Effect of amitriptyline on adrenergic receptor number and second messenger function in rat brain

Radioligand binding studies were done to investigate the effect of chronic administration of Amitriptyline on alpha1-adrenoceptor (alpha1-AR) receptor mediated response to inositol triphosphate (IP3) in rat brain. Our studies revealed a significant decrease in the densities of alpha1-ARs in cortex and cerebellum of rat brain after chronic administration of Amitriptyline (10 mg kg-1 b.wt.). However, there was no significant change in the affinity of [3H]prazosin to alpha1-ARs. Displacement studies showed that Amitriptyline has higher affinity for alpha1-AR with a Ki value of 182+/-16 nM. Significant change was observed in basal IP3 activity in cortex and cerebellum after Amitriptyline exposure. In cortex and cerebellum of experimental rats the NE (Norepinephrine) stimulated IP3 activity was significantly decreased (1460+/-102 DPM/g tissue; p<0.0001; 1188+/-112 DPM/g tissue; p<0.0001), when compared to NE stimulated IP3 activity (4152+/-286 and 3952+/-245 DPM/g tissue, respectively) in control rats. The decrease in NE stimulated IP3 activity in both regions may be due to the significant downregulation of alpha1-ARs in cortex after Amitriptyline exposure as these sites are positively coupled to IP3. The observed significant decrease in alphal-ARs with concomitant decrease in NE stimulated IP3 activity, after Amitriptyline treatment, suggests that Amitriptyline which has high affinity for these sites, acts by modulating the alpha1-AR receptor mediated response in brain.

Study of pyruvate kinase activity in human astrocytomas - alanine-inhibition test revisted

BACKGROUND

Recent studies have confirmed that alterations in the isoenzyme of pyruvate kinase (PK) provide tumor cells with selective growth advantage.

AIMS

Our aim was to establish the mean activity of the enzyme PK in human astrocytomas and to look for any trends in the activity with relation to histological grade.

MATERIALS AND METHODS

The PK (EC 2.7.1.40) activity was measured in the tumor homogenate by spectrophotometric rate determination. DeltaAbsorbance at 340 nm (A 340 nm ) per minute was obtained using the maximal linear rate for both the test and the blank. Enzyme activity was estimated in the presence and absence of amino acid alanine.

RESULTS

The mean PK level in astrocytomas was 3.5 +/- 2.0 mmol/min/mg protein, which was significantly higher (24%; P < 0.001) when compared to 2.8 +/- 0.3 mmol/min/mg protein in control brain. Highest PK activity was noted in grade 2 astrocytomas. In controls there was no change in PK activity in the presence of alanine. In grade 2 astrocytomas there was 7% decrease in mean PK activity in the presence of alanine, this difference in grade 3 astrocytomas was 33% and in grade 4 astrocytomas it was 61%. As the tumors were becoming malignant there was a graded increase in the levels of PK inhibition.

CONCLUSIONS

Mean PK activity was significantly higher in astrocytomas. There was a graded increase in level of PK inhibition as the tumors were becoming more malignant.

Muscarinic receptor 1 agonist activity of novel N-aryl carboxamide substituted 3-morpholino arecoline derivatives in Alzheimer's presenile dementia models

Earlier we have reported the effect of arecoline thiazolidinone and morpholino arecoline derivatives as muscarinic receptor 1 agonists in Alzheimer's presenile dementia models. To elucidate further our Structure-Activity Relationship (SAR) studies on the chemistry and muscarinic receptor 1 binding efficacy, a series of novel carboxamide derivatives of 2-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)morpholine molecule have been designed and synthesized as a new class of M1 receptor agonists with a low toxicity effect profile that enhances memory function in animal models of Alzheimer's presenile dementia and also modulates the APP secretion from rat brain cerebrocortical slices by activating M1 receptor in vitro. Results suggest that compound 9b having methyl group at the para position of the aryl group attached to the carboxamide of morpholino arecoline could emerge as a potent molecule having antidementia activity.

Effect of novel N-aryl sulfonamide substituted 3-morpholino arecoline derivatives as muscarinic receptor 1 agonists in Alzheimer's dementia models

A series of novel, potent, and selective muscarinic receptor 1 agonists (M1 receptor agonists) that employ a key N-substituted morpholine Arecoline moiety has been synthesized as part of research effort for the therapy of Alzheimer's diseases. The ester group of arecoline (which is reported as muscarinic agonist) has been replaced by N-substituted morpholine ring. The structure-activity relationship reveals that the electron donating 4-substituted sulfonyl derivatives (9a, 9b, 9c, and 9e) on the nitrogen atom of the morpholine ring increases the affinity of M1 receptor binding 50- to 80-fold greater than the corresponding arecoline. Other derivatives also showed considerable M1 receptor binding affinity.

Effect of novel arecoline thiazolidinones as muscarinic receptor 1 agonist in Alzheimer's dementia models

The discovery of cholinergic deficit in Alzheimer's disease (AD) patient's brain has triggered research efforts, using cholinomimetic approaches for their efficacy in AD therapy. Various therapies may be of potential clinical use in AD. Among these are cholinergic agents, which include muscarinic agonists, acetylcholinesterase inhibitors, and acetylcholine releasing agents. One of the muscarinic agonists tested in AD is arecoline and its bioisosters, which are widely explored as muscarinic receptor 1 agonist (M1 receptor agonist) in AD research. In this regard, five-membered heterocyclic ring system attached arecoline basic nucleus (N-methyl tetrahydropyridines) at third position has been extensively researched on. The present research involved synthesis of arecoline thiazolidinones 5(a-j) by using dipolar addition of 3-aminopyridine and alkyl/aryl carboxaldehydes in presence of gamma ferrite as catalyst. The resulting products were methylated and reduced to get desired products. Subsequently the synthesized arecoline thiazolidinones were subjected to in vitro muscarinic receptor binding studies using male Wistar rat brain (cerebral cortex) membrane homogenate and extended this in vitro study to in vivo pharmacological evaluation of memory and learning in male Wistar rats. Four derivatives (5a-5c and 5e) showed considerable M1 receptor binding affinity (in vitro) and elicited beneficial effects in vivo memory and learning models (Rodent memory evaluation, plus and Y maze studies).

