Effects of combined administration of imipramine and chlorpromazine on beta- and alpha 2-adrenergic receptors in rat cerebral cortex

Administration of the combination of antidepressant and neuroleptic drugs has been reported to have a synergistic effect in the treatment of delusional depression. The effects of chronic coadministration of imipramine (IMIP) and chlorpromazine (CPZ) on beta-adrenergic and alpha 2-adrenergic binding sites in rat cerebral cortex were studied. The combination caused the same reduction in the number of beta-adrenergic receptors as IMIP alone. No changes in alpha 2-adrenergic receptors were observed with IMIP and/or CPZ.     

The effect of p-chloromercuribenzoate on structure-binding relationships of muscarinic receptors in the rat cerebral cortex

Muscarinic receptors in the rat cerebral cortex, reacted with p-chloromercuribenzoate (PCMB) under different conditions (Phase I and II), have modified binding sites. These exhibit remarkable changes in the structural dependence of the binding of drugs. In Phase I, the structure-binding profile of agonists for both the high and low affinity agonist sites are altered. In Phase II, the structure-binding profile of antagonists is also observed. In Phase II, the ability of potent agonists to discriminate between sub-classes of agonist binding sites is eliminated. There is also a loss of heterogeneity in the binding of the selective antagonist pirenzepine. Of the 16 agonists examined, only pilocarpine has a heterogeneous binding profile in Phase II, the dispersity of binding being increased. The changes in binding properties of the receptors are discussed in terms of general theories of drug-receptor interactions.     

The effect of McN-A-343 on muscarinic receptors in the cerebral cortex and heart.

McN-A-343 behaves as a competitive agonist in binding to muscarinic receptors in the cerebral cortex. In its interaction with myocardial muscarinic receptors it is not competitive but it retains features of agonist binding.     

Effects of imipramine treatment on delta-opioid receptors of the rat brain cortex and striatum

Imipramine (CAS 113-52-0) is being utilized widely for the treatment of major depression. In recent years, there has been evidence of the involvement of the endogenous opioid system in major depression and its treatment. There is some evidence indicating that opioid receptors could be involved in the antidepressant mechanism of action. Regarding this topic, mood-related behavior of endogenous enkephalins seems to be mediated by delta-opioid receptors. In this work, the effects of subacute (5 day) and chronic (15 day) treatments of imipramine on the density and the affinity of the delta-receptors in the striatum and in the parietal and frontal cortices of the rat brain are described. Studied parameters (Bmax and Kd) were calculated by a saturation binding assay with the delta-opioid agonists [3H]-DPDPE (tyrosyl-2,6-3H(N)-(2-D-penicillamine-5-D-penicillamine)-enkephalin) as specific ligand and DSLET ([D-serine2]-D-leucine-enkephalin-threonine) as non-radioactive competing ligand. It was found that 15 days treatment significantly decreased the delta-opioid receptor density,without changing the affinity, in the frontal cortex of the rat brain. That decrease was confirmed by delta-opioid receptor immunostaining. These results suggest that delta-opioid receptors could play a role in the chronic action mechanism of imipramine.     

The effects of p-chloromercuribenzoate on muscarinic receptors in the cerebral cortex

The action of p-chloromercuribenzoate (PCMB) on the ligand binding properties of the muscarinic receptors in the rat cerebral cortex has been examined. At low concentrations, PCMB produces a selective change in the binding of agonists without any effect on the binding of antagonists. At higher concentrations, the structure-binding profile for binding antagonists is changed. The affinity of agonists is greatly reduced and the heterogeneity of binding eliminated. The effects of both high and low concentrations of PCMB can be reversed by dithiothreitol. Inactivation of receptors proceeds in parallel and is kinetically complex. It can only be partially reversed by dithiothreitol. Evidence is presented connecting the low affinity agonist binding site with the high affinity pirenzepine binding site. The changes produced by PCMB have been interpreted in terms of the modification of receptor conformation.     

Loss of muscarinic M1 receptors with aging in the cerebral cortex of Fisher 344 rats

Age-related changes in central cholinergic muscarinic receptors were measured in young (3-6 month), middle-aged (15-17 month), and aged (22-26 month) male Fisher 344 rats by receptor binding techniques. Using [3H]-quinuclidinyl benzilate as the ligand, a significant decrease (14-19%) in the number of muscarinic cortical receptors was measured in aged rats compared to both young and middle-aged rats. With the selective M1 antagonist, [3H]-pirenzepine, a 17% decrease in receptor density was observed in the cortex of aged animals compared to young rats. For both ligands no differences were observed in the striatum or hippocampus between any age group and there was no change in affinity (Kd) in any of the three brain regions for the three age groups. Additionally, there was no difference in choline acetyltransferase activity measured in cortex, hippocampus, or striatum of young and aged rats. Thus, there is a loss of M1 muscarinic receptors in the cerebral cortex of aged male Fisher 344 rats.     

