title: Psychostimulants and G tolerance in rhesus monkeys: effects of oral modafinil and injected caffeine.
abstract: BACKGROUND
  Caffeine and modafinil are psychostimulants that may be taken by fighter aircraft pilots to reduce fatigue. Fighter pilots are subjected to high positive G loads that reduce cerebral blood flow and consequently may induce G-LOC. The aim of the experiment was to determine whether these drugs may reduce tolerance to G stress.
  
  
  METHODS
  Seven adult male rhesus monkeys participated in the experiment. Five were equipped with ECoG and ECG wires and underwent two G tests (A and B). Each experiment consisted of five centrifuge runs. Before the runs, the monkeys received no drug (control) or were given either 7.5 mg x kg(-1) caffeine IM or 64 mg x kg(-1) modafinil PO or the corresponding vehicles. The runs were performed up to +13 Gz with an onset rate of 0.1 G x s(-1) (test A) or 3 G x s(-1) (test B). The run was ended when the electrical activity of one ECoG channel had disappeared (i.e., G-LOC).
  
  
  RESULTS
  In experiment A, drug administration had no significant effect. In experiment B, the injection of the caffeine-free solvent caused a delay in G-LOC compared with the control condition (no administration). Caffeine solvent also induced an increase in plasma osmolality.
  
  
  CONCLUSIONS
  Modafinil administration has no significant effect on the G tolerance of rhesus monkeys. Regarding caffeine, the drug seems to have caused the reverse effect compared with the solvent.
  
  
  CONCLUSIONS
  Caffeine and modafinil administration had no significant effect on the G-tolerance of rhesus monkeys when compared with controls. This result needs to be confirmed in humans.
authors.affiliation: Institut de Medecine Aerospatiale du Service de Santé des Armees, Brétigny sur Orge, France. gflorence@imassa.fr
authors.forename: Geneviève
authors.initials: G
authors.lastname: Florence
authors.forename: Laurent
authors.initials: L
authors.lastname: Riondet
authors.forename: André
authors.initials: A
authors.lastname: Serra
authors.forename: Xavier
authors.initials: X
authors.lastname: Etienne
authors.forename: Bruno
authors.initials: B
authors.lastname: Huart
authors.forename: Pascal
authors.initials: P
authors.lastname: van Beers
authors.forename: Dominique
authors.initials: D
authors.lastname: Bonneau
authors.forename: Danièle
authors.initials: D
authors.lastname: Gomez-Merino
authors.forename: Catherine
authors.initials: C
authors.lastname: Drogou
authors.forename: Pascal
authors.initials: P
authors.lastname: Pradeau
mesh_terms: D000054:Acceleration; D000337:Aerospace Medicine; D000818:Animals; D001559:Benzhydryl Compounds / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002498:Centrifugation; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology; D004569:Electroencephalography; D004585:Electrooculography; D005221:Fatigue / Q000209:etiology / Q000517:prevention & control*; D018471:Hypergravity; D008253:Macaca mulatta; D008297:Male; D000077408:Modafinil; D018709:Statistics, Nonparametric; D014474:Unconsciousness / Q000209:etiology / Q000517:prevention & control*
chemical_list: D001559:Benzhydryl Compounds; D000697:Central Nervous System Stimulants; D002110:Caffeine; D000077408:Modafinil