Jerry J. Warsh

Cerebral cortex Gsα protein levels and forskolin-stimulated cyclic AMP formation are increased in bipolar affective disorder

Abstract: Experimental animal and peripheral blood cell studies point to guanine nucleotide regulatory (G) protein disturbances in bipolar affective disorder. We have previously reported elevated prefrontal cortex Gsα protein in bipolar affective disorder and have now extended these preliminary observations in a larger number of subjects, assessing the brain regional specificity of these changes in greater detail, determining the functional biochemical correlates of such changes, and evaluating their diagnostic specificity. Membrane G protein (Gsα, Giα, Goα, and Gβ) immunoreactivities were estimated by western blotting in postmortem brain regions obtained from 10 patients with a DSMIII‐R diagnosis of bipolar affective disorder and 10 nonpsychiatric controls matched on the basis of age, postmortem delay, and brain pH. To examine whether there were functional correlates to the observed elevated Gsα levels, basal and GTPγS‐and forskolin‐stimulated cyclic AMP production was determined in the same brain regions. Compared with controls, Gsα (52‐kDa species) immunoreactivity was significantly (p < 0.05) elevated in prefrontal (+36%), temporal (+65%), and occipital (+96%) cortex but not in hippocampus (+28%), thalamus (‐23%), or cerebellum (+21%). In contrast, no significant differences were found in the other G protein subunits (Giα, Goα, Gβ) measured in these regions. Forskolin‐stimulated cyclic AMP production was significantly increased in temporal (+31%) and occipital (+96%) cortex but not in other regions. No significant differences were apparent in basal or GTPγS‐stimulated cyclic AMP production. A significant correlation (r= 0.60, p < 0.001) was observed between forskolin‐stimulated cyclic AMP formation and Gsα (52 kDa) immunoreactivity when examined across these cortical regions. The observed increase in Gsα may be specific to bipolar disorders as no significant differences were detected in Gsα levels in temporal cortex from patients with either schizophrenia (n = 7) or Alzheimers disease (n = 7). In summary, the present study confirms and extends our earlier findings and supports the notion that increased Gsα levels and possibly Gsα‐adenylyl cyclase‐mediated signal transduction are relevant to the pathophysiology of bipolar affective disorder.

Brain serotonin transporter binding in non-depressed patients with Parkinson's disease

Early post‐mortem data suggest that damage to brain serotonin neurones might play a role in some features (e.g., depression) of Parkinsons disease (PD). However, it is not known whether such damage is a typical characteristic of living patients with PD or whether the changes are regionally widespread. To address this question we measured, by positron emission tomography imaging, levels of the brain serotonin transporter (SERT), a marker for serotonin neurones, as inferred from binding of [11C]‐3‐amino‐4‐(2‐dimethylaminomethyl‐phenylsulfanyl)‐benzonitrile (DASB), a second generation SERT radioligand, in subcortical and cerebral cortical brain areas of clinically advanced non‐depressed (confirmed by structured psychiatric interview) patients with PD. SERT binding levels in PD were lower than those in controls in all examined brain areas, with the changes statistically significant in orbitofrontal cortex (−22%), caudate (−30%), putamen (−26%), and midbrain (−29%). However, only a slight non‐significant reduction (−7%) was observed in dorsolateral pre‐frontal cortex, an area implicated in major depression. Our imaging data suggests that a modest, regionally widespread loss of brain serotonergic innervation might be a common feature of advanced PD. Further investigation will be required to establish whether SERT binding is more or less decreased in those patients with PD who also have major depressive disorder.

Reduced brain 5-HT and elevated NE turnover and metabolites in bipolar affective disorder☆

Levels of norepinephrine (NE), serotonin (5-HT), dopamine (DA), and their major metabolites were determined in postmortem brain obtained from nine subjects with antemortem histories meeting DSM-III-R criteria for bipolar affective disorder. Compared with controls, no statistically significant differences were found in mean levels of NE, 5-HT, or DA in any brain area of bipolar subjects. NE turnover as estimated by the ratio of the major NE metabolite, 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) to NE was increased in frontal (+107%), temporal (+103%), and occipital (+64%) cortex and thalamus (+83%). Significant decreases were found in the major 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA), in frontal (-54%) and parietal cortex (-64%), and in 5-HIAA/5-HT ratio in temporal cortex (-55%), with a trend for decreases in both measures in caudate nucleus. In addition, levels of the major DA metabolite, homovanillic acid (HVA) were significantly decreased (-46%) in parietal cortex and HVA/DA ratios were significantly reduced (-66%) in occipital cortex obtained from bipolar compared to control subjects. Our data, taken together with previous findings regarding monoamines in postmortem brain of depressed and suicide subjects, suggest that decreased 5-HT metabolite levels and turnover may be common to all mood disorders. Increased cortical NE turnover, however, may be a more important component in the pathophysiology of bipolar disorder.