Evidence of linkage and association on 18p11.2 for psychosis

The genetic basis of bipolar disorder (BPD) and schizophrenia (SCZ) has been established through numerous clinical and molecular studies. Although often considered separate nosological entities, evidence now suggests that the two syndromes may share some genetic liability. Recent studies have used a composite phenotype (psychosis) that includes BPD, SCZ, psychosis not otherwise specified, and schizoaffective disorder, to identify shared susceptibility loci. Several chromosomal regions are reported to be shared between these syndromes (18p, 6q, 10p, 13q, 22q). As a part of our endeavor to scan these regions, we report a positive linkage and association finding at 18p11.2 for psychosis. Two-point linkage analysis performed on a series of 52 multiplex pedigrees with 23 polymorphic markers yielded a LOD score of 2.02 at D18S37. An independent set of 159 parent offspring trios was used to confirm this suggestive finding. The TDT analysis yielded support for association between the marker D18S453 and the disease allele (chi2 = 4.829, P < 0.028). This region has been implicated by several studies on BPD [Sjoholt et al. (2004); Mol Psychiatry 9(6):621-629; Washizuka et al. (2004); Biol Psychiatry 56(7):483-489; Pickard et al. (2005); Psychiatr Genet 15(1):37-44], SCZ [Kikuchi et al. (2003); J Med Dent Sci 50(3):225-229; Babovic-Vuksanovic et al. (2004); Am J Med Genet 124(3):318-322] and also as a shared region between the two diseases [Ishiguro et al. (2001); J Neural Transm 108(7):849-854; Reyes et al. (2002); Mol Psychiatry 7(4):337-339; Craddock et al. (2005); J Med Genet 42(3):193-204]. Our findings provide an independent validation of the above reports, and suggest the presence of susceptibility loci for psychoses in this region.

Cortical alpha-adrenoceptor downregulation by tricyclic antidepressants in the rat brain

The aim of the present study was to examine the effect of chronic tricyclic antidepressants (TCAs) treatment on the density of alpha-adrenoceptors in the rat brain. Density of alpha1- and alpha2-adrenoceptors was measured in cortex and hippocampus of rats treated with imipramine (IMI, 5mg/kg body weight), desipramine (DMI, 10mg/kg body weight), clomipramine (CMI, 10mg/kg body weight) and amitriptyline (AMI, 10mg/kg body weight), for 40 days, using [3H]prazosin and [3H]clonidine, respectively. The density of cortical alpha1-adrenoceptors was significantly decreased with IMI (46%), DMI (21%), CMI (50%) and AMI (67%) treatment, without altering the affinity of the receptor. The density of cortical alpha2-adrenoceptors was also significantly decreased with DMI (69%), CMI (81%) and AMI (80%) treatment, without affecting the affinity for [3H]clonidine. The density of hippocampal alpha1-adrenoceptors was significantly decreased only with AMI treatment (47%), without affecting the affinity for [3H]prazosin. However, no change in hippocampal alpha2-adrenoceptor density was observed with any of these TCAs. The results suggest that chronic antidepressant (AD) treatment downregulates the cortical, but not hippocampal, alpha1- and alpha2-adrenoceptors in rat brain. The region-specific downregulation of alpha1- and alpha2-adrenoceptors density, which occur after prolonged AD treatment, may underline the therapeutic mechanism of action.

Alterations in 5-HT(1A) receptors and adenylyl cyclase response by trazodone in regions of rat brain

The in vivo effect of trazodone on the density of [(3)H]5-HT binding sites and 5-HT(1A) receptors and adenylyl cyclase (AC) response was studied in regions of rat brain. The chronic administration of trazodone (10 mg/Kg body wt, 40 days) resulted in a significant downregulation of [(3)H]5-HT binding sites and 5-HT(1A) receptors in cortex and hippocampus. Trazodone significantly (p < 0.0001) decreased the density of [(3)H]5-HT binding sites in cortex (42.6 +/- 3.6 fmol/mg protein, 65%) and hippocampus (12.6 +/- 1.6 fmol/mg protein, 87%) when compared to control values of 121.9 +/- 5.4 and 99.3 +/- 7.5 fmol/mg protein in these regions, respectively. Similarly there was a significant (p < 0.0001) decrease in the density of 5-HT(1A) receptors in both cortex (7.2 +/- 0.5 fmol/mg protein, 70%) and hippocampus (6.3 +/- 1.2 fmol/mg protein, 79%) when compared to control values of 24.2 +/- 2.1 and 30.6 +/- 3.7 fmol/mg protein, in these regions respectively. However, the affinity of [(3)H]5-HT to 5-HT binding sites (1.83 +/- 0.26 nM, p < 0.0001) and [(3)H]8-OH-DPAT to 5-HT(1A) receptors (0.60 +/- 0.06 nM, p < 0.05) was significantly decreased only in cortex when compared to the control K(d) values of 0.88 +/- 0.04 nM and 0.47 +/- 0.02 nM in these regions, respectively. The basal AC activity did not alter in treated rats, where as, the inhibition of forskolin-stimulated AC activity by 5-HT (10 microM) was significantly (p < 0.0001) decreased both in cortex (43%) and hippocampus (40%) when compared to control levels. In conclusion, chronic treatment with trazodone results in downregulation of 5-HT(1A) receptors in cortex and hippocampus along with concomitant increased AC response, suggesting the involvement of 5-HT(1A) receptor-mediated AC response in the mechanism of action of trazodone.

