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Biomedical subjects

D L Murphy

Publications and source records attributed to D L Murphy.

At least 163 records · Page 9Linked to original sources
PubMed1993

Fluoxetine and desipramine selectively attenuate 2'-NH2-MPTP-induced depletions in serotonin and norepinephrine.

We recently reported that the novel MPTP analog 1-methyl-4-(2'-aminophenyl)-1,2,3,6-tetrahydropyridine (2'-NH2-MPTP) administered to C57BL/6 mice produced substantial decreases in forebrain serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), and norepinephrine, with negligible effects on brain dopamine or dopamine metabolites. In the present report, we confirm and extend our original results to include dose-response data and the effect of selective uptake inhibition on the levels of monoamine neurotransmitters in various regions of the mouse brain following treatment with 2'-NH2-MPTP. In a dose-ranging study, 2'-NH2-MPTP (10 mg/kg x 4) produced a 25-30% reduction in frontal cortex 5-HT, 5-HIAA, and norepinephrine. When 4 x 20 mg/kg 2'-NH2-MPTP was administered, 70-75% reductions in 5-HT, 5-HIAA, and norepinephrine in both frontal cortex and hippocampus were seen 1 week after treatment. No changes in dopamine were found in striatum or in any of the other brain regions examined at either dose. Doses of 40 and 60 mg/kg were lethal shortly after a single injection. In mice receiving either fluoxetine or desipramine (10 mg/kg) prior to 2'-NH2-MPTP (20 mg/kg x 4), decreases in 5-HT and norepinephrine, respectively, were significantly attenuated by approximately 30-40%. These data suggest that 2'-NH2-MPTP acts in a dose-dependent manner and that the serotonergic and noradrenergic uptake systems are involved in the mechanism by which 2'-NH2-MPTP causes selective deficits in cortical and hippocampal 5-HT and norepinephrine.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

Apparent antioxidant effect of l-deprenyl on hydroxyl radical formation and nigral injury elicited by MPP+ in vivo.

Using a modified microdialysis procedure, we confirmed that intrastriatal administration of 1-methyl-4-phenylpyridinium ion (MPP+) induced a sustained overflow of dopamine accompanied by increased formation of hydroxyl free radicals (.OH) as reflected by salicylate hydroxylation. Pretreatment with l-deprenyl (selegiline 60 pmol, intrastriatal perfusion) significantly decreased the .OH formation elicited by MPP+ (75 nmol). There was a small decrease of dopamine efflux and an insignificant change of the ratio of 3,4-dihydroxyphenylacetic acid (DOPAC)/dopamine following l-deprenyl pretreatment. These in vivo findings support prior in vitro data that an unique antioxidant property of l-deprenyl may be independent of its inhibition of type B monoamine oxidase. In addition, intranigral co-administration of l-deprenyl (4.2 nmol) with MPP+ (4.2 nmol) completely protected nigral neurons from probable oxidative injuries induced by MPP+ (4.2 nmol), as reflected by a near 50% loss of striatal dopamine ipsilateral to the side of infusion of drug into the substantia nigra. This apparent neuroprotective effect of l-deprenyl on midbrain nigral neurons was also confirmed by histological findings. The present in vivo data clearly demonstrate that l-deprenyl can protect nigral neurons against dopamine neurotoxicity produced by MPP+, as suggested by an earlier in vitro study. Thus, l-deprenyl can preserve the function of MPP(+)-damaged nigral neurons perhaps by its apparent antioxidant property in addition to its blockade of the bioactivation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to toxic pyridinium metabolites by type B monoamine oxidase.

1-Methyl-4-phenylpyridinium↗
PubMed1993

Attenuation of hypercortisolemia in fawn-hooded rats by antidepressant drugs.

Long-term (21 days) treatment with imipramine, clomipramine (tricyclic antidepressants) and clorgyline (monoamine-oxidase type A inhibiting antidepressant) produced significant decreases in plasma corticosterone levels in fawn-hooded (FH) rats. In contrast, plasma adrenocorticotropic hormone (ACTH) levels were not altered by chronic imipramine or clorgyline treatment but were significantly higher in chronic clomipramine-treated FH rats. These findings demonstrate a differential effect of chronic antidepressant treatment on plasma ACTH and corticosterone concentrations in FH rats and, furthermore, support the results of earlier studies suggesting that the FH rat strain may represent a genetic model of depression.

Adrenocorticotropic Hormone↗
PubMed1993

Seasonal variation in behavioral responses to m-CPP in patients with seasonal affective disorder and controls.

