Biomedical subjects

A J Lawrence

Publications and source records attributed to A J Lawrence.

At least 37 records · Page 2Linked to original sources

PubMed2001

On the immunohistochemical distribution of ionotropic P2X receptors in the nucleus tractus solitarius of the rat.

ATP has been shown to excite neurones of the nucleus tractus solitarius (NTS) via the activation of P2X receptors. In the present study, the distribution of six P2X receptors (P2X(1)-P2X(6)) within the rat NTS was investigated by peroxidase immunohistochemistry. Immunopositive neurones for P2X receptor subtypes were detected in all divisions of the NTS, although the staining densities differed according to receptor subtype and sub-nuclei. P2X(1)-immunopositive cells were distributed throughout the rostro-caudal extent of the NTS, while varicose fibres were mainly located along the postremal border. P2X(2) immunoreactivity was present in neurones and fibres located throughout the NTS. In the commissural NTS intense staining was observed medial of the solitary tract while in the sub-postremal NTS neurones were observed along the postremal border. A high density of P2X(3)-positive neurones and fibres was observed in the sub-postremal NTS along the border of the area postrema and in the rostral NTS in the medial subdivision. In comparison to the staining observed with the other receptor antibodies, there was considerably reduced P2X(4) receptor immunoreactivity. P2X(4)-positive neurones tended to be more sparsely distributed, and found mainly in the intermediate portion of the commissural NTS, and along the postremal border. In contrast, we observed dense staining for the P2X(5) receptor subtype in a majority of regions within the NTS. The most striking staining was observed in the intermediate subdivision at the level of the sub-postremal NTS and the medial portion of the rostral NTS. P2X(6) immunoreactive neurones were observed in the medial commissural NTS, along the postremal border and in the dorso-medial and medial subdivisions of the rostral NTS.Taken together, our findings confirm the presence of six P2X receptor subtypes within the NTS of the rat, consistent with a neurotransmitter role for ATP in the rat NTS. These results indicate the need for more extensive functional studies to elucidate the roles of the individual and heterodimeric assemblies of P2X receptor subtypes within the NTS.

Animals↗

PubMed2001

The effect of acute and chronic restraint on the central expression of prepro-neuropeptide Y mRNA in normotensive and hypertensive rats.

Neuropeptide Y (NPY), one of the most abundant neuropeptides found in the central nervous system (CNS), has been implicated in the regulation of many autonomic functions, including cardiovascular control and the central stress response. The present study represents a detailed investigation of the effects of acute and chronic restraint stress on the expression of the mRNA encoding the NPY precursor, prepro-NPY, in the CNS of normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) using in situ hybridization histochemistry. Basal (unstressed) levels of prepro-NPY mRNA expression were found to be significantly increased in the hypothalamic arcuate nucleus of SHR compared to WKY rats, with similar levels of prepro-NPY mRNA expression found in the remaining central nuclei. Following exposure to both acute and chronic restraint, significant changes in prepro-NPY mRNA expression were found in a variety of central regions in both strains, including the arcuate nucleus and hippocampus (both strains), medial amygdala and cortex (WKY only), and dentate gyrus, nucleus of the solitary tract and ventrolateral medulla (SHR only). A comparison of the temporal response to restraint revealed that significant differences between strains existed in regions such as the arcuate nucleus, hippocampus and dentate gyrus, providing further evidence that hypertensive rats apparently have an impaired neural stress response. The present study demonstrates that exposure to restraint results in significant changes in prepro-NPY mRNA expression in specific nuclei of both WKY and SHR that are components of not only the central circuitry regulating the stress response, but also the neural network modulating autonomic function.

Animals↗

PubMed2001

[(3)H](2S,4R)-4-Methylglutamate: a novel ligand for the characterization of glutamate transporters.