Lamotrigine induced selective changes in 5-HT(1A) receptor mediated response in rat brain

A new anticonvulsant drug lamotrigine (LTG) has recently been reported to be effective in treating patients with bipolar affective disorder, depression and schizoaffective disorder, suggesting that it is a mood stabilizer. However, the mechanism of action underlying its efficacy in mood disorders is not understood. This study examined the in vivo effect of LTG on 5-HT(1A) receptor-mediated adenylyl cyclase (AC) response in regions of rat brain, as this pathway has been implicated in the therapeutic action of various classes of mood stabilizers. The density of 5-HT(1A) receptors was measured by radioligand binding assay using [(3)H]8-OH-DPAT (0.05-0.8nM) in frontal cortex and hippocampus of rats treated orally with LTG (5mg/kg) for 7 days. AC activity was assayed using [(3)H]ATP. The oral administration of LTG significantly decreased the density of cortical (50%, P<0.001) but not hippocampal 5-HT(1A) receptors, without significant change in the affinity of [(3)H]8-OH-DPAT to 5-HT(1A) receptor in these regions. There was no significant alteration in basal or forskolin-stimulated AC activity in either of regions. However, a significant decrease (P<0.01) in the inhibition of forskolin-stimulated AC activity by 8-OH-DPAT was observed only in cortical membranes of LTG treated rats when compared to control. These results suggest that one mode of action of LTG may be by the downregulation of cortical 5-HT(1A) receptor-mediated AC response.

Cortical 5-HT(1A) receptor downregulation by antidepressants in rat brain

Total 5-HT binding sites and 5-HT(1A) receptor density was measured in brain regions of rats treated with imipramine (5 mg/kg body wt), desipramine (10 mg/kg body wt) and clomipramine (10 mg/kg body wt), for 40 days, using [3H]5-HT and [3H]8-OH-DPAT, respectively. It was observed that chronic exposure to tricyclic antidepressants (TCAs) results in significant downregulation of total [3H]5-HT binding sites in cortex (42-76%) and hippocampus (35-67%). The 5-HT(1A) receptor density was, however, decreased significantly (32-60%) only in cortex with all the three drugs. Interestingly, in hippocampus imipramine treatment increased the 5-HT(1A) receptor density (14%). The affinity of [3H]8-OH-DPAT was increased only with imipramine treatment both in cortex and hippocampus. The affinity of [3H]5-HT to 5-HT binding sites in cortex was increased with imipramine treatment and decreased with desipramine and clomipramine treatment. 5-HT sensitive adenylyl cyclase (AC) activity was significantly increased in cortex with imipramine (72%) and clomipramine (17%) treatment, whereas in hippocampus only imipramine treatment significantly increased AC activity (50%). In conclusion, chronic treatment with TCAs results in downregulation of cortical 5-HT(1A) receptors along with concomitant increase in 5-HT stimulated AC activity suggesting the involvement of cortical 5-HT(1A) receptors in the mechanism of action of TCAs.

Differential protection and recovery of 5-HT1A receptors from N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) inactivation in regions of rat brain

The effect of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) on 5-HT1A receptors was studied in Sprague Dawley rats. A single dose of EEDQ (4 mg/kg body wt., i.p.) significantly inactivated 5-HT1A receptors, as measured by [3H]8-hydroxy-2-[di-n-propylamino]-tetralin ([3H]8-OH-DPAT), in cortex (64%, p < 0.0001) and hippocampus (48%, p < 0.0001). A significant (p < 0.01) increase in the affinity of 5-HT1A receptors for radioligand was observed in both regions. A dose dependent protection of cortical 5-HT1A receptors from EEDQ inactivation with pre-treatment of different doses of 8-OH-DPAT (4-20 mg/kg) was observed, along with recovery of affinity of [3H]8-OH-DPAT for 5-HT1A receptors in both regions. Although, a dose of 4 mg/kg of 8-OH-DPAT failed to attenuate the effect of EEDQ on hippocampal 5-HT1A receptors, a significant protection of these receptors was observed with 10 and 20 mg/kg of 8-OH-DPAT. Displacement studies revealed that EEDQ has more affinity for cortical (Ki = 101.3 +/- 11.8 nM) than hippocampal (Ki = 133.5 +/- 25.8 nM) 5-HT1A receptors. A time dependent natural recovery of 5-HT1A receptors from inactivation by a single dose of EEDQ (4 mg/kg) was observed more in cortex compared to hippocampus over a period from 1 day to 14 days. The results of this study suggest that 8-OH-DPAT inhibited EEDQ inactivation of cortical and hippocampal 5-HT1A receptors in a concentration dependent manner. The synthesis and turnover of 5-HT1A receptors differ in cortex and hippocampus, as evident by earlier recovery in the cortex.

