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PubMed1995

Influences of neuronal uptake and D2 autoreceptors on regulation of extracellular dopamine in the core, shell and rostral pole of the rat nucleus accumbens.

Fast cyclic voltammetry in rat brain slices containing the nucleus accumbens, was used to examine the regulation of the extracellular concentration of electrically stimulated dopamine overflow in the core, shell and rostral pole. One microM (-)-sulpiride, significantly increased dopamine overflow in all 3 regions but only when the duration of stimulation was greater than 500 ms. One microM cocaine, significantly potentiated dopamine overflow in all 3 regions following all patterns of stimulation. In the presence of 1 microM cocaine, superfusion with 1 microM (-)-sulpiride did not result in a further increase in dopamine overflow at any frequency of stimulation in the rostral pole, but significant increases in dopamine overflow were observed after stimulation with 20 pulses at 10 or 20 Hz in the core or shell; the degree of potentiation was greater in the shell than core. Quinpirole inhibited single pulse stimulated dopamine overflow in a concentration dependent manner (maximum inhibition (100%) in all regions) but was significantly less potent in the rostral pole than in the core or shell. Increasing the number of pulses to 2 or 4 pulses at 50 Hz resulted in a shift of the quinpirole dose-response curve to the right in all regions and in the rostral pole, a significant reduction in the maximum inhibition of dopamine overflow to both stimulation parameters. In the shell a significant reduction in maximum inhibition was only seen with 4 pulses at 50 Hz stimulation, whereas in the core there was no change in the maximum inhibitory effect of quinpirole. Neuronal uptake and D2 autoreceptor activity contribute to regulation of the extracellular concentration of dopamine in core, shell and rostral pole. The relative importance of either uptake or autoreceptor control is region and stimulus dependent.

Animals↗

PubMed1989

Increases in calbindin D 28K mRNA in the uterus of the domestic fowl induced by sexual maturity and shell formation.

Uterine concentrations of calbindin D 28K mRNA were measured in immature pullets and laying hens by dot-blot hybridization using a [32P]cRNA probe prepared from the calbindin cDNA. In immature pullets, estrogen increased the calbindin mRNA level and the plasma concentration of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. When testosterone was administered with estrogen there was a further increase in calbindin and its mRNA and an increase in the free 1,25-(OH)2D3 index calculated as the ratio of the molar concentrations of total 1,25-(OH)2D3 and vitamin D-binding protein (DBP). In laying hens the uterine concentration of calbindin mRNA was low 4 hr after ovulation, but increased most markedly 12 and 18 hr later, when shell calcification took place. Calbindin concentration remained unchanged during the different stages of egg formation but was much higher in laying hens than in pullets treated with sex steroids. Suppression of shell formation by premature expulsion of the egg decreased the concentrations of calbindin mRNA and uterine calbindin and the free 1,25-(OH)2D3 index in the plasma. A concomitant increase in calbindin and its mRNA was observed at resumption of shell formation in hens previously laying shell-less eggs. Withdrawal of food for 44 hr decreased the uterine concentration of calbindin and its mRNA without a change in the free 1,25-(OH)2D3 index in the blood. It is concluded that the synthesis of uterine calbindin is stimulated primarily at sexual maturity and at calcification of the first shell by transcriptional processes. The daily increase in calbindin mRNA associated with shell formation and the absence of a concomitant change in calbindin concentration suggest that post-transcriptional processes exist and that stimuli other than the sex steroid or the 1,25-(OH)2D3 are involved in regulation of calbindin synthesis in the uterus.

Animals↗

PubMed1995

Continuous gradient index and shell models of the human lens.

Because of the complexity of tracing rays through a gradient refractive index medium, the human eye's lens is sometimes approximated by a shell structure with constant refractive index within shells. In the shell model, power arises from a combination of an axial variation in index and the curvatures of the shell surfaces. We develop an equation which gives the power due to the gradient index of the lens, and use this to choose shell models that have the same power as the continuous gradient index model. Some types of shell models are described and evaluated.

