Acute intraperitoneal injection of caffeine improves endurance exercise performance in association with increasing brain dopamine release during exercise

Pharmacol Biochem Behav. 2014 Jul;122:136-43. doi: 10.1016/j.pbb.2014.03.027. Epub 2014 Apr 12.

Abstract

The purpose of this study was to examine changes of thermoregulation, neurotransmitters in the preoptic area and anterior hypothalamus (PO/AH), which is the thermoregulatory center, and endurance exercise performance after the intraperitoneal injection of caffeine in rats. Core body temperature (Tcore), oxygen consumption (VO₂) and tail skin temperature (Ttail) were measured. A microdialysis probe was inserted in the PO/AH, and samples for the measurements of extracellular dopamine (DA), noradrenaline (NA) and serotonin (5-HT) levels were collected. During the rest experiment, 1 h after baseline collections in the chamber (23 °C), the rats were intraperitoneally injected with saline, or 3 mg kg(-1) or 10 mg kg(-1) caffeine. The duration of the test was 4 h. During the exercise experiment, baseline collections on the treadmill were obtained for 1 h. One hour before the start of exercise, rats were intraperitoneally injected with either 10 mg kg(-1) caffeine (CAF) or saline (SAL). Animals ran until fatigue at a speed of 18 m min(-1), at a 5% grade, on the treadmill in a normal environment (23 °C). At rest, 3 mg kg(-1) caffeine did not influence Tcore, Ttail, VO₂, extracellular DA, NA and 5-HT. 10 mg kg(-1) caffeine caused significant increases in Tcore, VO₂, Ttail and extracellular DA in the PO/AH. In addition, 10 mg kg(-1) caffeine increased the run time to fatigue (SAL: 104.4 ± 30.9 min, CAF: 134.0 ± 31.1 min, p<0.05). The combination of caffeine and exercise increased Tcore, VO₂, Ttail and extracellular DA in the PO/AH. NA increased during exercise, while neither caffeine nor exercise changed 5-HT. These results indicate that caffeine has ergogenic and hyperthermic effects, and these effects may be related to changes of DA release in the brain.

Keywords: Caffeine; Core temperature; Dopamine; Ergogenic effect; PO/AH.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / drug effects*
  • Brain / metabolism*
  • Caffeine / administration & dosage*
  • Cross-Over Studies
  • Dopamine / metabolism*
  • Double-Blind Method
  • Exercise Tolerance / drug effects*
  • Exercise Tolerance / physiology
  • Injections, Intraperitoneal
  • Male
  • Physical Conditioning, Animal / methods*
  • Physical Conditioning, Animal / physiology
  • Random Allocation
  • Rats
  • Rats, Wistar

Substances

  • Caffeine
  • Dopamine