NE Levels Research Articles

Changed central and peripheral catecholamines and indoleamines in one-way crossed-intestine rats: Relationship to changes in feeding behavior and metabolism

The involvement of central and peripheral catecholamines and serotonin (5-HT) in regulation of feeding and energy metabolism was examined in one-way crossed intestine rats that show large and sustained changes in daily food intake. Five to six weeks after the crossed-intestinal surgery, catecholamines and indoleamines in dissected major brain regions and in the heart, intrascapular brown adipose tissue (IntBAT), pancreas, and serum were determined using HPLC with electrochemical detection. The food-losing rats increased daily food intake from 70.8 to 126.3 g, whereas their partners decreased daily food intake from 67.1 to 38.7 g ( p < .001). Compared with the partners and sham-operated controls, the food-gaining rats had increased 5-hydroxy-indoleacetic acid (5-HIAA) throughout the brain [hypothalamus, 442.8 vs. 383.5 ( p < .05) and 404.2 ng/ g ( p < .05), Lateral cortex plus amygdala (LC + A), 236.6 vs. 216.8 ( p < .05) and 212.0 ng/g ( p < .05), brain stem, 282.8 vs. 238.7 ( p > .05) and 245.1 ng/g (p = .05), cerebellum, 56.7 vs. 49.6 ( p < .05) and 44.4 ng/g ( p < .05). Higher 5-HIAA in food-gaining rats that were undereating are consistent with serotonin's role in inhibiting food intake. Peripherally, the rats gaining food showed significantly lower NE, 5-HT, and 5-HIAA in IntBAT compared with their partners (NE, 994.2 vs. 1236 ng/g, 5-HT 338.0 vs. 527 ng/g, and 5-HIAA, 39 vs. 51 ng/g). Because NE and 5-HT have been shown to exert stimulating effects on BAT-mediated thermogenesis, lower levels of NE, 5-HT, and 5-HIAA In IntBAT of food gaining rats are compatible with the lower metabolic rate observed in these animals. The results show that both central and peripheral catecholamines and serotonin are involved in regulation of food intake and energy metabolism.

The kinetics of nutrient incorporation into body tissues of gilthead seabream (Sparus aurata) females and the subsequent effects on egg composition and egg quality.

The interaction between essential dietary components and changes in tissue nutrient reserves, egg quality and egg composition, were studied from 60 d before and during the spawning of Sparus aurata broodstock. Fish were given isonitrogenous (550 g/kg dry weight) and isolipidic (100 g/kg dry weight) diets, based on protein and lipid extracts of squid meal. Diets differed in the levels of n-6 (10-30 mg/g dry weight) and n-3 (0-10 mg/g dry weight) essential fatty acids. The effects of these diets on biochemical and fatty acid composition of body tissues, and the subsequent effects on egg composition and egg viability were measured. Dietary essential fatty acids were mostly incorporated into the liver, ovaries, digestive tract and associated adipose tissues. The lipid composition of these tissues reached an equilibrium with dietary lipid composition within 15 d of feeding on any given diet. Muscle and gill cartilage tissues did not show any significant changes in their biochemical and fatty acid composition, even after 60 d feeding. Egg viability decreased significantly within 10 d of feeding the broodstock with a diet deficient in n-3 highly unsaturated fatty acids (n-3 HUFA). The levels of n-3 HUFA in both polar and neutral fractions of egg lipid were directly correlated with their levels in the broodstock diet. When the total amount of egg n-3 HUFA dropped below 17 mg/g dry weight, egg viability and larvae hatching rate decreased by 53% and 47% respectively. These results suggest that the biochemical composition of organs involved in S. aurata reproduction are highly sensitive to the nutritional value of the diet, which affects egg and larval quality rapidly.

