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Increase in cerebral blood flow but not metabolism by adrenergic systems in rat brain
Basic and Clinical Studies
BIOL PSYCHIATRY 1990;27:41A-179A
77A
agent. The PMEs found to be elevated in AD are structurally similar to the amino acid neurotransmitters GABA and L-glutamate, and L-PS has been shown to inhibit binding at the N-methyl-D-asparlate (NMDA) subtype of glutamate receptors. It is possible that L.-PS could exert a neurotoxic effect through action at the NMDA receptor. ~Ilae present study examines the conformational similarity, of L-PS to selected agonists and antagonists active at the NMDA receptor site. The conformationally rigid cis-2,4-methanoglutarnate, a potent and selective agonist of the NMDA receptor (Lanthoru et al., 1989), provides a good spatial model of the conformation of L-glutamate, which is active at the NMDA site. L-PS was modeled to the active conformation of L-glutamate and energy minimized using the MacroModel suite of programs with AMBER force fields. Thi~ conformation of L-PS was energy minimized (-185 vv,~,, angles, and the spatial overlap with L-ghtamate is excellent. We have modeled L-PS to the conformationally restricted NMDA antagonist CGS 19755. This conformation of L-PS (-22! ld/M) did not give a good spatial overlap with CGS. We plan to utilize structure-activity information on conformationally restricted analogs of L-glutamate and GABA as it becomes available to further investigate the possible role of PMEs at these receptors.
83
EFFECTS OF STRESS IN AN ANIMAL MODEL FOR POST-TRAUMATIC STRESS DISORDER (PTSD) Bruce I. Diamond, Ph.D., Mark B. Hamner, M.D. (by invitation), Thomas L. Chalker, B.S. (by invitation), Emelia O'Neal, M.Ed. (by invitation) Department of Psychiatry, Medical College of Georgia, Augusta, GA 30907. It has been hypothesized that exposure to inescapable stress resulting in learned helplessness may provide an animal tnodel for PTSD. Moreover, it has been proposed that chronic stress may be more relevant than a single exposure to acute stress (SA). Changes in norepinephrine (NE) function may occur in both learned helplessness and PTSD. In this study, male Sprague Dawley rats (160 g) underwent either a single episode of SA 6 day~ of either chronic variable (CV), or chronic homogeneous (CH) stress. At the end of the stress period, ra~s were challenged with either i.p. yohimbine (7.5 mg/kg) or clonidine (1 mg/kg Dody weight) to stimulate or inhibit NE release. Immobility was quantified using a 5 min swim test. In all stress groups, clonidine was able to antagonize the effects of stress (CONT 4.7 -+ 0.3 versus CLON 7 - 1.2 min; p < 0.05). As measured by immobilization scores, SA produced the same effeJt as did CV or CH. The differential effects of yehimbine and clonidine were most noticeable in the SA group (4.25 ± 0.59 and 1.18 ± 0.17 min, respectiively). These results :uggest that NE is involved and that S ~'~may be a better model for PTSD.
84
INCKEASE IN CEREBRAL BLOOD FLOW BUT NOT METABOLISM BY ADRENERGIC SYSTEMS IN RAT BRAIN M.D. Underwood, Ph.D., V. Arango, Ph.D., M.J. Bakalian, B.A., D.J. Reis, M.D., J.J. Mann, M.D. Laboratories of Neuropharmacology, Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh, Pittsburgh, PA /5213. Reduced ca~ecbolmi~ine neurotransmission, cerebral blood flow (CBF), and cerebral glucose utilization (CGU) has been reported in suicidal behavior, schizophrenia, dep~ssion, and personality disorders. However, the role of brain catecholmnines in regulation of CBF or CGU is not well understood. We sought to determine whether adrenaline neurons in :~su~'~ v~troleter~! r~et~ulla (RVLM) contribute to regulation of CBF and CGU. Rats were anesthetized (chloralose), p~alyzed (curare), and artificially ventilated, with arterial pressure and blood gases :naintaip~d in normal range. The RVLM was stimulated electrically or chemically (kainic acid, 5 nM in 100 nL). CBF was measured using m4C-iodoantipyrine and CGU with ~4C-deoxyg.~ucose. Electrical (n = 5) or chemical (n = 5) stimulation of RVLM increased CBF globally (1.3 to 1.6 times; p < 0.05) without change in CGU (p > 0.05). The increase in CBF was not affected (p > 0.05) by adrenalectomy (n = 5), transection of ~Ul~60,,"ee,'vical ganglion (n = 5) or atropine sulphate
BIOL PSYCHIATRY 1990;27:41A-179A
78A
Basic and Clinical Studies
(n = 3). In contrast to decreased CBF elicited by stimulation of noradrenergic neurons of locus coemleus, activation of RVLM-adrenergic systems results in widespread increases in CBF. Thus, brain catecholarnine modulation of CBF may operate not only dkectly (CGU-dependent) but also indirectly by changing CBF alone (CGU-independent).