Humans↗

PubMed1992

Enhanced detection of respiratory viruses using the shell vial technique and monoclonal antibodies.

The shell vial technique using A549 and MDCK cells, coupled with the use of Bartels respiratory viral monoclonal antibodies, was evaluated initially for the detection of 28 previously isolated respiratory viruses. All viruses were recovered and correctly identified. The shell vial-monoclonal antibody technique was then evaluated for virus isolation from 338 respiratory specimens and compared with the conventional tube method. Both methods gave rise to a total of 83 virus isolates. Of these isolates, 68 (20.1%) were isolated and identified by the shell vial-monoclonal method; 60 (17.8%) were culture-positive by the conventional tube method; forty-five (13.3%) were positive by both methods. The shell vial-monoclonal antibody method yielded 12 isolates of influenza A, two isolates of parainfluenza type 3 and one each of parainfluenza types 1 and 3, which were missed by the conventional tube method, indicating the superior sensitivity and specificity of the shell vial-monoclonal antibody method (Chi-square analysis, P = 0.001) for the detection of these viruses. Of the 50 RSV isolates, 29 were detected by both methods and there were 21 discrepancies between the two methods. The shell vial-monoclonal antibody method also improved the turn-around time for the respiratory virus groups.

Adenoviruses, Human↗

PubMed1996

Marginal shell of the anteroventral cochlear nucleus: intensity coding in single units of the unanesthetized, decerebrate cat.

Single units were recorded in the marginal shell (38 units in 10 cats) and central core (62 units in 15 cats) of the anteroventral cochlear nucleus (AVCN) in unanesthetized decerebrate cats. The recording sites of the shell units were verified in reconstructed electrode tracks, and those of the core units were verified for 18 units and based on the recording depth for 44 units. There was a substantial presence of strongly driven units in the AVCN shell exhibiting non-saturating rate-level functions to pure tone, noise or both with dynamic ranges as wide as 89 dB. This finding supports a hypothesis that the AVCN shell may play a role in encoding acoustic stimulus intensity. The AVCN shell and core populations were different as follows. The shell population had more units which had wide dynamic ranges, low spontaneous rates (SRs) or were acoustically weakly or not driven than the core population. These differences were statistically significant (P < 0.001, Fisher's exact test).

Animals↗

PubMed1992

Morphological differences between projection neurons of the core and shell in the nucleus accumbens of the rat.

The somatodendritic morphology of projection neurons in the shell and core of the rat nucleus accumbens was studied. These cells were retrogradely labelled with Fast Blue from the ventral mesencephalon (substantia nigra/ventral tegmental area) and subsequently injected intracellularly with Lucifer Yellow and processed immunocytochemically. Digitized reconstructions revealed that the cell bodies of neurons located throughout the nucleus are small-to-medium in size. Neurons in the shell have significantly fewer dendritic arbours with fewer branch segments, fewer terminal segments, and lower spine densities than those in the core. Values for the same parameters are significantly greater for cells in lateral than in medial parts of the shell but the same for neurons located within and without enkephalin enriched parts of the core, with an exception of spine density being significantly greater in the enkephalin-rich compartment. Calculations based on these data reveal that neurons in the core have as much as 50% more surface area than those in the shell, which suggests that core neurons have a greater potential for collecting synaptic information than have shell cells. Furthermore, the differential distribution and action of various neurochemicals such as dopamine in the shell and core, supports the idea that different morphologies reflect the presence of distinct neuronal circuits in these two territories.

Amidines↗

PubMed2005

Rate of iron transfer through the horse spleen ferritin shell determined by the rate of formation of Prussian Blue and Fe-desferrioxamine within the ferritin cavity.

