Methohexital and cocaine self-administration under fixed-ratio and second-order schedules

D. J. Spear, Carles Muntaner, Steven R. Goldberg, Jonathan L. Katz

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


Behavior maintained by either cocaine or methohexital was compared under two different schedules of drug delivery. Under a fixed-ratio 10 schedule, each tenth response produce an injection and responding was characterized by pauses alternating with high rates that were sustained until the drug injection. Under a second-order schedule, each tenth response produceda brief visual stimulus, and the first sequence of ten responses emitted after the lapse of a ten-minute interval produced the stimulus and the drug injection. Responding under the second-order schedule was characterized by an overall positive acceleration in responding that consistent of fixed-ratio response patterns terminating in the presentation of a brief stimulus. Under either schedule, each drug maintained maximal rates of responding at intermediate doses. In most respect, rates and patterns of responding depended more on the schedule of drug delivery than on the particular drug maintaining responding.

Original languageEnglish
Pages (from-to)411-416
Number of pages6
JournalPharmacology, Biochemistry and Behavior
Issue number2
Publication statusPublished - 1991 Feb


  • Cocaine
  • Fixed-ratio schedule
  • Methohexital
  • Second-order schedule
  • Self-administration
  • Squirrel monkey

ASJC Scopus subject areas

  • Biochemistry
  • Toxicology
  • Pharmacology
  • Clinical Biochemistry
  • Biological Psychiatry
  • Behavioral Neuroscience


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