[(3)H](2S,4R)-4-Methylglutamate ([(3)H]4MG), used previously as a ligand for low-affinity kainate receptors, was employed to establish a binding assay for glutamate transporters (GluTs), as 4MG has also been shown to have affinity for the glial GluTs, GLT1 and GLAST. In rat brain membrane homogenates in the presence of Na(+) ions at 4 degrees C, specific binding of [(3)H]4MG was rapid and saturable (t(1/2) approximately 15 min), representing > 90% of total binding. Dissociation of [(3)H]4MG occurred in a biphasic manner, however, saturation studies and Scatchard analysis indicated a single site of binding (n(H) = 0.85) and a K(d) of 6.2 +/- 0.8 microM with a B(max) of 111.8 +/- 23.8 pmol/mg protein. Specific binding of [(3)H]4MG was Na(+)-dependent and inhibited by K(+) and HCO(3-). Pharmacological inhibition with compounds acting at GluTs revealed that Glu, D- and L-aspartate, L-serine-O-sulfate and Ltrans-pyrrolidine-2,4-dicarboxylate fully displaced specific binding. Drugs having preferential affinity for GLT1, kainate, dihydrokainate and Lthreo-3-methylglutamate, all inhibited approximately 40% of specific binding. The inhibition pattern of L-serine-O-sulfate in the presence of a saturating concentration of dihydrokainate was suggestive of [(3)H]4MG also labelling GLAST. 6-Cyano-7-nitroquinoxaline, a kainate receptor antagonist, and a range of Glu receptor agonists and antagonists failed to significantly inhibit [(3)H]4MG binding. The pharmacological profile of binding of [(3)H]4MG resembled that found for [(3)H]D-aspartate, a ligand specific for GluTs, reinforcing the hypothesis that [(3)H]4MG was labelling GluTs in this assay. Together, these data illustrate the development of an efficient, economic binding assay that is suitable for the characterization of different subtypes of GLuTs.

ATP-Binding Cassette Transporters↗

PubMed2001

Alterations in central preproenkephalin mRNA expression after chronic free-choice ethanol consumption by fawn-hooded rats.

BACKGROUND: Neurotransmission mediated via opioid and dopamine receptors is believed to be involved in the reinforcing and/or rewarding effects of ethanol consumption. We previously examined the effect of ethanol consumption (and naltrexone treatment, used clinically to treat alcoholism) on micro-opioid receptor density. We describe here the effect of free-choice ethanol consumption and naltrexone treatment on preproenkephalin, preprodynorphin, and dopamine D1 and D2 receptor mRNA expression in the central nervous system. METHODS: Fawn-hooded rats were given continual free-choice access to a 5% ethanol solution or water (4 weeks) followed by 2 weeks of water alone. At the end of this abstinence period, osmotic minipumps were implanted subcutaneously to deliver saline (n = 4) or naltrexone (n = 4; 8.4 mg/kg/day for 4 weeks). After recovery from surgery, the rats again were given access to 5% ethanol under the same free-choice conditions (4 weeks). A third group of age-matched controls drank only water during the behavioral trial. At the end of the behavioral trial, the rats were decapitated, and a quantitative examination of peptide precursor mRNAs was made by using in situ hybridization histochemistry. RESULTS: Naltrexone treatment significantly decreased preprodynorphin expression in the nucleus accumbens, but neither naltrexone treatment nor ethanol consumption significantly affected dopamine D1 and D2 receptor mRNA expression. In contrast, ethanol consumption increased preproenkephalin mRNA in the central and intercalated nuclei of the amygdala but decreased preproenkephalin mRNA in the nucleus accumbens and olfactory tubercle. The decreased level of preproenkephalin mRNA in the nucleus accumbens may reflect a neuroadaptive response to increased release of dopamine, whereas the increased level of preproenkephalin mRNA in the central nucleus of the amygdala may be associated with an anxiolytic effect of ethanol consumption. CONCLUSIONS: The data support the putative role of opioid peptides in the effects of ethanol and suggest that the nucleus accumbens and central nucleus of the amygdala are loci for the reinforcing effects of ethanol.

Amygdala↗

PubMed2000

Comparative study on the distribution patterns of P2X(1)-P2X(6) receptor immunoreactivity in the brainstem of the rat and the common marmoset (Callithrix jacchus): association with catecholamine cell groups.

