Grant Number: 5R01DA016589-04
Project Title: Transitional States in Drug Addiction
PI Information: RESEARCH ASSOCIATE PROFESSOR, LEONARD L. HOWELL,  leonard@rmy.emory.edu 

Abstract: DESCRIPTION (provided by applicant):
The progression of drug addiction in humans typically involves a transition from casual, recreational drug use to compulsive drug use that leads to serious adverse consequences. Hence, the frequency and pattern of drug use changes as a function of drug history. The proposed studies will utilize i.v. drug self-administration protocols in rhesus monkeys to identify critical behavioral endpoints indicative of transitional states in drug addiction. Efforts will focus on the importance of response-contingent drug history and drug-related environmental stimuli. Subjects will be exposed to a limited-access condition designed to incorporate features of recreational drug use in humans, followed by a binge period with increased duration of access and marked elevations in drug intake. Changes in the pattern and frequency of drug intake during the limited-access and binge conditions will be a major focus (Specific Aim 1). Reinstatement of drug-seeking behavior by cocaine priming injections and drug-paired stimuli will provide another objective behavioral measure indicative of transitional states in drug use (Specific Aim 2). Parallel studies will utilize in vivo microdialysis in awake subjects to characterize functional changes in monoamine neurochemistry associated with the behavioral changes observed (Specific Aim 3). In addition, positron emission tomography will document the pattern of drug-induced brain activation at different transitional states observed in behavioral and neurochemical studies (Specific Aim 4). Brain tissue obtained at different transitional states will be assayed for gene expression profiles and protein products, providing relevant molecular markers to complement in vivo functional measures in a nonhuman primate model of drug use (Specific Aim 5). These integrated efforts, including behavioral and mechanistic approaches, will provide a comprehensive analysis to elucidate transitional states in cocaine addiction.

Thesaurus Terms:
cocaine, drug addiction, pathologic process, psychopathology, substance abuse related behavior biomarker, brain, craving, gene expression, intravenous administration, neurochemistry, neuropathology, neurophysiology, self medication, stimulus /response Macaca mulatta, behavior test, behavioral /social science research tag, microdialysis, positron emission tomography

Institution: EMORY UNIVERSITY
1599 CLIFTON ROAD, 4TH FLOOR
ATLANTA, GA 30322
Fiscal Year: 2006
Department: PSYCHIATRY AND BEHAVIORAL SCIS
Project Start: 01-SEP-2003
Project End: 31-MAY-2008
ICD: NATIONAL INSTITUTE ON DRUG ABUSE
IRG: ZRG1

Neuropsychopharmacology (2006) 31, 585–593. doi:10.1038/sj.npp.1300828; published online 27 July 2005

Preclinical Research
Olanzapine-Induced Suppression of Cocaine Self-Administration in Rhesus Monkeys

Leonard L Howell^1,2, Kristin M Wilcox¹, Kimberly P Lindsey¹ and Heather L Kimmel<sup>1

1</sup>Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA ²Department of Psychiatry and Behavioral Sciences, Emory University, Atlanta, GA, USA

MATERIALS AND METHODS

General Methods
Subjects

Six female and four male adult rhesus monkeys (Macaca mulatta) weighing 7.5–13.0 kg were used as subjects. Each subject was housed individually and fed Purina monkey chow, fruits, and vegetables. Water was continuously available. Animal care procedures strictly followed the NIH 'Guide for the Care and Use of Laboratory Animals' and were approved by the Institutional Animal Care and Use Committee of Emory University.

