title: SR146131, a cholecystokinin-A receptor agonist, antagonizes prepulse inhibition deficits produced by dizocilpine and DOI.
abstract: BACKGROUND
  Converging evidence has demonstrated that cholecystokinin (CCK) inhibits mesolimbic brain dopamine (DA) function via activation of CCK-A (CCK-1) receptors. These effects of CCK have stimulated interest in the potential use of CCK agonists as antipsychotic drugs. Most research on the antipsychotic-like drug effects of CCK has used CCK or CCK analogues that nonselectively activate both CCK-A and CCK-B (CCK-2) receptors, which may produce opposite effects. SR146131, a CCK-A selective nonpeptide agonist, has recently been developed (Sanofi-Synthelabo).
  
  
  OBJECTIVE
  To determine whether SR146131 exhibits antipsychotic-like qualities in the prepulse inhibition (PPI) paradigm.
  
  
  METHODS
  We performed experiments to determine whether SR146131 (vehicle, 0.01, 0.1, 1.0 mg/kg) would attenuate PPI deficits induced by amphetamine (2.0 mg/kg), an indirect dopamine agonist, and dizocilpine (0.1 mg/kg), a noncompetitive N-methyl-D-aspartate (NMDA) antagonist. Since SR146131 demonstrated significant effects on PPI disrupted by the noncompetitive NMDA antagonist, an effect associated with drugs that inhibit serotonin (5HT)2A transmission, we also tested the effects of SR146131 on PPI disruption produced by 2,5-dimethoxy-4-iodoamphetamine (DOI, 0.5 mg/kg), a direct 5HT2A agonist.
  
  
  RESULTS
  SR146131 did not significantly affect startle magnitude, baseline PPI, or amphetamine-induced PPI deficits. However, it dose-dependently antagonized dizocilpine and DOI-induced PPI deficits.
  
  
  CONCLUSIONS
  The lack of an effect of SR146131 on amphetamine-induced disruption of PPI suggests that a selective nonpeptide CCK-A agonist may not produce antipsychotic-like effects on dopamine transmission. However, the unexpected effects of SR146131 on dizocilpine and DOI-induced PPI deficits are consistent with the effects of drugs that inhibit transmission in the 5HT2A receptor system, including atypical antipsychotic drugs. Possible mechanisms underlying these findings are discussed.
authors.affiliation: Department of Psychiatry, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Shilling
authors.forename: D
authors.initials: D
authors.lastname: Feifel
mesh_terms: D000661:Amphetamine / Q000009:adverse effects; D000662:Amphetamines / Q000009:adverse effects; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000009:adverse effects; D016291:Dizocilpine Maleate / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000009:adverse effects; D007211:Indoles / Q000494:pharmacology*; D007266:Inhibition, Psychological; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D011949:Receptors, Cholecystokinin / Q000037:antagonists & inhibitors*; D013216:Reflex, Startle / Q000187:drug effects* / Q000502:physiology; D013844:Thiazoles / Q000494:pharmacology*
chemical_list: D000662:Amphetamines; D000697:Central Nervous System Stimulants; D018691:Excitatory Amino Acid Antagonists; D007211:Indoles; D011949:Receptors, Cholecystokinin; C118846:SR 146131; D013844:Thiazoles; C041336:4-iodoamphetamine; D016291:Dizocilpine Maleate; D000661:Amphetamine