The present study investigated the topographical distribution of P2X(1)-P2X(6) receptor subtypes in the rat and common marmoset hindbrain by immunohistochemistry. In addition, double-labeling immunofluorescence was used to determine the extent of colocalization between catecholamine cell groups and the various P2X receptors. The data demonstrate a widespread distribution pattern for all six P2X receptors throughout both the rat hindbrain and the marmoset hindbrain, although distinctions between species, brain nuclei, and P2X receptor subtypes exist. In rat, dense staining for the P2X receptors was found in the nucleus of the solitary tract (NTS), medial vestibular nucleus, and medial and lateral parabrachial nuclei. Moderate staining was observed in the hypoglossal nucleus, cuneate nucleus, inferior olive, prepositus hypoglossi, rostral ventrolateral medulla (RVLM), and locus coeruleus. Staining was also observed in the gracile nucleus, the mesencephalic trigeminal nucleus, and the central pontine gray. In marmoset, prominent P2X receptor-like immunoreactivity occurred in the NTS, medial cuneate nucleus, prepositus hypoglossi, and medial vestibular nucleus. Moderate staining was observed in the area postrema, dorsal motor nucleus of the vagus, lateral cuneate, lateral reticular, spinal trigeminal nucleus, RVLM, and inferior olive. Immunofluorescent double labeling of tyrosine hydroxylase (TH)-containing cells revealed that all subtypes of P2X receptors show some degree of colocalization with TH. The highest proportion of TH and P2X receptor double labeling was in the A5 region (with the P2X(2) subunit), whereas the lowest proportion of double-labeled cells occurred in the C2 region of the NTS for the P2X(5) subunit. These findings support a role for extracellular adenosine 5'-triphosphate in fast synaptic neurotransmission within the brainstem.

Adenosine Triphosphate↗

PubMed2000

Characterisation of vasopressin V(1A), angiotensin AT(1) and AT(2) receptor distribution and density in normotensive and hypertensive rat brain stem and kidney: effects of restraint stress.

In the present study, we have examined neurochemical correlates that may be involved in the differential cardiovascular responses observed in normotensive and hypertensive rats during stress. Using a restraint stress paradigm, both normotensive Wistar Kyoto (WKY) and Spontaneously Hypertensive rats (SHR) underwent acute (1 h restraint in a perspex tube), chronic (1 h restraint for ten consecutive days) or no restraint (control) stress. Following cessation of restraint, rats were processed by incubating sections of brain stem and kidney with [125I]-HO-LVA (0.03 nM) or [125I]Sar(1)Ile(8)-AngiotensinII (0.5 nM), in the presence of PD123319 (10 microM) or losartan (10 microM), to determine the distribution and density of vasopressin V(1A), angiotensin AT(1) and AT(2) receptors, respectively. Analysis of autoradiograms indicated changes in the density of radioligand binding in acutely and chronically-stressed rats, as compared to controls. For example, V(1A) binding in the medial nucleus tractus solitarius (SolM) decreased in the WKY but increased in the SHR. AT(1) binding in SolM did not significantly change in the WKY but decreased in the SHR with repeated restraint. In kidney slices, AT(1) binding decreased with stress in the WKY (-17%) but increased in SHR (+10-15%). AT(2) binding in the kidney showed a pattern similar to that of AT(1) binding in SHR, but not WKY. Graded increases in V(1A) binding were measured in kidney medulla and cortex of both strains (+50-60% with chronic restraint). These results suggest that physiological adaptation to restraint is associated with specific changes in V(1A), AT(1) and AT(2) receptor density within brain nuclei and kidney.

Acute Disease↗

PubMed2000

Study of projections from the entopeduncular nucleus to the thalamus of the rat.

The entopeduncular nucleus (EP) is a major outflow nucleus of the basal ganglia and innervates the lateral habenula, parafascicular, pedunculopontine, ventrolateral (VL), ventromedial (VM), and mediodorsal thalamic nuclei. This study investigated the morphology of single axons of entopeduncular neurons projecting to the motor thalamus by placing small injections of dextran biotin into the EP and reconstructing drawings of single axons from serial sections. There were two populations of entopeduncular-thalamic projection axons: those that projected only to the motor thalamus (VL and VM) and those that projected to both the motor thalamus and other nuclei (e.g., the habenula). The neurochemistry of EP neurons projecting to the thalamus was investigated by injecting the retrograde tracer FluoroGold into the VL and VM thalamic nuclei to retrogradely fill entopeduncular projection neurons. These were subsequently immunohistochemically labeled for choline acetyl transferase, gamma-aminobutyric acid (GABA), and glutamate. Consistent with previous studies, significant proportions of these neurons were GABA immunoreactive. In addition, approximately half of the entopeduncular-thalamic projecting neurons were found to be cholinergic. This excitatory input is most likely derived from axons that branch as they pass through the motor thalamus to the lateral habenula.

