Decreased binding capacity (Bmax) of muscarinic acetylcholine receptors in fibroblasts from boys with attention-deficit/hyperactivity disorder (ADHD)

Monoaminergic dysregulation is implicated in attention-deficit/hyperactivity disorder (ADHD), and methylphenidate and amphetamines are the most frequently prescribed pharmacological agents for treating ADHD. However, it has recently been proposed that the core symptoms of the disorder might be due to an imbalance between monoaminergic and cholinergic systems. In this study, we used fibroblast cell homogenates from boys with and without ADHD as an extraneural cell model to examine the cholinergic receptor density, that is, muscarinic acetylcholine receptors (mAChRs). We found that the binding capacity (B_max) of [³H] Quinuclidinyl benzilate (³H-QNB) to mAChRs was decreased by almost 50 % in the children with ADHD (mean = 30.6 fmol/mg protein, SD = 25.6) in comparison with controls [mean = 63.1 fmol/mg protein, SD = 20.5, p ≤ 0.01 (Student’s unpaired t test)]. The decreased B_max indicates a reduced cholinergic receptor density, which might constitute a biomarker for ADHD. However, these preliminary findings need to be replicated in larger ADHD and comparison cohorts.

Topography of 3H-DHA, 3H-QNB, 3H-dopamine, and 3H-DAGO binding sites distribution in the central part of the sinoatrial node in rat heart

The topography of distribution of 3H-dihydroalprenolol, 3H-quinucledinyl benzilate, 3H-dopamine, and 3H-DAGO binding sites in the central part of the sinoatrial node in rat heart was studied by autoradiography after electrophysiological identification of the dominant pacemaker region location. Receptor asymmetry between the lateral and median regions of the central part of the sinoatrial node was shown. The dominant pacemaker region lay in the lateral area of the sinoatrial node; the number of binding sites for all four ligands was minimum in it. The number of binding sites gradually increased in the cranial and caudal directions from the dominant pacemaker region along the sinoatrial node artery (more smoothly in the caudal direction). The relative densities of bindings sites for 3H-dihydroalprenolol and 3H-dopamine were higher in the lateral region compared to the perinodal working myocardium, while the densities for 3H-quinucledinyl benzilate and 3H-DAGO were virtually the same. The distribution of binding sites along the artery in the median region of the sinoatrial node was even for 3H-quinucledinyl benzilate and 3H-DAGO. For 3H-DAGO these parameters were close to those in the perinodal atrial myocardium, for 3H-quinucledinyl benzilate somewhat lower. Curves presenting the distribution of binding site densities for 3H-dihydroalprenolol and 3H-dopamine in the median region of the sinoatrial node were similar, with a pronounced peak in the region contralateral to the dominant pacemaker region, and significantly higher binding parameters compared to those for the perinodal atrial myocardium. The difference consisted in higher density of 3H-dopamine binding sites in the median region of the sinoatrial node in comparison with the lateral region. Binding activity was maximum in the wall of the sinoatrial node artery. The distribution of binding sites for ligands to the main autonomic nervous system neurotransmitters in the rat heart sinoatrial node is heterogeneous.

Simultaneous determination of chlordiazepoxide and clidinium bromide in pharmaceutical formulations by derivative spectrophotometry

A direct and simple first derivative spectrophotometric method has been developed for the simultaneous determination of clidinium bromide and chlordiazepoxide in pharmaceutical formulations. Acetonitrile was used as solvent for extracting the drugs from the formulations and subsequently the samples were evaluated directly by derivative spectrophotometry. Simultaneous determination of the drugs can be carried out using the zero-crossing method for clidinium bromide at 220.8 nm and the graphical method for chlordiazepoxide at 283.6 nm. The calibration graphs were linear in the ranges from 0.983 to 21.62 mg/l of clidinium bromide and from 0. 740 to 12.0 mg/l of chlordiazepoxide. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets.

The determination of a degradation product in clidinium bromide drug substance by capillary electrophoresis with indirect UV detection

A capillary electrophoresis (CE) method utilizing indirect ultraviolet (UV) detection was developed for the determination of a non-UV absorbing degradation product, Ro 5-5172, in clidinium bromide drug substance. The electrophoresis buffer consisted of sodium phosphate and benzyltrimethylammonium bromide. Rinsing the capillary with sodium hydroxide followed by water then fresh capillary electrophoresis buffer was found to significantly improve the reproducibility of the migration times of the analytes. To further improve run-to-run reproducibility, an internal marker was used to account for differences in injection volumes and migration times between runs. The precision of the method was found to be less than 1% relative standard deviation for the migration time ratio and peak area ratio of Ro 5-5172 to the internal standard. The method was found to be linear for 0.05-1% Ro 5-5172 with respect to a 10 mg ml-1 sample preparation. The limit of detection was found to be less than 0.01% Ro 5-5172. Results obtained for the analysis of a clidinium bromide drug substance lot using this CE method and a thin layer chromatography method were compared and found to be in agreement.

