Quinuclidinyl Benzilate Binding Research Articles

α2‐Adrenergic and Muscarinic Cholinergic Receptors Have Oposing Actions on Cyclic AMP Levels in SK‐N‐SH Human Neuroblastoma Cells

Forskolin and vasoactive intestinal polypeptide (VIP) were shown to increase cyclic AMP accumulation in a human neuroblastoma cell line, SK-N-SH cells. The alpha 2-adrenergic agonist UK 14304 decreased forskolin-stimulated cyclic AMP levels by 40 +/- 2%, with an EC50 of 83 +/- 20 nM. This response was blocked by pretreatment with pertussis toxin (PT) (EC50 = 1 ng/ml) or by the alpha 2-antagonists yohimbine, idazoxan, and phentolamine. Antagonist IC50 values were 0.3 +/- 0.1, 2.2 +/- 0.3, and 1.4 +/- 0.1 microM, respectively. This finding suggests the presence of normal inhibitory coupling of SK-N-SH cell alpha 2-adrenergic receptors to adenylate cyclase via the inhibitory GTP-binding protein species, Gi. Muscarinic receptors in many target cell types are coupled to inhibition of adenylate cyclase. However, in SK-N-SH cells, muscarinic agonists synergistically increased (67-95%) the level of cyclic AMP accumulation elicited by forskolin or VIP. EC50 values for carbamylcholine (CCh) and oxotremorine facilitation of the forskolin response were 1.2 +/- 0.2 and 0.3 +/- 0.1 microM, respectively. Pharmacological studies using the muscarinic receptor subtype-preferring antagonists 4-diphenylacetoxy-N-methylpiperidine, pirenzepine, and AF-DX 116 indicated mediation of this response by the M3 subtype. IC50 values were 14 +/- 1, 16,857 +/- 757, and 148,043 +/- 16,209 nM, respectively. CCh-elicited responses were unaffected by PT pretreatment. Muscarinic agonist binding affinity was indirectly measured by the ability of CCh to compete for [3H]quinuclidinyl benzilate binding sites on SK-N-SH cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of central injection of phencyclidine on QNB accumulation and motor activity

The purpose of the present research was to determine if central administration of phencyclidine (PCP) would increase the in vivo accumulation of the muscarinic ligand, [ 3H]quinuclidinyl benzilate (QNB) in mouse brain as has been reported after peripheral administration of PCP. Secondly, in order to provide a behavioral reference against which to compare any biochemical changes, the effects of peripheral vs. central PCP administration on motor activity were compared. When given into the lateral ventricle (i.c.v.) 20 min before QNB, PCP increased the accumulation of QNB in brain striatum and cortex, but not cerebellum. This finding replicates results of previous studies in which the drug was given i.p. The dose required to enhance QNB binding after central injection was, on a mg/kg body weight basis, approximately 10-fold less than that previously found necessary after i.p. injection. In contrast, PCP given centrally was markedly more potent in the motor activity tests than when given i.p. In addition, the behaviorally effective dose (0.4 μg) was substantially less than that needed for the QNB change (25.6 μg). Therefore, though PCP was more active in both measures after central than peripheral administration, the changes in QNB accumulation cannot, at this time, be related to changes in motor activity.

Changes in Cholinergic but Not in GABAergic Markers in Amygdala, Piriform Cortex, and Nucleus Basalis of the Rat Brain Following Systemic Administration of Kainic Acid