Animals↗

PubMed2000

[125I]-galanin binding sites in the human nodose ganglion.

The cell bodies of centrally-projecting vagal afferent neurons are contained in the inferior vagal (nodose) ganglion. Although binding sites for a number of different neuropeptides/modulators have been detected in the human nodose ganglion, the presence of galanin binding sites has not been reported. In vitro receptor autoradiography using [125I]-galanin enabled visualisation of binding sites for galanin in the human nodose ganglion. The presence of such binding sites suggests a potential role for galanin in the neuromodulation of vagal transmission in humans.

Adolescent↗

PubMed2000

Axonal transport of NADPH-diaphorase and [(3)H]nitro-L-arginine binding, but not [(3)H]cGMP binding, by the rat vagus nerve.

Previous studies have shown that the NO(ccirf)-cGMP pathway may be functionally relevant in the nodose ganglion and at afferent terminations of the vagus nerve. The technique of unilateral vagal ligations, using double ligatures, was combined with the techniques of NADPH-diaphorase histochemistry, as an index of nitric oxide synthase (NOS) activity, and autoradiography using the radioligands [(3)H]nitro-L-arginine and [(3)H]cGMP, to examine axonal transport of NOS and cGMP-dependent effectors by the rat vagus nerve. A population of perikarya in the nodose ganglia was NADPH-diaphorase positive, and binding of both [(3)H]nitro-L-arginine and [(3)H]cGMP was found on the nodose ganglia. Following vagal ligation, NADPH-diaphorase reactivity accumulated proximal to the proximal ligature and distal to the distal ligature. Vagus nerve transection beyond the distal ligature eliminated NADPH-diaphorase reactivity at the distal ligature. Similarly, [(3)H]nitro-L-arginine binding was found over the nodose ganglion; and after vagal ligation, an accumulation of [(3)H]nitro-L-arginine binding was seen adjacent to the proximal ligature, though little binding was found adjacent to the distal ligature. No accumulation of [3H]cGMP binding was found adjacent to either the proximal or the distal ligatures. These findings suggest that the rat vagus nerve bidirectionally transports NOS, the enzyme involved in biosynthesis of NO(ccirf) by nitroxidergic nerves. As anticipated, [(3)H]nitro-L-arginine, a competitive inhibitor of the amino acid precursor for NO(ccirf), binds only to a centrifugally transported moiety that we conjecture is NOS, while cGMP apparently is not subject to transport. These data further support the use of NO(&z.ccirf;) in transmission at vagal afferent terminals.

Animals↗

PubMed2000

Characterisation of central adenosine A(1) receptors and adenosine transporters in mice lacking the adenosine A(2a) receptor.

The present study was designed to assess whether adenosine A(2a) receptor knockout mice exhibit altered purine utilisation in brain nuclei. Specifically, the properties of adenosine transporters and adenosine A(1) receptors were characterised in brain membranes and on slide-mounted sections. The B(MAX) for [(3)H]nitrobenzylthioinosine ([(3)H]NBTI) binding (adenosine transporter density) was significantly reduced in brainstem membranes of homozygotes (560+/-52 fmol/mg protein, n=5, P<0.05, Kruskal-Wallis ANOVA) compared to wildtype (1239+/-213 fmol/mg protein) and heterozygous mice (1300+/-558 fmol/mg protein). Quantitative autoradiography data indicated that [(3)H]NBTI binding in the medulla oblongata of heterozygous mice was seen to decrease significantly (P<0.05) in the subpostremal nucleus tractus solitarius (NTS), medial NTS, inferior olive and area postrema (AP). On the other hand, in the homozygous mice a decrease was seen in the medial NTS and AP. In the pons, [(3)H]1, 3-dipropyl-8-cyclopentylxanthine ([(3)H]DPCPX) (adenosine A(1) receptor density) binding increased significantly (P<0.05, Kruskal-Wallis ANOVA) in the lateral parabrachial nucleus, caudal pontine reticular nucleus and locus coeruleus of homozygotes compared to wildtype. In higher brain centres, [(3)H]NBTI binding was reduced in the paraventricular thalamic nucleus of both heterozygous and homozygous mice, whereas [(3)H]DPCPX binding was reduced in the hippocampus and lateral hypothalamus of heterozygotes. In homozygotes, [(3)H]DPCPX binding in the hippocampus increased compared to wildtype mice. The present study indicates that deletion of the A(2a) receptor may have contributed to region-specific compensatory changes in purine utilisation in brain nuclei associated with autonomic, neuroendocrine and behavioural regulation.

