Domperidone Binding Research Articles

Domperidone resinate complex as new formulation for gastroretentive drug delivery

PurposeThe present work aims to develop and characterize domperidone resinate complex to be loaded into a gastroretentive delivery system. The formed resinate complex will be used to control the drug release in the stomach from inside the gastroretentive delivery system. MethodsResinate complexes were formulated by a simple aqueous binding method. Screening of different types of resins was carried out. Domperidone binding study was tested at various drug and resin concentrations. Physicochemical characterizations were carried out to evaluate the prepared resinate complex. These studies included flow properties, in vitro drug release in simulated gastric fluid (SGF), Differential scanning calorimetry (DSC), Mass spectroscopy and XPRD evaluations. Also, the stability study of the selected resinate complex was conducted at 25 °C and 40 °C for up to one month. ResultsDomperidone and Dowex 50WX2 in a ratio of 1:3 have formed a resinate complex that has shown acceptable flow properties, thermal properties and short-term chemical stability at 25 °C and 40 °C. Domperidone release profile from resinate in SGF has shown slow controlled release characteristics. ConclusionThe domperidone stable complex with Dowex ion exchange resin has the potential for further development as gastroretentive drug delivery system as a mean of controlling the drug release.

Clozapine administered repeatedly following pretreatment with ketamine enhances dopamine D2 receptors in the dopamine mesolimbic pathway in mice brain

The mechanisms underlying the beneficial effects of clozapine (CLZ) in the treatment of schizophrenia still remains far from clear. In the present work we studied the effect of CLZ on the dopamine D2 receptors (D2R) in the mouse brain. CLZ was administered after ketamine (KET) in a paradigm strictly matching the one used in KET-induced attentional set-shifting task (ASST). It has been shown previously that CLZ reversed KET-induced cognitive impairments. In the present study we used in situ hybridization to estimate the level of mRNA, together with specific D2R radioligand, [3H]domperidone binding in the ventral tegmental area (VTA) as well as in the striatum, and observed an increase in the [3H]domperidone binding in the striatum and an increase in D2R mRNA level in the VTA following repeated (but not acute) CLZ administration in mice pre-treated repeatedly with KET. The obtained results allow for conclusion that CLZ in this experimental paradigm enhances biosynthesis of presynaptic D2R.

P.1.031 Changes in [ 3H]domperidone binding in rat brains after chronic mild stress

P.1.031 Changes in [ 3H]domperidone binding in rat brains after chronic mild stress

Cocaine self‐administration markedly increases dopamine D2 receptor negative cooperativity for dopamine binding: A receptor dimer‐based analysis

The proportion of dopamine D(2)(High) receptors has been reported to increase after cocaine self-administration without a significant change in the total number of D(2) receptors. In the present article, the data of competition by dopamine of [(3)H]domperidone binding to striatal samples from naïve and cocaine-addicted animals (Briand et al., [2008] Eur Neuropsychopharmacol 18:551-556) are analyzed assuming that D(2) receptors are constitutive dimers. The results show another way of interpreting those previous results and lead to the finding that cocaine affects agonist affinity and may strongly affect the receptor-receptor cooperation between dimers, a result that can contribute to dopamine supersensitivity.

Dopamine receptor contribution to the action of PCP, LSD and ketamine psychotomimetics

Although phencyclidine and ketamine are used to model a hypoglutamate theory of schizophrenia, their selectivity for NMDA receptors has been questioned. To determine the affinities of phencyclidine, ketamine, dizocilpine and LSD for the functional high-affinity state of the dopamine D2 receptor, D2High, their dissociation constants (Ki) were obtained on [3H]domperidone binding to human cloned dopamine D2 receptors. Phencyclidine had a high affinity for D2High with a Ki of 2.7 nM, in contrast to its low affinity for the NMDA receptor, with a Ki of 313 nM, as labeled by [3H]dizocilpine on rat striatal tissue. Ketamine also had a high affinity for D2High with a Ki of 55 nM, an affinity higher than its 3100 nM Ki for the NMDA sites. Dizocilpine had a Ki of 0.3 nM at D2High, but a Kd of 1.8 nM at the NMDA receptor. LSD had a Ki of 2 nM at D2High. Because the psychotomimetics had higher potency at D2High than at the NMDA site, the psychotomimetic action of these drugs must have a major contribution from D2 agonism. Because these drugs have a combined action on both dopamine receptors and NMDA receptors, these drugs, when given in vivo, test a combined hyperdopamine and hypoglutamate theory of psychosis.

