Robert Hitzemann

Repeated electroconvulsive shock or chronic morphine treatment increases the number of 3HDALA2, DLEU5enkephalin binding sites in rat brain membranes

Experiments were performed in rats to evaluate the possible mechanisms responsible for the pharmacological cross-sensitization observed between repeated electroconvulsive shock (ECS) and chronic morphine administration. Repeated daily ECS for 9 days as well as chronic morphine pellet implantation resulted in a significant increase in the number of 3H-DADLE binding sites (Bmax values of 231 and 196 fmoles/mg protein, respectively). By contrast, single ECS, repeated sham ECS, and placebo pellet-treated rats all had significantly lower Bmax values (approx. 170 fmoles/mg protein). Affinities were not significantly altered by these treatments (Kd values between 3.1 and 4.0 nM). These data may link pharmacological cross-sensitization (repeated ECS and chronic morphine treatment) with a functional increase in the number of available opioid receptors.

Membrane abnormalities in the psychoses and affective disorders

Erythrocyte ghost phospholipid data were collected on 67 psychotic and/or manic patients and compared to a group of 35 age and sex matched controls. Patients meeting DSM-III criteria for schizophreniform disorder or schizophrenia but not mania showed a small but significant decrease in membrane phosphatidylcholine (PC). In 53 of the patients data were available on lithium transport across red cell membranes. Patients in the upper quartile of the PC distribution showed a significant (-47%) decrease in the 24 h in vitro lithium ratio as compared to patients in the lower PC quartile. This difference was due to an increase in Na-Li+ counterflow activity in the upper PC quartile and not to a change in passive lithium leak. These data illustrate one example of a possible relationship between membrane composition and a membrane function, counterflow activity, which has been associated with the underlying mechanism(s) of lithium action.

Developmental changes in the fatty acids of synaptic membrane phospholipids: Effect of protein malnutrition

The acyl-linked fatty acid composition of the major phospholipid species in rat cortical synaptic membranes was determined at various stages of development. For most species there was a decrease during development in the short chain saturated fatty acids, 14∶0 and 16∶0, an increase in 18∶0 and 22∶6 (n-3) and an increase in the ratio of 22∶6 (n-3)/22∶5 (n-6). Pups were protein deprived by feeding the dams a 12% casein diet as compared to the 24% casein control diet. Protein malnutrition markedly affected the composition of acyl-linked fatty acids in the synaptic membranes. The increases in the ratio of 22∶6 (n-3)/22∶5 (n-6) fatty acids were especially compromised.

Growth hormone response to apomorphine and diagnosis: A comparison of three diagnostic systems

Our study takes a further look at the apomorphine test in the psychoses and affective disorders, with special reference to the use of different diagnostic systems. Patients meeting Research Diagnostic Criteria (RDC) for schizophrenia, schizoaffective disorder, or manic disorder were included. In addition to the RDC, diagnosis was also made using the DSM-III and ICD-9. All patients underwent an evaluation of peak GH response to apomorphine administration. The results show that RDC and ICD-9 are similar, in that for both systems, a high GH response correlates with a schizoaffective disorder and distinguishes those patients significantly from manic patients. The DMS-III brings in some new dimensions, in that schizophreniform disorder (6-month cut-off) is distinguished from schizophrenia. In addition, patients with affective symptoms and mood-incongruent psychoses are more closely related to schizophreniform disorder than to classical manic disorder.

Characteristics of phospholipid methylation in human erythrocyte ghosts: Relationship(s) to the psychoses and affective disorders

Recent studies have shown that patients with a schizophrenic-like illness have a significant deficit in erythrocyte ghost membrane (EGM) phosphatidylcholine (PC); patients with the most severe deficiency showed a marked decrease in Na+-Li+ counterflow activity (Hitzemann et al. 1984a and b). The present study was undertaken to see if the decrement in PC is associated with a decrease in phospholipid methylation activity. Phospholipid methylation in human EGMs is distinctly different from that in rat EGMs (Hirata and Axelrod 1980) in that the human activity is not Mg++-dependent, and apparent methyltransferase I activity is located in the external membrane surface. The patient population consisted of 20 DSM-III schizophrenics (SCZ), 13 DSM-III schizophreniform (SF) disorder patients, and 11 DSM-III manics (M). Twelve age- and sex-matched controls were used for the comparison group. Methylation activity was significantly decreased in all three patient groups, although the M group had significantly higher activity than the SF group. Twenty-four of the SCZ and SF patients entered a Li+ trial. The Li+ responder group (n = 8) showed significantly lower activity than the nonresponder group (n = 16). Overall, we conclude that the decrement in phospholipid methylation activity partially contributes to the decrement in PC levels.

