Changes in serum proteins after endotoxin administration in healthy and choline-treated calves.

BACKGROUND: This study aimed to investigate the possible serum protein changes after endotoxin administration in healthy and choline-treated calves using proteomics. These results are expected to contribute to the understanding of the pathophysiological mechanisms of endotoxemia and the beneficial effect of choline administration in this clinical situation. METHODS: Healthy-calves (n = 20) were divided into 4 groups: Control, Choline treated (C), Lipopolysaccharide administered (LPS), and LPS + C. Control calves received 0.9 % NaCl injection. Calves in C and LPS + C groups received choline chloride (1 mg/kg/iv). Endotoxin (LPS) was injected (2 µg/kg/iv) to the calves in LPS and LPS + C groups. Serum samples were collected before and after the treatments. Differentially expressed proteins (> 1.5 fold-change relative to controls) were identified by LC-MS/MS. RESULTS: After LPS administration, 14 proteins increased, and 13 proteins decreased within 48 h as compared to controls. In the LPS group, there were significant increases in serum levels of ragulator complex protein (189-fold) and galectin-3-binding protein (10-fold), but transcription factor MafF and corticosteroid binding globulin were down regulated (≥ 5 fold). As compared with the LPS group, in LPS + C group, fibrinogen gamma-B-chain and antithrombin were up-regulated, while hemopexin and histone H4 were down-regulated. Choline treatment attenuated actin alpha cardiac muscle-1 overexpression after LPS. CONCLUSIONS: LPS administration produces changes in serum proteins associated with lipid metabolism, immune and inflammatory response, protein binding/transport, cell adhesion, venous thrombosis, cardiac contractility and blood coagulation. The administration of choline is associated with changes in proteins which can be related with its beneficial effect in this clinical situation.

Nasal secretory protein changes following intravenous choline administration in calves with experimentally induced endotoxaemia.

Nasal secretory fluid proteomes (NSPs) can provide valuable information about the physiopathology and prognosis of respiratory tract diseases. This study aimed to determine changes in NSP by using proteomics in calves treated with lipopolysaccharide (LPS) or LPS + choline. Healthy calves (n = 10) were treated with LPS (2 µg/kg/iv). Five minutes after LPS injection, the calves received a second iv injection with saline (n = 5, LPS + saline group) or saline containing 1 mg/kg choline (n = 5, LPS + choline group). Nasal secretions were collected before (baseline), at 1 h and 24 h after the treatments and analysed using label-free liquid chromatography-tandem mass spectrometry (LCMS/MS). Differentially expressed proteins (>1.2-fold-change) were identified at the different time points in each group. A total of 52 proteins were up- and 46 were downregulated at 1 h and 24 h in the LPS + saline group. The upregulated proteins that showed the highest changes after LPS administration were small ubiquitin-related modifier-3 (SUMO3) and glutathione peroxidase-1 (GPX1), whereas the most downregulated protein was E3 ubiquitin-protein ligase (TRIM17). Treatment with choline reduced the number of upregulated (32 proteins) and downregulated proteins (33 proteins) in the NSPs induced by LPS. It can be concluded that the proteome composition of nasal fluid in calves changes after LPS, reflecting different pathways, such as the activation of the immunological response, oxidative stress, ubiquitin pathway, and SUMOylation. Choline treatment alters the NSP response to LPS.

Choline administration: activation of tyrosine hydroxylase in dopaminergic neurons of rat brain.

The administration of choline in doses previously shown to elevate brain acetylcholine concentrations also increases the activity of tyrosine hydroxylase in rat caudate nuclei. This response can be blocked by atropine, a muscarinic antagonist. These findings indicate that choline-induced increases in acetylcholine concentrations may be associated with parallel changes in the amount of the neurotransmitter released into synapses.

Synapse formation is enhanced by oral administration of uridine and DHA, the circulating precursors of brain phosphatides.

