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001-es BibID:BIBFORM073591
Első szerző:Homicskó Krisztián Gy.
Cím:Binding site of salsolinol : its properties in different regions of the brain and the pituitary gland of the rat / Krisztián Gy. Homicskó, István Kertész, Balázs Radnai, Béla E. Tóth, Géza Tóth, Ferenc Fülöp, Márton I. K. Fekete, György M. Nagy
Dátum:2003
ISSN:0197-0186
Megjegyzések:It has been recently shown that salsolinol (SAL) is present in the hypothalamic neuroendocrine dopaminergic (NEDA) system and appears to be a selective and potent stimulator of prolactin (PRL) secretion in the rat. Furthermore, the lack of interference of SAL with -spiperone binding in the striatum and the anterior lobe (AL) of the pituitary gland has been also demonstrated. These data clearly indicate that SAL does not act at the dopamine (DA) D2 receptors, and suggest that SAL supposedly has a binding site through which the secretion of PRL may be affected. Therefore, binding of -SAL to different regions of the central nervous system (CNS) has been investigated. Specific and saturable binding has been detected in the striatum, cortex, median eminence and in the hypothalamus as well as in the AL and the neuro-intermediate lobe (NIL) of the pituitary gland. KD values of the bindings were in the nanomolar range in all tissue tested. -SAL displacing activity of several agonists and antagonists of known DA receptors have also been tested. It has been found that DA and in a lesser extent, apomorphine could displace -SAL, but other DA receptor specific ligands have not been able to affect it. Furthermore, several pharmacologically active compounds, selected on the basis of their influence on DA synthesis, transport mechanisms and signal transduction, have also been tested. Neither mazindol (a selective DA transporter inhibitor) nor clonidine (an ?2-adrenoreceptor agonist) could alter SAL binding. At the same time, l-dopa, carbidopa, benserazide and ?-methyldopa were able to displace -SAL. The possible changes in SAL binding due to physiological and pharmacological stimuli, like suckling stimulus and reserpine pretreatment (that blocks vesicular monoamine transport in DA terminals), respectively, have also been investigated. In the NIL of the pituitary gland and in the median eminence of the hypothalamus the binding decreased following 10 min of suckling stimulus compared to the binding detected in the same tissues obtained from mothers separated from their pups for 4 h and not allowed to be suckled. At the same time, there were no changes in the binding at the AL and striatum. Following reserpine pretreatment that has completely prevented PRL releasing effect of SAL, the binding was significantly augmented. These results support our assumption that SAL should have specific binding sites through which it can affect PRL secretion. Furthermore, it clearly suggests that it may regulate DAergic neurotransmission of NEDA neurons by an altered intracellular or intraterminal synthesis and/or distribution of hypophysiotropic DA.
Tárgyszavak:Orvostudományok Gyógyszerészeti tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Neurochemistry International 42 : 1 (2003), p. 19-26. -
További szerzők:Kertész István (1966-) (vegyész) Radnai Balázs Tóth E. Béla (1960-) (orvos) Tóth Géza Fülöp Ferenc Fekete I. K. Márton Nagy György M.
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2.

001-es BibID:BIBFORM073602
Első szerző:Horváth Katalin M.