Effects of Excessive Supplemental Fat on Feedlot Cattle Growth Performance and Digestive Function

Ninety medium-framed crossbred steers (245kg) were used in a 205-d feeding trial to evaluate the influence of 4, 8, and 12% supplemental fat (tallow soap stock) on feedlot growth performance. Increasing level of fat supplementation depressed ADG (P<.01), DM conversion (P<.01), and dietary NE (P<.05). Depressions in DM conversion and dietary NE were more marked at the 12% level of fat supplementation. There was a quadratic effect (P<.01) of level of fat supplementation on DM intake, with intake being higher for 12% supplemental fat than for 8% supplemental fat. Observed:expected diet NEm was 1.00 with 4% supplemental fat and declined (P<.01) to .86 with 12% supplemental fat. The NEm of tallow soap stock declined in a near rectilinear fashion from 5.65 Mcal/kg at the 4% level of supplementation to 2.85 Mcal/kg at the 12% level of supplementation. Six Holstein steers (296kg) with T cannulas in the rumen and proximal duodenum were used to evaluate treatment effects on digestive function. Ruminal digestion of OM (P<.01), feed N (P<.01), and ADF (P<.05) decreased linearly with increasing level of fat supplementation. Most (55%) of the decline in ruminal OM digestion could be directly attributed to ruminal indigestibility of dietary fat. Increasing level of fat supplementation did not influence (P>.10) postruminal digestion of OM, ADF, starch, and N. Postruminal digestion of lipid decreased (P<.01) with increasing level of fat supplementation. Total lipid intake was a better predictor of postruminal lipid digestibility than percentage supplemental fat. True digestibility of supplemental tallow soap stock at the 8 and 12% levels of supplementation averaged 63 and 40%, respectively. Total tract OM digestion declined linearly (P<.01) with increasing level of supplemental fat. This decline was due to differences in lipid digestion. There were no associative effects of supplemental fat on total tract digestion of ADF, starch, and N. It is concluded that optimal growth performance response to supplemental fat will be obtained when levels of total lipid intake are less than 1.6g/kg body weight. Detrimental effects of excessive supplemental fat are primarily associated with depressed intestinal lipid digestibility.

Conditioned cocaine induced hyperactivity: an association with increased medial prefrontal cortex serotonin

Two sets of contextual stimuli, only one of which was associated with drug treatment, were employed in a new paradigm to assess the conditioned effects of ten cocaine (20 mg/kg) treatments on motoric behavior. Two matched groups of Sprague-Dawley rats were sequentially placed into two similar but distinct test compartments. The drug treatment was administered immediately prior to placement into the second test compartment in one group (paired group) but 2 h later in the other group (unpaired group). Changes in the non drug behavioral baseline were assessed in the non drug compartment immediately prior to each drug treatment and provided the referent baseline for determining stimulus specificity of the observed behavioral effects in the drug compartment. Both groups had equivalent activity levels in the non-drug compartment. In the drug compartment, however, the paired group showed an overall cocaine stimulant effect expressed as a marked increase in distance traversed in the drug box. Additionally, the repeated cocaine treatment induced a conditioned drug effect as revealed by the higher level of motor activity in the paired compared to the unpaired treatment group exclusively in the drug compartment in two post-treatment non-drug tests for conditioning after 1-day and 21-day withdrawal and non-testing intervals. The biochemical assay results showed no significant group differences in DA and dopamine metabolites, DOPAC, HVA and 3-MT, in striatal, limbic or cortical tissue. No differences were observed either in NE or plasma corticosterone levels. Importantly, the analysis for serotonin revealed higher levels of 5-HT and 5-HIAA selectively in the prefrontal cortex. These results suggest a role for the prefrontal cortex in the mediation of conditioned stimulant effects of cocaine.