Postmortem cerebral cortex Gs α-subunit levels are elevated in bipolar affective disorder

We examined the relative abundance of G-protein subunits in postmortem brain obtained from 7 patiebts with bipolar affective disorder (BAD) compared with 7 age- and sex-matched controls. G-protein subunit immunoreactivities were determined in membranes prepared from postmortem prefrontal cortex using SDS-PAGE and immunoblotting with specific polyclonal antisera against selected G-protein subunits: Gsα, Gi(1&2)α, Goα and Gβ(1&2). Of these G-protein subunits, only Gsα immunoreactivity was found to be significantly elevated in frontal (+ 34%), and occipital (+ 80%) cortex (P < 0.05) in BAD compared with control subjects. Smaller increments (+ 22%) in cerebellar Gsα immunoreactivity were also found but were not statistically significant. On the basis that increased Gsα immunoreactivity may reflect enhanced functional responsiveness of the receptor-effector units to which this coupling protein is integral, the present findings suggest that disturbances in Gs-mediated signal transduction may be involved in the pathophysiology of BAD.

The phosphoinositide signal transduction system is impaired in bipolar affective disorder brain.

Abstract: The function of the phosphoinositide second messenger system was assessed in occipital, temporal, and frontal cortex obtained postmortem from subjects with bipolar affective disorder and matched controls by measuring the hydrolysis of [3H]phosphatidylinositol ([3H]PI) incubated with membrane preparations and several different stimulatory agents. Phospholipase C activity, measured in the presence of 0.1 mM Ca2+ to stimulate the enzyme, was not different in bipolar and control samples. G proteins coupled to phospholipase C were concentration‐dependently activated by guanosine 5′‐O‐(3‐thiotriphosphate) (GTPγS) and by NaF. GTPγS‐stimulated [3H]PI hydrolysis was markedly lower (50%) at all tested concentrations (0.3–10 µM GTPγS) in occipital cortical membranes from bipolar compared with control subjects. Responses to GTPγS in temporal and frontal cortical membranes were similar in bipolars and controls, as were responses to NaF in all three regions. Brain lithium concentrations correlated directly with GTPγS‐stimulated [3H]PI hydrolysis in bipolar occipital, but not temporal or frontal, cortex. Carbachol, histamine, trans‐1‐aminocyclopentyl‐1,3‐dicarboxylic acid, serotonin, and ATP each activated [3H]PI hydrolysis above that obtained with GTPγS alone, and these responses were similar in bipolars and controls except for deficits in the responses to carbachol and serotonin in the occipital cortex, which were equivalent to the deficit detected with GTPγS alone. Thus, among the three cortical regions examined there was a selective impairment in G protein‐stimulated [3H]PI hydrolysis in occipital cortical membranes from bipolar compared with control subjects. These results directly demonstrate decreased activity of the phosphoinositide signal transduction system in specific brain regions in bipolar affective disorder.

Differential alteration of phospholipase A2 activities in brain of patients with schizophrenia

We recently reported that the activity of a calcium-independent subtype of phospholipase A2 is increased in blood of patients with schizophrenia. The present investigation examined whether similar changes take place in brain of patients with this disorder, and for comparison, in patients with bipolar disorder. The activity of two classes of PLA2, calcium-stimulated and independent, were assayed in autopsied temporal, prefrontal and occipital cortices, putamen, hippocampus and thalamus of 10 patients with schizophrenia, 8 patients with bipolar disorder and 12 matched control subjects. Calcium-independent PLA2 activity was increased by 45% in the temporal cortex of patients with schizophrenia as compared with the controls but was not significantly altered in other brain areas. In contrast, calcium-stimulated PLA2 activity was decreased by 27-42% in the temporal and prefrontal cortices and putamen, with no significant alterations in other brain regions. Brain PLA2 activity was normal in patients with bipolar disorder. Calcium-stimulated PLA2 activity was normal in cortex, cerebellum and striatum of rats treated acutely or chronically with haloperidol, whereas calcium-independent PLA2 activity was decreased in striatum of chronically treated animals, indicating that altered PLA2 activity in patients with schizophrenia is unlikely to be a direct effect of medication. Studies of the cellular role played by PLA2 suggest that decreased calcium-stimulated PLA2 activity, as also occurs in striatum of chronic human cocaine users, may be due, in part, to increased dopaminergic activity in the disorder, whereas increased calcium-independent PLA2 activity may be related to abnormal fatty acid metabolism and oxidative stress in schizophrenia.