Cím:Inhibition of protein phosphatase 2A (PP2A) mimics suckling-induced sensitization of mammotropes : involvement of a pertussis toxin (PTX) sensitive G-protein and the adenylate cyclase (AC) / Katalin M. Horváth, Balázs Radnai, Tóth E. Béla, Márton I. K. Fekete, György M. Nagy
Dátum:1999
ISSN:0303-7207
Megjegyzések:In lactating rats, suckling renders mammotropes more responsive to prolactin (PRL)-releasing stimuli and less responsive to PRL-inhibiting secretagogues. We have previously shown that a decrease in the activity of protein phosphatase 2A (PP2A) may be responsible for the decrease in responsiveness to the inhibitory secretagogue dopamine (DA). In our present experiments, we have studied the involvement of the adenylate cyclase (AC), stimulatory and inhibitory GTP-binding proteins and also the role of PP2A in the sensitization phenomenon. Pituitary cells obtained from mother rats separated from their pups for 4 h prior to dispersion (non-suckled), suckled for 10 or 30 min after the separation period (suckled) and without separation (continual suckling) were incubated in the presence of different doses of forskolin to activate AC and DA. In a further study, pituitary cells of non-suckled rats were pretreated with cholera toxin (CTX) or pertussis toxin (PTX) and tested for the stimulatory action of forskolin or TRH on PRL release. Ocadaic acid (OA) pretreatment has been used to investigate the involvement of PP2A. Hormone secretion was measured by the reverse hemolytic plaque assay (RHPA). Our results have shown that cells from non-suckled rats were unresponsive to forskolin. A 10-min suckling stimulus sensitizes pituitary mammotropes to respond with a PRL release to a dose-dependent activation of AC by forskolin. This sensitization of AC becomes a permanent feature of the cells when suckling continues for an additional 20 min. We have also found that pituitary mammotropes from non-suckled dams respond to forskolin or TRH with PRL release when they were preincubated with either PTX or the PP2A inhibitor OA. It clearly indicates that the non-responsive pituitary can be shifted to the responsive stage by uncoupling of inhibitory G-protein from its receptor as well as by inhibition of PP2A. This latter finding, consonant with our previous results, suggests that suckling may cause selective changes in the function of Gi of mammotropes due to a rapid phosphorylation which can remove tonic, GTP-dependent inhibitory function.
Tárgyszavak:Orvostudományok Gyógyszerészeti tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Molecular And Cellular Endocrinology 149 : 1-2 (1999), p. 1-7. -
További szerzők:Radnai Balázs Tóth E. Béla (1960-) (orvos) Fekete I. K. Márton Nagy György M.
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3.

001-es BibID:BIBFORM031973
Első szerző:Tóth E. Béla (orvos)
Cím:Salsolinol is putative endogenous Neuro-intermediate lobe prolactin-releasing factor / Tóth B. E., Homicskó K., Radnai B., Maruyama W., DeMaria J. E., Vecsernyés M., Fekete M. I. K., Fülöp F., Naoi M., Freeman M. E., Nagy G. M.
Dátum:2001
ISSN:0953-8194
Megjegyzések:The isolation and identification of a prolactin-releasing factor (PRF) from the neuro-intermediate lobe of the pituitary gland has been pursued for over a decade. Using high-pressure liquid chromatography with electrochemical detection (HPLC-ECD) and gas chromatography/mass spectrometry (GC/MS) (R)-salsolinol (SAL) (a dopamine-related stereo-specific tetrahydroisoquinoline) was found to be present in neuro-intermediate lobe as well as median eminence extracts of male, intact-, and ovariectomized female rats. Moreover, analysis of SAL concentrations in neuro-intermediate lobe revealed parallel increases with plasma prolactin in lactating rats exposed to a brief (10 min) suckling stimulus following 4-h separation. SAL appears to be a selective and potent stimulator of prolactin secretion in vivo and it was without effect on the secretion of other pituitary hormones. We have also found that SAL can elevate prolactin release, although to a lesser extent, in pituitary cell cultures as well as in hypophysectomized rats bearing anterior lobe transplants under the kidney capsule. Lack of interference of SAL with [3H]-spiperone binding to AP homogenates indicates that SAL does not act at the dopamine D2 receptor. Moreover, [3H]-SAL binds specifically to homogenate of AL as well as neuro-intermediate lobe obtained from lactating rats. Taken together, our data clearly suggest that SAL is synthesized in situ and this compound can play a role in the regulation of pituitary prolactin secretion.
Tárgyszavak:Orvostudományok Gyógyszerészeti tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Journal Of Neuroendocrinology 13 : 12 (2001), p. 1042-1050. -
További szerzők:Homicskó Krisztián Gy. Radnai Balázs Maruyama W. DeMaria, Jamie E. Vecsernyés Miklós (1959-) (gyógyszertechnológus, endokrinológus) Fekete I. K. Márton Fülöp Ferenc Naoi, M. Freeman, Marc E. Nagy György M.
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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