Three days after systemic administration of kainic acid (15 mg/kg, s.c.), selected cholinergic markers (choline acetyltransferase, acetylcholinesterase, muscarinic acetylcholine receptor, and high-affinity choline uptake) and GABAergic parameters [benzodiazepine and gamma-aminobutyric acid (GABA) receptors] were studied in the frontal and piriform cortex, dorsal hippocampus, amygdaloid complex, and nucleus basalis. Kainic acid treatment resulted in a significant reduction of choline acetyltransferase activity in the piriform cortex (by 20%), amygdala (by 19%), and nucleus basalis (by 31%) in comparison with vehicle-injected control rats. A lower activity of acetylcholinesterase was also determined in the piriform cortex following parenteral kainic acid administration. [3H]Quinuclidinyl benzilate binding to muscarinic acetylcholine receptors was significantly decreased in the piriform cortex (by 33%), amygdala (by 39%), and nucleus basalis (by 33%) in the group treated with kainic acid, whereas such binding in the hippocampus and frontal cortex was not affected by kainic acid. Sodium-dependent high-affinity choline uptake into cholinergic nerve terminals was decreased in the piriform cortex (by 25%) and amygdala (by 24%) after kainic acid treatment. In contrast, [3H]flunitrazepam binding to benzodiazepine receptors and [3H]muscimol binding to GABA receptors were not affected 3 days after parenteral kainic acid application in any of the brain regions studied. The data indicate that kainic acid-induced limbic seizures result in a loss of cholinergic cells in the nucleus basalis that is paralleled by degeneration of cholinergic fibers and cholinoceptive structures in the piriform cortex and amygdala, a finding emphasizing the important role of cholinergic mechanisms in generating and/or maintaining seizure activity.

Effect of dopaminergic drugs on enhancement of the binding of quinuclidinyl benzilate by phencyclidine in vivo

Phencyclidine has been shown to enhance the specific binding of [ 3H]quinuclidinyl benzilate (QNB) in the brain of the mouse when both compounds are given in vivo. Since a variety of studies indicate that dopaminergic (DA) systems are involved in the action of phencyclidine, it seemed that DA systems might mediate the enhancement of the binding of QNB by phencyclidine. The results of the present studies demonstrate that the neurotoxin 6-hydroxydopamine, the DA D 1 antagonist ((R)-8)-[chloro]-2,3,4, 5-tetrahydro-3-methyl-5-phenyl-1-H-3-benzazepine-7-ol) (SCH23390), the DA D 1 agonist p-dibenzylamino benzonitrile (SKF38393) and the DA D 2 antagonist spiperone, all failed to modify the ability of phencyclidine to enhance the accumulation of QNB in brain. Quinpirole, a DA D 2 agonist diminished accumulation of QNB after phencyclidine, however, this effect was confounded by quinpirole decreasing the non-specific binding of QNB, as well as increasing concentrations of QNB in plasma, when given with phencyclidine. In contrast, haloperidol, a DA antagonist, decreased the enhanced specific binding of QNB after phencyclidine without any apparent confounding influences. Since haloperidol is also known to strongly inhibit the binding of ligands to the sigma receptors, it was hypothesized that the actions of phencyclidine and haloperidol on the binding of QNB in vivo may be through sigma receptors rather than DA systems.

Characterization of Muscarinic Cholinergic Receptors on the Endothelium and the Smooth Muscle of the Rabbit Thoracic Aorta

Pharmacodynamic and quantitative autoradiographic studies were performed to characterize the muscarinic receptors on the endothelium and smooth muscle of the rabbit thoracic aorta. The antagonistic effect of atropine and pirenzepine on the relaxation induced by acetylcholine showed that the relaxation was mediated by muscarinic receptors with pA2 values of 9.4 and 6.6, respectively, suggesting the presence of muscarinic receptors on the endothelium with low affinity for pirenzepine. The quantitative autoradiographic study using [3H]-propylbenzilylcholine mustard (3H-PrBCM) showed that the specific 3H-PrBCM binding was time dependent and saturable. Saturation times of the bindings were not significantly different between the receptors on the endothelium and those on the smooth muscle layer. The density of the receptors was higher in the smooth muscle layer than in the endothelium. The specific [3H]-quinuclidinyl benzilate (3H-QNB) binding was displaced by atropine or pirenzepine dose dependently. IC50 of pirenzepine for the receptors on the endothelium was not significantly different from that for the receptors on the smooth muscle layer. These findings suggest that there is a smaller density of muscarinic receptors on the endothelium than on the smooth muscle layer of the rabbit thoracic aorta. The muscarinic receptors on the endothelium can be subclassified into the same subtype as the receptors on the smooth muscle layer, which have low affinity for pirenzepine.