This paper reports the behavioral responses to m-chlorophenylpiperazine (m-CPP), a serotonin agonist, in patients with seasonal affective disorder (SAD) and controls during the summer. Results are compared with the responses of SAD patients and controls given m-CPP in the winter. Results of the winter study were reported earlier by our group. Baseline Hamilton depression ratings in SAD patients were significantly lower in the summer than in winter (p < 0.05). Additionally, in both SAD patients and controls, there were seasonal differences on the National Institute of Mental Health (NIMH) self-rating scale items: "depressed affect," "dysphoria," and "functional deficit" at baseline. The behavioral responses to m-CPP across seasons differentiated patients from normals only in the "activation/euphoria" item, on which a far greater response was seen in patients than in controls during the winter. This behavioral response may be a state marker for winter depression, as it was significantly reduced after light treatment of these patients in the winter, and in the summer. SAD patients responded differently from controls on "altered self-awareness" and "dysphoria" independently of seasons, and these responses may be considered as possible trait markers for this condition. These results provide further evidence of a possible deficiency in serotonergic transmission in seasonal affective disorder.

Adult↗
PubMed1993

Lack of evidence for Huntington's disease-like cognitive dysfunction in obsessive-compulsive disorder.

Cognitive deficits in patients with structural lesions of the basal ganglia (e.g., Huntington's disease) commonly include slowed processing, reduced verbal fluency, difficulty switching set, impaired egocentric spatial ability, poor recall, and impaired acquisition of motor skills. The goal of this study was to determine if patients with obsessive-compulsive disorder (OCD) would have a similar pattern of cognitive dysfunction. A battery of neuropsychological tests, including reaction time-based measures of cognitive processing speed and a test of procedural, motor-skill learning, was administered to 17 unmedicated OCD patients and 16 age-and education-matched normal controls. Eleven individuals with trichotillomania, matched with the OCD patients on age, education, age at symptom onset, depression, and anxiety were also tested. Contrary to expectation, neither the OCD nor trichotillomania patients were impaired on any of the measures in the battery. The essentially normal performance by these patients suggests that the brain regions responsible for cognitive dysfunction in patients with Huntington's disease may differ from those associated with OCD.

Adolescent↗
PubMed1993

A comparison of the behavioral effects of oral versus intravenous mCPP administration in OCD patients and the effect of metergoline prior to i.v. mCPP.

In prior studies form three centers, an exacerbation of obsessive-compulsive disorder (OCD) symptoms was reported in some (55%-83%) patients with OCD receiving the serotonergic agonist m-chlorophenylpiperazine (m-CPP) orally, whereas intravenously administered mCPP produced anxiety but no OCD symptom exacerbation. In the present replication attempt, 27 OCD patients were given mCPP either orally (n = 17) or intravenously (n = 10) under double-blind conditions, using identical behavioral rating measures. OCD symptoms were significantly increased after intravenous mCPP (0.1 mg/kg), but not after oral mCPP (0.5 mg/kg). Anxiety and other ratings were markedly elevated after intravenous mCPP administration. After oral mCPP administration, anxiety and most other self-ratings were only slightly elevated in comparison to placebo administration, and behavioral rating increases were no different for the OCD patients compared to age-matched healthy controls. Pretreatment with the potent serotonin (5-HT) antagonist, metergoline, prior to intravenous mCPP was associated with essentially complete blockade of the exacerbation in OCD symptoms and the other behavioral responses in the OCD patients. These results suggest that the behavioral response of OCD patients to mCPP are variable and depend on the route and dose of mCPP. In addition, the ability of metergoline to antagonize the behavioral effects of intravenous mCPP suggests that these responses are mediated by 5-HT1/5-HT2 receptors.

Administration, Oral↗
PubMed1993

Effects of clozapine and fluphenazine treatment on responses to m-chlorophenylpiperazine infusions in schizophrenia.

OBJECTIVE: To explore serotonin function in patients with schizophrenia during typical and atypical neuroleptic treatment. We hypothesized that clinically relevant doses of the atypical neuroleptic clozapine would attenuate responses to the serotonin agonist m-chlorophenylpiperazine (m-CPP). DESIGN AND INTERVENTIONS: m-CPP or placebo was administered intravenously over 90 seconds to patients who had been receiving no medications for at least 3 weeks. m-CPP was also administered during treatment with the typical neuroleptic fluphenazine and the atypical neuroleptic clozapine. PATIENTS: Fifteen inpatients (two women and 13 men) who met DSM-III-R criteria for chronic schizophrenia (n = 13) or schizoaffective disorder (n = 2) participated in the study. Mean age (+/- SD) was 33.8 +/- 8.0 years. MAIN OUTCOME MEASURES: Measures of m-CPP effects included plasma cortisol and prolactin, body temperature, and the Brief Psychiatric Rating Scale (BPRS). The final BPRS total score at approximately 12 weeks of treatment was used to assess response to clozapine. RESULTS: m-CPP infusion significantly increased plasma cortisol and prolactin levels in drug-free patients. There was a range of behavioral responses while drug-free, but no statistically significant effects on BPRS total or BPRS factor scores. Clozapine treatment significantly blocked neuroendocrine responses to m-CPP, whereas fluphenazine had no effect. Clozapine also appeared to attenuate behavioral responses. CONCLUSIONS: These results demonstrate that clozapine treatment has potent serotonin antagonist effects in patients with schizophrenia. This may be related to clozapine's therapeutic effects since patients with greater cortisol response to m-CPP while drug-free had a better subsequent response to clozapine.

