychological / Q000187:drug effects*; D000818:Animals; D001007:Anxiety / Q000378:metabolism / Q000503:physiopathology; D001362:Avoidance Learning / Q000187:drug effects; D001519:Behavior / Q000187:drug effects*; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology; D003345:Corticosterone / Q000494:pharmacology; D004644:Emotions / Q000187:drug effects; D005938:Glucocorticoids / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009490:Neurosecretory Systems / Q000187:drug effects*; D011804:Quinolines / Q000494:pharmacology*; D013315:Stress, Psychological / Q000378:metabolism / Q000503:physiopathology*; D013550:Swimming
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005938:Glucocorticoids; D011804:Quinolines; C402343:tariquidar; D003345:Corticosterone