Biomedical subjects

F Amenta

Publications and source records attributed to F Amenta.

At least 325 records · Page 18Linked to original sources

PubMedDate not supplied

Density and pattern of dopamine D2-like receptors in the cerebellar cortex of aged rats.

The pharmacological properties and the anatomical localization of dopamine (DA) D2-like receptors were studied in the cerebellum of 3 months, 12 months, and 24 months male Wistar rats using combined radioligand binding and autoradiographic techniques with [3H]-spiroperidol as a ligand. The binding was consistent with the labelling of the DA D3 receptor subtype. The affinity for DA D2-like receptors was similar in the cerebellar cortex of the three animal groups investigated, whereas the density of binding sites (Bmax value) assessed using conventional radioligand binding techniques was reduced as a function of aging. Light microscope autoradiography revealed the localization of binding sites primarily in the molecular layer and to a lesser amount in Purkinje neurons layer. A loss of binding sites was noticeable with aging in the grey matter of the cerebellar cortex. It affected primarily the molecular layer. Analysis of radioligand binding data and light microscope autoradiography suggests that age-related changes of DA D2-like receptors depend in part by structural alterations of cerebellar cortex and in part by modifications in receptor expression.

Aging↗

PubMedDate not supplied

3H-muscimol binding sites within the rat choroid plexus: pharmacological characterization and autoradiographic localization.

By using combined radioreceptor binding and autoradiographic techniques, we were able to localize the GABA 'A' receptor agonist 3H-muscimol in the rat choroid plexus. Within sections of rat choroid plexus, 3H-muscimol was bound specifically with a KD of 37 nM and a Bmax of 253 pmol/mg tissue. These values are consistent with the labelling of GABA 'A' receptor sites. The autoradiographic studies demonstrated that 3H-muscimol was attached to the epithelium of the choroid plexus. The blood vessels of the plexus did not exhibit specific labelling. Examination of these data suggests the existence of GABAergic mechanisms which control cerebrospinal fluid production or flow.

Animals↗

PubMedDate not supplied

Evidence against the existence of GABA-B receptor sites in rat cerebrovascular tree.

By the use of combined radioreceptor binding and autoradiographic techniques we attempted to analyse the biochemical characteristics and the anatomical localization of GABA-B receptors in sections of rat circle of Willis and pialarachnoid arteries. 3H-GABA in the presence of 40 microM isoguvacine and 2.5 mM CaCl2 was used to label GABA-B receptor sites. Sections of rat cerebellar cortex were also processed as a reference tissue. No specific 3H-GABA binding was detectable either in radioreceptor binding or autoradiographic experiments. In contrast, the ligand was bound to sections of cerebellar cortex in a manner consistent with the labelling of GABA-B receptor sites. These findings indicate that cerebrovascular physiological responses to GABA are not linked, in the rat cerebrovascular tree, to the activation of GABA-B receptors.

Animals↗

PubMedDate not supplied

In situ hybridization and immunocytochemistry of alpha1-adrenoceptors in human peripheral blood lymphocytes.

1 alpha1-Adrenoceptor subtypes were investigated in cytospin centrifuged preparations of human peripheral blood lymphocytes by in situ hybridization and immunocytochemistry. 2 In situ hybridization cytochemistry revealed alpha1A-, alpha1B-, and alpha1D-receptor mRNA in human peripheral blood lymphocytes. Lymphocytes hybridized for alpha1A receptor subtype represented approximately 30% of total lymphocytes, those hybridized for alpha1Beta- and alpha1D-receptor subtypes averaged 42 and 25% of total lymphocytes, respectively. 3 Cytospin centrifuged lymphocytes exposed to anti-alpha1A-, alpha1Beta- or alpha1D-receptor protein antibodies, developed specific immunostaining. Approximately 27% of total lymphocytes were immunoreactive for alpha1A-receptor protein, 40% displayed alpha1B-receptor protein immunoreactivity and 22% alpha1D-receptor protein immunoreactivity. Analysis of percentages as well as of lymphocyte morphology of in situ hybridized and immunolabelled lymphocytes suggests the co-expression of mRNA receptor signal and protein receptor immunostaining in the same lymphocyte. 4 The demonstration of both alpha1-adrenoceptor mRNA and receptor protein subtypes suggests that alpha1-adrenoceptors may have a role in regulating lymphocyte function. 5 The possibility of demonstrating receptor protein immunoreactivity in a small amount of blood, such as that required for preparing cytospin-centrifuged lymphocytes, may stimulate research to evaluate the role of these receptors in lymphocytes and to establish if assessment of lymphocyte alpha1-adrenoceptors may represent a marker of their status in health and disease.