High-resolution electronic spectroscopy of the Ne·OH and Ne·OD Ã ← X̃ bands

The high-resolution laser-induced fluorescence spectra of the Ne·OH A˜(0,11,1)←X˜(0,00,0) and Ne·OD A˜(0,00,0)←X˜(0,00,0),A˜(0,00,1)←X˜(0,00,0),A˜(0,10,1)←X˜(0,00,0),A˜(0,11,1)←X˜(0,00,0) transitions were obtained. Analyses of these spectra determine precise bond lengths and reveal interesting spin–rotation and parity structure. In the A (0, 1K=0,1, 1) levels of Ne·OH and Ne·OD, the spin–rotation structure is described with the parameter γ, whose magnitude is larger than in the other observed levels of Ne·OH, Ne·OD, and Ar·OH, and Ar·OD. For the K = 1 level an additional term κ is introduced and is found to be an order of magnitude larger than γ. A model based on perturbation theory is proposed and successfully explains the peculiar spin–rotation structure in the A (0, 1K, 1) levels. In addition, a parity-splitting (P-type doubling) for the X˜(0,00,0) level of Ne·OD was determined to be a factor of 10 larger than that in Ar·OD. The parity splitting (K-type doubling) for the A (0, 11, 1) level of Ne·OH is also observed and measured.

Monoamine activity in anterior hypothalamus of guinea pig pups separated from their mothers.

Brief isolation in a novel environment increased the ratios of 3-methoxy-4-hydroxyphenylethylene glycol to norepinephrine (MHPG:NE) and dihydroxyphenylacetic acid to dopamine (DOPAC:DA) in the anterior hypothalamus of guinea pig pups. Ratios were significantly elevated after 90 min of isolation and for MHPG:NE, after 30 min of isolation; changes were due to increases in MHPG and DOPAC. Home cage isolation produced no change in any measure of catecholamine activity. No changes in levels of serotonin or its metabolite were observed. In 1 experiment, resting levels of NE and DOPAC:DA were predictive of the rate of separation-induced vocalization. Maternal separation in the context of novelty increases hypothalamic NE and DA activity; however, both isolation and novelty are required because neither maternal separation in the home cage nor exposure to a novel cage together with the mother had any discernible effect.

Rosenthal oscillations observed on the emission cross sections and the polarization degrees of Ne(2p53p) levels in He+-Ne collisions

Relative emission cross sections were measured for all Ne(2p53p) levels (2p1-2p10 in the Paschen notation) excited by He+ ions with incident energy E=0.2-20 keV. The polarization degree was also determined for each emission line. For most of the levels, the energy dependence of both the emission cross sections and the polarization degrees show oscillatory structures in the energy range observed. These were interpreted as Rosenthal oscillations. From the phase correlation between the oscillations of these emission cross sections and those of He I 31P, we conclude that the He I 31P level interferes with 2p2-2p8. From the polarization degree we determine the partial emission cross sections of the magnetic sublevels for J=1 (J is the total angular momentum) levels (2p2, 2p5 and 2p7). For 2p2 and 2p5, the magnetic sublevels with MJ=+or-1 (MJ is the magnetic quantum number) were dominantly excited over the sublevel with MJ=0 and showed oscillations with larger amplitude than that for the Mj=0 level.

Neuroendocrine and behavioral effects of vasopressin in resting and mild stress conditions

Neuroendocrine and behavioral effects of subcutaneously administered AVP (6 μg/kg b.wt.) were determined in resting conditions and after the mild stress of transportation to and placement in a novel environment. In resting conditions, systemic administration of AVP caused a rapid increase in blood glucose level and a long-lasting increase in CORT secretion. A decrease in circulating plasma NE level was observed. AVP did not affect adrenal medullary E secretion. The stress-induced sympathetic activation, as reflected in plasma NE level, was inhibited 60 min after AVP administration. Stress-induced increases in blood glucose, CORT, and E secretion were not influenced by AVP. In resting condition, AVP caused a 60-min lasting increase in grooming behavior with a concomitant decrease in time spent resting. Sixty minutes after administration, the behavioral activation after the stress of transportation and placement in a novel environment was more rapidly terminated in AVP-treated rats than in vehicle-treated control rats. The state- and time-dependent modulation of spontaneous behavior suggests that AVP has arousing properties shortly after administration when marked pressor and endocrine effects are apparent. In a later phase, AVP may facilitate dearousal mechanisms following stress-induced behavioral activation.

