Cocaine and exercise: α-1 receptor blockade does not alter muscle glycogenolysis or blood lactacidosis

Robert K. Conlee, K. Patrick Kelly, Edward O. Ojuka, Roger L. Hammer

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

In our previous work, we routinely observed that a combined cocaine- exercise challenge results in an abnormally rapid muscle glycogen depletion and excessive blood lactacidosis. These phenomena occur simultaneously with a rapid rise in norepinephrine and in the absence of any rise in epinephrine. We postulated that norepinephrine may cause vasoconstriction of the muscle vasculature through activation of α-1 receptors during cocaine-exercise, thus inducing hypoxia and a concomitant rise in glycogenolysis and lactate accumulation. To test this hypothesis, rats were pretreated with the selective α-1-receptor antagonist prazosin (P) (0.1 mg/kg iv) or saline (S). Ten minutes later, the animals were treated with cocaine (-C) (5 mg/kg iv) or saline (-S) and run for 4 or 15 min at 22 m/min at 10% grade. In the S-S group, glycogen content of the white vastus lateralis muscle was unaffected by exercise at both time intervals, whereas in S-C rats glycogen was reduced by 47%. This effect of cocaine-exercise challenge was not attenuated by P. Similarly, blood lactate concentration in S-C rats was threefold higher than that of S-S after exercise, a response also not altered by pretreatment with P. On the basis of these observations, we conclude that the excessive glycogenolysis and lactacidosis observed during cocaine-exercise challenge is not the result of vasoconstriction secondary to norepinephrine activation of α-1 receptors.

Original languageEnglish
Pages (from-to)77-81
Number of pages5
JournalJournal of Applied Physiology
Volume88
Issue number1
DOIs
StatePublished - Jan 2000
Externally publishedYes

Keywords

  • Carbohydrate metabolism
  • Prazosin

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