Surgery
Each subject was prepared with a chronic indwelling venous catheter under sterile surgical conditions using a technique described previously (Wilcox et al, 2002). Preoperative antibiotics (Rocephin, 25 mg/kg or Cefazolin, 25 mg/kg) were given on the day of surgery to help prevent infection. A silicone catheter (0.65 mm ID, 1.75 mm OD; Access Technologies, Skokie, IL) was implanted under a combination of Telazol (4.0 mg/kg) and isoflurane anesthesia using aseptic techniques. The proximal end of the catheter terminated in the vena cava above the right atrium, and the distal end was routed under the skin and attached to a subcutaneous vascular access port (Access Technologies, Skokie, IL) located in the center of the lower back. After surgery, the subject was returned to its home cage and received Banamine (1.0 mg/kg) every 6 h for 24 h postoperatively to reduce pain and discomfort associated with surgery. Catheters were flushed daily with 100 U/ml heparinized saline to maintain patency. In experiments involving in vivo microdialysis, guide cannulae were implanted bilaterally into the caudate nucleus under sterile conditions. The positioning of the guide cannulae allowed for targeting of the ventral striatum corresponding to the nucleus accumbens. Preoperative antibiotics (Rocephin, 25 mg/kg) were given on the day of surgery to help prevent infection. The animals were sedated with Telazol (4.0 mg/kg) and maintained on isoflurane anesthesia during the surgery. The subjects were positioned in a stereotaxic frame, and coordinates derived from MRI were used for accurate probe placement. A trephine drill was used to make two small burr holes directly above the ventral striatum, and the guide cannulae were inserted to the appropriate depth. Teflon screws attached to the skull were used to anchor cranioplastic cement, and the guide cannulae were enclosed within a small plastic chamber to prevent access by the monkeys. Stainless-steel stylets were placed in the guide cannulae when not in use. Monkeys were allowed to recover from surgery for 2 weeks before initiating microdialysis experiments. All animals received Banamine (1.0 mg/kg) every 6 for 24 h postoperatively, or longer if they exhibited signs of discomfort.

Drugs
Cocaine HCl (National Institute on Drug Abuse, Rockville, MD) and fluoxetine HCl (Eli Lilly and Company) were dissolved in 0.9% saline. Drug doses were determined as salts. Olanzapine (Eli Lilly and Company) was dissolved in 0.01 N HCl and diluted with distilled water to appropriate concentrations.
 
BEHAVIORAL METHODS
During behavioral testing, each monkey was seated in a commercially available primate chair (Primate Products, Redwood City, CA, USA), and a response panel with one lever was mounted on the front of chair. Located above the lever in the center of the response panel were red and white stimulus lights. Once the monkey was seated in the chair, a Huber needle (Access Technologies, Skokie, IL) was inserted into the venous access port. The polyvinyl-chloride tubing attached to the Huber needle was connected to a motor-driven syringe (Coulbourn Instruments, Allentown, PA) located outside of the chamber containing the drug solution. A volume of 2.0 ml/infusion was delivered over 7 s. Testing during daily 1-h sessions occurred in a ventilated, sound-attenuating chamber. IBM compatible computers controlled experimental events and recorded data.
Subjects responded for i.v. infusions of cocaine under a second-order schedule of reinforcement, as described previously (Wilcox et al, 2002). The training dose of cocaine was 0.1 mg/kg/infusion. When the daily session began, the red light on the response panel was illuminated and responding resulted in the delivery of a drug infusion and brief 2-s illumination of the white light. Initially, the fixed ratio (FR) was one (FR 1) and gradually increased to FR 20. Ultimately, a second-order schedule of reinforcement was in effect, with the first FR 20 completed after 10 min (fixed-interval, FI 10) resulting in a drug infusion. FR 20 components completed within the 10-min FI resulted in illumination of the white light for 2 s. There was a 30-s limited hold for completion of the first FR 20 after the FI 10 had elapsed, and a drug infusion was not delivered if the limited hold expired. Drug infusions were signaled by a change in the lights from red to white for 15 s. Following each drug infusion there was a 1-min timeout during which responding on the lever had no programmed consequences. A total of five infusions could be delivered during a daily session comprising five FI 10-min (FR 20:s) components.

The training sequence remained in effect until responding for cocaine was stable (<20% variance in daily response rate over five consecutive days), after which saline was substituted for cocaine until responding decreased to below 30% of responding for the training dose of cocaine. After saline extinction, the maintenance dose (0.1 mg/kg/infusion) of cocaine was reinstated and responding was allowed to stabilize. For pretreatment studies, a given dose of drug was administered i.v. 15 min presession on three consecutive days, typically Tuesday, Wednesday, and Thursday. Vehicle was administered on all days that subjects did not receive a drug pretreatment, and these data contributed to ongoing calculations of baseline stability. Pretreatment doses were administered on two separate occasions in an ascending order. All doses of a particular drug were studied in combination with 0.1 mg/kg/infusion cocaine first. Subsequently, the maintenance dose of cocaine was changed to 0.3 mg/kg/infusion, and drug pretreatments were repeated as described above. For drug-substitution studies, each subject was allowed to self-administer several doses of olanzapine in a randomized order. Substitution for each drug dose continued for at least five consecutive sessions, or until responding stabilized (<20% variance in daily response rate).