Adrenaline, noradrenaline and dopamine levels in specific brain stem areas of acutely immobilized rats

Catecholamines (adrenaline, noradrenaline and dopamine) have been measured in specific areas of the rat brain stem after acute immobilization stress.Adrenaline levels were significantly decreased after 240 min of immobilization in all areas studied: A1 area, nucleus commissuralis (NCO), A2 area, anterior part of the nucleus tractus solitarii (NTS), and the locus coeruleus. Noradrenaline concentrations in stressed rats were significantly reduced only in the NTS area. In contrast, during stress there were no significant changes in dopamine concentrations with respect to control values in any of the areas studied.These results implicate the participation of central adrenalin neurons, localized in specific brain stem areas, and noradrenaline neurons innervating the rostral part of the nucleus tractus solitarii, in the mechanism of central response acute stress.     

Effects of monoamine oxidase inhibitors on levels of catechols and homovanillic acid in striatum and plasma

Levels of homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC) and dihydroxyphenylglycol (DHPG) in plasma and the striatium were measured after inhibition of monoamine oxidase type A (MAO-A) by clorgyline (4 mg/kg i.p.), MAO-B by (-)deprenyl (1 mg/kg i.p.), both MAO-A and MAO-B by nialamide (75 mg/kg i.p.) or peripheral neuronal MAO by debrisoquin (40 mg/kg i.p.). Levels of HVA in plasma decreased by about 60% after single doses of nialamide or clorgyline, by about 80% after repeated doses of nialamide, by about 40% after a single dose of debrisoquin and by about 50% after repeated doses of debrisoquin. The administration of clorgyline, nialamide or debrisoquin significantly decreased concentrations of DOPAC and DHPG in plasma, whereas (-)deprenyl did not affect levels of DHPG or HVA. None of the MAO inhibitors produced more than about 80% depression of levels of any of the deaminated metabolites. The results suggest that most of the HVA in plasma is derived from deamination of DA by MAO-A in peripheral neurons; that DOPAC in plasma is derived from cells outside the central nervous system; that DHPG in plasma is derived virtually exclusively from the metabolism of norepinephrine in sympathetic nerve endings and that residual levels of HVA after treatment with debrisoquin provide an improved but limited indication of central dopaminergic activity.     

Dopaminergic Neuronal Sprouting and Behavioral Recovery in Hemi-Parkinsonian Rats after Implantation of Amnion Cells

Cells obtained from human, monkey, or rat term amnion membrane produce an activity which, in vitro, increases process outgrowth front rat sympathetic neurons and from dopaminergic neurons of the rat ventral mesencephalon. To determine if these cells could induce sprouting of dopaminergic nerve fibers in vivo, the substantia nigra of rats was lesioned unilaterally with 6-hydroxydopamine and live-rat-term amnion cells, or killed-rat-term amnion cells were implanted into the denervated striata. A control group of rats received saline injections into the denervated striata. Rats implanted with live amnion cells had a significant decrease in turning in response to amphetamine. The lesioned and implanted striata of live-amnion-cell-implanted rats contained significantly greater areas of tyrosine hydroxylase-immunoreactive fibers that the lesioned and implanted striatum of rats in the killed-amnion-cell or saline groups. Differences in the area of tyrosine hydroxylase-immunoreactive fibers in the implanted striata or in amphetamine-induced rotation between killed amnion cell-implanted and saline-injected rats did not reach significance. Implants of live amnion cells into the striatum of a parkinsonian animal model can evoke the de novo appearance of dopaminergic fibers in the denervated striatum and behavioral recovery, most likely through a trophic mechanism.     

Quantification of the putative neurotoxin 2-amino-3-(methylamino)propanoic acid (BMAA) in cycadales: analysis of the seeds of some members of the family Cycadaceae

Over the past 30 years there have been attempts to link the unusually high incidence of amyotrophic lateral sclerosis (ALS) among the Chamorros native to the island of Guam to the consumption of the seeds of Cycas circinalis L., the false sago palm. In support of this relationship it was recently shown that, when given to primates, 2-amino-3-(methylamino)-propanoic acid (BMAA), a minor cycad component, can cause selective degeneration of upper and lower motor neurons in the spinal cord and clinical features similar to those of ALS. In order to test the relationship between ALS and cycads, we have developed a sensitive and precise gas chromatographic/mass spectrometric (GC/MS) assay for BMAA which allows direct assessment of the BMAA content in foods and is directly applicable to the assay of BMAA in biologic tissues and fluids. After the addition of a deuterated isotopomer as an internal standard and transesterication with 2-methyl-1-propanol, BMAA was extracted into dichloromethane and then acylated with pentafluoropropionic anhydride before GC/MS. This method permits precise quantification of BMAA in the low picogram/sample range. Direct quantification of the BMAA content in the female gametophyte tissue (endosperm) of a range of cycad seeds collected from Guam confirmed the presence of BMAA at levels of approximately 1 g/g (dry weight). The presence of BMAA in the seed extract was confirmed after derivatization of an aliquot of the extract and GC/MS analysis in the scanning mode. BMAA was found to be present, albeit at lower levels, in the endosperm of the seeds of C. revoluta (0.32 mg/g) and C. media (0.29 mg/g).     

Patterns of plasma levels of catechols in neurogenic orthostatic hypotension

Patients with neurogenic orthostatic hypotension can have deficits in sympathetic neural function at any of several levels of the sympathetic neuraxis. We determined whether patterns of plasma levels of dopa, norepinephrine, dihydroxyphenylglycol, and dihydroxyphenylacetic acid would distinguish patients with orthostatic hypotension associated with multiple system atrophy, pure autonomic failure, or deficiency of dopamine-beta-hydroxylase. Plasma levels of catechols were normal in most patients with multiple system atrophy, consistent with relatively intact peripheral sympathetic neurons; in contrast, most patients with pure autonomic failure had decreased levels of all four catechols, consistent with degenerative loss of sympathetic nerve endings. Patients with deficiency of dopamine-beta-hydroxylase had increased levels of dopa and dihydroxyphenylacetic acid and markedly decreased levels of norepinephrine and dihydroxyphenylglycol, suggesting compensatory increases in sympathetic nerve activity in the absence of norepinephrine biosynthesis. Subgroups of patients with pure autonomic failure or multiple system atrophy had low levels of norepinephrine with normal levels of dopa, dihydroxyphenylglycol, and dihydroxyphenylacetic acid, consistent with normal catecholamine biosynthesis and decreased postganglionic sympathetic nerve traffic or decreased exocytotic release from sympathetic nerve endings. The results demonstrate the value of examining patterns of plasma levels of catechols to elucidate mechanisms of neurogenic orthostatic hypotension.