Affinity Labels↗

PubMed2000

Visualisation of AMPA binding sites in the brain of mice lacking the adenosine A(2a) receptor.

Adenosine A(2a) receptor knockout mice (A(2a)R k/o) have been characterised as hypertensive, aggressive, anxious and hypoalgesic [12]. Thus, the present study was designed to investigate markers of glutamatergic transmission in specific brain nuclei associated with autonomic regulation. Visualisation of alpha-amino-3-hydroxy-5-methylisoxasole-4-propionic acid binding sites in the brains of A(2a)R k/o mice was achieved by utilising quantitative receptor autoradiography with (S)-[(3)H]-5-fluorowillardiine ([(3)H]FW:10 nM) on slide-mounted sections of mouse-brain. [(3)H]FW binding significantly increased in the nucleus tractus solitarius and area postrema of A(2a)R k/o mice compared with wildtype CD-1 mice. In other autonomic nuclei examined, binding was unchanged between wildtype and knockout mice. The present study suggests that glutamatergic neurotransmission within certain neural pathways involved in autonomic and motor control is altered in the brains of A(2a)R k/o mice.

Animals↗

PubMed2000

Acute and chronic restraint stress: effects on [125I]-galanin binding in normotensive and hypertensive rat brain.

The neuropeptide galanin (GAL) has been implicated in the neural response to a number of stressors including restraint; however, the effect of restraint stress on GAL receptor density in the central nervous system (CNS) has not been investigated. Normotensive (Wistar-Kyoto; WKY) and hypertensive (spontaneously hypertensive; SHR) rats were subjected to a daily 60-min restraint stress paradigm for 0 (control), 1, 3, 5 or 10 consecutive days, and the density of [125I]-GAL binding sites following exposure to restraint was compared between strains using quantitative autoradiography. Significant differences in basal (no stress) levels of GAL receptor density between WKY and SHR were detected in regions such as the central nucleus of the amygdala (Ce) and ventromedial hypothalamus (VMH) (P<0.05). In WKY, restraint stress (1 day) induced significant decreases in GAL receptor density in forebrain regions such as the Ce (-41%) and medial nucleus of the amygdala (-41%) (P<0.05). Chronic restraint (10 days) did not induce significant decreases in these nuclei in WKY, indicating that forebrain neurons containing GAL receptors in WKY possessed a functional ability to adapt to repeated restraint. In addition, restraint stress induced significant decreases in GAL receptor density in SHR in regions such as the lateral parabrachial nucleus (-43%; 5 days of restraint) and hypoglossal nucleus ( approximately -18% for entire restraint period) (P<0.05). In conclusion, restraint stress resulted in region- and strain-specific alterations in GAL receptor density, some of which may contribute to the altered stress response previously observed in hypertensive rats. The results clearly support the hypothesis that neuropeptides such as GAL are an integral component of the neural response to psychological stress, although the functional significance of the changes in GAL receptor density described in this study awaits elucidation.

Acute Disease↗

PubMed2000

CCK/dopamine interactions in Fawn-Hooded and Wistar-Kyoto rat brain.

The aim of this study was to compare the actions of CCK neuropeptides within the nucleus accumbens (N.Acc) of alcohol preferring (Fawn-Hooded, FH) and alcohol nonpreferring (Wistar-Kyoto, WKY) rats. CCK-8S (30-300 nM) facilitated the K(+) stimulated release of [(3)H]dopamine (DA) from N.Acc prisms in both rat strains, whereas CCK-4 (30 nM-1 microM) caused a significant decrease of evoked [(3)H]DA in the FH rat only. A scattered distribution of CCK-A and -B receptor immunopositive varicose fibers were visualized throughout the N.Acc of both rat strains along with a topographic distribution of CCK receptor positive cells throughout the ventral mesencephalon.

Alcohol Drinking↗

PubMed2000

Tissue characterization using magnetic resonance elastography: preliminary results.