Adult↗

PubMedDate not supplied

Dopamine receptor immunohistochemistry in the rat choroid plexus.

1. Earlier studies have demonstrated a high density of dopamine D1-like receptor binding in the choroid plexus by light microscope autoradiography, but the dopaminergic specificity of this binding was questioned. 2. In this study the localization of dopamine receptor subtypes was investigated in the rat choroid plexus by Western blot analysis and immunohistochemistry using antibodies raised against dopamine D1-D5 receptor protein. 3. Western blot analysis revealed reactivity with immune bands of approximately 50 and 51 KDa corresponding to dopamine D1 and D5 receptors, respectively. Dopamine D1-like (D1 and D5) receptor protein immunoreactivity insensitive to superior cervical ganglionectomy was located in smooth muscle of choroid arteries and to a larger extent within choroid plexus epithelium. 4. Western blot analysis revealed reactivity with immune bands of approximately 53 KDa and 40-42 KDa corresponding to dopamine D2 and D4 receptors, respectively, and no dopamine D3 receptor reactivity. Dopamine D2-like receptor protein immunoreactivity displayed a distribution similar to that of tyrosine-hydroxylase (TH)-immunoreactive sympathetic fibres and disappeared after superior cervical ganglionectomy. It consisted in the expression of dopamine D2 and to a lesser extent of D4 receptor protein immunoreactivity perivascularly and associated with choroid epithelium. No D3 receptor protein immunoreactivity was found in rat choroid plexus. 5. The above results indicate that rat choroid plexus expresses dopamine receptor protein, being dopamine D1-like receptors predominant in epithelium and arterial smooth muscle and D2-like receptors in sympathetic nerve fibres supplying choroid plexus epithelium and vasculature. 6. These findings suggests that dopamine receptors with a different anatomical localization may modulate production of cerebrospinal fluid.

Animals↗

PubMedDate not supplied

The dopaminergic system in hypertension.

Dopamine exerts cardiovascular and renal actions mediated through interaction with specific dopamine receptors. Dopamine receptors are cell surface receptors coupled to G-proteins and classified into two main super families based on biochemical, pharmacological and molecular characteristics. The dopamine D1-like receptor super family includes D1 and D5 receptors, known also in rodents as D1A and D1B sites. These receptors are linked to stimulation of adenylate cyclase. The dopamine D2-like receptor super family includes D2, D3 and D4 receptors. These receptors are linked to inhibition of adenylate cylase or not related with this enzyme activity. They also interfere with opening of Ca+2 channels and are linked to stimulation of K+ receptors. Dopamine receptor subtypes are expressed in brain as well as in extracerebral structures such as the heart, blood vessels, carotid body, kidney, adrenal gland, parathyroid gland and gastrointestinal tract. In the kidney, which represents the peripheral organ where dopamine receptors were more extensively investigated, dopamine receptors are involved in regulation of hemodynamic, electrolyte and water transport, as well as renin secretion. Hypertension-related dopamine receptor changes were also investigated primarily in the kidney. Defective renal dopamine production and/or dopamine receptor function have been reported in human primary hypertension as well as in genetic models of animal hypertension. There may be a primary defect in D1-like receptors and an altered signalling system in the proximal tubules that lead to reduced dopamine-mediated effects on renal sodium excretion in hypertension. Studies on the influence of hypertension on dopamine D2-like receptors are sparse Disruption of either D1A or D3 receptors at the gene level causes hypertension in mice. Using peripheral blood lymphocytes as possible markers of the status of dopamine receptors in essential hypertension, no changes of dopamine D1-like receptors were noticeable, whereas an increase of dopamine D2-like receptors likely representing an up-regulation mechanism was reported. Available information collectively indicates an involvement of peripheral dopaminergic system in hypertension consisting either in impaired receptor transduction mechanisms and/or in receptor loss. A better knowledge of molecular bases of these changes may contribute to the development of specific therapeutic approaches in the future.

Animals↗

PubMedDate not supplied

Occupancy by oral administration of nicardipine of L-type calcium channels in rat brain.

