title: The H3 antagonist, ciproxifan, alleviates the memory impairment but enhances the motor effects of MK-801 (dizocilpine) in rats.
abstract: Antagonists of H(3)-type histamine receptors exhibit cognitive-enhancing properties in various memory paradigms as well as evidence of antipsychotic activity in normal animals. The present study determined if a prototypical H(3) antagonist, ciproxifan, could reverse the behavioral effects of MK-801, a drug used in animals to mimic the hypoglutamatergic state suspected to exist in schizophrenia. Four behaviors were chosen for study, locomotor activity, ataxia, prepulse inhibition (PPI), and delayed spatial alternation, since their modification by dizocilpine (MK-801) has been well characterized. Adult male Long-Evans rats were tested after receiving a subcutaneous injection of ciproxifan or vehicle followed 20 min later by a subcutaneous injection of MK-801 or vehicle. Three doses of MK-801 (0.05, 0.1, & 0.3 mg/kg) increased locomotor activity. Each dose of ciproxifan (1.0 & 3.0 mg/kg) enhanced the effect of the moderate dose of MK-801, but suppressed the effect of the high dose. Ciproxifan (3.0 mg/kg) enhanced the effects of MK-801 (0.1 & 0.3 mg/kg) on fine movements and ataxia. Deficits in PPI were observed after treatment with MK-801 (0.05 & 0.1 mg/kg), but ciproxifan did not alter these effects. Delayed spatial alternation was significantly impaired by MK-801 (0.1 mg/kg) at a longer delay, and ciproxifan (3.0 mg/kg) alleviated this impairment. These results indicate that some H(3) antagonists can alleviate the impact of NMDA receptor hypofunction on some forms of memory, but may exacerbate its effect on other behaviors.
authors.affiliation: Department of Psychological Science, Northern Kentucky University, 1 Nunn Drive, Highland Heights, KY 41076, USA. bardgettm@nku.edu
authors.forename: Mark E
authors.initials: ME
authors.lastname: Bardgett
authors.forename: Megan
authors.initials: M
authors.lastname: Points
authors.forename: Jennifer
authors.initials: J
authors.lastname: Kleier
authors.forename: Meredith
authors.initials: M
authors.lastname: Blankenship
authors.forename: Molly S
authors.initials: MS
authors.lastname: Griffith
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D054828:Histamine H3 Antagonists / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology*; D008297:Male; D008568:Memory / Q000187:drug effects*; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D020318:Rats, Long-Evans; D013216:Reflex, Startle / Q000187:drug effects; D055139:Sensory Gating / Q000187:drug effects
chemical_list: D018691:Excitatory Amino Acid Antagonists; D054828:Histamine H3 Antagonists; D007093:Imidazoles; C115705:ciproxifan; D016291:Dizocilpine Maleate