Effects of chronic corticosterone ingestion on spatial memory performance and hippocampal serotonergic function

The effects of chronic ingestion of corticosterone (8 weeks via the drinking water, 400 μg/ml) on spatial memory performance and on monoamine levels in brain areas related to memory were investigated. Corticosterone treatment was associated with a long lasting (5 weeks post treatment) increase in 5-HT levels (44%) in the dentate gyrus of the hippocampus and decrease in 5-HT (50%) and NE (36%) levels in the frontal cortex. No effects were found in CA1, CA3 or in nucleus basalis. Performance of the rats on an 8-arm radial arm maze showed no overall effect of corticosterone treatment on trials to criterion or choice accuracy scores. However, three of the treated rats, who had consumed the most corticosterone during treatment, 12.5±0.3mg/day, were impaired relative to all subjects. Thus, these results that hippocampal serotonergic terminals show long lasting effects from corticosterone and may also be an early indicator of deleterious effects of glucocorticoids on hippocampal function. However, since only a small number of corticosterone-treated rats showed behavioral changes, future experiments are necessary to address the possibility that a higher level of corticosterone intake alters spatial memory as well as brain morphology and neurochemistry. Additional studies are also needed to determine whether such changes represent a threshold effect of the steroid or a dose-response function.

Effect of fluvoxamine, imipramine and placebo on catecholamine function in depressed outpatients

Many of the specific serotonin reuptake inhibitors appear to have some effect on noradrenergic function. Fluvoxamine is one of the newer agents and its specificity has not been fully assessed. Depressed patients participating in a study comparing the efficacy of fluvoxamine with imipramine and placebo collected 24 hour urine samples ( N = 38) and had plasma samples drawn ( N = 38) prior to and after 6 weeks of double blind treatment. Urine samples were analyzed for 24 hour output of MHPG, VMA, NMN, MN and HVA. Plasma samples were analyzed for NE levels. Imipramine treatment produced a reduction in urinary MHPG, an increase in the ratio of NMN to MHPG plus VMA, and a trend towards an increase in plasma NE which was significantly different than the effects seen in the fluvoxamine and placebo groups. There was an additional finding in the imipramine group of a significant correlation between percentage change in plasma NE and clinical improvement. Fluvoxamine treatment, on the other hand, produced no clear effect on any measure of noradrenergic function and the antidepressant efficacy of fluvoxamine was unrelated to any noradrenergic variable. These findings lend support to the hypothesis that fluvoxamine does not have significant effects on noradrenergic function.

Clozapine response and plasma catecholamines and their metabolites

The atypical neuroleptic clozapine has an unusual profile of clinical effects and a distinctive spectrum of pharmacological actions. Plasma measures of catecholamines and their metabolites have been used in the past to study the action of typical neuroleptics. We obtained longitudinal assessments of plasma measures of dopamine (pDA), norepinephrine (pNE), and their metabolites, homovanillic acid (pHVA) and 3-methoxy-4-hydroxyphenylglycol (pMHPG), in eight treatment-resistant or treatment-intolerant schizophrenic patients who were treated with clozapine for 12 weeks following a prolonged drug-washout period. Our findings from the study of these eight patients suggest the following: Plasma levels of HVA and possibly NE derived from the neuroleptic-free baseline period may predict response to clozapine; plasma levels of HVA and MHPG decrease during the initial weeks of treatment in responders but not in nonresponders; and plasma levels of DA and NE increase in both responders and nonresponders to clozapine.

Relationship between decrements in glucose level and metabolic response to hypoglycemia in absence of counterregulatory hormones in the conscious dog.