OBJECTIVE: The loss of cortical and hippocampal synapses is a universal hallmark of Alzheimer's disease, and probably underlies its effects on cognition. Synapses are formed from the interaction of neurites projecting from "presynaptic" neurons with dendritic spines projecting from "postsynaptic" neurons. Both of these structures are vulnerable to the toxic effects of nearby amyloid plaques, and their loss contributes to the decreased number of synapses that characterize the disease. A treatment that increased the formation of neurites and dendritic spines might reverse this loss, thereby increasing the number of synapses and slowing the decline in cognition. DESIGN SETTING, PARTICIPANTS, INTERVENTION, MEASUREMENTS AND RESULTS: We observe that giving normal rodents uridine and the omega-3 fatty acid docosahexaenoic acid (DHA) orally can enhance dendritic spine levels (3), and cognitive functions (32). Moreover this treatment also increases levels of biochemical markers for neurites (i.e., neurofilament-M and neurofilament-70) (2) in vivo, and uridine alone increases both these markers and the outgrowth of visible neurites by cultured PC-12 cells (9). A phase 2 clinical trial, performed in Europe, is described briefly. DISCUSSION AND CONCLUSION: Uridine and DHA are circulating precursors for the phosphatides in synaptic membranes, and act in part by increasing the substrate-saturation of enzymes that synthesize phosphatidylcholine from CTP (formed from the uridine, via UTP) and from diacylglycerol species that contain DHA: the enzymes have poor affinities for these substrates, and thus are unsaturated with them, and only partially active, under basal conditions. The enhancement by uridine of neurite outgrowth is also mediated in part by UTP serving as a ligand for neuronal P2Y receptors. Moreover administration of uridine with DHA activates many brain genes, among them the gene for the m-1 metabotropic glutamate receptor [Cansev, et al, submitted]. This activation, in turn, increases brain levels of that gene's protein product and of such other synaptic proteins as PSD-95, synapsin-1, syntaxin-3 and F-actin, but not levels of non-synaptic brain proteins like beta-tubulin. Hence it is possible that giving uridine plus DHA triggers a neuronal program that, by accelerating phosphatide and synaptic protein synthesis, controls synaptogenesis. If administering this mix of phosphatide precursors also increases synaptic elements in brains of patients with Alzheimer 's disease, as it does in normal rodents, then this treatment may ameliorate some of the manifestations of the disease.

Serum choline and butyrylcholinesterase changes in response to endotoxin in calves receiving intravenous choline administration.

Endotoxemia treatment options are still of interest due to high mortality and choline treatment is one of them because of its role in the cholinergic anti-inflammatory pathway. This study investigated serum choline and butyrylcholinesterase (BChE) responses, and their correlations with inflammatory, oxidative stress and tissue damage biomarkers, including paraoxanase-1 (PON1), and clinical signs in calves with endotoxemia and the effect of choline treatment in these responses. Healthy calves (n = 20) were divided equally into 4 groups: Control (0.9% NaCl, iv), Choline (C; 1 mg/kg/iv,once), Lipopolysaccharide (LPS; 2 µg/kg/iv,once) and LPS + C. Clinical and laboratory examinations were performed before and 0.5-48 h (hrs) after treatments. Following LPS administration, serum choline level increased at 0.5-24 h (P < .01), whereas serum BChE and PON1 level decreased at 48 h (P < .01) compared to their baselines. In LPS + C group, the increase in serum choline level was significantly higher (P < .01) than that of C and LPS groups. LPS did not decrease serum BChE levels significantly in calves treated with choline. Serum choline and BChE results correlated negatively with white blood cell count and positively (P < .001) with PON1 levels, oxidative stress index, inflammation and hepato-muscular injury markers. In conclusion serum choline and BChE may have a role in the pathophysiology of endotoxemia in calves. High serum choline concentration is associated with an improvement in response to LPS administration in calves treated with choline, probably by preventing the imbalances between oxidative stress and anti-oxidant capacity, preventing the serum BChE and PON1 decreases, and inhibition/attenuation of acute phase reaction and hepato-muscular injury in calves with endotoxemia.