Modulation of 5-HT1A receptor mediated response by fluoxetine in rat brain

Radioligand binding studies were done to investigate the effect of chronic administration of fluoxetine on 5-HT1 receptor mediated response to adenylate cyclase (AC) in rat brain. Our studies revealed a significant decrease in the densities of 5-HT1 and 5-HT1A receptor sites in cortex and hippocampus of rat brain after chronic administration of fluoxetine (10 mg/Kg body wt.). However there was no significant change in the affinity of [3H]5-HT and [3H]DPAT for 5-HT1 and 5-HT1A receptor sites, respectively. However, in striatum, along with a significant (75%) downregulation of 5-HT1 sites, the affinity of [3H]5-HT to these sites was increased, as revealed by decrease in Kd (0.50 +/- 0.08 nM). Displacement studies showed that fluoxetine has higher affinity for 5-HT1A receptors with a Ki value of 14.0 +/- 2.8 nM, than 5-HT1 sites. No significant change was observed in basal AC activity in any region after fluoxetine exposure. However, in cortex of experimental rats the 5-HT stimulated AC activity was significantly increased (16.03 +/- 0.97 pmoles/mg protein; p < 0.01), when compared to 5-HT stimulated AC activity (12.98 +/- 0.78 pmoles/mg protein) in control rats. The increase in 5-HT stimulated AC activity in cortex may be due to the significant downregulation of 5-HT1A sites in cortex after fluoxetine exposure as these sites are negatively coupled to AC. The observed significant decrease in 5-HT1 sites with concomitant increase in 5-HT stimulated AC activity, after fluoxetine treatment, suggests that fluoxetine, which has high affinity for these sites, acts by modulating the 5-HT1A receptor mediated response in brain.

Differential effect of lithium on 5-HT1 receptor-linked system in regions of rat brain

The effect of chronic administration (0.4% for 30 days) of lithium carbonate (Li2CO3) on 5-HT1 receptor-linked second messenger system was studied in regions of rat brain. We observed that chronic treatment of Li2CO3, significantly decreased the density of [3H]5-HT binding sites in cortex (62%), hippocampus (64%) and striatum (65%), compared to the control levels. The affinity of [3H]5-HT to 5-HT1 binding sites was significantly decreased in all the regions. A significant decrease in the density of high affinity 5-HT1A receptor sites was observed in cortex (81%) and hippocampus (42%), without change in the affinity of [3H]8-OH-DPAT for 5-HT1A sites in these regions. 5-HT-stimulated, but not basal, adenylyl cyclase activity was significantly increased in all the regions after Li treatment. The present study concludes that the increase in the 5-HT-stimulated adenylyl cyclase activity might be attributed to the functional downregulation of 5-HT1 receptors, as these are negatively coupled to adenylyl cyclase, suggesting the involvement of 5-HT1 receptor mediated response in the therapeutic efficacy of lithium.

Inactivation of 5-HT1A and [3H]5-HT binding sites by N-ethoxycarbonyl-2-ethoxy-1, 2-dihydroquinoline (EEDQ) in rat brain

Inactivation of 5-HT1A and [3H]5-HT binding sites by N-Ethoxycarbonyl-2-ethoxy-1, 2-dihydroquinoline (EEDQ) was studied in regions of rat brain. After exposure to EEDQ (4 mg/kg body wt.) for 7 days, it is observed that the density of 5-HT1 receptor sites was decreased by nearly 20% in both cortex and hippocampus. The decrease, however, in 5-HT1A sites was more significant (70%) in both the regions. The affinity of [3H]5-HT to 5-HT1 sites was decreased significantly in both cortex and hippocampus after exposure to EEDQ, without affecting the Kd of 5-HT1A sites. Displacement studies suggested that EEDQ has high affinity to 5-HT1 sites with a Ki of 42.9+/-2.4 nM. After exposure neither basal nor 5-HT stimulated adenylyl cyclase activity was changed in cortex. The results of this study suggest that EEDQ decreases the density of 5-HT1 and 5-HT1A receptor sites but does not cause functional downregulation of these sites in rat brain.

Effect of antidepressants on intracellular Ca++ mobilization in human frontal cortex

BACKGROUND

It is well documented that central serotonin (5-HT)2 receptor dysfunction is involved in the biochemistry and pathophysiology of depression and might be corrected by antidepressant drug treatment.

METHODS

The effect of imipramine (IMI) and fluoxetine (FLX) on 5-HT2A receptor-mediated intracellular calcium ([Ca++]i) mobilization in synaptosomes of human frontal cortex was studied. [Ca++]i was measured using Fura-2AM.

RESULTS

It was observed that in response to 5-HT (10 mumol/L) there was a significant increase (254%; p < .001) in [Ca++]i compared to basal level (140.00 +/- 31.77 nmol/L/mg protein). Both IMI and FLX (10-1000 nmol/L) induce mobilization of basal [Ca++]i in a dose-dependent manner. IMI and FLX antagonize the 5-HT-stimulated [Ca++]i mobilization in a dose-dependent manner. IMI showed higher antagonizing effect at lower concentration (10 nmol/L); however, FLX showed maximum antagonizing effect at higher concentration (1000 nmol/L).

CONCLUSIONS

It is observed that imipramine and fluoxetine have different effects on antagonizing the 5-HT response in frontal cortex. One mode of action of these antidepressants might be by decreasing the intracellular calcium.

Imipramine-induced changes in 5-HT2 receptor sites and inositoltrisphosphate levels in rat brain

The effect of chronic administration of Imipramine on [3H]Spiperone binding to 5-HT2 sites and inositoltrisphosphate (IP3) levels in rat cerebral cortex was studied. Our data shows that treatment with imipramine (5 mg/kg body weight, intraperitoneally) for 30 days significantly down regulates 5-HT2 receptors sites (262 +/- 29 fmol/mg protein) in cerebral cortex (38%), compared to control rats (425 +/- 60 fmol/mg protein., P < 0.001). However there was no significant change in the affinity of [3H]-Spiperone binding (kd) to 5-HT2 sites in cerebral cortex after exposure to imipramine (Kd = 0.84 +/- 0.11 nM). It is also observed that imipramine treatment significantly reduces 5-HT stimulated [3H]IP3 formation in cerebral cortex (6,411 +/- 708 dpm/mg protein), compared to the saline treated rats (12,238 +/- 1,544 dpm/mg protein; P < 0.001), with concomitant decrease in Pdtlns-4-5-P2. This study suggests that the therapeutic action of imipramine in brain might be by reducing hypersensitivity of 5-HT2 receptors by down regulation, which leads to reduced levels of inositolphospholipids. This inturn reduces the levels of IP3. In conclusion, imipramine acts at presynaptic site by blocking the reuptake of serotonin and at post synaptic site it downregulates 5-HT2 sites with decreased IP3 levels after chronic exposure.