Peripheral vascular and neuronal effects of dopamine receptor agonists. A comparison with receptor binding studies in rat striatum

A series of dopamine (DA)-receptor agonists was tested in vitro on vascular DA1- and neuronal DA2-receptors and the activity observed was compared to their ability to compete with [3H]-SCH23390 and [3H]-domperidone binding to rat striatal membranes. In rabbit splenic artery, where the presence of the DA1-receptor is established, DA and related agonists produced a complete concentration-dependent relaxation of the thromboxane A2-mimetic U46619-induced tone in IBMX (3-isobutyl-1-methylxanthine) treated preparations. The DA vasorelaxant effect proved to be mediated by DA1-receptors, being inhibited by the selective DA1-receptor antagonist SCH23390. Fenoldopam proved to be the most potent agonist in the rabbit splenic artery consistent with the result obtained in the D1-receptor binding assay. Epinine was about 5 times more potent than DA and only 3 times less active than fenoldopam on DA1-receptors although the D1-receptor binding study did not reveal major differences from DA. An opposite profile was observed with N,N-di-n-propyl dopamine (DPDA) showing a functional potency lower than that expected from the binding assay. In cat right atrium, DA and related agonists caused concentration-dependent inhibition of the tachycardia induced by electrical stimulation. The DA effects proved to be mediated by presynaptic DA2-receptor activation, being inhibited by the selective DA2-receptor antagonist domperidone. The DA2-receptor agonist 6-(di-n-propylamino)-5,6,7,8-tetrahydro-1,2-naphthalenediol (DP-5,6-ADTN) was the most potent compound both in the cat atrium and in the binding assay. Epinine was 2 times more potent than DA on DA2-receptors but it showed no differences in the D2-receptor binding assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of the serotonin S2-receptor in brain after chronic lithium.

In vivo effects of chronic lithium administration on dopaminergic and serotonergic receptor binding were studied in the striatum and cerebral cortex of the rat. [3H]Domperidone was used as the ligand for the dopaminergic receptor, and [3H]ketanserin for the serotonergic system. Long-term ingestion of lithium (2-3 months) resulted in high levels of lithium in the cerebral cortex and significantly higher potassium levels; the sodium content remained at normal levels. The kinetic constants (Kd and Bmax) of [3H]domperidone binding sites measured in the striatum did not show any deviation from control values, but the receptor concentration (Bmax) of [3H]ketanserin binding sites was significantly reduced in the cerebral cortex of lithium-treated rats. The apparent dissociation constant (Kd) was not changed. The results indicate that the serotonergic component of the [3H]spiperone binding site, which we had previously found to be affected by chronic lithium treatment and which was shown by Peroutka and Snyder to be the 5-HT2 receptor, is selectively affected by lithium.

3H]-domperidone labels only a single population of receptors which convert from high to low affinity for dopamine in rat brain.

Dopamine recognized and competed for a single population of [3H]-domperidone-binding sites in rat striatum and olfactory tubercle when tested in the presence of sodium ions and guanine nucleotide [Gpp(NH)p]. In the absence of Na+ and Gpp(NH)p, however, dopamine recognized two components of [3H]-domperidone binding. Thus, [3H]-domperidone labelled only a single population of dopamine receptors (type D2) which fully converted from high to low affinity for dopamine. These results agree with those found previously using [3H]-spiperone and [3H]-YM-09151-2.

In vitro and in vivo antagonistic regulation by estradiol and progesterone of the rat pituitary domperidone binding sites: correlation with ovarian steroid regulation of the dopaminergic inhibition of prolactin secretion in vitro.