Loss of neurotransmitter receptors by hyperphenylalaninemia in the HPH-5 mouse brain

The binding of the muscarinic acetylcholine antagonist quinuclinidylbensilate to its specific receptors was measured by quantitative autoradiography in the brain of the HPH-5 mouse, a phenylalanine hydroxylase-deficient mouse mutant, as a model for human PKU. Three types of response to a hyperphenylalaninemic condition were observed: no effect as in the putamen; a gradual decrease over time such as in several areas of the cerebral cortex and the hippocampus; a transient increase, followed by a decrease, such as in the frontal area of the cerebral cortex. Of particular significance is the effect on the CA1 and CA3 layer of the hippocampus, since this structure has been implicated in the acquisition and storage of long-term memory. Hyperphenylalaninemia leads to a decrease in neurotransmitter receptor density and, therefore, to a decrease in connectivity, which may form the basis for the mental retardation in this condition.

Evidence for cholinergic vagal afferents and vagal presynaptic M1 receptors in the ferret

The distribution of muscarinic receptor binding was examined in the ferret brainstem vagal nuclei using the non-selective ligand [3H]quinuclidinyl benzilate and the relatively M1 receptor-selective ligand [3H]pirenzepine. The highest density of receptor sites are found in the subnucleus gelatinosus and lower levels in the other subnuclei of the nucleus of the tractus solitarius and in the area postrema and dorsal motor nucleus of the vagus nerve. Dense binding was also seen in the adjacent hypoglossal nucleus. Following unilateral cervical nodose ganglion excision binding in the subnucleus gelatinosus was attenuated ipsilateral to the lesion compared with the contralateral side. In contrast, [3H]pirenzepine binding was only seen in the subnucleus gelatinosus and in no other region at this level of the brainstem. This binding was reduced in the subnucleus as a whole by 52% ipsilateral to a cervical vagotomy. In the more rostral parts of the subnucleus gelatinosus, binding was undetectable ipsilateral to the lesion but more caudally, appreciable levels of binding persisted. This distribution parallels the known rostro-caudal variation in cross-over of vagal afferent fibres in the ferret dorsal vagal complex and indicates a presynaptic localization of [3H]pirenzepine binding sites on vagal afferent terminals. The distribution of binding of the high affinity choline uptake site blocker, [3H]hemicholinium-3, was also examined in the ferret brainstem using autoradiography. High densities of [3H]hemicholinium-3 binding were seen in the hypoglossal nucleus, the subnucleus gelatinosus and in the area postrema, with lower levels in the dorsal motor nucleus of the vagus, the trigeminal nucleus and other subnuclei of the nucleus of the tractus solitarius.(ABSTRACT TRUNCATED AT 250 WORDS)

Liquid chromatographic determination of clidinium bromide and clidinium bromide-chlordiazepoxide hydrochloride combinations in capsules

A specific liquid chromatographic method was developed for determination of clidinium bromide and clidinium bromide-chlordiazepoxide hydrochloride combinations in capsules. The procedure uses a Partisil 10 ODS-3 column and a mobile phase consisting of acetonitrile-0.3M ammonium phosphate (32 + 68) (pH = 4.3). The detection wavelength is 235 nm. Accuracy, reproducibility, and linearity were within accepted criteria. Four commercial samples of the single ingredient were tested; results compared favorably with the compendial method. Two commercial samples of the combination product were tested by the proposed method and results reported. The system was found to be free from any interferences from the 4 known related compounds of the 2 major components and is useful as a screening procedure for 7-chloro-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one-4-oxide, the principal degradation product of chlordiazepoxide hydrochloride.

Cholinergic receptor binding in the frontal cortex of suicide victims

Muscarinic binding sites were assessed in the frontal cortex of 22 suicide victims and 22 control subjects. There were no significant differences between the two groups in either the number of binding sites (Bmax) or their relative affinity (Kd). The results of this study are discussed in reference to the cholinergic hypothesis of affective disorders.