Gender but not stimulus parameters influence prolactin response to electroconvulsive therapy

The post-ictal prolactin (PRL) response represents one of the most consistent findings of electroconvulsive therapy (ECT), but correlates variably with the gender of the patient, ECT stimulus waveform, dose and electrode placement. Forty patients with endogenous depression (29 drug-naive) received either high-energy (240 mC) or low-energy (60 mC) bilateral brief-pulse ECT once or three times a week. The PRL and growth hormone (GH) levels were estimated using double antibody radioimmunoassay. The average post-ECT PRL levels differed significantly from the pre-ECT levels, with a seven- to nine-fold increase in PRL at each week of treatment. No such difference was observed in the GH levels. All patients showed an increase in PRL levels, whereas 42% failed to show an increase in GH levels. The delta PRL response (difference between post-ECT and pre-ECT serum hormone levels) was not significantly different between the drug-naive and medicated patients nor between the high-energy and low-energy groups at first ECT. Similarly, no difference was observed between the once-weekly and thrice-weekly groups at the third week of ECT. At each week of treatment, the delta PRL was significantly higher in females than in males, unlike the GH response. Electroencephalographic (EEG) seizure duration did not correlate with either delta PRL or delta GH at first ECT and third week ECT. Apart from gender, none of the variables, such as age, baseline severity of illness, presence of psychotic symptoms, drug-naive status, stimulus dose, seizure duration, seizure strength, pattern and symmetry, frequency of ECT and degree of improvement predicted the delta PRL response. Neither stimulus energy nor frequency of ECT had a significant effect on PRL response. Gender differences in PRL response to ECT merit further investigations.

Increased acetylcholinesterase activity in selected regions of rat brain after chronic (-)-deprenyl administration

(-)-Deprenyl, 0.05, 1.0, 2.0, and 10.0 mg/kg body weight, was administered intraperitonially to Wistar rats for 30 days. The activity of acetylcholinesterase, and monoamine oxidase A and B were assayed in different brain regions. After the experimental period acetyl cholinesterase activity was found to be significantly increased in frontal cortex [P < 0.001] and hippocampus [P < 0.001] but not in striatum and brainstem at 0.1, 1.0, and 2.0 mg/kg dose, the maximum increase being at 0.1 mg/kg dose. Monoamine oxidase B activity was inhibited by more than 90% at 1.0, 2.0, and 10.0 mg/kg dose while 0.05 and 0.1 dose inhibited only about 55% and 70% respectively. Monoamine oxidase A activity was inhibited to more than 70% at 1.0 mg dose and to more than 90% at 2.0 and 10.0 mg/kg dose. At 0.05 and 0.1 mg/kg dose monoamine oxidase A activity was not significantly altered.

Monoamine oxidase isoenzymes in rat brain: differential changes during postnatal development but not aging

Differential development of monoamine oxidase (MAO) isoenzymes in rat whole brain is described in postnatally developing Sprague-Dawley rats. Total MAO and isoenzyme activity was measured using nonspecific and specific substrates. Total MAO activity measured using tyramine, increased postnatally up to 24 weeks of age and attained a plateau afterward. The increase in total MAO activity was significant at all age groups (18 days to 36 months) investigated as compared to new born rats. MAO-A and MAO-B activities were measured using octopamine and benzylamine respectively. We also observed a marginal increase of MAO-A activity and a significant increase of MAO-B activity upon development. Furthermore, at 12 weeks of age, MAO-B activity increased by 10-fold as compared to new born and was consistent up to 36 months of age. The qualitative localization of the enzyme activity on non SDS-PAGE by nitroblue tetrazolium staining confirmed the increase of MAO-B during the development. It is suggested that the maturational increase of total MAO activity in brain is predominantly due to the increase of MAO-B isoenzyme.

Effect of chronic administration of phenytoin on regional monoamine levels in rat brain

Phenytoin (DPH) is a widely used anticonvulsant drug but a conclusive mode of action is not yet clear. This study was undertaken to assess the effects of chronic administration of DPH on monoamine levels. DPH (50 mg/kg body weight) was administered to adult male Wistar rats by intraperitoneal injections for 45 days and the regional brain levels of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) were assayed using high performance liquid chromatographic (HPLC) method. The experimental rats revealed no behavioral deficits of any kind nor body and brain weight deficits were observed. Increased NE levels were observed after DPH administration in motor cortex (P < 0.05), striatum-accumbens (P < 0.01) and hippocampus (P < 0.01), whereas, NE level was decreased in brain stem (P < 0.05). DA levels were increased in striatum-accumbens (P < 0.05), hypothalamus (P < 0.001) and cerebellum (P < 0.001) but decreased in brainstem (P < 0.01). In DPH treated rats, 5-HT levels were increased in motor cortex (P < 0.001) but decreased in cerebellum (P < 0.001) when compared to control group of rats. The present study suggest that chronic administration of DPH induces alterations in monoamine levels in specific brain regions. DPH seems to mediate its anticonvulsant action by selectively altering the monoamine levels in different brain regions.