Muscarinic receptor subtypes in human and guinea pig lung

Muscarinic receptor subtypes in human and guinea pig lung membranes were characterised using selective muscarinic antagonists. Competition experiments were carried out against [ 3H](−)-quinuclidinyl benzilate binding at 25°C in Tris-HCl buffer; non-specific binding was determined in the presence of 1 μM atropine. Of all the antagonists examined, only the M 1-selective antagonist pirenzepine exhibited a heterogeneous binding profile (n H < 1.0), best described by two-binding sites of high and low affinity. Binding of [ 3H]pirenzepine confirmed the presence of a high proportion of high affinity (M 1) receptors (60% of total) in human peripheral lung. The high potency of M 3-selective antagonists 4-diphenylacetoxy-N-methyl-piperidine methiodide (4-DAMP) and hexahydrosiladifenidol suggested the presence of M 3 receptors, but the low potency of AF-DX 116 and methoctramine indicated that there was no significant population of M 2 receptors present. The existence of muscarinic receptor subtypes in lung may have important clinical implication but their cellular localisation remains to be determined.

Repeated noise exposure affects muscarinic cholinergic receptors in the rat brain

We examined the effect of repeated exposure to 100-dB white noise (10 daily 45-min sessions) on muscarinic cholinergic receptors in different regions of the rat brain. Twenty-four hours after the last exposure session, increase in concentration ( B max) of [ 3H]quinuclidinyl benzilate ([ 3H]-QNB) binding sites was observed in the hippocampus, but no significant change was seen in the striatum, frontal cortex, and hypothalamus. No significant effect of noise on receptor binding affinity ( K d) was found. Pretreating the rats with naltrexone (1 mg/kg, IP) before exposure blocked the noise-induced increase in cholinergic receptors in the hippocampus.

Effects of neonatal capsaicin treatment and streptozotocin-induced diabetes on urinary bladder function in rats

A significant increase in the size and weight of the urinary bladder was observed 2 weeks after streptozotocin treatment and 2 months after neonatal capsaicin treatment. Both treatments induced a significant increase in the level of [ 3H]quinuclidinyl benzilate binding to muscarinic cholinergic receptors in the urinary bladder membranes. However, contractile responses of urinary bladder muscle strips to carbachol (0.3–20 μM) were not significantly affected by either treatment. On the other hand, neonatal capsaicin treatment, but not streptozotocin treatment, significantly enhanced contractile responses of bladder strips to electric field stimulation.

Characterization of ion movements and their relationship to muscarinic receptor binding and excitation-contraction coupling in guinea pig ileal longitudinal smooth muscle.

The relationship between ion movements (sodium uptake and potassium release) and agonist-induced contractile responses or muscarinic receptor binding was investigated in the guinea pig ileal longitudinal muscle (GPLM). Sodium uptake and potassium release were agonist-dependent, concentration-dependent, and stereoselective, with the following rank order of maximum ion movement: muscarinic agonists greater than histamine greater than substance P = serotonin. Potassium depolarization did not initiate sodium uptake or potassium release. Sodium uptake was rapid and monophasic, preceding potassium release which was biphasic in nature. Full muscarinic agonists produced equal maximal increases in sodium uptake, while maximal potassium release varied for all muscarinic agonists and in addition differed from sodium uptake in the following ways: time course, stereoselectivity, sensitivity to calcium antagonists, modulation by the guanylyl nucleotide derivative, 5'-guanylylimidodiphosphate (Gpp(NH)p), and inhibition by muscarinic receptor blockade with benzilylcholine mustard. The calcium ionophores A23187 and ionomycin (SQ23377) did not produce any sodium uptake; A23187 but not ionomycin produced potassium release comparable to that evoked by muscarinic agonists. Ion movement in response to combinations of agonists were not additive. Muscarinic agonist binding as measured by competition for [3H]quinuclidinyl benzilate ([3H]QNB) binding, was best described by multiple sites and was regulated by Gpp(NH)p. Excellent correlations were observed between the dissociation constants for binding and sodium uptake, potassium release, and contraction. The best correlations were those between the pharmacologic responses and the high affinity binding site in the absence, and the low affinity site in the presence, of Gpp(NH)p, respectively. Furthermore, the potencies of muscarinic agonists to evoke ion movements and to inhibit [3H]QNB binding were similar, and from one to two orders of magnitude less than those for contraction. It is suggested that contraction and potassium release were mediated by the high affinity, and sodium uptake by the low and average affinity muscarinic agonist binding sites, respectively. These findings suggest an agonist-activated receptor-effector coupling model in GPLM that leads to the activation of sodium uptake, potassium release, and subsequently, contraction.