Elevated Serotonin Transporter Binding in Depressed Patients with Parkinson's Disease : A Preliminary PET Study with [11C]DASB

This study investigated whether abnormalities in serotonin transporter binding occur in Parkinsons disease (PD) patients with concurrent depression. We estimated serotonin transporter levels in seven clinically depressed early‐stage PD patients and in seven healthy matched‐control subjects during a single positron emission tomography (PET) scan with the serotonin transporter radioligand, [11C]DASB. Depressed PD patients displayed a wide‐spread increase (8–68%) in [11C]DASB specific binding outside of the striatum, which was significant in dorsolateral (37%) and prefrontal (68%) cortices. Elevated [11C]DASB binding was positively correlated with depressive symptoms but not with disease severity or duration. Compatible with recent PET/[11C]DASB findings in major depression, the present preliminary data suggest that increased [11C]DASB binding, possibly reflecting greater serotonin transporter density (up‐regulation), might be a pathological feature of depression in Parkinsons disease—and possibly a characteristic of depressive illness in general.

Decreased brain [3H]inositol 1,4,5-trisphosphate binding in Alzheimer's disease

Inositol 1,4,5-trisphosphate (IP3) receptor binding sites were studied in autopsied brains from 10 subjects with dementia of the Alzheimer type (DAT) and 10 age-matched controls. In the parietal cortex and hippocampus, there was a 50-70% loss of [3H]IP3 binding whereas no significant changes were observed in frontal, occipital and temporal cortices, caudate or amygdala. Scatchard analysis confirmed a reduction in receptor density rather than a change in affinity. Since muscarinic receptors are robustly coupled to IP3 formation, our data demonstrate abnormalities beyond the muscarinic receptor recognition site in DAT.

The D2/3 dopamine receptor in pathological gambling: a positron emission tomography study with [11C]‐(+)‐propyl‐hexahydro‐naphtho‐oxazin and [11C]raclopride

AIMS Pathological gambling (PG) shares diagnostic features with substance use disorder (SUD), but the neurochemical mechanisms underlying PG are poorly understood. Because dopamine (DA), a neurotransmitter implicated in reward and reinforcement, is probably involved, we used positron emission tomography (PET) to test whether PG is associated with abnormalities in D2 and D3 receptor levels, as observed in SUD. DESIGN Case-control study comparing PG to healthy control (HC) subjects. SETTING Academic research imaging centre. PARTICIPANTS Thirteen non-treatment-seeking males meeting DSM-IV criteria for PG, and 12 matched HC (11 of whom completed PET). MEASUREMENTS Two PET scans (one with the D3 receptor preferring agonist [11C]-(+)-propyl-hexahydro-naphtho-oxazin (PHNO) and the other with [11C]raclopride) to assess D(2/3) DA receptor availability, and behavioural measures (self-report questionnaires and slot-machine game) to assess subjective effects and relationships to PET measures. FINDINGS Binding of both radiotracers did not differ between groups in striatum or substantia nigra (SN) (all P > 0.1). Across PG, [11C]-(+)-PHNO binding in SN, where the signal is attributable primarily to D3 receptors, correlated with gambling severity (r = 0.57, P = 0.04) and impulsiveness (r = 0.65, P = 0.03). In HC, [11C]raclopride binding in dorsal striatum correlated inversely with subjective effects of gambling (r = -0.70, P = 0.03) and impulsiveness (r = -0.70, P = 0.03). CONCLUSIONS Unlike with substance use disorder, there appear to be no marked differences in D2 /D3 levels between healthy subjects and pathological gamblers, suggesting that low receptor availability may not be a necessary feature of addiction. However, relationships between [11C]-(+)-PHNO binding and gambling severity/impulsiveness suggests involvement of the D3 receptor in impulsive/compulsive behaviours.

In vivo evidence for greater amphetamine-induced dopamine release in pathological gambling: a positron emission tomography study with [ 11 C]-(+)-PHNO

Drug addiction has been associated with deficits in mesostriatal dopamine (DA) function, but whether this state extends to behavioral addictions such as pathological gambling (PG) is unclear. Here we used positron emission tomography and the D3 receptor-preferring radioligand [11C]-(+)-PHNO during a dual-scan protocol to investigate DA release in response to oral amphetamine in pathological gamblers (n=12) and healthy controls (n=11). In contrast with human neuroimaging findings in drug addiction, we report the first evidence that PG is associated with greater DA release in dorsal striatum (54–63% greater [11C]-(+)-PHNO displacement) than controls. Importantly, dopaminergic response to amphetamine in gamblers was positively predicted by D3 receptor levels (measured in substantia nigra), and related to gambling severity, allowing for construction of a mechanistic model that could help explain DA contributions to PG. Our results are consistent with a hyperdopaminergic state in PG, and support the hypothesis that dopaminergic sensitization involving D3-related mechanisms might contribute to the pathophysiology of behavioral addictions.