The well-documented effectiveness of palpation as a diagnostic technique for detecting cancer and other diseases has provided motivation for developing imaging techniques for noninvasively evaluating the mechanical properties of tissue. A recently described approach for elasticity imaging, using propagating acoustic shear waves and phase-contrast MRI, has been called magnetic resonance elastography (MRE). The purpose of this work was to conduct preliminary studies to define methods for using MRE as a tool for addressing the paucity of quantitative tissue mechanical property data in the literature. Fresh animal liver and kidney tissue specimens were evaluated with MRE at multiple shear wave frequencies. The influence of specimen temperature and orientation on measurements of stiffness was studied in skeletal muscle. The results demonstrated that all of the materials tested (liver, kidney, muscle and tissue-simulating gel) exhibit systematic dependence of shear stiffness on shear rate. These data are consistent with a viscoelastic model of tissue mechanical properties, allowing calculation of two independent tissue properties from multiple-frequency MRE data: shear modulus and shear viscosity. The shear stiffness of tissue can be substantially affected by specimen temperature. The results also demonstrated evidence of shear anisotropy in skeletal muscle but not liver tissue. The measured shear stiffness in skeletal muscle was found to depend on both the direction of propagation and polarization of the shear waves.

Animals↗

PubMed2000

Activation of phospholipase A(2) by long chain fatty acyl groups involves a novel unstable linkage.

The acidic isoform of phospholipase A(2) from Naja mossambica mossambica was activated by treatment with a molar equivalent of oleoyl imidazolide. Modification of the protein was accompanied by 50% quenching of tryptophan fluorescence and a significant red shift. The (3)H(9,10) labeled oleoyl residue was co-eluted with the enzyme during gel filtration in the presence of 20% 1-propanol or excess albumin, both of which remove free oleic acid from the enzyme. In contrast, the adduct was labile as to electrophoresis on SDS-PAGE and acid or alkali urea PAGE. The formation of a covalently linked adduct was demonstrated by electrospray mass spectrometry in the presence of 2% formic acid. No such adduct was formed by the phospholipase A(2) isoform from Naja naja atra, which differs in sequence from the N. mossambica mossambica isoform by seven residues including 2 histidine residues and 1 lysine residue. We conclude that oleoyl imidazolide activates the N. mossambica mossambica enzyme by forming an acyl adduct which is unstable as to protein denaturation. The magnitude of tryptophan fluorescence quenching indicates that the site of acylation lies in the sequence WWHF.

Acylation↗

PubMed2000

Restraint stress : differential cardiovascular responses in Wistar-Kyoto and spontaneously hypertensive rats.

With the use of a restraint stress paradigm, both normotensive Wistar-Kyoto (WKY ) rats and spontaneously hypertensive rats (SHR) underwent acute (1-hour restraint in a Perspex tube), chronic (1-hour restraint for 10 consecutive days), or no-restraint (control) stress. Rats experiencing chronic restraint were previously implanted with telemetric probes to measure heart rate and blood pressure. Basal (prestress session) cardiovascular variables did not change during the course of the study (SHR: mean arterial pressure 129+/-1 mm Hg, heart rate 288+/-4 bpm; WKY rats: mean arterial pressure 103+/-1 mm Hg, heart rate 285+/-3 bpm). Restraint caused tachycardia and pressor responses in the WKY rats and SHR, but these effects were greater in the hypertensive strain. The duration of restraint-induced tachycardia did not change in the WKY rats between acute and chronic stress; however, a graded reduction in the duration of restraint-induced tachycardia occurred in the SHR, decreasing to WKY rat levels by day 7 of the 10-day regimen. These data indicate that although the WKY rats can effectively "cope" within a single period of restraint, the coping mechanism is apparently impaired in the SHR compared with the WKY rats. A reduced capacity to cope with processive stressors may thus have an affect on cardiovascular regulation and represent an additional risk factor in hypertension.

Acute Disease↗

PubMed2000

Effect of chronic ethanol and withdrawal on the mu-opioid receptor- and 5-Hydroxytryptamine(1A) receptor-stimulated binding of [(35)S]Guanosine-5'-O-(3-thio)triphosphate in the fawn-hooded rat brain: A quantitative autoradiography study.