Adult↗
PubMed1993

Isolation of a cDNA encoding the human brain serotonin transporter.

A cDNA encoding a serotonin transporter (5-HTT) in the human dorsal raphe nucleus was isolated and sequenced using cross-species amplification of human 5-HTT partial cDNA by the polymerase chain reaction (PCR) and the RACE-PCR procedure, designed for rapid amplification of 3' and 5' cDNA ends. The cDNA contains an open reading frame encoding a hydrophobic polypeptide of 630 amino acids with a calculated molecular weight of approximately 70 kDa. The human 5-HTT is approximately 92% homologous to the rat protein but contains an additional consensus phosphorylation site for cAMP-dependent protein kinase recognition located in the cytoplasmic N-terminal region, while a potential protein kinase C phosphorylation site identified in the rat homolog is not conserved in the human 5-HTT. Hydropathicity analysis revealed twelve membrane spanning segments, a topology proposed for other cloned sodium-dependent transporters.

Amino Acid Sequence↗
PubMed1993

Extensive sequence divergence between the human and rat brain vesicular monoamine transporter: possible molecular basis for species differences in the susceptibility to MPP+.

A cDNA encoding the human brain vesicular monoamine transporter (VMT) was isolated and sequenced using PCR. The cDNA contains an open reading frame encoding a hydrophobic polypeptide of 514 amino acids with twelve membrane spanning segments, a calculated molecular weight of 55,709 Da, and an estimated isoelectrical point of 5.62. A structurally identical transporter is expressed in human platelets. Two intraplasmatic consensus phosphorylation sites of cAMP-dependent protein kinase recognition and two potential protein kinase C phosphorylation sites may be central to the regulation of the VMT. Although the human brain VMT is 90.7% homologous to the rat protein, an extensive sequence divergence occurs in the large luminal loop located between the first two transmembrane domains. This loop displays a remarkably reduced homology of 64.0% with several deletions and insertions, although four putative glycosylation sites are conserved. Since functional vesicular monoamine transport suppresses MPP+ toxicity and sequence divergence in the large luminal loop of the VMT expressed in rat brain and adrenal medulla may play a role in differential neurotoxic effects of MPP+, our findings indicate one possible molecular basis for the substantial species differences in the susceptibility to MPP+ demonstrated among humans, non-human primates, and rodents. They are also likely to facilitate molecular pharmacologic and genetic investigations of the human VMT in neurodegenerative disorders.

Amino Acid Sequence↗
PubMed1993

Regional brain expression of serotonin transporter mRNA and its regulation by reuptake inhibiting antidepressants.

Regional expression and antidepressant drug-induced regulation of mRNA encoding the serotonin (5-HT) transporter were studied in rat brain. While 5-HT transporter mRNA is abundantly expressed in the midbrain raphe complex, lower concentrations were also found in frontal cortex, hippocampus, and neostriatum using a combination of reverse transcriptase-polymerase chain reaction (RT-PCR), Southern hybridization, and sequence analysis. Long-term administration of antidepressants which inhibit 5-HT reuptake, but not monoamine oxidase inhibitors or 5-HT receptor agonists, decrease 5-HT transporter mRNA steady-state concentrations. Based on these observations, we conclude that (1) mRNA coding for the 5-HT transporter is present in several brain areas associated with ascending HT pathways, and (2) chronic treatment with reuptake inhibiting antidepressants may be associated with regulation of the 5-HT transporter at the level of gene expression which may contribute to the neuroadaptive mechanisms that likely underlie their therapeutic efficacy.

Animals↗
PubMed1993

Sustained depletion of cortical and hippocampal serotonin and norepinephrine but not striatal dopamine by 1-methyl-4-(2'-aminophenyl)-1,2,3,6-tetrahydropyridine (2'-NH2-MPTP): a comparative study with 2'-CH3-MPTP and MPTP.