The effect of chronic chlorpromazine administration on monoamine levels in various regions of rat brain

The neuroleptic drug, chlorpromazine (CPZ) has been shown to exert its antipsychotic effect by blocking post synaptic dopamine receptors. However, its effect on steady state levels of monoamines is still in discrepancy. In the present study, CPZ (4 mg/kg body weight) was administered intraperitoneally to adult Wistar rats chronically for 75 days and the levels of norepinephrine (NE), dopamine (DA) and 5-hydroxytryptamine (5-HT) were assayed in various brain regions by high performance liquid chromatography (HPLC). After the experimental period body and brain weights were not statistically different from controls. NE and 5-HT levels were increased only in hippocampus by 15% (p < 0.01) and 16% (p < 0.01) respectively. DA levels were consistently increased in cortex by 39% (p < 0.001), striatum-accumbens by 18% (p < 0.01), hippocampus by 27% (p < 0.01), hypothalamus by 34% (p < 0.001), cerebellum by 36% (p < 0.001) and brainstem by 40% (p < 0.001) in CPZ treated rats compared to controls. The results suggest that chronic CPZ administration increases DA levels in almost all regions of brain and reflect the ability of CPZ to preferentially interfere with synaptic transmission mediated by DA in brain. It also suggests that this increase in DA might be responsible for certain side effects seen in patients after chronic CPZ treatment.

Disulfiram lowers Ca2+, Mg(2+)-ATPase activity of rat brain synaptosomes

The chronic administration of disulfiram (DS) to rats resulted in significant decrease of synaptosomal Ca2+, Mg(2+)-ATPase activity. In vitro studies indicated that DS (ID50 = 20 microM) produced a dose-dependent inhibition of Ca2+, Mg(2+)-ATPase. However, diethyldithio-carbamate, a metabolite of DS, failed to modify Ca2+, Mg(2+)-ATPase activity, implying that the decrease in ATPase activity in DS administered rats was due to the effect of parent compound. The DS-mediated inhibition (48%) of ATPase activity was comparable with a similar degree of inhibition (49%) achieved by treating the synaptosomal membranes with N-ethylmaleimide (ID50 = 20 microM) in vitro. Furthermore, the inhibition by DS was neither altered by washing the membranes with EGTA nor reversed by treatment with sulfhydryl reagents such as GSH or dithiothreitol. About 74% and 68% decrease of synaptosomal Ca2+, Mg(2+)-ATPase specific activity was observed when treated with DS (30 microM) and EGTA (100 microM) respectively. The remaining 25-30% of total activity is suggested to be of Mg(2+)-dependent ATPase activity. This indicates that both these drugs may act on a common target, calmodulin component that represents 70-75% of total Ca2+, Mg(2+)-ATPase activity. Therefore, DS-mediated modulation of synaptosomal Ca2+, Mg(2+)-ATPase activity could affect its function of maintaining intracellular Ca2+ concentration. This could contribute to the deleterious effects on CNS.

Early onset Parkinson's disease: are juvenile- and young-onset different?

It is controversial if early onset Parkinson's disease (EOPD) (onset at < 41 years of age) is Parkinson's disease (PD) occurring at a younger age or a different disease. This controversy is due to some clinical and pathological differences between EOPD and PD. Within EOPD, there appear to be two groups namely: young onset Parkinson's disease (YOPD), with onset between 21 and 40 years, and juvenile parkinsonism (JP), with onset at < 20 years. The two major clinical differences between these groups are a higher familial occurrence of PD and dystonia in JP. In this study, we determine if the two groups have the classical features of PD, namely rest tremors, rigidity, bradykinesia, and postural instability, and have a meaningful response to levodopa. Furthermore, we compare their other clinical features, autonomic and cognitive functions, and levels of CSF monoamine metabolites to determine differences between these groups. We observe that all YOPD (100%) and JP (85%) patients had rest tremors. Most of these patients also had a meaningful response to levodopa (YOPD: 72%; JP: 100%). The prevalence of family history of PD was similar, whereas dystonia was more frequent in JP (43%) compared to YOPD (9%). Autonomic symptoms were twice as common in JP (42%) compared to YOPD (17%). However, bedside autonomic functions were abnormal in similar proportions and, like in PD, suggest involvement of parasympathetic nervous system. Cognitive dysfunction does occur but with no difference in severity between the two groups. The difference in number of patients between YOPD and JP groups makes statistical comparison of the occurrence of clinical features like dystonia and autonomic dysfunction difficult.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in monoamine levels in discrete regions of rat brain after chronic administration of carbamazepine

Carbamazepine (25 mg/kg body weight) was administered intraperitoneally to adult male Wistar rats for 45 days and norepinephrine (NE), dopamine (DA) and serotonin (5-HT) levels were simultaneously assayed in discrete brain regions by high performance liquid chromatographic (HPLC) method. Experimental rats displayed no behavioral abnormalities. Body and brain weights were not significantly different from control group of rats. After exposure it was observed that norepinephrine levels were elevated in motor cortex (P < 0.01) and cerebellum (P < 0.05), while dopamine levels were decreased in these two regions (P < 0.001, P < 0.05). However, dopamine levels were increased in hippocampus (P < 0.01). Serotonin levels were significantly decreased in motor cortex (P < 0.001) and hypothalamus (P < 0.001) but increased in striatum-accumbens (P < 0.001) and brainstem (P < 0.001). These results suggest that carbamazepine may mediate its anticonvulsant effect by differential alterations of monoamine levels in discrete brain regions particularly in motor cortex and cerebellum.