The influences of in vivo and in vitro estradiol (E2) and progesterone (P) treatments on the characteristics of [3H]domperidone binding to intact and ovariectomized (OVX) rat pituitary membranes were analyzed and compared to the modulation by these steroids of dopamine (DA) inhibition of PRL secretion in vitro from intact and OVX rat pituitaries. Using intact rat pituitaries, high and low affinity binding sites for domperidone were detected; the dose-dependent DA inhibition curve of PRL secretion was biphasic (range, 10(-13) - 10(-10) M DA, IC50 = 6 X 10(-12) M; range, 10(-10) - 10(-6) M DA, IC50 = 2 X 10(-8) M). Using OVX rat pituitaries, only the high affinity sites for domperidone were detected, and the dose-dependent DA inhibition curve of PRL secretion was monophasic (range, 10(-10) - 10(-6) M DA, IC50 = 10(-8) M). E2 and P did not modify the characteristics of the high affinity sites either after in vivo treatment or when directly added to the in vitro binding assay. However, using in vivo and in vitro tests, a modulation of the low affinity sites by E2 and P was demonstrated. When E2 is in excess and P levels are low or undetectable, these sites are not detectable, and P is able to restore there presence. A parallelism has been established between this antagonistic E2 and P regulation and the modulation of DA inhibition of PRL secretion (range, 10(-13) - 10(-10) M DA). When intact rat pituitaries are perifused in the presence of 10(-8) M E2, the biphasic dose-dependent inhibition curve of the control is changed into the monophasic curve of the OVX rat pituitaries. Conversely, when OVX rat pituitaries are perifused in the presence of 10(-6) M P, the monophasic curve of the control is changed into the biphasic curve of the intact rat pituitaries. Thus, the DA inhibition in the range 10(-13) - 10(-10) M might result from an interaction between DA and the low affinity site for domperidone. In summary, the biological regulation of PRL by DA at the pituitary level may be mediated by two different DA sites, one being submitted to an antagonistic E2 and P regulation directly at the membrane level. The consequence of this regulation is that, whereas E2 decreases the sensitivity of the cell to DA, P is necessary for a normal DA response of the lactotroph.

Effect of lead exposure on dopaminergic D2 receptor binding in the 21-day-old rat

The effect of lead on dopaminergic D2 receptor binding, as measured by butaclamol-displaceable [ 3H]domperidone binding, was studied in the 21-day-old lead-dosed rat. Maternal rats were dosed with 300 ppm and 1000 ppm Pb in drinking water from conception to weaning as previously described [1]. Samples of limbic forebrain and striatum were taken from 21-day-old offspring and assayed for dopamine D2-receptor binding, as outlined by Lazareno and Nahorski [2]. There was a significant ( P < 0.05) decrease in body weight in the animals from which limbic forebrain samples were taken. There were no other significant effects of lead on body- or brain weight. Dopaminergic D2 receptor binding was unaffected by lead administration. These preliminary findings show that dopamine D2 receptor binding is not affected by lead at the doses and exposures used.

Modifications of the high and low affinity pituitary domperidone-binding sites in chronic estrogenized rats.

The effect of chronic estrogen treatment on the anterior pituitary domperidone-binding sites was studied in female rats. The rats were implanted from 1-6 months with a Silastic capsule containing 17 beta-estradiol. The Feldman analysis of [3H]domperidone binding to anterior pituitary membranes of control or estrogenized rats revealed the presence of two sites. The binding characteristics of the higher affinity site were identical for both groups (Kd of the high affinity site, 0.30-0.45 nM; maximum number of binding sites of the high affinity site, 74-95 fmol/mg protein); however, those of the lower affinity site were affected by the estrogen treatment: the Kd of the low affinity site increased from 17.4 +/- 3.2 to 41.5 +/- 9 (+/- SE) nM, and the maximum number of binding sites of the low affinity site increased from 214 +/- 22 to 343 +/- 35 fmol/mg protein. Thus, in chronic estrogenized rats, the total number of binding sites was increased by 54%. These changes, induced by chronic estrogenization, were reversible, since 2 weeks after removal of the 17 beta-estradiol pellet, the binding characteristics were no longer different from those observed in control rats. In contrast to chronic estrogen treatment, ovariectomy reduced markedly the total number of [3H]domperidone-binding sites in anterior pituitary membranes (-70%). Feldman analysis revealed that this reduction resulted from the complete disappearance of the low affinity sites in those membranes. No significant change in the binding characteristics of the high affinity site was detected in ovariectomized rats. Since estradiol induces a decrease in the anterior pituitary content of dopamine, a denervation supersensitivity-like mechanism might be responsible for the increase in pituitary domperidone-binding sites in estrogenized rats. Conversely, a hyposensitivity mechanism could be implicated in the decrease in the total number of the pituitary domperidone-binding sites in ovariectomized rats, since pituitary dopamine levels are increased in those animals. Whether the antidopaminergic properties of estrogen are also involved in this modulation after chronic estradiol treatment requires further investigation.