Iron (2+ and 3+) is believed to transfer through the three-fold channels in the ferritin shell during iron deposition and release in animal ferritins. However, the rate of iron transit in and out through these channels has not been reported. The recent synthesis of [Fe(CN)6]3-, Prussian Blue (PB) and desferrioxamine (DES) all trapped within the horse spleen ferritin (HoSF) interior makes these measurements feasible. We report the rate of Fe2+ penetrating into the ferritin interior by adding external Fe2+ to [Fe(CN)6]3- encapsulated in the HoSF interior and measuring the rate of formation of the resulting encapsulated PB. The rate at which Fe2+ reacts with [Fe(CN)6]3- in the HoSF interior is much slower than the formation of free PB in solution and is proceeded by a lag period. We assume this lag period and the difference in rate represent the transfer of Fe2+ through the HoSF protein shell. The calculated diffusion coefficient, D approximately 5.8x10(-20) m2/s corresponds to the measured lag time of 10-20 s before PB forms within the HoSF interior. The activation energy for Fe2+ transfer from the outside solution through the protein shell was determined to be 52.9 kJ/mol by conducting the reactions at 10 approximately 40 degrees C. The reaction of Fe3+ with encapsulated [Fe(CN)6]4- also readily forms PB in the HoSF interior, but the rate is faster than the corresponding Fe2+ reaction. The rate for Fe3+ transfer through the ferritin shell was confirmed by measuring the rate of the formation of Fe-DES inside HoSF and an activation energy of 58.4 kJ/mol was determined. An attempt was made to determine the rate of iron (2+ and 3+) transit out from the ferritin interior by adding excess bipyridine or DES to PB trapped within the HoSF interior. However, the reactions are slow and occur at almost identical rates for free and HoSF-encapsulated PB, indicating that the transfer of iron from the interior through the protein shell is faster than the rate-limiting step of PB dissociation. The method described in this work presents a novel way of determining the rate of transfer of iron and possibly other small molecules through the ferritin shell.

Animals↗

PubMed2004

Opioid receptor subtype antagonists differentially alter GABA agonist-induced feeding elicited from either the nucleus accumbens shell or ventral tegmental area regions in rats.

Food intake is significantly increased by administration of either GABAA (e.g., muscimol) or GABAB (e.g., baclofen) agonists into either the shell region of the nucleus accumbens (NAC) or the ventral tegmental area (VTA); these responses are selectively blocked by pretreatment with corresponding GABAA and GABAB antagonists. Previous studies found that a single dose (5 microg) of the general opioid antagonist, naltrexone reduced feeding elicited by muscimol, but not baclofen in the NAC shell, and reduced feeding elicited by baclofen, but not muscimol in the VTA. The present study compared feeding responses elicited by either muscimol or baclofen in either the VTA and NAC shell following pretreatment with equimolar doses of selective mu (0.4, 4 microg), delta (0.4, 4 microg), or kappa (0.6, 6 microg) opioid receptor subtype antagonists. Muscimol (25 ng) and baclofen (200 microg) each significantly and equi-effectively increased food intake over 4 h following VTA or NAC shell microinjections. Muscimol-induced feeding elicited from the VTA was significantly enhanced by mu or delta antagonists, and was significantly reduced by kappa antagonists. Baclofen-induced feeding elicited from the VTA was significantly reduced by mu or kappa, but not delta antagonists. Muscimol-induced feeding elicited from the NAC was significantly reduced by either mu, kappa or delta antagonists. Baclofen-induced feeding elicited from the NAC was significantly reduced by kappa or delta, but not mu antagonists. These data indicate differential opioid receptor subtype antagonist-induced mediation of GABA receptor subtype agonist-induced feeding elicited from the VTA and NAC shell. This is consistent with previously demonstrated differential GABA receptor subtype antagonist-induced mediation of opioid-induced feeding elicited from these same sites. Thus, functional relationships exist for the elaborate anatomical and physiological interactions between these two neurochemical systems in the VTA and NAC shell.