Sodium valproate induced alterations in monoamine levels in different regions of the rat brain

Sodium valproate is a well established anticonvulsant drug but its exact mode of action is not yet clear. With a view to find out whether the mechanism of action of sodium valproate is mediated by alteration in monoamine levels, apart from GABA, in brain, sodium valproate (200 mg/kg body wt) was administered i.p. to male adult Wistar rats for 45 days. The levels of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) were assayed in different brain regions using high performance liquid chromatographic (HPLC) method. It was noted that at the end of the experimental period there was no change in body or brain weight nor were there any neurological deficits as a result of sodium valproate administration. However, after administration of sodium valproate there was a significant increase in norepinephrine levels in hippocampus (P < 0.01) and brainstem (P < 0.01) while a significant decrease was noted in hypothalamus (P < 0.001). Dopamine levels were significantly increased in motor cortex (P < 0.01), hippocampus (P < 0.01) and hypothalamus (P < 0.001). Serotonin levels were significantly increased in striatum-accumbens and brain stem (P < 0.001). However a marginal increase was also observed in motor cortex and hippocampus. 5-HT levels were significantly decreased in hypothalamus (P < 0.001) and cerebellum (P < 0.01). The present findings suggest the possibility that the anticonvulsant effect of sodium valproate could be due to alterations in monoamine levels apart from its action on GABA, which would indicate also the efficacy of this drug in different types of seizures.

Visual and auditory evoked potentials in early onset Parkinson's disease and their relationship to cerebrospinal fluid monoamine metabolites

We studied visual (VEP) and brainstem auditory (BAEP) evoked potential changes in 23 patients with early onset Parkinson's disease (EOPD) to establish the nature of the changes as well as their relationship to dopaminergic (DA) and serotonergic (5-HT) disturbances, as determined by cerebrospinal fluid levels of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA). We also compared these parameters between the young onset (YOPD) and juvenile Parkinsonism (JP), the two subgroups of EOPD, to look for any possible differences between the two. In EOPD, the mean P100 latency of the VEP was significantly prolonged compared to controls (p < 0.001). However, within EOPD the evoked potential parameters were not significantly different between YOPD and the JP subgroups. P100 latency was abnormal in six patients (YOPD: 5, JP: 1) (26%). Six patients (YOPD: 3, JP:3) (26%) had abnormal BAEP. A significant negative correlation (r: -0.89, p < 1%) was observed between the P100 latency and CSF HVA levels. No correlation was observed between the BAEP interpeak latencies and either CSF HVA or 5-HIAA levels. This study suggests that VEP and BAEP abnormalities do occur in EOPD (in both YOPD and JP), and that the prolongation of P100 latency is secondary to DA deficiency as in PD. The cause of BAEP abnormalities is probably independent of DA and 5-HT disturbances. The only difference between EOPD and classical PD was the higher incidence of BAEP abnormalities in EOPD. There was no correlation between the VEP or BAEP changes to either the age at onset or duration of EOPD.

Changes in lactate dehydrogenase isoenzyme pattern in patients with tumors of the central nervous system

Lactate dehydrogenase (LDH) isoenzymes were studied in biopsy samples obtained from 100 benign and malignant brain tumors. Diagnosis was confirmed by histopathology. It is observed that all tumors investigated had elevated LDH activity and showed a LDH isoenzyme pattern which is different from that of normal brain. A pronounced cathodal shift was seen in malignant tumors like medulloblastoma, grade 3-4 astrocytomas and neuroblastomas, whereas anodal pattern was seen in benign tumors like grade 1-2 astrocytomas and oligodendrogliomas. Some tumors like meningiomas showed a midzone pattern like increased LDH3. It was possible to differentiate certain tumors on the basis of LDH isoenzyme pattern like medulloblastomas into differentiated and undifferentiated; craniopharyngiomas into recurring and non-recurring ones. LDH1/LDH5 ratio was low (< 1.0) in malignant tumors and high (5.0-14.0) in benign tumors and it was useful in differentiating tumors according to the degree of malignancy and biological behavior. It is observed that both LDH isoenzyme pattern and LDH1/LDH5 ratio could be used as an adjuvant to histopathological grading of brain tumors.

Effect of disulfiram administration on brain tryptophan, serotonin and peripheral tryptophan content

The prophylactic deterrent effect of disulfiram (DS) has been attributed to its ability to exacerbate sympathetic function. Though there are reports to indicate that DS administration could as well affect the neurotransmitter metabolism, few reports implicate the possibility of central nervous system (CNS) mediated anticraving effect of the drug. The present study involving the oral administration of DS to rats for 45 days has clearly shown a significant increase in 5-HT (815.4 +/- 74.7 ng/g, P < 0.01) and 5-HIAA (506.1 +/- 86.3 ng/g, P < 0.02) contents in brain when compared to control rats. The observed increase in 5-HT and 5-HIAA content was found to correlate (zeta = 0.89) with the concomitant increase in brain tryptophan content (4.15 +/- 1.05 nmol/g, P < 0.001) following DS administration. Further, the study on peripheral tryptophan content has shown an increase in both total and free fraction (ultrafiltrate) of plasma, which in turn was found to have an inverse relationship (zeta = -0.94, P < 0.05) with the decrease in liver tryptophan content following DS administration. Thus the observed increase in brain 5-HT level is attributed to the ability of DS to mobilise peripheral tryptophan for 5-HT synthesis in CNS. As there are reports to imply the hyposerotonergic function as responsible for craving, the present findings, that DS could enhance the 5-HT metabolism in brain, may partially explain the CNS mediated anticraving effect of DS.

Erythrocyte membrane sodium-potassium adenosine triphosphatase activity in affective disorders

Erythrocyte membrane Na+,K(+)-ATPase activity was studied in drug naive patients with bipolar (BP) mania (n = 62) and unipolar (UP) depression (n = 60) and normal controls (n = 66). Compared to controls there was a significantly decreased Na+,K(+)-ATPase activity in UP depressives but no change in BP manics. However, lithium treatment caused a significant increase in Na+,K(+)-ATPase activity although there was no correlation between plasma lithium levels and enzyme activity. Plasma cortisol correlated inversely with Na+,K(+)-ATPase in UP depressives. Interestingly, the lithium responders [less than 50% Beck Rafaelson's Mania Rating Scale (BRMS) score] showed a significant increase in Na+,K(+)-ATPase activity compared to lithium nonresponders (greater than 50% BRMS score). These observations indicate that monitoring of Na+,K(+)-ATPase activity during lithium therapy is useful to predict a therapeutic response.