Unlike 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces consistent decreases in levels of striatal dopamine (DA) with considerably smaller and more variable effects on mouse brain levels of serotonin (5-HT) and norepinephrine (NE), a novel amine-substituted MPTP analogue, 1-methyl-4-(2'-aminophenyl)-1,2,3,6-tetrahydropyridine (2'-NH2-MPTP), administered in a standard mouse dosing paradigm for MPTP (20 mg/kg x 4) did not affect striatal DA but led to marked reductions (60-70%) in levels of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), and NE measured in frontal cortex and hippocampus 1 week after treatment. Another 2'-substituted MPTP analogue, 1-methyl-4-(2'-methylphenyl)-1,2,3,6- tetrahydropyridine, affected cortical and hippocampal 5-HT, 5-HIAA, and NE only minimally, while markedly reducing the DA content in striatum (90%), thus indicating that the substituent (-NH2 versus -CH3) at the 2' position is important for the differential effects of these MPTP analogues. In a replication study with a 3-week end point, hippocampal and cortical 5-HT, 5-HIAA,, and NE levels remained depressed with no indication of recovery. These results suggest that 2'-NH2-MPTP may be a novel, regionally selective neurotoxin for serotonergic and noradrenergic nerve terminals.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

Primary structure of the human platelet serotonin uptake site: identity with the brain serotonin transporter.

A cDNA encoding the human platelet serotonin (5-HT) uptake site was isolated and sequenced using the PCR. The cDNA represents a approximately 3.1-kb mRNA transcript and contains an open reading frame encoding a hydrophobic polypeptide of 630 amino acids with 12 membrane-spanning segments, a calculated molecular mass of 70,320 Da, and an estimated isoelectrical point of 5.84. The human platelet 5-HT uptake site is identical with the human brain 5-HT transporter and approximately 92% homologous to the rat protein. Hydropathicity analysis indicates 12 membrane-spanning segments with two putative glycosylation sites within the second extracellular loop. The human platelet 5-HT uptake site contains two intraplasmatic consensus phosphorylation sites for cyclic AMP-dependent protein kinase recognition located in the cytoplasmatic N-terminal region and three potential protein kinase C phosphorylation sites. The identity of the human platelet 5-HT uptake site and the brain 5-HT transporter indicates that both proteins are encoded by the same single-copy gene, which has been assigned to the human chromosome 17. Our findings are likely to facilitate molecular pharmacologic and genetic investigations of the 5-HT transporter in psychiatric disorders.

Adult↗
PubMed1993

Differential effect of short- and long-term lithium treatment on m-CPP-induced neuroendocrine changes in rats.

Intravenous administration of the serotonergic agent m-chlorophenylpiperazine (m-CPP) to rats produced increases in plasma prolactin and corticosterone and a decrease in plasma growth hormone concentrations. Short-term (2-4 days) and long-term (21-23 days) lithium treatment did not affect baseline levels of prolactin, corticosterone or growth hormone. Long-term lithium treatment accentuated m-CPP's effect on plasma prolactin and corticosterone but not on growth hormone levels. On the other hand, short-term lithium treatment attenuated m-CPP's effect on plasma corticosterone but not on plasma prolactin or growth hormone levels. These findings demonstrate a differential effect of the duration of lithium treatment on m-CPP-induced neuroendocrine changes. One possible explanation for this differential effect may be that different 5-HT receptor subtypes are involved in mediating different neuroendocrine functions and, furthermore, these different 5-HT receptor subtypes may be affected differentially following lithium treatment. Alternatively, lithium-induced changes in other neurotransmitter systems may be responsible for this differential effect.

Animals↗
PubMed1993

CSF somatostatin in obsessive-compulsive disorder.

OBJECTIVE: Because the central administration of somatostatin to experimental animals produces behaviors with some similarities to the compulsions of patients with obsessive-compulsive disorder and because serotonin reuptake inhibitors have been reported to reduce brain content of somatostatin, the authors examined central somatostatin activity in patients with obsessive-compulsive disorder. METHOD: CSF for measurement of somatostatin was obtained from 15 drug-free outpatients with obsessive-compulsive disorder and 27 normal volunteers. RESULTS: The mean CSF somatostatin level was significantly higher in the patients with obsessive-compulsive disorder than in the normal subjects. CONCLUSIONS: Although the functional significance of this finding is unknown, these data are consistent with a role for somatostatin in the clinical symptomatology of obsessive-compulsive disorder and its response to neuropharmacological agents. The high levels of CSF somatostatin reported here in a patient subgroup whose predominant symptoms consisted of overly focused, perseverative thought processes are in contrast to the consistently low levels of CSF somatostatin seen in patients with a spectrum of disorders characterized by substantial cognitive deficits.

Adolescent↗