The effect of tri-iodothyronine in combination with imipramine on [H]-cyclic AMP production in slices of rat cerebral cortex

Tri-iodothyronine (T₃; 15 μg) was administered to rats, alone or in combination with imipramine (20 mg/kg), for 5 days. The net synthesis of [³H]-cyclic AMP in cerebral cortex slices of animals so treated and control rats was then measured. The dose-dependent stimulation of [³H]-cyclic AMP by norepinephrine (NE) was significantly reduced in imipramine-treated rats. Tri-iodothyronine treatment had no effect on the enhanced net synthesis of [³H]-cyclic AMP produced by NE. In cortex slices of rats given both T₃ and imipramine, NE produced less stimulation of [³H]-cyclic AMP than in control rats. The magnitude of this inhibitory effect was less than that observed in animals treated with imipramine alone. In vitro addition of imipramine to the cortex slice preparation reduced the stimulation of [³H]-cyclic AMP caused by NE; treatment of rats with T₃ did not modify this inhibitory effect of imipramine in vitro. Isoproterenol produced significantly less stimulation of [³H]-cyclic AMP net synthesis than did NE; imipramine added in vitro had no effect on the stimulation produced by isoproterenol. It is concluded that the reason for the enhanced clinical effect of imipramine when given together with T₃ is not due to the hormone exaggerating the effect of the antidepressant on NE stimulated adenylate cyclase. Furthermore, for NE to produce maximal stimulation of [³H]-cyclic AMP, uptake of the catecholamine is necessary.     

The ontogeny of opioid receptors mediating opiate-induced feeding in rats

Acute administration of naloxone to preweanling rats does not attenuate independent ingestion of milk until 14 days of age suggesting that the full expression of an endogenous opioid system(s), regulating feeding rats, is not complete prior to this age. The present study was undertaken to examine the functional ontogeny of opioid receptors mediating opiate-induced feeding in rats. Rat pups, satiated with milk, were given intraperitoneal injections of the opiate receptor agonist, morphine, and were allowed free access to milk. Morphine stimulated the intake of milk at 3, 5, 7, 14 and 21 days of age, within 2 hr of injection. A time-course analysis in 7-day-old pups showed greater enhancement of intake between hours 2 and 4, than between hours 0 and 2, for large doses of morphine (0.3 and 1.0 mg/kg) suggesting that morphine-induced behavioral depression, which was observed early in the test session, confounded intake at earlier hours. Administration of the opiate receptor antagonist, naltrexone, produced no effect on intake of its own, but blocked the stimulation of intake by morphine in 5-day-old pups confirming that the effect of morphine on the intake of milk was mediated by opioid receptors. Thus, while a functional endogenous opioid system(s), regulating feeding in rats, is not fully mature until 14 days postpartum, the present results suggest that opioid receptors mediating feeding are functional very early in the postnatal development of the rat.     

Neuropeptide modulation of muscarinic receptors and function in cerebral cortex of young and senescent rats

The possible influence of several neuropeptides on muscarinic receptor binding and function in fronto-parietal cortex of young and senescent Fischer 344 rats was examined. Low concentrations (100 nM) of cholecystokinin, neurotensin and vasoactive intestinal polypeptide (VIP), added in vitro, enhanced carbachol-stimulated phosphoinositide metabolism in cortical miniprisms from both young and senescent rats, while somatostatin was ineffective. Interestingly, the VIP receptor antagonist [d-parachloro-Phe⁶, Leu¹⁷]VIP shifted the dose-response curve for carbachol significantly to the right, indicating inhibition of phosphoinositide hydrolysis. No direct actions of neuropeptides on the number or affinity of [³H]-quinuclidinyl benzilate binding sites nor on agonist conformation states of the muscarinic receptor were noted in cortex from young animals. The neuropeptide modulation of phosphoinositide metabolism was selective for muscarinic systems, as norepinephrine-stimulated phosphoinositide hydrolysis was not altered. Pretreatment with hemicholinium-3, an inhibitor of high-affinity choline uptake, did not prevent the neuropeptide effects, indicating the interaction was probably postsynaptic. It is possible that pharmacologic manipulation of peptidergic processes could improve cholinergic neurotransmission in brain.     

