Effects of self-administered cocaine on plasma adrenocorticotropic hormone and cortisol in male rhesus monkeys.
This study was designed to examine the effects of self-administered cocaine on hypothalamic-pituitary-adrenal (HPA) axis activity in rhesus monkeys. Initially, basal release of cortisol and adrenocorticotropic hormone (ACTH) was measured in singly housed male and female monkeys (n = 9) over a 24-h period using plasma samples obtained from indwelling venous catheters. Basal cortisol and ACTH levels in both male and female rhesus monkeys demonstrated a circadian pattern of release, with peak levels for cortisol (19.60 +/- 2.16 microgram/dl) and ACTH (19.63 +/- 2.56 pg/ml) measured at 6:00 AM. The nadir for ACTH (6.27 +/- 0.62 pg/ml) occurred at 6:00 PM, preceding the cortisol nadir (5.55 +/- 1.21 microgram/dl) at 9:00 PM. The reinforcing effects of saline, 0.01, 0.03, 0.1, and 0.3 mg/kg/injection cocaine were then evaluated using a fixed-ratio 30, time-out 10-min schedule of reinforcement in seven male monkeys. Blood was sampled before, during, and after self-administration sessions. Self-administration of cocaine produced dose-dependent increases in cortisol and ACTH. One dose of cocaine (0.03 mg/kg/injection), although reliably self-administered, did not produce a significant increase in HPA axis activity. These results indicate that although cocaine dose-dependently increases HPA axis activity, the HPA effect is more likely a consequence of overall cocaine intake than it is an indicator of cocaine doses that are sufficient to maintain self-administration behavior.
Broadbear
J H
JH
Department of Psychology, University of Michigan Medical School, Ann Arbor, Michigan, USA. jillianb@umich.edu
Winger
G
G
Cicero
T J
TJ
Woods
J H
JH
D000324:Adrenocorticotropic Hormone / Q000097:blood* / Q000378:metabolism; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003042:Cocaine / Q000008:administration & dosage* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology; D012646:Self Administration; D012727:Sex Characteristics; D013997:Time Factors
D000324:Adrenocorticotropic Hormone; D003042:Cocaine; D006854:Hydrocortisone