Autoradiographic localisation of muscarinic receptors in guinea-pig intestine: distribution of high and low affinity agonist binding sites

Muscarinic receptors mediate a variety of intestinal functions including smooth muscle contraction, ganglionic transmission and water and electrolyte secretion. In this study, we have used [3H]quinuclidinyl benzilate ([3H]QNB) in an in vitro autoradiographic method to map the distribution of muscarinic receptors in guinea-pig ileum, colon and caecum. In addition, the relative distribution of low and high affinity agonist binding sites was assessed by the addition of the muscarinic agonist, carbachol, to selectively inhibit the binding of [3H]QNB to the high affinity sites. Although quantitative differences existed, the overall distribution of muscarinic receptors was similar in the 3 regions of intestine examined. Autoradiograph grains were found distributed over the myenteric and sub-mucous plexuses, the longitudinal and circular muscle layers and in the case of the colon, the muscularis mucosa. The inclusion of carbachol demonstrated that a greater proportion of high affinity sites were associated with the musculature than with the enteric plexuses. These findings are discussed in relation to the role of muscarinic mechanisms in intestinal motility and secretion.

Autoradiographic localization of quinuclidinyl benzilate binding to rat pituitary gland

The location of muscarinic receptors in the rat pituitary gland was examined with an autoradiographic technique. Slides containing 10 or 20 micron horizontal sections of tissue were incubated in a solution of 1 n M[3H]quinuclidinyl benzilate (QNB) in phosphate-buffered saline to label muscarinic receptors. Autoradiograms were produced by placing the slides into X-ray cassettes with tritium-sensitive film and processing the film 8-10 weeks later. Minimal binding occurred when sections were incubated in 1 nM[3H]QNB plus 1 microM atropine. Highest specific binding of QNB was found in the anterior and intermediate lobes along their border with the pituitary cleft. Patches of high binding were also seen penetrating the intermediate lobe and at the border between the intermediate and neural lobes. The remainder of the intermediate lobe had background density of autoradiographic grains. Moderate density of specific binding was found throughout the anterior lobe. Low specific binding occurred in the neural lobe.

Metabolic and cardiovascular adaptations in trained hypophysectomized rats

Metabolic and cardiovascular changes resulting from acute and chronic exercise were examined in male Sprague-Dawley rats assigned to sham-control or hypophysectomized groups. Two weeks after surgery, the hypophysectomized rats had decreased their maximum oxygen consumption (VO2 max) and heart rate values by 4 ml X min-1 X kg-1 and 142 beats X min-1, respectively. Twenty weeks later, hypophysectomy was associated with a 22 ml X min-1 X kg-1 decrease in VO2 max and a 215 beat X min-1 decline in their maximal heart rates when compared with sham-control means. Endurance training was responsible for the significantly higher O2 consumption values. Additionally, trained animals exhibited longer run times, higher muscle cytochrome oxidase activity, and reduced food consumption. Measurements of right atrial choline acetyltransferase (CAT) activity and [3H]quinuclidinyl benzilate (QNB) binding revealed significantly higher CAT values and fewer muscarinic receptors. However, training had no significant effect on resting blood pressure, blood pressure changes with conditions of lower body negative pressure, muscle glycogen concentrations, CAT levels and QNB binding of the left atrium and ventricular regions, or receptor density. These results indicated that many of the adaptations that are characteristic of normal populations can occur in the absence of the hormones from the pituitary gland.

Evidence for cholinergic participation in the control of bird song; acetylcholinesterase distribution and muscarinic receptor autoradiography in the zebra finch brain

Brain regions thought to be involved in the control of song in the zebra finch (Poephila guttata), were examined histochemically using the Karnovsky and Roots direct-coloring method for the detection of acetylcholinesterase (AChE) and the autoradiographic method for the localization of muscarinic cholinergic receptors following injection of tritiated quinuclidinyl benzilate (3H QNB). All presently identified vocal control nuclei in both males and females contain AChE. These nuclei include Area X, magnocellular nucleus of the anterior neostriatum (MAN), nucleus interface (NIF), caudal nucleus of the hyperstriatum ventrale (HVc), intercollicular nucleus (ICo), nucleus uva, robust nucleus of the archistriatum (RA), and tracheosyringeal portion of the hypoglossal nerve nucleus (nXIIts). All nuclei except Area X contain mostly AChE-synthesizing cell bodies. All of these nuclei contain some AChE in the neuropil, with particularly intense staining in Area X, the surrounding LPO, and the dorsomedial portion of ICo. In agreement with this description are very high concentrations of 3H QNB in both Area X and the dorsomedial ICo. HVc also appears specifically labeled. Evidence from these two histological technique suggests that efferent projections of most vocal control area may utilize acetylcholine, and that several of the vocal control nuclei may themselves receive muscarinic cholinergic projection. In Area X, there are sex differences of AChE neuropil staining. This evidence suggesting that sexually dimorphic projections to or within Area X are cholinergic or cholinoceptive.