85
LACK OF ASYMMETRY IN SEROTONIN UPTAKE SITES IN HUMAN BRAIN Bruce Parsons, M.D., Ph.D., Yung-Yu Huang, M.S., Narendra Badhakar, M.D., Shaoning Wang, M.D., Michael Stanley, Ph.D. New York State Psychiatric Institute, New York, NY 10032. Serotonin (5-HT) has been implicate~ ~n a variety of physiological functions and pathological conditions, including depression, obsessive compulsiv.~ disorder, and the anxiety disorders. The serotonergic system in r~an has been assessed by a variety of techniques that range from peripkeral studies of 5-HT uptake in plate!ets to more central measurements of CSF 5-HIAA concentration and quantification of brain 5-HT receptors and uptake sites. Using 3H-imipramine (3H-IMI), Demeter et al. (1989) recently reported that an asymmetry of 5-HT uptake sites is present in frontal cortices obtained from normal controh, with the right hemisphere ~owing three times the concentration of uptake sites as the left. If such an observation could be replicated, the interpretation of many previous studies on serotonergie functioning in humans would be subject to question. We report here that there is no demonstrable asymmetry in 5-HT uptake sites ,~btained from frontal cortices of normal controls. This conclusion is based on experiments that estimate the number of 5-HT uptake sites by employing the conventional ligand 3H-IMI, as well as the more selective 5-HT reuptake-blocker 3H-paroxetine (3H-PAR). Samples corresponding to Brodmann area 9 were dissected from the left and right hemispheres of control brain and stored at - 70"C. For 3H-IMI assays, crude homogenates were prepared according to method of Demeter. For 3H-PAR assays, synaptosomal preparations were made according to the method of Cheetham. Saturation binding isotherms were carried out at 12 concentrations (0.3-10 nM/liter) of 3H-imipramine (NEN, 48 Cil/mM) and 8 concentrations (0.013-0.5 aM/liter) of 3Hparoxetine (NEN, 19 Ci/mM). No asymmetry of 3H-IMI sites was observed: left, Bm,~ = 144 _ 25 fM/ mg protein, Kd = 4.8 ± 1.4 nM; right, Bm~ = 126 ± 15, Kd = 4.0 ± 0.7. In addition, no asymmetry in 3H.paroxetin~,binding was observed: left, Bma, = 40 ± 7 fM/mg protein, Kd = 0.1 --. 0.01 nM; right, Bm,~ "-- 37 ± 6, Kd = 0. I - 0.01 t~M. These findings, which indicate no asymmetry using either ligand, are consistent with those of Horton et al. (p.c.) and question the validity of the findings of Demeter et al.