Animals↗

PubMed2005

Effect of 3,4-methylendioxymethamphetamine (MDMA, "ecstasy") on dopamine transmission in the nucleus accumbens shell and core.

It is known that most of drugs abused by humans preferentially stimulate dopamine transmission in the shell subdivision of the nucleus accumbens as compared to the core. The aim of the present study was to evaluate whether this applies also to intravenous 3,4-methylendioxymethamphetamine (MDMA, "ecstasy") administered at doses that sustain self-administration behavior in rats. The effect of 0.32, 0.64, 1.0, 2.0 and 3.2 mg/kg i.v. of MDMA on dopamine transmission in the nucleus accumbens shell and core was studied in freely moving rats by means of dual probe microdialysis. MDMA dose-dependently stimulated dopamine transmission both in the shell and in the core but the increase in the shell was more pronounced compared to the core at doses of 0.64, 1.0 and 2.0 mg/kg. The increase of dialysate dopamine obtained after 0.32 mg/kg and after 3.2 mg/kg was not significantly different in the shell compared to the core of nucleus accumbens. This study extends to MDMA the property of other drugs of abuse to increase preferentially nucleus accumbens shell dopamine.

Analysis of Variance↗

PubMed2006

GABA receptor subtype antagonists in the nucleus accumbens shell and ventral tegmental area differentially alter feeding responses induced by deprivation, glucoprivation and lipoprivation in rats.

GABA(A) and GABA(B) receptor agonists stimulate feeding following microinjection into the nucleus accumbens shell and ventral tegmental area, effects blocked selectively and respectively by GABA(A) and GABA(B) receptor antagonists. GABA antagonists also differentially alter opioid-induced feeding responses elicited from these sites. Although GABA agonists and antagonists have been shown to modulate feeding elicited by deprivation or glucoprivation, there has been no systematic examination of feeding elicited by homeostatic challenges following GABA antagonists in these sites. Therefore, the present study examined the dose-dependent ability of GABA(A) (bicuculline, 75-150 ng) and GABA(B) (saclofen, 1.5-3 microg) antagonists administered into the nucleus accumbens shell or ventral tegmental area upon feeding responses elicited by food deprivation (24 h), 2-deoxy-D-glucose-induced glucoprivation (500 mg/kg) or mercaptoacetate-induced lipoprivation (70 mg/kg). A site-specific effect of GABA receptor antagonism was observed for deprivation-induced feeding in that both bicuculline and saclofen administered into the nucleus accumbens shell, but not the ventral tegmental area, produced short-term (1-4 h), but not long-term (24-48 h) effects upon deprivation-induced intake without meaningfully altering body weight recovery. In contrast to the relative inability of GABA receptor antagonism in both sites to alter 2-deoxy-D-glucose-induced intake, mercaptoacetate-induced intake was eliminated by saclofen and significantly reduced by bicuculline in the nucleus accumbens shell and eliminated by both bicuculline and saclofen in the ventral tegmental area. These data reinforce the findings that GABA(A) and GABA(B) receptors in the nucleus accumbens shell and ventral tegmental area are not only important in the modulation of pharmacologically induced feeding responses, but also participate in differentially mediating the short-term feeding response to food deprivation in the nucleus accumbens shell as well strongly modulating lipoprivic, but not glucoprivic feeding responses in both sites.

Animals↗

PubMed2004

Shell protein characteristics and vitellogenin-like proteins in brine shrimp Artemia franciscana exposed to municipal effluent and 20-hydroxyecdysone.

