Grant Number: 2R01DA010344-10
Project Title: PET Imaging and Cocaine Neuropharmacology in Monkeys
PI Information: RESEARCH ASSOCIATE PROFESSOR, LEONARD L.
HOWELL leonard@rmy.emory.edu 

Abstract: DESCRIPTION (provided by applicant):
The proposed research will characterize interactions between monoamine transporter inhibitors and cocaine in nonhuman primate models of i.v. drug self-administration, neuroimaging with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), and in vivo microdialysis. Emphasis will be directed toward combined inhibition of the dopamine transporter (DAT) and the serotonin transporter (SERT) in the context of cocaine self-administration. A second-order schedule of i.v. drug self-administration in rhesus monkeys will be used to evaluate the effectiveness of combined inhibition of DAT and SERT to reduce cocaine self-administration, and to maintain self-administration when substituted for cocaine (Aim 1). Similarly, extinction conditions will be used to evaluate the effectiveness of combined inhibition of DAT and SERT to attenuate cocaine-induced reinstatement, and to induce reinstatement in the absence of cocaine (Aim 2). PET neuroimaging techniques will be used to quantify DAT and SERT occupancy at drug doses shown to be effective in drug self-administration and reinstatement studies (Aim 3). In addition, in vivo microdialysis techniques will be used to correlate DAT and SERT occupancy measures with drug-induced changes in dopamine, serotonin and their primary metabolites (Aim 4). Lastly, fMRI protocols will be implemented in awake, behaving monkeys in order to characterize functional changes in CNS activity during self- administration of cocaine or selective DAT inhibitors. Studies conducted during the previous funding period documented the effectiveness of selective DAT inhibitors to reduce or eliminate cocaine self-administration, but only at high levels of DAT occupancy. Moreover, selective DAT inhibitors reliably maintained drug self- administration and induced reinstatement of extinguished cocaine self-administration behavior. It is hypothesized that combined inhibition of DAT and SERT will lower the level of DAT occupancy required to reduce cocaine self-administration, and limit the reinforcing and reinstatement effects of DAT inhibitors. It is also hypothesized that selective DAT inhibitors will induce a pattern of brain activation similar to that observed for cocaine. In contrast, combined inhibition of DAT and SERT will limit brain activation induced by cocaine and DAT inhibitors, and by drug-associated stimuli. Collectively, the integration of behavioral pharmacology, functional neuroimaging and in vivo neurochemistry will enhance our understanding of the neurobiological mechanisms involved in cocaine self-administration and reinstatement in nonhuman primates. The results obtained will also evaluate the effectiveness of monoamine transporters as potential targets for cocaine medications development.

Thesaurus Terms:
cocaine, drug abuse, drug abuse chemotherapy, drug addiction antagonist, nonhuman therapy evaluation rain circulation, brain imaging /visualization /scanning, dopamine, dopamine antagonist, dopamine transporter, drug interaction, neuropharmacology, self medication, serotonin, serotonin inhibitor, substance abuse related behavior Macaca mulatta, 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: 15-AUG-1997
Project End: 30-APR-2011
ICD: NATIONAL INSTITUTE ON DRUG ABUSE
IRG: NMB

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).