Effect of in vivo exposure to hypoxia on muscarinic cholinergic receptor-coupled phosphoinositide turnover in the rat brain

We examined the effects of a transient exposure of rats to severe (5% O 2, 95% N 2 for 30 min) or mild (10% O 2, 90% N 2 for 30 min) hypoxia and a chronic exposure to mild hypoxia (10% O 2, 90% N 2 up to 48 h) on carbachol-stimulated phosphoinositide (PI) turnover and [ 3H]quinuclidinyl benzilate (QNB) binding in 4 regions of the brain (cerebral cortex, striatum, hippocampus and cerebellum). When the rats were exposed to hypoxia transiently, significant changes were caused only by severe hypoxia. In all 4 regions examined, basal incorporation of [ 3H]inositol into inositol phosphates (IPs) in the absence of carbachol was significantly increased following transient severe hypoxia and remained high for 48 h. Carbachol stimulation of PI turnover (% of basal) was significantly enhanced only in the hippocampus. The increase in carbachol stimulation in the hippocampus was exposure to room air following the severe hypoxia and lasted for at least 48 h. In Ca 2+-free incubation medium, the increase in basal incorporation of [ 3H]inositol into IPs elicited by severe hypoxia was not observed but carbachol still had an enhanced stimulatory effect. Binding studies showed that maximum binding capacity ( B max values) of [ 3H]QNB binding was significantly increased only in the hippocampus and only after a 6-h exposure to room air following the severe hypoxic exposure and remained increased for 48 h. K d values showed no significant change. While a transient exposure of rats to mild hypoxia caused no significant change either in carbachol-stimulated PI turnover or in [ 3H]QNB binding parameters, a chronic exposure to mild hypoxia for more than 6 h caused a significant increase in [ 3H]QNB binding capacity localized in the hippocampus, which was accompanied by an enhanced stimulatory effect of carbachol on PI turnover. These changes observed with mild hypoxia, however, were transient and tended to return to control levels following a 48-h exposure. These results suggest an up-regulation of muscarinic cholinergic receptor-coupled PI turnover in the rat brain caused either by transient severe hypoxia or by chronic mild hypoxia.

Autoradiographic analyses of agonist binding to muscarinic receptor subtypes

The binding of four muscarinic receptor agonists to regions of rat brain was examined through quantitative autoradiographic techniques. Oxotremorine, arecoline, pilocarpine and bethanechol were chosen based on their different potencies and efficacies in muscarinic second messenger systems. Overall, the order of potency for inhibition of [ 3 H]-l- quinuclidinyl benzilate ([ 3 H]-l- QNB) binding to rat brain slices was oxotremorine > pilocarpine = arecoline > bethanecol. Regional assays of agonist potency indicated that all agonists were more selective for brainstem and thalamic regions than for hippocampal and cortical regions. The high selectivity of agonists for areas such as the paraventricular thalamus and the superior colliculus, which also display low affinity for pirenzepine, suggests that muscarinic agonists bind with higher affinity to M 2 receptors. Of the four agonists examined, pilocarpine displayed the lowest selectivity for M 2 receptors in that ic 50 values for pilocarpine were only 3-fold higher in the hippocampal and striatal regions (e.g. CA3: 40.6 ± 9.4 μM) than in thalamic and brainstem regions (e.g. paraventricular thalamus: 14.9 ± 6.2 μM). Oxotremorine was 8-fold more potent in the brainstem and thalamus, while arecoline and bethanechol were, respectively, 19- and 100-fold more selective for brainstem and thalamic receptors. Scatchard analyses revealed heterogeneous binding profiles for some agonists within single brain regions, suggesting that multiple agonist sites exist even within regions of predominately M 1 or M 2 receptors. For example, arecoline displayed curved Scatchard plots within the external layers of the cerebral cortex, layer CA1 of the hippocampus (predominantly M 1 subtype), and the paraventricular thalamus (predominantly M 2 subtype). The ability of agonists to recognize multiple sites within a single region may reflect the ability to recognize receptors coupled or uncoupled to second messenger systems through G-proteins