Intraperitoneal administration of CDP-choline and its cholinergic and pyrimidinergic metabolites induce hyperglycemia in rats: involvement of the sympathoadrenal system.

CDP-choline is an endogenous metabolite in phosphatidylcholine biosynthesis. Exogenous administration of CDP-choline has been shown to affect brain metabolism and to exhibit neuroprotective actions. On the other hand, little is known regarding its peripheral actions. Intraperitoneal administration of CDP-choline (200-600 micromol/kg) induced a dose- and time-dependent hyperglycemia in rats. Hyperglycemic response to CDP-choline was associated with several-fold elevations in serum concentrations of CDP-choline and its metabolites. Intraperitoneal administration of phosphocholine, choline, cytidine, cytidine monophosphate, cytidine diphosphate, cytidine triphosphate, uridine, uridine monophosphate, uridine diphosphate and uridine triphosphate also produced significant hyperglycemia. Pretreatment with atropine methyl nitrate failed to alter the hyperglycemic responses to CDP-choline and its metabolites whereas hexamethonium, the ganglionic nicotinic receptor antagonist which blocks nicotinic cholinergic neurotransmission at the autonomic ganglionic level, blocked completely the hyperglycemia induced by CDP-choline, phosphocholine and choline, and attenuated the hyperglycemic response to cytidine monophosphate and cytidine. Increased blood glucose following CDP-choline, phosphocholine and choline was accompanied by elevated plasma catecholamine concentrations. Hyperglycemia elicited by CDP-choline and its metabolites was entirely blocked either by pretreatment with a nonselective -adrenoceptor antagonist phentolamine or by the 2-adrenoceptor antagonist, yohimbine. Hyperglycemic responses to CDP-choline, choline, cytidine monophosphate and cytidine were not affected by chemical sympathectomy, but were prevented by bilateral adrenalectomy. Phosphocholine-induced hyperglycemia was attenuated by bilateral adrenalectomy or by chemical sympathectomy. These data show that CDP-choline and its metabolites induce hyperglycemia which is mediated by activation of ganglionic nicotinic receptors and stimulation of catecholamine release that subsequently activates 2-adrenoceptors.

Restoration of blood pressure by choline treatment in rats made hypotensive by haemorrhage.

1. Intracerebroventricular (i.c.v.) injection of choline (25-150 micrograms) increased blood pressure in rats made acutely hypotensive by haemorrhage. Intraperitoneal administration of choline (60 mg kg-1) also increased blood pressure, but to a lesser extent. Following i.c.v. injection of 25 micrograms or 50 micrograms of choline, heart rate did not change, while 100 micrograms or 150 micrograms i.c.v. choline produced a slight and short lasting bradycardia. Choline (150 micrograms) failed to alter the circulating residual volume of blood in haemorrhaged rats. 2. The pressor response to i.c.v. choline (50 micrograms) in haemorrhaged rats was abolished by pretreatment with mecamylamine (50 micrograms, i.c.v.) but not atropine (10 micrograms, i.c.v.). The pressor response to choline was blocked by pretreatment with hemicholinium-3 (20 micrograms, i.c.v.). 3. The pressor response to i.c.v. choline (150 micrograms) was associated with a several fold increase in plasma levels of vasopressin and adrenaline but not of noradrenaline and plasma renin. 4. The pressor response to i.c.v. choline (150 micrograms) was not altered by bilateral adrenalectomy, but was attenuated by systemic administration of either phentolamine (10 mg kg-1) or the vasopressin antagonist [beta-mercapto-beta,beta-cyclopenta-methylenepropionyl1, O-Me-Tyr2,Arg8]-vasopressin (10 micrograms kg-1). 5. It is concluded that the precursor of acetylcholine, choline, can increase and restore blood pressure in acutely haemorrhaged rats by increasing central cholinergic neurotransmission. Nicotinic receptor activation and an increase in plasma vasopressin and adrenaline level appear to be involved in this effect of choline.