86 REDISTRIBUTION OF SEQUESTERED CEREBRAL IRON SUGGESTS POSSIBLE ROLE IN NEUROTRANSMISSION Natasha Margolin, A.B.~ Gregory Lawler, B.A., and Andrew J. Dwork, M.D. Division of Neu~opathology, Columbia University, New York, N¥ amt Department of Neuropathology and Neurot~xicology, New York State Psychiatric Institute, New York, IvY 10032. Peak upt~e of iron by the brain of the postnatal rat occurs at age 12-18 days,. Dietary iron deficiency during the first "1 weeks of life produces perma~gnt behavioral abnormalgfies and deficits of cerebral iron, even if hematological paramete~ ~etum to normal. To determine potential roles of iron acquired during this period ~nd to study the effects of dict~ry, deficiency, rats were iajected intraperitoneally with a trace dose of 39iron ~t age 15 days and killed at various intervals. Gamma counting revealed constant radioactivity in the brains despite rapidly diminish~nfgspecific radioactivity of serum, indicating that cerebral iron acquired at age 15 days does not exchange readily with plasma iron. Autoradiography of the brains showed striking changes in distribution of this sequestered iroa. At 2 days after injection, caudate-putamen was more
BIOL PSYCHIATRY 1990;27:41A-179A
77A
agent. The PMEs found to be elevated in AD are structurally similar to the amino acid neurotransmitters GABA and L-glutamate, and L-PS has been shown to inhibit binding at the N-methyl-D-asparlate (NMDA) subtype of glutamate receptors. It is possible that L.-PS could exert a neurotoxic effect through action at the NMDA receptor. ~Ilae present study examines the conformational similarity, of L-PS to selected agonists and antagonists active at the NMDA receptor site. The conformationally rigid cis-2,4-methanoglutarnate, a potent and selective agonist of the NMDA receptor (Lanthoru et al., 1989), provides a good spatial model of the conformation of L-glutamate, which is active at the NMDA site. L-PS was modeled to the active conformation of L-glutamate and energy minimized using the MacroModel suite of programs with AMBER force fields. Thi~ conformation of L-PS was energy minimized (-185 vv,~,, angles, and the spatial overlap with L-ghtamate is excellent. We have modeled L-PS to the conformationally restricted NMDA antagonist CGS 19755. This conformation of L-PS (-22! ld/M) did not give a good spatial overlap with CGS. We plan to utilize structure-activity information on conformationally restricted analogs of L-glutamate and GABA as it becomes available to further investigate the possible role of PMEs at these receptors.
83
EFFECTS OF STRESS IN AN ANIMAL MODEL FOR POST-TRAUMATIC STRESS DISORDER (PTSD) Bruce I. Diamond, Ph.D., Mark B. Hamner, M.D. (by invitation), Thomas L. Chalker, B.S. (by invitation), Emelia O'Neal, M.Ed. (by invitation) Department of Psychiatry, Medical College of Georgia, Augusta, GA 30907. It has been hypothesized that exposure to inescapable stress resulting in learned helplessness may provide an animal tnodel for PTSD. Moreover, it has been proposed that chronic stress may be more relevant than a single exposure to acute stress (SA). Changes in norepinephrine (NE) function may occur in both learned helplessness and PTSD. In this study, male Sprague Dawley rats (160 g) underwent either a single episode of SA 6 day~ of either chronic variable (CV), or chronic homogeneous (CH) stress. At the end of the stress period, ra~s were challenged with either i.p. yohimbine (7.5 mg/kg) or clonidine (1 mg/kg Dody weight) to stimulate or inhibit NE release. Immobility was quantified using a 5 min swim test. In all stress groups, clonidine was able to antagonize the effects of stress (CONT 4.7 -+ 0.3 versus CLON 7 - 1.2 min; p < 0.05). As measured by immobilization scores, SA produced the same effeJt as did CV or CH. The differential effects of yehimbine and clonidine were most noticeable in the SA group (4.25 ± 0.59 and 1.18 ± 0.17 min, respectiively). These results :uggest that NE is involved and that S ~'~may be a better model for PTSD.
84
INCKEASE IN CEREBRAL BLOOD FLOW BUT NOT METABOLISM BY ADRENERGIC SYSTEMS IN RAT BRAIN M.D. Underwood, Ph.D., V. Arango, Ph.D., M.J. Bakalian, B.A., D.J. Reis, M.D., J.J. Mann, M.D. Laboratories of Neuropharmacology, Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh, Pittsburgh, PA /5213. Reduced ca~ecbolmi~ine neurotransmission, cerebral blood flow (CBF), and cerebral glucose utilization (CGU) has been reported in suicidal behavior, schizophrenia, dep~ssion, and personality disorders. However, the role of brain catecholmnines in regulation of CBF or CGU is not well understood. We sought to determine whether adrenaline neurons in :~su~'~ v~troleter~! r~et~ulla (RVLM) contribute to regulation of CBF and CGU. Rats were anesthetized (chloralose), p~alyzed (curare), and artificially ventilated, with arterial pressure and blood gases :naintaip~d in normal range. The RVLM was stimulated electrically or chemically (kainic acid, 5 nM in 100 nL). CBF was measured using m4C-iodoantipyrine and CGU with ~4C-deoxyg.~ucose. Electrical (n = 5) or chemical (n = 5) stimulation of RVLM increased CBF globally (1.3 to 1.6 times; p < 0.05) without change in CGU (p > 0.05). The increase in CBF was not affected (p > 0.05) by adrenalectomy (n = 5), transection of ~Ul~60,,"ee,'vical ganglion (n = 5) or atropine sulphate
BIOL PSYCHIATRY 1990;27:41A-179A
78A
Basic and Clinical Studies
(n = 3). In contrast to decreased CBF elicited by stimulation of noradrenergic neurons of locus coemleus, activation of RVLM-adrenergic systems results in widespread increases in CBF. Thus, brain catecholarnine modulation of CBF may operate not only dkectly (CGU-dependent) but also indirectly by changing CBF alone (CGU-independent).