The occupancy of L-type Ca2+ channels by treatment with an oral dose of the dihydropyridine-type Ca2+ antagonist nicardipine (sustained-release formulation) was evaluated in membrane preparations of rat frontal cortex and hippocampus using a radioligand binding assay technique, with [3H]-nicardipine as a ligand. Three hours after nicardipine administration, specific binding was decreased by about 15-20%, both in the frontal cortex and hippocampus. This indicates that oral nicardipine occupied approximately 15-20% of L-type Ca2+ channels. A progressive occupancy of Ca2+ channels was observed between six and 12 h after nicardipine administration. Twelve hours after drug administration, approximately 65-70% of Ca2+ channels were occupied. These findings indicate that oral treatment with 3 mg/kg of nicardipine (sustained-release formulation) occupies L-type Ca2+ channels in rat brain by more than 40% from the 6th to the 24th h after drug administration. This suggests that an oral dose of nicardipine (sustained-release formulation) in duces a significant occupancy of L-type Ca2+ channels in rat frontal cortex and hippocampus for about one day. The possible clinico-therapeutic relevance of this observation is discussed.

Administration, Oral↗

PubMedDate not supplied

Effect of nicardipine treatment on the expression of neurofilament 200 KDa immunoreactivity in the brain of spontaneously hypertensive rats.

Neurofilaments (NFP) are components of neuronal cytoskeleton involved primarily in axonal transport and in the regulation of dynamic activities of nerve cells. NFP consist of three subunits denominated high- (200 kDa, NFP-H), intermediate- (160 kDa, NFP-I), and low-molecular weight (68 kDa, NFP-L) neurofilament proteins. Their function and polymerization depends on phosphorylation status, and is regulated by Ca2+ influx. Ca2+ overload enhances degradation of NFP and may compromise axonal transport. An increased susceptibility to ischemia occurs in hypertension, which is also a cause of brain damage. In this study, the expression of phosphorylated NFP (P-NFP) was investigated in the brain of spontaneously hypertensive rats (SHR) using immunohistochemical techniques with antibodies against the phosphorylated epitope of NFP RT-97. Microanatomical analysis included frontal cortex, occipital cortex, hippocampus and cerebellar cortex. The effect of long-term treatment with the dihydropyridine-type Ca2+ antagonist nicardipine on the expression of P-NFP was investigated as well. In hypertension a decreased P-NFP immunoreactivity was observed in frontal and occipital cortex, in the CA1 subfield of hippocampus and in the dentate gyrus, but not in the CA3 subfield of hippocampus or in the cerebellar cortex. Treatment with a daily dose of 3 mg/kg of nicardipine and 10 mg/kg of hydralazine significantly reduced systolic pressure in SHR. The above dose of nicardipine and to a lesser extent a non-hypotensive dose of the compound (0.1 mg/kg/day), but not hydralazine, increased P-NFP immunoreactivity in the cerebral cortex and hippocampus, except the CA3 subfield. The possibility that rescued P-NFP immunoreactivity by treatment with nicardipine depends on improved brain perfusion caused by the compound and/or by countering neuronal Ca2+ overload is discussed.

Animals↗

PubMedDate not supplied

Protective effect of treatment with nicardipine on cerebrovascular tree of spontaneously hypertensive rats.

The effect of an eight-week treatment with the Ca2+ channel blocker nicardipine on different-sized pial arteries and intracerebral arteries was assessed in spontaneously hypertensive rats (SHR) by microanatomical techniques. Normotensive Wistar-Kyoto (WKY) rats were used as normotensive reference animals. In SHR a significant increase of systolic blood pressure (SBP) in comparison with WKY rats was noticeable. An increased thickness of tunica media and luminal narrowing were also seen in medium- and small-sized pial arteries, and in intracerebral arteries of SHR in comparison with WKY rats. The media-to-lumen ratio was also increased in medium (diameter between 150 and 50 microm) and small-sized (diameter < than 50 microm) pial and intracerebral arteries. Treatment with nicardipine significantly reduced SBP, the thickness of tunica media, media-to-lumen ratio and increased luminal area of medium- and small-sized pial arteries and of intracerebral arteries. These findings demonstrate that treatment of SHR with nicardipine induces a moderate vasodilatation of both pial and intracerebral arteries regulating cerebrovascular resistance. This property may be useful in avoiding generalized or exaggerated cerebrovascular dilatation in hypertension which could be accompanied by impaired brain perfusion.