Characterization of phentermine and related compounds as monoamine oxidase (MAO) inhibitors.

Phentermine was shown in the 1970s to inhibit the metabolism of serotonin by monoamine oxidase (MAO), but never was labeled as an MAO inhibitor; hence, it was widely used in combination with fenfluramine, and continues to be used, in violation of their labels, with other serotonin uptake blockers. We examined the effects of phentermine and several other unlabeled MAO inhibitors on MAO activities in rat lung, brain, and liver, and also the interactions of such drugs when administered together. Rat tissues were assayed for MAO-A and -B, using serotonin and beta-phenylethylamine as substrates. Phentermine inhibited serotonin-metabolizing (MAO-A) activity in all three tissues with K(i) values of 85-88 microM. These potencies were similar to those of the antidepressant MAO inhibitors iproniazid and moclobemide. When phentermine was mixed with other unlabeled reversible MAO inhibitors (e.g. pseudoephedrine, ephedrine, norephedrine; estradiol benzoate), the degree of MAO inhibition was additive. The cardiac valvular lesions and primary pulmonary hypertension that have been reported to be associated with fenfluramine-phentermine use may have resulted from the intermittent concurrent blockage of both serotonin uptake and metabolism.

Choline as an agonist: determination of its agonistic potency on cholinergic receptors.

These experiments examined the potency of choline as a cholinergic agonist at both muscarinic and nicotinic receptors in rat brain and peripheral tissues. Choline stimulated the contraction of isolated smooth muscle preparations of the stomach fundus, urinary bladder and trachea and reduced the frequency of spontaneous contractions of the right atrium at high micromolar and low millimolar concentrations. The potency of choline to elicit a biological response varied markedly among these tissues; EC50 values ranged between 0.41 mM in the fundus to 14.45 mM in the atrium. Choline also displaced [3H]quinuclidinyl benzilate binding in a concentration-dependent manner although, again, its potency varied among different brain regions (Ki = 1.2 to 3.5 mM) and peripheral tissues (Ki = 0.28 to 3.00 mM). Choline exhibited a comparable affinity for nicotinic receptors. It stimulated catecholamine release from the vascularly perfused adrenal gland (EC50 = 1.3 mM) and displaced L-[3H]nicotine binding to membrane preparations of brain and peripheral tissues (Ki = 0.38 to 1.17 mM). However, the concentration of choline required to bind to cholinergic receptors in most tissues was considerably higher than serum levels either in controls (8-13 microM) or following the administration of choline chloride (200 microM). These results clearly demonstrate that choline is a weak cholinergic agonist. Its potency is too low to account for the central nervous system effects produced by choline administration, although the direct activation of cholinergic receptors in several peripheral tissues may explain some of its side effects.

Choline increases acetylcholine release and protects against the stimulation-induced decrease in phosphatide levels within membranes of rat corpus striatum.

This study examined the possibility that membrane phospholipids might be a source of choline used for acetylcholine (ACh) synthesis. Slices of rat striatum or cerebellum were superfused with a choline-free or choline-containing (10, 20 or 40 microM) physiological solution with eserine, for alternating 20 min periods of rest or electrical stimulation. Superfusion media were assayed for choline and ACh, and slice samples taken before and after stimulation were assayed for choline, ACh, various phospholipids, protein and DNA. The striatal slices were able to sustain the stimulation-induced release of ACh, releasing a total of about 3 times their initial ACh contents during the 8 periods of stimulation and rest. During these 8 cycles, 885 pmol/micrograms DNA free choline was released from the slices into the medium, an amount about 45-fold higher than the initial or final free choline levels in the slices. Although repeated stimulation of the striatal slices failed to affect tissue levels of free choline or of ACh, this treatment did cause significant, dose-related (i.e., number of stimulation periods) stoichiometric decreases in tissue levels of phosphatidylcholine (PC) and of the other major phospholipids; tissue protein levels also declined significantly. Addition of exogenous choline to the superfusion medium produced dose-related increases in resting and evoked ACh release. The choline also fully protected the striatal slices from phospholipid depletion for as many as 6 stimulation periods. Cerebellar slices liberated large amounts of free choline into the medium but did not release measurable quantities of ACh; their phospholipid and protein levels did not decline with electrical stimulation. These data show that membrane phospholipids constitute a reservoir of free choline that can be used for ACh synthesis. When free choline is in short supply, ACh synthesis and release are sustained at the expense of this reservoir. The consequent reduction in membrane PC apparently is associated with a depletion of cellular membrane. The use of free choline by cholinergic neurons for two purposes, the syntheses of both ACh and membrane phospholipids, may thus impart vulnerability to them in situations where the supply of free choline is less than that needed for acetylation.