To determine the relationship between decreases in glucose and metabolic regulation in the absence of counterregulatory hormones, we infused overnight-fasted, conscious, adrenalectomized dogs (lacking cortisol and EPI) with somatostatin (to eliminate glucagon and growth hormone) and intraportal insulin (30 pmol.kg-1.min-1), creating arterial insulin levels of approximately 2000 pM. Glucose was infused during one 120-min period, two 90-min periods, and one 45-min period to establish levels of 5.9 +/- 0.1, 3.4 +/- 0.1, 2.5 +/- 0.1, and 1.7 +/- 0.1 mM, respectively. NE levels were 1.24 +/- 0.23, 1.85 +/- 0.27, 2.04 +/- 0.26, and 2.50 +/- 0.20 nM, respectively. During the euglycemic control period, the liver took up glucose (7.5 +/- 1.9 mumol.kg-1.min-1), but hypoglycemia triggered successively greater rates of net hepatic glucose output (3.0 +/- 0.7, 4.6 +/- 0.9, and 6.9 +/- 1.4 mumol.kg-1.min-1). Total gluconeogenic precursor uptake by the liver increased with hypoglycemia. Intrahepatic gluconeogenic efficiency rose progressively (by 106 +/- 42, 199 +/- 56, and 268 +/- 55%). Both glycerol and NEFA levels rose, indicating lipolysis was enhanced. Net hepatic NEFA uptake and ketone production increased proportionally, but the ketone level rose only with severe hypoglycemia. In conclusion, despite marked hyperinsulinemia and the absence of glucagon, EPI, and cortisol, we observed that lipolysis and glucose and ketone production increase in response to decreases in glucose. This suggests that neural and/or autoregulatory mechanisms can play a role in combating hypoglycemia.

Urinary catecholamines and cortisol in parasuicide

A relationship of urinary catecholamines and of urinary free cortisol with violent suicide attempts has been reported. We have reexamined this issue in patients within 24 hours of hospital admission. Suicide attempters had significantly higher norepinephrine (NE: mean ± SD = 58.3 ± 27.0 μg/24 hours; n = 27) than did control patients with suicidal ideation (mean ± SD = 37.1 ±21.3; n = 10). Among suicide attempters, those who used physical means had the highest NE levels (mean ± SD = 69.7 ± 21.3) and those who took overdoses of antidepressants (mean ± SD = 51.9 ± 17.3; n = 6), benzodiazepines (mean ± SD = 65.1 ± 29.7; n = 5), or miscellaneous drugs (mean ± SD = 59.1 ± 36.5; n = 11) had lower NE values. In contrast to NE, urinary dopamine (mean ± SD = 402.6 ± 392 μg/24 hours, epinephrine (EPI: mean ± SD = 14.3 ± 4.0 μg/24 hours), the NE/EPI ratio (mean ± SD = 8.3 ± 0.9), urinary free cortisol (mean ± SD = 157.9 ± 11.5 μg/24 hours) and serum cortisol (mean ± SD = 35.0 ± 13.1 n M/1) did not differ between groups. There were no group differences in age (mean ± SD = 36.3 ± 16.5 years), Beck Depression Inventory score (mean ± SD = 26.3 ± 12.9), Beck Hopelessness Scale score (mean ± SD = 10.0 ± 5.6), Beck Scale for Suicidal Ideation score (mean ± SD = 13.6 ± 9.3), or Hamilton Rating Scale for Depression score (mean ± SD = 19.5 ± 9.8). In the four parasuicide groups, there was no difference in suicide intent (mean ± SD = 13.3 ± 7.9). These findings indicate that there is increased NE output shortly after suicide attempts. Previous reports of a low NE/EPI ratio in suicidal patients may reflect adaptive changes rather than the acute state of the patient at the time of the attempt.

Value of the plasma norepinephrine/3,4-dihydroxyphenylglycol ratio for the diagnosis of pheochromocytoma