Animals↗

PubMedDate not supplied

Effect of antihypertensive treatment on peripheral nerve vasculature in spontaneously hypertensive rats.

The influence of hypertension and of treatment with the dihydropyridine-type Ca+2 antagonist nicardipine on peripheral nerve vasculature were investigated in spontaneously hypertensive rats (SHR). Male SHR were treated from the 16th to the 26th week of age with vehicle (control group), with nicardipine, at the hypotensive dose of 3 mg/kg/day, or at the nonhypotensive dose of 0.1 mg/kg/day or with an equihypotensive dose (10 mg/kg/day) of the nondihydropyridine-type vasodilator hydralazine. Age-matched normotensive Wistar-Kyoto (WKY) rats were left untreated and used as normotensive reference animals. In SHR a significant increase of systolic pressure values accompanied by sciatic nerve microvascular changes, involving primarily interfascicular arteries and to a lesser extent intrafascicular arteries, was observed. Treatment with the hypotensive dose of nicardipine countered hypertension-dependent microvascular changes occurring in both interfascicular and intrafascicular arteries. The nonhypotensive dose of nicardipine and hydralazine displayed a modest activity on interfascicular arteries, but significantly countered hypertension-related changes involving intrafascicular arteries. The above findings indicate the occurrence of hypertension-related changes of peripheral nerve microvasculature and of positive effects induced by appropriate pharmacological treatment. Further work is in progress to identify the functional relevance of microanatomical observations of the present study.

Animals↗

PubMedDate not supplied

Neurotrophins and neurotrophin receptors in human pulmonary arteries.

The localization of neurotrophins (NTs) and NT receptors was analyzed in sections of human extra- and intrapulmonary arteries by Western blot analysis and immunohistochemistry. In extrapulmonary branches of human pulmonary artery, NT and NT receptor immunoreactivity was located in the tunica intima, within endothelium, in the tunica media, within smooth muscle and in the tunica adventitia. In different sized intrapulmonary arteries, NT and NT receptor immunoreactivity was observed primarily in the tunica adventitia. A faint NT and NT receptor immunoreactivity was observed in the tunica media of large-sized branches of intrapulmonary arteries, but not within medium- or small-sized intrapulmonary vessels or in tunica intima of different sized intrapulmonary arteries. These findings suggest that NTs may have a role in the control of vascular responses in the pulmonary system acting as local paracrine or autocrine mediators. The possible relevance of the NT system in human pulmonary vasculature identified in this study is discussed.

Adolescent↗

PubMedDate not supplied

Localization of dopamine receptors in the rabbit lung vasculature.

The localization of dopamine receptor subtypes in the rabbit pulmonary circulation was investigated by using combined radioligand binding and light microscope autoradiography techniques. Dopamine D1-like receptors, probably belonging to the dopamine D1 receptor subtype, were demonstrated in sections of rabbit lung using [3H]-SCH 23390 as a ligand. This site is located within the tunica intima and the tunica media of large intrapulmonary artery branches (diameter > 300 microns) as well as within the tunica media of medium-sized pulmonary artery branches (diameter between 100 and 300 microns). No [3H]-SCH 23390 binding sites were found in small-sized pulmonary artery branches (diameter < 100 microns) or in pulmonary veins. Dopamine D2-like receptors, probably belonging to the dopamine D2 receptor subtype, were demonstrated with radioligand binding techniques in sections of extrapulmonary arteries but not of lung using [3H]-spiroperidol as a ligand. Light microscope autoradiography revealed the localization of this site within the tunica adventitia of extrapulmonary arteries as well as of large- and medium-sized intrapulmonary artery branches. The different anatomical localization of dopamine D1- and D2-like receptors in the rabbit pulmonary vasculature suggests that these sites are involved in the modulation of pulmonary vascular tone by interacting with different receptors having endothelial, muscular and probably prejunctional localization. The functional significance of the uneven distribution of dopamine receptor subtypes throughout the pulmonary vascular bed should be clarified in future studies.

Analysis of Variance↗

PubMedDate not supplied

Light microscope autoradiography of peripheral dopamine receptor subtypes.