We developed biomarkers to monitor the endocrine-disrupting potential of contaminants and municipal effluents in aquatic arthropods. Artemia fransciscana shrimp were cultured and exposed to increasing concentrations of 20-hydroxyecdysone (20HE) and solid phase (C-8) municipal effluent extract (MEE) for 48 h at 20 degrees C. The levels of vitellogenin (Vtg)-like proteins, alkali-labile phosphates in total proteins and acetylcholinesterase (AChE) activity were determined in soft tissues. The levels of acid-soluble, alkali-soluble (sclerotin), neutral-soluble (arthropodin) proteins and chitin were determined to characterize the maturation state of shells. Both 20HE and the municipal effluent extract readily increased the total activity of acetylcholinesterase, alkali-labile phosphates in proteins and vitellogenin-like proteins in brine shrimp. In shells, 20HE and the effluent extract increased the proportion of chitin in shells and acid-soluble proteins but were not statistically significant for the latter. The proportion of sclerotin was increased by 20HE but was not changed by the effluent extract. The proportion of arthropodin was decreased by both 20HE and the effluent extract. Correlation analysis revealed that, as expected, the proportion of acid-soluble protein for biomineralisation and chitin levels were positively correlated and the proportion of arthropodin and sclerotin were negatively correlated in shells exposed to 20HE. Principal component analysis revealed that the proportion of chitin, arthropodin, sclerotin and acid-soluble proteins explained 63% of the responses. Shell protein and carbohydrate contents, controlled by the molting hormone 20HE, could be used as efficient markers for ecdysial properties of various contaminants. The municipal effluent appears to contain ecdysial-like chemicals that are capable of producing changes in shell protein composition that are similar to 20HE.

Acetylcholinesterase↗

PubMed2006

Adrenergic receptors in the nucleus accumbens shell differentially modulate dopamine and acetylcholine receptor-mediated turning behaviour.

The role of alpha- and beta-adrenoceptors in the nucleus accumbens shell in turning behaviour of rats was investigated. Unilateral injections of the alpha-adrenoceptor agonist (phenylephrine; 10 microg) and antagonist (phentolamine; 10 microg) as well as the beta-adrenoceptor agonist (isoprenaline; 1 microg) and antagonist (propranolol; 5 microg) into the nucleus accumbens shell did not produce turning behaviour more than that of control vehicle injection. Unilateral injection of a mixture of dopamine D(1) ((+/-)-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7,8-diol, SKF 38393; 5 microg) and D(2) (quinpirole; 10 microg) receptor agonists into the nucleus accumbens shell has been found to elicit contraversive pivoting. Such pivoting was dose-dependently inhibited by phenylephrine (5, 10 microg), injected into the nucleus accumbens shell, and the inhibitory effect of phenylephrine (10 microg) was antagonised by phentolamine (10 microg) that per se had no effect on this pivoting. Isoprenaline (0.5, 1 microg) dose-dependently increased the contraversive pivoting induced by the mixture of SKF 38393 (1 microg) and quinpirole (10 microg) injected into the nucleus accumbens shell. The effect of isoprenaline (1 microg) was antagonised by propranolol (5 microg) that per se had no effect on this pivoting. It is concluded that stimulation of accumbal alpha-adrenoceptors inhibits the dopamine-dependent pivoting in contrast to stimulation of accumbal beta-adrenoceptors that facilitates this dopamine-dependent pivoting. Unilateral injection of the acetylcholine receptor agonist carbachol (5 microg) into the nucleus accumbens shell has been found to elicit contraversive circling. Such circling was significantly reduced by accumbal administration of either phenylephrine (10, 20 microg) or phentolamine (5, 10 microg) in a dose-independent manner; moreover, both drugs potentiated, but did not counteract, each other's effects. Carbachol-induced circling was also reduced by propranolol (2.5, 5 microg), but again in an aspecific manner. It is concluded that alpha- and beta-adrenergic agents have an effect on accumbal acetylcholine receptor-mediated circling through a non-adrenergic mechanism. The impact of the present study for putative new treatments of various neuropsychiatric and neurological disorders is discussed.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2006

Development of 5-fluorouracil loaded poly(acrylamide-co-methylmethacrylate) novel core-shell microspheres: in vitro release studies.