85
LACK OF ASYMMETRY IN SEROTONIN UPTAKE SITES IN HUMAN BRAIN Bruce Parsons, M.D., Ph.D., Yung-Yu Huang, M.S., Narendra Badhakar, M.D., Shaoning Wang, M.D., Michael Stanley, Ph.D. New York State Psychiatric Institute, New York, NY 10032. Serotonin (5-HT) has been implicate~ ~n a variety of physiological functions and pathological conditions, including depression, obsessive compulsiv.~ disorder, and the anxiety disorders. The serotonergic system in r~an has been assessed by a variety of techniques that range from peripkeral studies of 5-HT uptake in plate!ets to more central measurements of CSF 5-HIAA concentration and quantification of brain 5-HT receptors and uptake sites. Using 3H-imipramine (3H-IMI), Demeter et al. (1989) recently reported that an asymmetry of 5-HT uptake sites is present in frontal cortices obtained from normal controh, with the right hemisphere ~owing three times the concentration of uptake sites as the left. If such an observation could be replicated, the interpretation of many previous studies on serotonergie functioning in humans would be subject to question. We report here that there is no demonstrable asymmetry in 5-HT uptake sites ,~btained from frontal cortices of normal controls. This conclusion is based on experiments that estimate the number of 5-HT uptake sites by employing the conventional ligand 3H-IMI, as well as the more selective 5-HT reuptake-blocker 3H-paroxetine (3H-PAR). Samples corresponding to Brodmann area 9 were dissected from the left and right hemispheres of control brain and stored at - 70"C. For 3H-IMI assays, crude homogenates were prepared according to method of Demeter. For 3H-PAR assays, synaptosomal preparations were made according to the method of Cheetham. Saturation binding isotherms were carried out at 12 concentrations (0.3-10 nM/liter) of 3H-imipramine (NEN, 48 Cil/mM) and 8 concentrations (0.013-0.5 aM/liter) of 3Hparoxetine (NEN, 19 Ci/mM). No asymmetry of 3H-IMI sites was observed: left, Bm,~ = 144 _ 25 fM/ mg protein, Kd = 4.8 ± 1.4 nM; right, Bm~ = 126 ± 15, Kd = 4.0 ± 0.7. In addition, no asymmetry in 3H.paroxetin~,binding was observed: left, Bma, = 40 ± 7 fM/mg protein, Kd = 0.1 --. 0.01 nM; right, Bm,~ "-- 37 ± 6, Kd = 0. I - 0.01 t~M. These findings, which indicate no asymmetry using either ligand, are consistent with those of Horton et al. (p.c.) and question the validity of the findings of Demeter et al.
86 REDISTRIBUTION OF SEQUESTERED CEREBRAL IRON SUGGESTS POSSIBLE ROLE IN NEUROTRANSMISSION Natasha Margolin, A.B.~ Gregory Lawler, B.A., and Andrew J. Dwork, M.D. Division of Neu~opathology, Columbia University, New York, N¥ amt Department of Neuropathology and Neurot~xicology, New York State Psychiatric Institute, New York, IvY 10032. Peak upt~e of iron by the brain of the postnatal rat occurs at age 12-18 days,. Dietary iron deficiency during the first "1 weeks of life produces perma~gnt behavioral abnormalgfies and deficits of cerebral iron, even if hematological paramete~ ~etum to normal. To determine potential roles of iron acquired during this period ~nd to study the effects of dict~ry, deficiency, rats were iajected intraperitoneally with a trace dose of 39iron ~t age 15 days and killed at various intervals. Gamma counting revealed constant radioactivity in the brains despite rapidly diminish~nfgspecific radioactivity of serum, indicating that cerebral iron acquired at age 15 days does not exchange readily with plasma iron. Autoradiography of the brains showed striking changes in distribution of this sequestered iroa. At 2 days after injection, caudate-putamen was more