Dopamine and non-dopamine psychoses

The time course of antipsychotic response following the initiation of an antipsychotic drug and functional dopamine receptor sensitivity were explored in a cohort of recently admitted psychotic (mood-incongruent) patients. The distribution of the latencies of antipsychotic response suggested at least two populations. Rapid responders (RRs) had 60% reduction of baseline psychotic symptoms by a mean of 5.5 days of drug treatment. Delayed/nonresponders required 2–7 weeks for a similar reduction of psychotic symptoms.The sensitivity of postsynaptic dopamine receptors was explored using a neuroendocrine probe: growth hormone response to the dopamine agonist, apomorphine (AP). RRs had an exaggerated growth hormone response to AP in comparison to delayed/nonresponders (P<0.05).Exaggerated sensitivity of postsynaptic dopamine receptors and rapid antipsychotic response following dopamine receptor blockade in RRs suggest a true functional dopamine hypersensitivity disorder in the RR group. In contrast, lower postsynaptic receptor sensitivity (as reflected by lower growth hormone response to AP) and failure of early response following dopamine receptor blockade focus attention away from dopamine hyperactivity as a relevant etiologic mechanism in delayed/nonresponders.Response rates to neuroleptic drugs and neuroendocrine probes of receptor sensitivity may separate two or more etiologically distinct diseases with schizophrenic-like symptoms.

On the physical properties of red cell ghost membranes in the affective disorders and psychoses. A fluorescence polarization study

Membrane order was measured in the erythrocyte ghost membranes of DSM-III schizophreniform disorder (SF), DSM-III schizophrenic (SCZ) and DSM-III manic (bipolar) (M) patients and a group of age- and sex-matched controls. Fluorescence polarization with the probe 1,6-diphenyl-1,3,5-hexatriene was used to determine the steady-state fluorescence anisotropy (rs). The SF group showed a significant increase in rs (delta rs = 0.037) from the control group. Although the means were not significantly different, 3 of 8 Ms and 5 of 8 SCZs also had rs values greater than the highest control value. Thermotropic behavior of the membranes was evaluated over the range of 40 to 20 degrees C. No difference among groups in membrane enthalpy was detected. Thus, the differences in rs appear to be associated with differences in entropy. Phosphatidylcholine (PC) levels, which were known to be abnormal in these patients, were compared with the rs values. A significant (P less than 0.001, r = -0.63) linear correlation between rs and membrane PC levels was observed. Overall these data further support the view that unusual membrane biophysical factors may occur with high frequency in the psychoses and affective disorders.

Developmental regulation of phospholipid methylation in rat brain synaptosomes

Phospholipid methylation was studied in cortical synaptosomes prepared from 7 and 14 day and adult rat brain. Using varying concentrations of [3H] S-adenosylmethionine, Km and Vmax values were determined for the formation of [3H] phosphatidylmonomethylethanolamine (PME), [3H] phosphatidyl-dimethylethanolamine and [3H] phosphatidylcholine (PC). At 25 degree C, the Km values for the formation of all three products, significantly decreased with development. Increasing the temperature to 37 degree C increased the Km values in the 14 day and adult but not the 7 day preparation. The Vmax values at 25 degree C were highest at 7 and 14 days, depending on the product and then decreased in the adult. At 37 degree C, the Vmax values were highest in the 14 day preparation. The overall results are discussed in terms of the developmentally regulated decrease in both synaptic membrane PC and membrane fluidity.

Fluphenazine activity and antipsychotic response

Plasma fluphenazine levels and plasma total neuroleptic activity (as quantitated by the neuroleptic receptor binding assay) were related to therapeutic response in 15 DSM-III schizophrenic patients who received a predetermined, fixed dose of fluphenazine for 14 days. Mean neuroleptic activity of the plasma was 84% greater than can be accounted for by the parent fluphenazine alone, and varied widely between patients. A sigmoidal relationship between total neuroleptic activity of plasma and response was found, with a continued plateau of response at higher total neuroleptic levels. Furthermore, the RBA data suggested (P<0.002) that two populations of drug-responsive schizophrenics exist which may be discriminated by the total D2 binding activity of plasma required for response.

Developmental changes in synaptic membrane order: a comparison of regions in the rat brain

Developmental changes in synaptic membrane order were followed in 5 regions of the rat brain, the cortex (Cx), cerebellum (Cb), brainstem (BS), lateral subcortex (LSCx) and midline subcortex (MSCx). Membrane order was assessed by the fluorescence polarization technique, using 1,6-diphenyl-1,3,5-hexatriene (DPH) as the probe. The results illustrate that the developmental increase in membrane order proceeds from caudal to rostral brain regions. Thus, at the earliest time point examined (day 3) steady-state anisotropy (rs) in the BS was significantly higher than in the Cx and reached adult values by day 14 while the Cx values were still significantly less than the adult value even at day 30. The thermotropic behavior of the membranes was investigated over the range of 20-37 degrees C. The Arrhenius slopes among the Cx, BS, LSCx and MSCx were similar across all ages studied, suggesting that the developmental increase in order primarily results from a change in entropy. In contrast, the Arrhenius slopes for the Cb increase greater than 100% during development, suggesting that a change in enthalpy is important for the increase in membrane order. Multilamellar liposomes prepared from membrane lipid extracts generally showed the same developmental changes in order as the intact membranes. These data indicate that the increase in membrane order results from a marked change in bulk lipid composition rather than a secondary lipid matrix change (e.g. in membrane asymmetry) and/or from the developmental increase in the protein/lipid ratio.