Novel poly(acrylamide-methylmethacrylate) copolymeric core-shell microspheres crosslinked with N,N'-methylene bisacrylamide have been prepared by free radical emulsion polymerization using varying amounts of acrylamide (AAm), methylmethacrylate (MMA) and N,N'-methylene bisacrylamide (NNMBA). 5-Fluorouracil was loaded into these microspheres during in situ polymerization (method-I) as well as by the absorption and adsorption technique (method-II). The core-shell microspheres have been characterized by differential scanning calorimetry (DSC) and X-ray diffractometry (X-RD) to understand about the drug dispersion in microspheres. Scanning electron microscopy (SEM) was used to assess the surface morphology of particles prepared. In vitro release of 5-fluorouracil has been studied in terms of core-shell composition, amount of crosslinking agent and amount of 5-fluorouracil in the microspheres. Core-shell microspheres with different copolymer compositions have been prepared in yields ranging 80-85%. DSC and X-RD techniques indicated a uniform distribution of 5-fluorouracil particles in core-shell microspheres, whereas SEM suggested the formation of well-defined core-shell structures. The in vitro drug release indicated that particle size and release kinetics depend upon copolymer composition, amount of crosslinking agent used and amount of 5-fluorouracil present in the microspheres. Prolonged and controlled release of 5-fluorouracil was achieved when drug was loaded by method-I instead of method-II.

Absorption↗

PubMed2006

A finite shell element for heart mitral valve leaflet mechanics, with large deformations and 3D constitutive material model.

This paper presents a shell finite element formulation appropriate for simulating the heart valve leaflet mechanics, including three-dimensional (3D) stress and strain effects. A 4-node mixed-interpolation shell is formulated in convected coordinates. This shell model is made capable of handling arbitrary 3D material models by use of an algorithm that satisfies the shell stress assumption at every element integration point. A method for tracking the fiber direction is incorporated. The resulting shell element operates under the same conditions as a standard 4-node shell element with 5 degrees of freedom per node, but extends the modeling capabilities to handle large-deformation and anisotropic behavior.

Biomechanical Phenomena↗

PubMed2006

Pentachlorophenol removal from aqueous matrices by sorption with almond shell residues.

Sorption with activated carbon has been the technique preferred for pentachlorophenol (PCP) removal from contaminated waters, but regeneration needs and high operation costs are supporting a renewed interest in the search for alternative sorbents. Among them, almond shell, an agricultural by-product, provides interesting economical advantages, once shells account for 50% (in mass) of the whole almond. In this work, the capacity of almond shells to remove PCP from waters without previous activation was studied in batch conditions. While PCP analysis was performed solid-phase microextraction (SPME) followed by gas chromatography with electron capture detection (GC-ECD), mercury porosimetry and Fourier transform infrared spectroscopy (FTIR) provided a preliminary physical and chemical characterization of the sorbent. Almond shells were essentially a macroporous material, with an average surface area of 12.9+/-2.8 m2/g. The efficiency of PCP removal was 93+/-14%, in 24 h, with an initial concentration of 100 microg/l PCP and 5 microg PCP/g shell. Isotherm data adjusted better to Freundlich equation, where K(F) and 1/n were 0.075+/-0.081 mg(1-1/n) l(1/n) and 1.882+/-0.289, respectively. Average desorption efficiency was 7%, indicating strong adsorption capacity. Results proved that almond shells may be an excellent low-cost alternative for PCP removal from contaminated waters.

Adsorption↗

PubMed2005

Inter- and intra-annual variations of Pb/Ca ratios in clam shells (Mercenaria mercenaria): a record of anthropogenic lead pollution?