Muscarinic receptor-mediated regulation of OM-853-enhanced dopamine release in striatum of rat

The effect of OM-853, a new vincamine analogue, on cerebral dopaminergic neurons was investigated in male Wistar rats. The administration of OM-853 (200 mg/kg p.o.) induced facilitation of the metabolic turnover of dopamine (DA) in all brain areas except the cerebral cortex. Addition of OM-853 enhanced the release of [ 3H]DA from striatal slices; this release was antagonized by atropine (10 −7 M). However, pretreatment with scopolamine (0.5 mg/kg s.c.) inhibited the enhancement of striatal DA turnover induced by OM-853 (11 −4 M) inhibited [ 3H]quinuclidinyl benzilate binding to muscarinic cholinergic receptors in a striatal particulate fraction more potently than carbachol (10 −4 M). These results suggest that OM-853 may induce facilitation of striatal DA turnover by enhancing DA release via the stimulation of muscarinic cholinergic receptor.

An autoradiographic analysis of cholinergic receptors in mouse brain

Autoradiographic techniques were used to localize cholinergic receptors in the central nervous system of female DBA mice. Nicotinic receptors were identified using [ 3H]-L-nicotine and alpha-[ 125I]-bungarotoxin (BTX); [ 3H]-quinuclidinyl benzilate (QNB) was used to examine muscarinic receptor binding. There was little overlap between the regional distribution of binding sites for these ligands. Nicotine binding was highest in thalamic nuclei, the superior colliculus and the interpeduncular nucleus. For BTX binding, high density receptor populations were identified in the hippocampus, caudate putamen, colliculi (superior and inferior) and various nuclei in the hypothalamus and hindbrain. Muscarinic receptors were distributed more uniformly than nicotinic receptors; the colliculi, hippocampus and cerebral cortex had the highest level of QNB binding. Species differences between rats and mice in terms of cholinergic receptor binding are discussed.

Characterization of the effects of AHN 086, an irreversible ligand of "peripheral" benzodiazepine receptors, on contraction in guinea-pig atria and ileal longitudinal smooth muscle

The effects of AHN 086 and its reversibly acting structural analogue Ro 5-4864 were studied in the spontaneously beating guinea-pig atria and field-stimulated guinea-pig ileal longitudinal smooth muscle in the presence and absence of dihydropyridine calcium channel modulators. The treatment of guinea-pig atria with AHN 086 followed by extensive washing did not alter contraction. However, AHN 086 (0.5 microM) potentiated (88%) the positive inotropic responses by BAY K 8644, an effect that was not reversed by extensive washing of the tissue. Higher concentrations of AHN 086 (greater than 2 microM) irreversibly inhibited the intropic, but not the chronotropic responses to BAY K 8644, nifedipine, and isoproterenol. Ro 5-4864 (10 microM) produced a reversible enhancement of the inotropic responses and block of the chronotropic responses to BAY K 8644. In guinea-pig ileal longitudinal smooth muscle, both AHN 086 and Ro 5-4864 reversibly inhibited field-stimulated contractions. Neither Ro 5-4864 nor AHN 086 affected the ability of nifedipine to inhibit field-stimulated contractions of ileal longitudinal smooth muscle. Treatment of intact atrial with 5 microM AHN 086 followed by extensive washing resulted in a significant inhibition (30-50%) of [3H]Ro 5-4864 binding to peripheral benzodiazepine receptors and of [3H]nitrendipine binding to voltage-operated calcium channels, but did not affect [3H]dihydroalprenolol binding to beta-adrenergic receptors on atrial membranes. The same treatment applied to intact ileal longitudinal smooth muscle affected neither [3H] (-)-quinuclidinyl benzilate binding to muscarine receptors nor [3H]nitrendipine binding, but did result in a significant inhibition (30-50%) of [3H]Ro 5-4864 binding to ileal longitudinal smooth muscle membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Choline acetyltransferase activity and muscarinic binding in brain regions of aging fischer-344 rats