purpose: The purpose of this study was to assess whether the plasma norepinephrine/3,4-dihydroxyphenylglycol ratio (NE/DHPG) is of diagnostic relevance for patients with a pheochromocytoma. subjects and methods: In 18 patients with a histologically proven pheochromocytoma and in nine patients with congestive heart failure, plasma levels of NE, epinephrine (EPI), and DHPG (radioenzymatic method) were determined after 20 minutes of supine rest. In 10 healthy subjects, the plasma catecholamine responses to active standing (5 minutes) and mental arithmetic (5 minutes) were measured. From the plasma NE and DHPG levels, the plasma NE/DHPG ratio was calculated. In order to analyze whether NE or EPI was the major secreted catecholamine, the patients with a pheochromocytoma were divided into two groups based on the increase of plasma NE above normal relative to that of EPI: Group 1 included patients with increased plasma NE or increased plasma NE and EPI. Group 2 included patients with increased plasma EPI in combination with a nearly normal NE. results: Both active standing and mental arithmetic increased the plasma NE/DHPG ratio by 105% and 13.6%, respectively, but in all subjects the ratio did not exceed 1.0. Patients with heart failure demonstrated a threefold higher plasma NE/DHPG ratio than did healthy subjects, and the ratio also did not exceed 1.0. The plasma NE/DHPG ratio was about seven to eight times higher in Group 1 (mean: 1.62, range: 0.81 to 2.84) than in Group 2 (mean: 0.24, range: 0.12 to 0.68). Nearly all patients in Group 1 had a NE/DHPG ratio that was higher than 1.0. In contrast, five of six samples of Group 2 demonstrated a NE/DHPG ratio within the normal range. The calculated positive and negative predictive values of a basal plasma catecholamine level were higher than that for the plasma NE/DHPG ratio. conclusions: In contrast to earlier reports, a normal plasma NE/DHPG ratio does not exclude the presence of a pheochromocytoma. In patients with a pheochromocytoma that produces EPI predominantly, this ratio may be normal. On the other hand, in patients with congestive heart failure, the plasma NE/DHPG ratio is increased, although there is no clear overlap with values of patients with a pheochromocytoma. Although the prevalence of pure EPI-producing pheochromocytomas is low, the plasma NE/DHPG ratio should be used with caution in the diagnostic evaluation of patients with a suspected pheochromocytoma.

Free plasma catecholamine levels in healthy subjects: a basal and dynamic study. The influence of age.

We studied the levels of free plasma noradrenaline (norepinephrine, NE), adrenaline (epinephrine, E), and dopamine (DA) in 143 normal subjects, either basally or, in a part of them, in response to four tests stimulating the sympathoadrenomedullary activity: the tilt-table test (TTT), the cold-pressor test (CPT), the mental-arithmetic test (MAT), and the insulin tolerance test (ITT). In both cases we evaluated the influence of age, which is considered the main physiological variable affecting the peripheral sympathetic activity. A normal distribution of values was observed, in the basal study, only for NE, while E and particularly, DA levels were distributed in an non-homogeneous fashion; a direct correlation was observed between age of subjects and NE levels, while neither E, nor DA levels showed any correlation with the aging process; sex did not influence any of the catecholamines. In the dynamic study, CPT, ITT and, above all, TTT elicited a significant rise in NE levels, while the E release was greatly stimulated by the insulin-induced hypoglycaemia. Neither NE, nor E levels rose after the MAT stimulation. Also in this case, the elderly showed an increased noradrenergic responsiveness when compared with the young subjects, confirming the existence of an 'up-regulation' of the peripheral sympathetic tone in old people.

Regional studies of brain biogenic amines in castrated muricidal and non-muricidal wistar rats

Castrated Wistar rats were isolated for 8 months and their muricidal behavior was investigated. Significantly fewer (35%) of such rats became muricidal (CM) compared to controls. The steady-state levels of 5-HT, 5-HIAA, DA, DOPAC, and NE, as well as the changes in synthesis or utilization rats of 5-HT and DA, were analyzed in 15 brain areas derived from CM rats and non-muricidal (CNM) control subjects. In CM rats, higher 5-HT levels were recorded in 5 areas considered to be involved in muricidal behavior: raphe, amygdala, olfactory tubercles, olfactory bulbs, and striatum. The alterations of serotonergic neurotransmission in castrated muricidal rats differ strikingly from those observed in non-castrated muricidal rats. An increase of 5-HT level and in the 5-HT synthesis index as well as a lower 5-HT utilization index were recorded in the raphe of CM rats. Our data suggest that the decrease of 5-HT levels generally said to be the main alteration in the muricidal rat's brain has to be reconsidered. Increased DA levels were observed in CM rats: raphe (50%), amygdala, olfactory tubercles, striatum, and septum (40%), while DA was decreased in cortical areas. There were slight increases of DA synthesis indices in the septum, olfactory tubercles and striatum with a decreased utilization index in the olfactory tubercles. Few alterations in NE levels were observed in CM rats: a decrease in the olfactory tubercles, superior colliculus, and striatum and an increase in temporal cortex. The monoaminergic alterations correlate with the modulation of muricidal behavior. Some areas (the olfactory tubercles, raphe, striatum, and temporal cortex) seem to be particularly involved. © 1992 Wiley-Liss, Inc.

