Repeated limited access to i.v. cocaine self-administration: conditioned autonomic rhythmicity illustrating "predictive homeostasis".
BACKGROUND
Regular cocaine self-administration may act as a "Zeitgeber" in animals and humans, and physiological rhythms may peak at the time when the drug is usually self-administered.


OBJECTIVE
To investigate whether or not daily sessions of cocaine self-administration for 2 weeks would synchronize autonomic rhythms to the time of daily access.


METHODS
Two weeks after implant of a jugular catheter and telemetry sender, each rat's heart-rate (HR) and core temperature (Tc) rhythms were well entrained to the 12:12-h light:dark cycle (lights off: 0900 hours). For the next 2 weeks rats self-administered cocaine during daily sessions at 1300 hours. The circadian and ultradian oscillations of HR and Tc recorded during the 3 days after the last self-administration (SA) session were quantified by multi-oscillator cosinor analysis.


RESULTS
The HR and Tc were elevated during the initial 0.25 mg cocaine infusions of the daily session. This initial tachycardia disappeared as cocaine continued to be self-administered in accumulating amounts, while the locomotor activity remained elevated. After the last SA session the peak (acrophase) of the two cycles/day component in HR and Tc rhythms aligned to the time of day when cocaine self-administration had previously been scheduled. The amplitude of the circadian and ultradian HR and Tc oscillations as well as their circadian acrophase were not impacted by repeated daily time-limited cocaine self-administration.


CONCLUSIONS
Cocaine controls the behavior and autonomic functions of rats self-administering limited amounts of cocaine during regular daily sessions, and this controlling influence extends beyond the last daily access period.
Tornatzky
W
W
Department of Psychology, Tufts University, Medford, Massachusetts 02155, USA.
Miczek
K A
KA
D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D002940:Circadian Rhythm / Q000187:drug effects*; D003042:Cocaine / Q000008:administration & dosage*; D006339:Heart Rate / Q000187:drug effects*; D006706:Homeostasis; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D020318:Rats, Long-Evans; D012646:Self Administration
D003042:Cocaine