Multiple endocrine responses to clonidine in obsessive compulsive dissorder

Seventy two subjects with OCD were compared with 18 normal healthy volunteers on multiple neuroendocrine responses to clonidine. Significant heterogeneity in OCD was observed in responses of growth hormone. There was also significant disturbances in Cortisol and ACTH release. An interactional model for noradrenergic and serotonergic dysfunction in OCD is discussed.

CSF amine metabolites in depression

The amine metabolites, namely homovanillic acid (HVA) and 5-hydroxy indoleacetic acid (5-HIAA) were measured in cerebrospinal fluid (CSF) of depressives (n = 30) and controls (n = 30). Depressed patients had significantly lower HVA levels than controls. No significant differences were noted between the two groups in 5-HIAA levels. However, the differences between the groups for the CSF HVA/5-HIAA ratio were larger than those for the CSF HVA alone (p less than 0.01 versus p less than 0.025, respectively). HVA levels correlated positively with monoamine oxidase activity and adenosine deaminase activity.

Effect of manganese on biogenic amine metabolism in regions of the rat brain

The effect of prolonged exposure to low-level manganese (Mn) on regional levels of biogenic amines in the rat brain was studied. Rats were given Mn in drinking-water for 90 days, which resulted in a two- to three-fold accumulation of Mn in all regions of the brain. After exposure, dopamine beta-hydroxylase (DBH), monoamine oxidase (MAO), dopamine (DA) and serotonin (5-HT) were measured in regions of the brain. There was a significant inhibition of DBH in the striatum (P less than 0.01), hypothalamus (P less than 0.01), mid-brain (P less than 0.001) and cortex (P less than 0.01). MAO was also decreased significantly in the cerebellum and cortex (both P less than 0.01). The striatum showed a decrease in DA content, but this was not significant. However, the hippocampus showed a significant decrease (P less than 0.01) and the mid-brain showed a significant increase (P less than 0.01) in DA levels. No significant changes were observed in 5-HT levels in any region, except for an increase in the cortex (P less than 0.01). It was observed that prolonged exposure of rats to low-level Mn affects both DBH and MAO, and that this effect is region-specific. However, the effect of Mn on biogenic amines seems to be variable, and this might explain the variable signs and symptoms observed in the various phases of Mn toxicity in humans.

Calcium and phosphorus levels in serum and CSF in dementia

Marked differences in CSF levels of both calcium and phosphorus were observed in patients with dementia and aged controls when compared with adult controls. A significant decrease in both Ca and P in CSF was observed in Alzheimer's type dementia (p less than 0.01) and multi-infarct dementia cases (p less than 0.01). The geriatric controls also showed a significant decrease in both Ca and P. A 60% decrease in diffusible Ca in CSF was noted both in patients and geriatric controls when compared to adult controls (p less than 0.001). Diffusible P was also decreased in all three groups (p less than 0.05). A marginal decrease in serum Ca and slight increase in P was observed in both patients and geriatric controls. The significant decrease in CSF Ca and P in both groups of patients compared with aged controls suggests this lowering of Ca and P is not due to solely to the aging process and indicates a role in the pathology of age-related disorders.

Role of glutathione reductase system in disulfiram conversion to diethyldithiocarbamate

Experiments were carried out to establish the role of glutathione reductase (GR), if any, in the metabolic conversion of disulfiram (DS) to diethyldithiocarbamate (DDC). It was observed that, under standard assay conditions, whereas DS was incorporated as a substrate instead of oxidised glutathione (GSSG), the enzymes from both human liver extract and yeast sources failed to reduce the parent compound, implying that glutathione reductase perse do not reduce disulfiram. However, the incorporation of disulfiram into an assay system comprising of GSSG, NADPH and reductase resulted in DS reduction to DDC. Further, the observation, that the GR assay system devoid of either GSSG or NADPH was found to lack DS reducing ability, implies that GSH as a reaction product of GR system is responsible for the reduction of DS to DDC. The results of in-vitro experiments indicated that GSH perse could reduce DS to DDC nonenzymatically, with a stoichiometric relationship of 2:1. Thus it is inferred that GR perse do not reduce DS, whereas GSH, as an intermediary metabolite of GR system, brings about non-enzymatic reduction of DS via a sulfhydral group exchange reaction.

Regional distribution of dopamine beta-hydroxylase and monoamine oxidase in the brains of rats exposed to manganese

The regional distribution of dopamine beta-hydroxylase (DBH) and monoamine oxidase (MAO) in rat brain was compared in control rats and rats given manganese in drinking-water (1 mg Mn/ml) for 30 days. In treated rats there was a significant accumulation of Mn in almost all regions of the brain except the hippocampus. Accumulation was highest in the hypothalamus, cortex and striatum. After Mn exposure, DBH activity was significantly decreased (in comparison with the controls) in the hypothalamus, striatum, mid-brain, cerebellum and cortex. A significant increase in MAO activity was found in the striatum, hypothalamus, mid-brain, hippocampus and medulla. The effects of Mn on these enzymes suggests the involvement of biogenic amines like dopamine, norepinephrine and serotonin during Mn toxicity. The effect of Mn is region specific and in certain regions the action of Mn on DBH differs from that on MAO. These different effects of Mn on DBH and MAO in different regions of the brain might explain the variable symptoms seen in Mn-induced neurotoxicity in humans.