Previous studies have shown that chronic ethanol influences the density of central mu-opioid receptors and serotonin(1A) (5-hydroxytryptamine(1A)) receptors. To determine whether the functional coupling of these two receptors to G proteins in the rat brain, particularly in mesocorticolimbic regions, is affected by ethanol, receptor-mediated [(35)S]guanosine-5'-O-(3-thio)-triphosphate ([(35)S]GTPgammaS) binding stimulated by [D-Ala(2),N-MePhe(4),Gly-ol(5)]-enkephalin (DAMGO) or L694,247 was used. By quantitative autoradiography, receptor-mediated [(35)S]GTPgammaS binding activated by the two agonists was mapped throughout brain sections at the level of the nucleus accumbens and hippocampus from groups of alcohol-preferring Fawn-Hooded (FH) rats after different ethanol consumption paradigms. Significant DAMGO (mu-opioid receptor agonist)-stimulated binding of [(35)S]GTPgammaS was obtained in the striatum, nucleus accumbens, and lateral septum, whereas L694,247 (5-hydroxytryptamine(1A/1B/1D) receptor agonist)-stimulated binding of [(35)S]GTPgammaS was observed in the lateral septum, amygdala, and cingulate cortex. Chronic ethanol self-administration significantly reduced DAMGO-stimulated [(35)S]GTPgammaS binding in the nucleus accumbens (-19%), lateral septum (-15%), and striatum (-23%), which recovered toward control levels after ethanol withdrawal. However, chronic ethanol, as well as ethanol withdrawal, failed to produce any significant alteration in L694,247-stimulated [(35)S]GTPgammaS binding in all tested brain regions. The region-specific and receptor-specific alteration of agonist-stimulated [(35)S]GTPgammaS binding suggests that the change of functional coupling of mu-opioid receptors to G proteins induced by chronic ethanol drinking may have a pathophysiological role in the consequences of ethanol consumption.

Alcohol Drinking↗

PubMed2000

5-HT transporter sites and 5-HT1A and 5-HT3 receptors in Fawn-Hooded rats: a quantitative autoradiography study.

BACKGROUND: The neuroanatomical profiles of 5-HT1A receptors, 5-HT3 receptors, and 5-HT transporters (5-HTT) in the brain of the Fawn-Hooded (FH) rat, particularly mesocorticolimbic regions, are not fully elucidated. METHODS: By means of in vitro quantitative autoradiography, we used [3H]citalopram, [3H]8-OH-DPAT, and [3H]GR65630 to label 5-HTT, 5-HT1A receptors, and 5-HT3 receptors in the brain of alcohol-naïve FH rats, Wistar-Kyoto (WKY) rats, and FH rats given free access to 5% ethanol and/or after 24 to 48 hr withdrawal. RESULTS AND CONCLUSIONS: In alcohol-naïve rats, FH rats displayed significantly higher (p < 0.05) densities of [3H]citalopram binding in the nucleus accumbens (+30%), lateral septum (+37%), ventral pallidum (+21%), and ventral tegmental area (+24%), as well as an increased binding of [3H]8-OH-DPAT to 5-HT1A receptors in the frontal and parietal cortex (+33%), occipital and temporal cortex (+25%), and hippocampal CA3 region (+31%), compared with WKY rats, whereas both strains exhibited comparable [3H]GR65630 binding to 5-HT3 receptors. Compared with control FH (naive) rats, chronic ethanol consumption significantly decreased (p < 0.(15)[3H]8-OH-DPAT binding in the frontal and parietal cortex (-15%) but significantly increased binding (p < 0.05) in the entorhinal cortex (+25%), retrosplenial granular cortex (+20%), and hippocampal CA1 (+14%) and CA3 regions (+18%). Moreover, ethanol withdrawal induced the same extent of increased [3H]8-OH-DPAT binding in the entorhinal and retrosplenial cortex as seen in FH (chronic) rats. In contrast, [3H]8-OH-DPAT binding in the hippocampal CA1 and CA3 regions was decreased by -9% and -20% from the level of chronic ethanol-treated FH rat (p < 0.05) and returned to the control level seen in FH (naïve) rats. SIGNIFICANCE: The elevated 5-HT transporters and 5-HT1A receptors in the mesocorticolimbic areas in FH rats may reflect a potential innate altered transmission at serotonergic synapses, which possibly may affect the high intake of alcohol in FH rats. The region-specific alterations of 5-HT1A receptors in FH rat brain after ethanol challenges suggest that 5-HT1A receptors are sensitive to ethanol challenges, whereas 5-HTT are apparently insensitive.

8-Hydroxy-2-(di-n-propylamino)tetralin↗