Labelling of high (D-2 receptor) and low affinity sites by [ 3H]domperidone in homogenates of the corpus striatum of the rat

The binding of [ 3H]domperidone, a dopamine antagonist, to rat striatal membranes has been examined in vitro. Studies of the kinetics of [ 3H]domperidone binding and the saturation of binding sites at equilibrium revealed two specific binding sites for [ 3H]domperidone with apparent K d values of 0.1 and > 2 nM, and maximal numbers of binding sites of 2 and 40 pmol/g wet wt. for the high and low affinity sites, respectively. The pharmacological properties of the high affinity site, determined in displacement studies using various dopamine agonists and selective dopamine antagonists, strongly suggested that this site labelled by [ 3H]domperidone is a dopamine receptor of the D-2 type.

Comparison of the Binding of [3H]Spiperone and [3H]Domperidone in Homogenates of Mammalian Retina and Caudate Nucleus

The specific binding of [3H]spiperone and [3H]domperidone, as defined by 1 microM-(+)butaclamol, was compared in homogenates of bovine retina and caudate nucleus. Scatchard analyses of saturation data for [3H]spiperone binding yielded dissociation constants (Kd) of 0.35 nM in the retina and 0.64 nM in the caudate nucleus. Comparison of the maximum number of binding sites (Bmax) present in each tissue indicated that the density of sites in bovine caudate nucleus (270 fmol/mg protein) was approximately three times higher than in bovine retina (92 fmol/mg protein). This difference was even more marked in guinea pig tissues, with a ratio of 7:1 between corpus striatum and retina. The pharmacological analysis of [3H]spiperone binding in both the bovine retina and caudate nucleus indicated an interaction with dopaminergic rather than serotonergic sites. However, inhibition curves obtained to dopaminergic agonists in the bovine retina were significantly steeper than those observed in the bovine caudate nucleus, as reflected in the greater Hill coefficients obtained for these agents in the retina. Furthermore, only a small amount of specific [3H]domperidone binding was observed in either the bovine caudate nucleus or the guinea pig striatum, whilst no specific [3H]domperidone binding was detectable in homogenates of either bovine or guinea pig retina. These data suggest that the retina possesses only a small population of dopaminergic D2 sites and that these binding sites may differ from those present in the caudate nucleus.

Development of alpha-noradrenergic and Dopaminergic receptor systems depends on maturation of their presynaptic nerve terminals in the rat brain.

To study the relationship between ontogeny of rat brain catecholamine nerve terminals and the receptor systems for the catecholamine transmitters, the developmental patterns of synaptosomal uptake mechanisms were compared with those of alpha-noradrenergic and dopaminergic receptor-mediated effects. Uptakes of [(3)H]dopamine or [(3)H]norepinephrine into dopaminergic and noradrenergic nerve terminals were low during the 1st week postpartum and increased rapidly during the 2nd week. A similar pattern was obtained for ontogeny of dopaminergic receptor binding sites, as evaluated by [(3)H]domperidone binding. Stimulation of incorporation of (33)P(i) into brain phospholipids (elicited by intracisternal injection of dopamine), which is mediated by dopaminergic receptors, was shown to be highly correlated with the maturation of both receptor binding sites and presynaptic nerve terminal uptake. A similar result was seen with norepinephrine, in that the synaptosomal uptake mechanism and norepinephrine-induced stimulation (33)P(i) incorporation into phospholipids, an alpha-noradrenergic effect, developed in a parallel fashion. To test the hypothesis that development of the receptor systems is linked to nerve terminal ontogeny, presynaptic nerve terminals were destroyed in neonates by intracisternal administration of 6-hydroxydopamine. The lesions prevented the maturational increase in the number of dopamine receptor binding sites and produced a defect in development of the dopamine- and norepinephrine-induced stimulation of (33)P(i) incorporation. The results suggest that ontogeny of both dopaminergic and alpha-noradrenergic receptor systems depend upon development of the presynaptic nerve terminals containing the transmitters.