Radioligand binding assay techniques associated with light microscope autoradiography were used for investigating the pharmacological profile and the micro anatomical localization of peripheral dopamine receptor subtypes. In systemic arteries, the predominant dopamine D1-like receptor belongs to the D5 (or D1B) subtype. It is located within smooth muscle of the tunica media. In pulmonary arteries, dopamine D1-like receptors have primarily an endothelial localization and belong to the dopamine D1 (or D1A) receptor subtype. Both systemic and pulmonary arteries express a dopamine D2-like receptor belonging to the D2 receptor subtype. It has a prejunctional localization in the majority of vascular beds investigated. In cerebral, coronary and mesenteric arteries, it has also an endothelial localization. In the heart, a dopamine D4 receptor was identified. It is expressed by atrial tissue and has a widespread distribution overall atrial musculature. The kidney expresses both dopamine D1-like and D2-like receptors. Renal dopamine D1-like receptors have a vascular and tubular localization. The majority of these sites belongs to the D5 receptor subtype. A smaller D1 receptor population has primarily a tubular localization. Renal dopamine D2-like receptors belong to the dopamine D3 subtype and in lesser amounts to the D2 and D4 receptor subtypes. Renal dopamine D3 receptor has to a greater extent a tubular localization, whereas the D4 receptor is located within glomerular arterioles. The above results suggest that radioligand binding assay and autoradiographic techniques, if performed in the presence of compounds displaying specific receptor subtype selectivity, may contribute to characterize, mainly from a quantitative point of view, peripheral dopamine receptors.

Animals↗

PubMedDate not supplied

Dopamine D1-like receptor subtypes in the rat kidney: a microanatomical study.

The microanatomical localization of dopamine D1A and D1B receptor subtypes was investigated in sections of rat kidney using immunohistochemicals techniques with antidopamine D1A and D1B receptor antibodies. Microanatomical analysis was limited to the various components of nephron. Dopamine D1A receptor immunoreactivity was found primarily in the epithelium of loop of nephron (loop of Henle) and of collecting tubules. A less intense immunoreactivity was observed within proximal and distal convoluted tubules as well as in juxtaglomerular complex. Dopamine D1B receptor immunoreactivity was found primarily in proximal and distal convoluted tubules and within the juxtaglomerular complex. A less intense immunoreactivity was observed in the epithelium of collecting tubules followed by the loop of nephron. The demonstration of the localization of dopamine D1A and D1B, receptor subtypes along the nephron may contribute to better define their significance in physiological and pathological conditions.

Animals↗

PubMedDate not supplied

The peripheral dopaminergic system: morphological analysis, functional and clinical applications.

In vivo administration or in vitro application of dopamine or of dopamine receptor agonists induce vasodilatation in the cerebral, coronary, renal and mesenteric vascular beds and cause hypotension. Moreover, dopamine stimulates cardiac contractility and induces diuresis and natriuresis. Peripheral (cardiovascular and renal) dopamine receptors belong to the D1-like and D2-like receptor superfamilies, thought to be located post-junctionally and pre-junctionally respectively. Stimulation of vascular D1-like receptors causes direct vasodilatation and reduction of vascular resistance. Stimulation of vascular D2-like receptors causes indirect vasodilatation, resulting from inhibition of sympathetic vasoconstrictor tone. Combined radioligand binding assay and light microscope autoradiography have investigated the anatomical localization of cardiovascular and renal dopamine D1-like and D2-like receptors in different animal species including humans. The application of molecular biology techniques to dopamine receptor research has shown that the picture of dopamine receptor subtypes is more complicated than it was suggested in the past, with at least 5 subtypes belonging to the dopamine D1-like (D1 and D5 receptors) and D2-like (D2, D3 and D4 receptors) superfamilies. The development of antibodies raised against selected sequences of dopamine receptor subtypes has allowed a more detailed characterization of the density and pattern of peripheral dopamine receptors. Dopamine receptor protein immunohistochemistry confirmed the localization of dopamine D1 and D5 receptors in the tunica media of systemic arteries and of prejunctional dopamine D2-D4 receptors closely associated with sympathetic neuroeffector junctions. The distribution and the density of prejunctional dopamine D2-like receptors was different in various vascular beds investigated. The kidney expresses the 5 different subtypes of dopamine receptors, displaying a not homogeneous vascular and tubular localization. Dopamine acting as autocrine or paracrine substance is probably involved in the regulation of immune activity. Human peripheral blood lymphocytes contain dopamine and express plasma membrane and vesicular dopamine transporters as well as dopamine D3, D4 and D5 receptors. Another recently characterized peripheral dopaminergic system is located in the lung. Dopamine D1-like receptor immunoreactive structures were found in a small percentage of nerve fibres contained in pulmonary nerve trunks. D1-immunoreactive nerve fibres were approximately 2-3% of total fibres, whereas D5-immunoreactive fibres accounted approximately for 5-6% of total fibres. Also dopamine D2-like receptor immunoreactive fibres were found in pulmonary trunks. D2-immunoreactive fibres accounted for approximately 3-5% of total nerve fibres, D3 receptor-immnunoreactive fibres accounted for about 8-10% of total nerve fibres, whereas only rare profiles of D4 receptor protein-immunoreactive fibres were observed. Dopamine recepetor protein immunostaining was also found in neurons of nodose ganglion, that display immunoreactivity for different neuropeptides. Based on the correspondence between the number of dopamine receptor immunoreactive pulmonary nerve fibres and of vagal ganglionic neurons immunoreactive for dopamine receptors it is possible to hypothesize that these receptors are located on pulmonary afferents. In spite of the heterogeneity of peripheral systems expressing dopamine receptors, analysis of their localization with appropriate microanatomical techniques may contribute to investigate their role in health and disease.