In this study, we re-assess the use of bivalve shells as a proxy of lead pollution. Previous studies have stressed that shells display little variability compared to soft tissues and thus are better for pollution biomonitoring. However, in this manuscript we illustrate that there is large inter- and intra-annual Pb variability between shells of the clam Mercenaria mercenaria collected in North Carolina, USA. Therefore, year to year, as well as intra-annual variations in Pb/Ca ratios should be interpreted with caution. Despite this variability, we were able to obtain an annual Pb chronology from 1949 to 2002 using 11 shells collected at different times which clearly exhibited the late 1970's peak in Pb from leaded gasoline use. This indicates that when enough specimens are pooled together, bivalve shells can be used to reconstruct large, long term changes in environmental Pb concentrations. Our data compare well with other studies of aragonite clams from sites with low regional lead pollution. From this we conclude that the Cape Lookout region of North Carolina has not received extensive pollution over the 1949-2002 period. The Pb concentration in shells growing in the 1949-1976 period was not significantly different from those growing in the 1982-2002 period, although other proxies suggest that the 1949-1976 period should be considerably higher. Therefore, our data suggest that there is still a modern low-level source of Pb in the coastal North Carolina environment.

Animals↗

PubMed2005

Trace metal variations in the shells of Ensis siliqua record pollution and environmental conditions in the sea to the west of mainland Britain.

Shells of the pod razor shell (Ensis siliqua) from 13 locations around the west coast of mainland Britain have been analysed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for a range of trace metals including Zn, Cd, Pb, U, Ba, Sr and Mg. The trace metal record in these shells is a proxy record for changes in seawater chemistry during the 1990s. Regional variations exist in the median concentrations of the analysed metals. Barium concentrations are related to increased productivity from sewage sludge dumping at sea. Strontium shows a local relationship to salinity, but there is no clear relationship over the study area, instead high Sr is often associated with high Ba, and may reflect ontogenetic factors such as growth rate. Magnesium shows a seasonal variation within individual shells and can be used to calculate sea surface temperatures from groups of shells. Contaminant metals show a clear regional relationship with known sources, thus high Pb and Zn are typically associated with former metal mining areas (e.g. Cardigan Bay, Anglesey), and high Pb, Zn, Cd and U are associated with industrial activity in Liverpool Bay. Anomalies such as the high U in shells from northern Scotland cannot at present be explained. A seasonal variation of Pb is also seen in Cardigan Bay and Liverpool Bay, relating to increased winter fluxes of these metals to the marine environment. The regional distribution of these metals is consistent with known sources of contamination and patterns of seawater migration around the coast of Britain.

Animals↗

PubMed2004

A differential activation of dopamine output in the shell and core of the nucleus accumbens is associated with the motor responses to addictive drugs: a brain dialysis study in Roman high- and low-avoidance rats.

Addictive substances like morphine and psychostimulants induce a preferential increase in dopamine (DA) output in the nucleus accumbens (NAC), a major terminal field of the mesolimbic dopaminergic projection. Two subregions of the NAC, the dorsolateral core and the ventromedial shell, are thought to subserve different functions related to the reinforcing properties of natural and drug rewards. The selective breeding of Roman high- (RHA) and low-avoidance (RLA) rats, respectively, for rapid vs. extremely poor active avoidance acquisition in a shuttle-box has resulted in two phenotypes that differ in their behavioural and neurochemical responses to addictive drugs. We used brain dialysis to assess whether such differences in the responsiveness to drugs of abuse are related to differences in mesolimbic DA neuron function. In RHA rats, morphine, cocaine, and amphetamine caused a larger increase in DA efflux in the NAC shell vs. the NAC core, whereas the profile for the drug-induced increases in DA output was almost completely superimposable in the NAC shell and NAC core of RLA rats. Moreover, morphine, cocaine, and amphetamine caused a larger increment in basal DA output in the NAC shell of RHA rats vs. the NAC shell of RLA rats. These drugs also elicited a more robust increase in locomotion, rearing, sniffing, and grooming in RHA than in RLA rats. These results demonstrate that genetically determined differences in the functional properties of DA neurons projecting to the NAC shell may critically influence the behavioural response patterns to addictive drugs that distinguish the Roman lines.

Animals↗