Muscarinic receptor binding and choline acetyltransferase (EC 2.3.1.6.) activity were assayed in three brain regions of 4-, 12- and 24-month-old Fischer-344 rats. Statistically significant age differences in cholinergic parameters were observed in each region. The affinity for [ 3H]quinuclidinyl benzilate increased in the cortex (24 vs 12 and 4 months), but B max decreased in the cortex (24 vs 12 vs 4 months), striatum (24 vs 12 vs 4 months) and hippocampus (24 vs 12 and 24 vs 4). Assays of carbamylcholine inhibition of [ 3H]quinuclidinyl benzilate binding in the hippocampus showed that high affinity agonist binding increased with age (24 vs 12 and 4 months), and the percentage of muscarinic binding to high affinity agonist sites decreased (24 vs 12 vs 4 months). In addition, the affinity of the agonist oxotremorine for muscarinic binding sites also increased in the hippocampus (12 and 24 vs 4 months). Although the K m of choline acetyltransferase for choline chloride did not change in any region tested, the K m for acetyl coenzyme A decreased in the hippocampus (24 vs 12 months), but increased (4 vs 12 months) and then decreased (12 vs 24 months) in the striatum. Statistically significant age-related declines in V max for choline acetyltransferase were noted in the striatum (24 < 12 < 4 months), but no age differences in this parameter were observed in the cortex or the hippocampus. Statistically significant positive correlations between V max for choline acetyltransferase and B max for [ 3H]quinuclidinyl benzilate binding were observed in each of the brain regions of 4-, 12- and 24-month-old rats. The findings have implications for use of the Fischer-344 male rat as an animal model of aging and age-related disorders of the human brain, including dementia of the Alzheimer type.

Effect of buflomedil (4-(1-pyrrolidinyl)-1-(2,4,6-trimethoxy phenyl)-1-butanone hydrochloride) on the function of striatal dopaminergic neurons.

Effect of buflomedil (4-(1-pyrrolidinyl)-1-(2,4,6-trimethoxy phenyl)-1-butanone hydrochloride) on the release and uptake of dopamine (DA) and the function of DA receptors in the striatum was investigated using male Wistar rats. In vitro addition of buflomedil (10(-5)-10(-8) M) had no effect on the uptake of [3H]-DA in striatal slices. On the other hand, buflomedil (10(-5)-10(-7) M) increased the spontaneous as well as high K+ (30 mM)-evoked releases of [3H]DA from striatal slices. Buflomedil inhibited the bindings of [3H]SCH23390, [3H]spiperone and [3H]apomorphine to striatal D1, D2 and D3 receptors only at a high concentration. On the other hand, buflomedil inhibited [3H]quinuclidinyl benzilate (QNB) binding to striatal muscarinic cholinergic receptors, which was similar to the action of carbachol. Pretreatment with scopolamine (0.5 mg/kg) in vivo inhibited the facilitation of striatal DA turnover induced by oral administration of buflomedil (300 mg/kg). In contrast, continuous oral administration of buflomedil (30 mg/kg x 7 days) to rats had no significant effect on the specific bindings of [3H]SCH23390, [3H]spiperone, [3H]apomorphine and [3H]QNB to synaptic membrane preparations obtained from the striatum. These results suggest that buflomedil may enhance striatal DA release by stimulating muscarinic cholinergic receptor and that DA receptors may not be involved in the enhancing effect of buflomedil on DA release.

Nodose ganglionectomy selectively reduces muscarinic cholinergic and delta opioid binding sites in the dorsal vagal complex of the cat

The dorsal vagal complex of the medulla oblongata, comprising the nucleus tractus solitarii, the area postrema and the dorsal motor nucleus of the vagus nerve, is an important brainstem regulatory center for the autonomie nervous system. The major afferent input from abdominal and thoracic viscera to this region is via vagal sensory neurons which have their cell bodies in the nodose ganglion. Autoradiography has been used to study the effects of unilateral nodose ganglionectomy on receptor binding sites in this region of the brain for the neurotransmitters acetylcholine, norepinephrine, and opioids. Nodose ganglionectomy had no discernible effect on alpha 2; noradrenergic ([ 3H] p-aminoclonidine) or mu opioid ([ 3H]Tyr- d-Ala-Gly-(NMePhe)-Gly-ol) binding sites. However, ganglionectomy did produce a 25% decrease in [ 3H]quinuclidinyl benzilate (muscarinic cholinergic) binding in the subnucleus gelatinosus of the solitary nucleus, and a marked decrease in [ 3H][ d-Pen 2, d-Pen 5]enkephalin (delta opioid) binding in the dorsomedial subnucleus of the nucleus tractus solitarii, ipsilateral to the lesion. These data suggest that muscarinic cholinergic and delta opioid receptors may be present on terminals of vagal afferent neurons that project to these specific brainstem regions. Since these vagal afferent neurons are known to arise, at least in part, from the gastrointestinal tract, it is possible that cholinergic and/or opioid receptors modulate specific autonomie functions associated with gastric sensory information such as satiety or nausea and emesis.