The effect of parenteral imipramine on the oral absorption of lamotrigine in rats

The interaction between imipramine and lamotrigine was investigated following the acute administration of lamotrigine (20 mg kg⁻¹, p.o.) alone or together with imipramine (25 mg kg⁻¹, i.p.) to rats. Similarly, the same doses of lamotrigine alone or when they were given together with imipramine (15 mg kg⁻¹, i.p.) were administered to rats chronically for 5 days. Plasma samples were collected at 0.25, 0.5, 1.0, 2.0, 3.0, 4.0, 6.0, 8.0, 10.0, 12.0 and 24.0 h after lamotrigine administration. An assay of lamotrigine in plasma was performed using a high-performance liquid chromatographic (HPLC) method. The concomitant administration of imipramine (25 mg kg⁻¹, i.p) with lamotrigine (20 mg kg⁻¹, p.o.) acutely, resulted in a significant (P<0.05) decrease in the maximum plasma concentration (C_max), the mean area under the plasma concentration–time curve (AUC) and the half-life (t_1/2), and a significant decrease (P<0.001) in the time to reach maximum concentration (t_max), as compared to those obtained for lamotrigine alone. Similarly, the chronic administration of imipramine together with lamotrigine lead to significant decreases in C_max, AUC and t_1/2 while the t_max remained unchanged. These results suggest that a significant decrease in the absorption of lamotrigine occurs when it is given acutely or chronically together with the antidepressant imipramine.     

三羟异黄酮抑制脑缺血大鼠大脑皮层中铜蓝蛋白的表达

目的探讨植物性雌激素三羟异黄酮（genistein,GST）对局灶性永久性脑缺血成年雄性大鼠的大脑皮层铜蓝蛋白（ceruloplasmin,CP）表达的影响。方法实验分为假手术组、缺血组、GST组和溶剂对照组,利用流式细胞学方法,观察颈内动脉注射GST对雄性大鼠局灶性永久性脑缺血模型中大脑皮层CP阳性细胞荧光强度和CP阳性细胞百分率的影响。结果脑缺血过程中CP的表达呈时相性变化,缺血组、溶剂组、GST组、缺血6、12、24h低于假手术组（P＆lt;0.05或＆lt;0.01）,缺血48、72h高于假手术组（P＆lt;0.05）;GST组CP的表达变化在不同时段均明显低于溶剂组（P＆lt;0.01）。结论GST可抑制脑缺血时CP的时相性变化,提示GST可通过抑制脑内铁相关的氧化应激损伤提供神经保护作用。     

The properties of muscarinic receptors in mammalian cerebral cortex

1 The reaction of tritiated propylbenzilylcholine mustard ([(3)H]-PrBCM; N-2'-chloroethyl-N-[2',3'-(3)H(2)] -propyl-2-aminoethylbenzilate) with homogenates of mammalian brain has been studied.2 The uptake can be divided into an atropine-sensitive component of fixed capacity (380 pmol/g protein in the rat) and an atropine-insensitive part.3 The atropine-sensitive portion is identified as muscarinic receptor by its insensitivity to nicotinic antagonists and anticholinesterases and its sensitivity to a range of muscarinic antagonists.4 The uptake of [(3)H]-PrBCM is also inhibited by muscarinic agonists and there is reasonable quantitative agreement between the affinities of agonists estimated in this way and in intact tissues by physiological responses.5 The fraction of [(3)H]-PrBCM uptake inhibited by muscarinic antagonists and agonists is the same.6 The amount of receptor found in six mammalian species was inversely related to the size of the brain, but the rates of alkylation and the sensitivity to atropine were not dissimilar.     

