metabolite homovanillic acid in cerebrospinal fluid. We assessed the striatal presynaptic dopamine function using anatomical MRI and positron emission tomography (HR+ tomograph) with [ 18 F]fluorodopa in right-handed depressed patients selected for psychomotor retardation (n = 6) as compared with depressed patients selected for high impul- siveness (n = 6), and healthy subjects (n = 10). Depressed patients were matched for severity of depression on the MADRS Depression Rating Scale, with scores ranging from 25 to 37. The Depressive Retardation Rating Scale score was higher in retarded depressives than in impulsive depressives (mean  SD: 22  3 vs 12  4; p = 0.006). Impulsivity was defined as scoring 10 on the “loss of control” subscale of the Depressive Mood Scale, and 10 on the Tyrer anxiety scale. Loss of control score was lower in patients with retardation than in impulsive patients (6  4 vs 14  3; p = 0.004); anxiety mean score was lower in patients with retardation than in impulsive patients (14  5 vs 20  3; p = 0.02). While the mean caudate and putamen [ 18 F]fluorodopa uptake constant K i values were similar in patients and controls, the left caudate Ki value in patients with marked psychomotor retardation (113  8  10 -4 ) was significantly lower (p = 0.005) than that in controls (127  7  10 -4 ), and in patients without retardation (146  7  10 -4 ). Impulsive patients did not differ from controls. Thus, a decreased presynaptic dopamine function was found in the left caudate of retarded depressed patients only, providing direct evidence of a link between hypodopaminergia and depressive psychomotor retardation. 367. ASSESSING THE AGE-DEPENDENT PROFILE OF HEALTHY NORMAL CONTROLS USING IN VIVO 31 P MRS J.A. Stanley (1,2), N.J. Minshew (2), M.S. Keshavan (2), K. Panchalingam (1,2), R.J. McClure (1,2), and J.W. Pettegrew (1,2) (1) Neurophysics Laboratory, (2) Department of Psychiatry, Western Psychiatric Institution and Clinic, University of Pittsburgh, Pittsburgh, PA 15261 There is evidence of neurodevelopmental abnormalities in different psychi- atric illnesses, such as schizophrenia. In vivo phosphorus magnetic resonance spectroscopy ( 31 P MRS) is a non-invasive investigative tool that can assess the metabolism of membrane phospholipids and high-energy phosphates from specified, localized regions in the human brain. Consequently, MRS is well suited to assess and monitor neurodevelopmental processes. The purpose of this study is to establish the “normal” age-dependent profile of 31 P metabolite levels in different brain regions. A total of 231 in vivo 31 P MRS examinations were conducted on 151 healthy normal controls (from 7 up to 82 years old). The mole % phosphomonoester (PME), phosphodiester (PDE), phosphocreatine (PCr), adenosine triphosphate (ATP), and inorganic orthophophate (Pi), were measured in the combined right-left frontal lobe (FL) and the centrum semiovale, or white matter (SO-WM). The quantification also included the relatively broad peak underlying the PDE resonance (broad-PDE), which is due to less mobile molecules with PDE moieties (synaptic vesicles). The PME and PCr levels were significantly lower, and the broad-PDE was significantly higher, in the SO-WM compared to the FL. The age-dependent profile show greater changes in the membrane phospho- lipid turnover (PME/PDE) in both the FL and SO-WM (but more pronounced in the SO-WM) of pre-adolescent subjects (20 years old) and possibly synaptic vesicle contribution in SO-WM of pre-adolescent subjects. Likewise, relatively higher utilization of high-energy phos- phates in both FL and SO-WM of pre-adolescent subjects. Likewise, relatively higher utilization of high-energy phosphates in both FL and SO-WM of pre-adolescent subjects. These results show dynamic metab- olite changes with age, which differ between brain region and are important to the basic understanding of normal neurodevelopment. 368. MUSCARINIC 2 RECEPTORS IN COGNITIVELY NORMAL YOUNG AND OLD VOLUNTEERS T.A. Podruchny (1), C.A. Connolly (2), D.O. Kiesewetter (3), R.E. Carson (3), W.C. Eckelman (3), R.M. Cohen (1), T. Sunderland (1) (1) Geriatric Psychiatry Branch, NIMH Intramural Research Program, National Institute of Health, Bethesda, MD 20892; (2) Department of Gerontology, Beth-Israel Deaconess, Harvard Medical School, Boston, MA; (3) NIH PET Department, Warren G. Magnusen Clinical Center, Bethesda, MD 20892 Decreases in nicotinic and muscarinic type 2 (M2) receptors have been noted, at autopsy, in Alzheimer’s Disease, and this decrease correlates with decreases in choline acetyltransferase ( 1 ). This suggests that M2 receptors are presynaptic autoreceptors and that their decrease is related to the loss of acetylcholine neurons ( 1 ). Most radiotracers developed for muscarinic receptors either have inadequate subtype selectivity or do not easily cross the blood brain barrier. The PET Department at NIH recently developed a tracer that binds to M2 receptors in the brain ( 2 ). With the idea that there is selective vulnerability of M2 receptors in Alzheimer’s disease, we are using this tracer to evaluate whether it binds to M2 receptors in humans, cortical and subcortical distribution of receptors, and whether there are differences in binding between different subject populations. Currently, we have used this tracer in 8 younger subjects and 14 older subjects and this data is being analyzed. Our hypotheses are that binding will be seen throughout the cortex with the highest areas of concentration in medial temporal and hippocampal regions and that there will be decreases in receptor density with aging. Future studies will include “at risk” and subjects treated with cholinergic medications to examine markers for drug responsiveness. 1. Auber I, Araujo DM, Cecyre D, Robitaille Y, Gauthier S, Quirion R: Comparative alterations of nicotinic and muscarinic binding sites in Alzheimer’s and Parkinson’s Diseases. J Neurochem 1992;58(2):592–541. 2. Carson RE, Kiesewetter DO, Jagoda E, Der MG, Herscovitch P, Eckelman WC: Muscarinic cholinergic receptor measurements with [18F]FP-TZTP: control and competition studies. J Cerebral Blood Flow and Metabolism 1998;18:1130 –1142. 369. PSYCHOTROPIC DRUG NAIVE AND CURRENTLY TREATED PATIENTS WITH TOURETTE SYNDROME: A [ 123 I]--CIT SPECT-STUDY S.D. Schindler (1), M. Stamenkovic (1), S. Asenbaum (2), A. Neumeister (1), H.N. Aschauer (1), M. Willeit (1), U. Willinger (1), M. de Zwaan (1), S. Kasper (1) (1) Department of General Psychiatry, Div. of Biochem. Psychiatry University Hospital of Psychiatry, Wa ¨hringer Gu ¨rtel 18-20, A-1090 Vienna, Austria; (2) Department of Clinical Neurology, Vienna University Hospital for Neurology Malison et al. (1995) showed in their single photon emission computed tomography (SPECT) study that Tourette Disorder (TD) patients who were treated with antipsychotics (AP) had a higher striatal/occiptal ratio Friday Abstracts 111S BIOL PSYCHIATRY 2000;47:1S–173S