Electron impact excitation of Ne X: collision strengths and rate coefficients

Collision strengths have been computed for all transitions belonging to the states of up to the n = 5 levels of Ne X. Calculations have been done in a wide range of energy in the LS coupling scheme. The standard and no-exchange R-matrix programs have been used to compute collision strengths for L ⩽ 12 and for L > 12 respectively. Resonances have been highlighted and comparisons are made for collision strengths for the 1s-2s and 1s-2p transitions. Results have been tabulated in the energy range from thresholds to 116 Ry. Effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are also tabulated in a wide range below log Te = 6.2K.

Coherence parameter measurements for electrons scattering off heavy noble gas targets

Electron impact excitation of the resonance levels of Ne, Ar, Kr and Xe has been studied for electron scattering angles up to 50' and impact energies between 30 and 80 eV. The P1 and P4 Stokes parameters have been measured in each case so that the influence of spin in the excitation process could be studied through evaluation of rho 00, the relative spin-flip cross section. After careful account was taken of various depolarizing effects due particularly to the finite volume of the interaction region and, in the cases of Kr and Xe, to nuclear spin, very good agreement has been found with theoretical predictions thus resolving a previously reported discrepancy. No evidence has been found for spin-flip under the experimental parameters used in this study, even for the heaviest target studied.

Contribution of serotonin neurons to the functional recovery after spinal cord injury in rats

The contribution of serotonin neurons to the functional recovery after spinal cord injury was studied pharmacologically in rats with moderately severe neurologic impairment (complete paraplegia but responsive to tail pinching) 24 h after thoracic spinal cord (T 11) compression-induced injury. Fourteen days after cord injury the levels of endogenous norepinephrine (NE, −33%), dopamine (DA, −50%) and serotonin (5-HT, −55%) in the lumbar cord in the injury control rats were decreased and there were significant correlations between the neurologic score and the NE level(r s= 0.562, P 0.01) and the 5-HT level(r s= 0.745, P 0.001) but not the DA level. Bilateral i.c.v. injection of 5, 7-dihydroxytryptamine (200 μg/rat) 24 h after cord injury significantly retarded the neurologic recovery during the 14 days after injury, accompanied by a further reduction in the 5-HT level (−86%) but not in the NE or DA level. On the other hand, neitherp-chlorophenylalanine (PCPA) (300 mg/kg, i.p., once daily starting 24 h after injury for 13 consecutive days) nor reserpine (1 mg/kg, i.p., 4 times, once 24 h after injury and then every fourth day) had any influence on the time course of the neurologic recovery during the 14 days after injury, although PCPA treatment further reduced the levels of NE (−50%) and 5-HT (−91%), and reserpine treatment further reduced the levels of NE (−95%), DA (−73%) and 5-HT (−85%). From these results, it can be proposed that neither serotonergic nor catecholaminergic transmission but functions of the central 5-HT neurons other than serotonergic transmission contribute to the neurologic recovery after spinal cord injury in rats.

The effects of race on norepinephrine clearance

Eighteen normotensive and 19 unmedicated hypertensive black and white male subjects were studied twice, during a 10 meq sodium diet for 5 days and a 200 meq sodium diet for 4 days. The subjects received an infusion of 3H-norepinephrine ( 3HNE) during both low and high sodium diets to measure NE clearance. Dietary sodium and blood pressure classification had no effect on 3HNE clearance. Infusion of pressor doses of NE also failed to alter 3HNE clearance. Both normotensive and hypertensive blacks had increased 3HNE clearance rates (p < .001). The increased rate of 3HNE clearance among blacks was not affected by alterations in dietary sodium or by pressor doses of NE. Increased NE clearance by blacks may help explain obser-vations that white hypertensives in the age range we studied (25–46 years) have elevated plasma NE levels, while blacks have normal NE levels.