The effects of abnormalities of glucose homeostasis on the expression and binding of muscarinic receptors in cerebral cortex of rats

Glucose homeostasis in humans is an important factor for the functioning of nervous system. Both hypo and hyperglycemia contributes to neuronal functional deficit. In the present study, effect of insulin induced hypoglycemia and streptozotocin induced diabetes on muscarinic receptor binding, cholinergic enzymes; AChE, ChAT expression and GLUT3 in the cerebral cortex of experimental rats were analysed. Total muscarinic, muscarinic M(1) receptor showed a significant decrease and muscarinic M(3) receptor subtype showed a significant increased binding in the cerebral cortex of hypoglycemic rats compared to diabetic and control. Real-Time PCR analysis of muscarinic M(1), M(3) receptor subtypes confirmed the receptor binding studies. Immunohistochemistry of muscarinic M(1), M(3) receptors using specific antibodies were also carried out. AChE and GLUT3 expression up regulated and ChAT expression down regulated in hypoglycemic rats compared to diabetic and control rats. Our results showed that hypo/hyperglycemia caused impaired glucose transport in neuronal cells as shown by altered expression of GLUT3. Increased AChE and decreased ChAT expression is suggested to alter cortical acetylcholine metabolism in experimental rats along with altered muscarinic receptor binding in hypo/hyperglycemic rats, impair cholinergic transmission, which subsequently lead to cholinergic dysfunction thereby causing learning and memory deficits. We observed a prominent cholinergic functional disturbance in hypoglycemic condition than in hyperglycemia. Hypoglycemia exacerbated the neurochemical changes in cerebral cortex induced by hyperglycemia. These findings have implications for both therapy and identification of causes contributing to neuronal dysfunction in diabetes.     

Effect of chronic imipramine or baclofen on GABA-B binding and cyclic AMP production in cerebral cortex

Long-term (14 days) treatment of mice with the antidepressant drug imipramine increased the number of GABA-B receptors in the cerebral cortex and also led to an increase in the potentiation of norepinephrine-induced cAMP accumulation by baclofen (a GABA-B agonist) in cortical slices. Chronic baclofen treatment decreased both of these measures. These results suggest that previous evidence of increased GABA-B binding by antidepressants is coupled to a functional increase in adenylate cyclase activity, but that the mechanism responsible for this effect is not due simply to direct GABA-B receptor stimulation.     

Neuropeptide modulation of muscarinic receptors and function in cerebral cortex of young and senescent rats.

The possible influence of several neuropeptides on muscarinic receptor binding and function in fronto-parietal cortex of young and senescent Fischer 344 rats was examined. Low concentrations (100 nM) of cholecystokinin, neurotensin and vasoactive intestinal polypeptide (VIP), added in vitro, enhanced carbachol-stimulated phosphoinositide metabolism in cortical miniprisms from both young and senescent rats, while somatostatin was ineffective. Interestingly, the VIP receptor antagonist [d-parachloro-Phe6,Leu17[VIP shifted the dose-response curve for carbachol significantly to the right, indicating inhibition of phosphoinositide hydrolysis. No direct actions of neuropeptides on the number or affinity of [3H]l-quinuclidinyl benzilate binding sites nor on agonist conformation states of the muscarinic receptor were noted in cortex from young animals. The neuropeptide modulation of phosphoinositide metabolism was selective for muscarinic systems, as norepinephrine-stimulated phosphoinositide hydrolysis was not altered. Pretreatment with hemicholinium-3, an inhibitor of high-affinity choline uptake, did not prevent the neuropeptide effects, indicating the interaction was probably postsynaptic. It is possible that pharmacologic manipulation of peptidergic processes could improve cholinergic neurotransmission in brain.     

Actylcholine output from the cerebral cortex,choline uptake and muscarinic receptors in morphine-dependent,freely-moving rats

Spontaneous acetylcholine (ACh) output from the cerebral cortex, choline high affinity uptake and [³H]-QNB binding to muscarinic receptors in the cerebral cortex and caudate nucleus in freely moving rats made morphine-dependent by morphine pellet subcutaneous implantation were investigated before and during naloxone-induced withdrawal syndrome. The frequency and intensity of the withdrawal signs were also assessed.No significant change in ACh output was found in tolerant rats when compared with that of placebopellet implanted rats. During naloxone-induced withdrawal syndrome a 60% increase in ACh output occurred.In rats made dependent after a large septal lesion or treated for ten days with calcium gluconate (10 mg/kg i.m.) no increase in ACh output was found during the withdrawal syndrome. The intensity of some of its signs was also reduced.During the withdrawal syndrome a marked increase in choline high affinity uptake in the cerebral cortex and caudate nucleus was detected.The affinity of muscarinic receptors (K_D) for [³H]-QNB was significantly increased in the cerebral cortex and caudate nucleus of morphine-dependent rats before naloxone administration. It returned to normal during the withdrawal syndrome. In the caudate nucleus the number of binding sites (B_max) was decreased before and after the withdrawal syndrome.These findings emphasize the role of cholinergic mechanisms in opiate addiction.