Animals↗

PubMedDate not supplied

Autoradiographic localization of octylonium bromide binding sites in the rat gastrointestinal tract.

The anatomical localization of the binding sites of the spasmolytic drug octylonium bromide (OB) in the rat gastrointestinal tract was analyzed by use of light microscope autoradiography. The drug was visualized after in vitro incubation of frozen sections of the gastrointestinal tract with a 10 nM concentration of 14C-OB and after in vivo injection into the ascending, transverse, descending and sigmoidal portions of the colon. In vitro experiments demonstrated the specific accumulation of 14C-OB within the colonic and rectal smooth muscle. In contrast, no specific binding of the radiolabeled drug was noticeable in the stomach or in the small intestine. In vivo intracolonic injection of 14C-OB showed a significant accumulation of the drug in the colonic musculature 2 min after administration. The predominant localization of 14C-OB in the colonic and rectal musculature could explain its effectiveness in suppressing the amplitude and frequency of colonic contractions and in controlling the irritable bowel syndrome.

Animals↗

PubMedDate not supplied

Pharmacological characterization and autoradiographic localization of dopamine receptor sites in the caudal artery of the rat.

The existence and the localization of dopamine DA-1 and DA-2 receptors in the main ventral artery of the rat tail were studied using combined radioligand assay and autoradiographic techniques. [3H]-SCH 23390 was used as a ligand of DA-1 receptors, whereas [3H]-spiroperidol was used as a ligand of DA-2 receptors. No specific binding of [3H]-SCH 23390 was detectable in frozen sections of the caudal artery, neither in receptor binding nor in autoradiography experiments. In contrast, the ligand was specifically bound to sections of the rat brain including the neostriatum. [3H]-Spiroperidol was bound to sections of the caudal artery in a manner consistent with the labeling of DA-2 receptor sites. The dissociation constant value was 3.37 nM. The number of binding sites was 90 fmol/mg protein. Autoradiography demonstrated the localization of specific [3H]-spiroperidol binding sites in the adventitia and in the adventitia-media border. These sites disappeared after 6-hydroxydopamine sympathectomy, suggesting their prejunctional nature. The present results suggest the existence of DA-2 but not of DA-1 receptors in the rat caudal artery. These prejunctional DA-2 receptors are probably involved in the inhibition of noradrenaline release caused by DA-2 receptor agonists.

Animals↗

PubMedDate not supplied

Dopamine receptors in the cardiovascular system.

The pharmacological profile and the anatomical localization of dopamine (DA) DA-1 and DA-2 receptor sites were investigated in sections of rat cerebral, mesenteric, renal and caudal arteries. 3H-SCH 23390 (DA-1 ligand) was bound by the medial layer of cerebral, mesenteric, renal but not caudal arteries. 3H-Spiroperidol (DA-2 ligand) was bound by adventitial and adventitial medial sites (sensitive to chemical sympathectomy) and by the intimal layer of the arteries examined. These findings support the view that DA receptors involved in cardiovascular regulation are located in key areas of the arterial wall.

Animals↗