Effect of Buflomedil (4-(1-Pyrrolidinyl)-1-(2,4,6-Trimethoxy Phenyl)-1-Butanone Hydrochloride) on the Function of Striatal Dopaminergic Neurons

Effect of buflomedil (4-(1-pyrrolidinyl)-1-(2,4,6-trimethoxy phenyl)-1-butanone hydrochloride) on the release and uptake of dopamine (DA) and the function of DA receptors in the striatum was investigated using male Wistar rats. In vitro addition of buflomedil (10-5–10-8 M) had no effect on the uptake of [3H]-DA in striatal slices. On the other hand, buflomedil (10-5–10-7 M) increased the spontaneous as well as high K+ (30 mM)-evoked releases of [3H]DA from striatal slices. Buflomedil inhibited the bindings of [3H]SCH23390, [3H]spiperone and [3H]apomorphine to striatal D1, D2 and D3 receptors only at a high concentration. On the other hand, buflomedil inhibited [3H]quinuclidinyl benzilate (QNB) binding to striatal muscarinic cholinergic receptors, which was similar to the action of carbachol. Pretreatment with scopolamine (0.5 mg/kg) in vivo inhibited the facilitation of striatal DA turnover induced by oral administration of buflomedil (300 mg/kg). In contrast, continuous oral administration of buflomedil (30 mg/kg × 7 days) to rats had no significant effect on the specific bindings of [3H]SCH23390, [3H]spiperone, [3H]apomorphine and [3H]QNB to synaptic membrane preparations obtained from the striatum. These results suggest that buflomedil may enhance striatal DA release by stimulating muscarinic cholinergic receptor and that DA receptors may not be involved in the enhancing effect of buflomedil on DA release.

Organizational changes in cholinergic activity and enhanced visuospatial memory as a function of choline administered prenatally or postnatally or both.

This experiment was an examination of the effects of supplemental dietary choline chloride given prenatally (to the diet of pregnant rats) and postnatally (intubed directly into the stomachs of rat pups) on memory function and neurochemical measures of brain cholinergic activity of male albino rats when they became adults. The data demonstrate that perinatal choline supplementation causes (a) long-term facilitative effects on working and reference memory components of a 12-arm radial maze task, and (b) alternations of muscarinic receptor density as indexed by [3H]quinuclidinyl benzilate (QNB) binding and choline acetyltransferase (ChAT) levels in the hippocampus and frontal cortex of adult rats. An analysis of the relationship between these organizational changes in brain and memory function indicated that the ChAT-to-QNB ratio in the hippocampus is highly correlated with working memory errors, and this ratio in the frontal cortex is highly correlated with reference memory errors.

Chronic, oral aluminum administration to rats: Cognition and cholinergic parameters

Administration of aluminum sulfate in the drinking water of male Sprague-Dawley rats for thirty days resulted in an impairment of both consolidation and extinction of a passive avoidance task. No impairment of performance was observed on an active avoidance task, radial arm maze or open field activity measure. Biochemical analysis indicated a slight (<10%) but significant increase in hippocampal muscarinic receptor number after aluminum treatment as determined by tritiated quinuclidinyl benzilate ( 3H-QNB) binding. No changes were found in choline acetyltransferase (ChAT) activity, phosphoinositide hydrolysis, 3H-QNB binding in the cortex or tritiated pirenzepine ( 3H-PZ) binding in the hippocampus or cortex. These results indicate that cholinergic degeneration was not the cause of the observed cognitive impairments.