Intracerebroventricular injection of choline increases plasma oxytocin levels in conscious rats.

In the present study, we examined the effect of intracerebroventricularly (i.c.v.) injected choline on both basal and stimulated oxytocin release in conscious rats. I.c.v. injection of choline (50-150 micrograms) caused time- and dose-dependent increases in plasma oxytocin levels under normal conditions. The increase in plasma oxytocin levels in response to i.c.v. choline (150 micrograms) was greatly attenuated by the pretreatment of rats with atropine (10 micrograms; i.c.v.), muscarinic receptor antagonist. Mecamylamine (50 micrograms; i.c.v.), a nicotinic receptor antagonist, failed to suppress the effect of 150 micrograms choline on oxytocin levels. Pretreatment of rats with 20 micrograms of hemicholinium-3 (HC-3), a specific inhibitor of choline uptake into nerve terminals, greatly attenuated the increase in plasma oxytocin levels in response to i.c.v. choline injection. Osmotic stimuli induced by either oral administration of 1 ml hypertonic saline (3 M) following 24-h dehydration of rats (type 1) or an i.c.v. injection of hypertonic saline (1 M) (type 2) increased plasma oxytocin levels significantly, but hemorrhage did not alter basal oxytocin concentrations. The i.c.v. injection of choline (50, 150 micrograms) under these conditions caused an additional and significant increase in plasma oxytocin concentrations beyond that produced by choline in normal conditions. These data show that choline can increase plasma oxytocin concentrations through the stimulation of central cholinergic muscarinic receptors by presynaptic mechanisms and enhance the stimulated oxytocin release.

Central choline reverses hypotension caused by alpha-adrenoceptor or ganglion blockade in rats: the role of vasopressin.

The effect of intracerebrovenricularly (i.c.v.) injected choline on blood pressure was investigated in rats made hypotensive by blocking peripheral alpha-adrenoceptors or autonomic ganglionic transmission. Choline (50-150 micrograms; i.c.v.) increased blood pressure in a dose-dependent manner and 150 micrograms of choline restored blood pressure to the resting level. The pressor response to choline was associated with an increase in plasma vasopressin levels. Pretreatment with mecamylamine (50 micrograms; i.c.v.), but not atropine (10 micrograms; i.c.v.), blocked both the pressor and vasopressin responses to i.c.v. choline. The vasopressin receptor antagonist, [beta-mercapto-beta,beta-cyclopenta-methylene-propionyl1,O-Me-T ry2,Arg8] vasopressin (10 micrograms/kg; i.v.), given 5 min after i.c.v. choline (150 micrograms), abolished the pressor effect of choline and blood pressure returned to the pre-choline levels. It is concluded that the precursor of acetylcholine, choline, can increase blood pressure and reverse hypotension in alpha-adrenoceptor or ganglionic transmission blocked rats, by increasing plasma vasopressin.

The effects of choline on body temperature in conscious rats.

Choline (75-300 microg) produced dose-dependent hypothermia when injected intracerebroventricularly (i.c.v.). Pre-treatment with the muscarinic receptor antagonist, atropine (10 microg, i.c.v.), blocked the hypothermic effect of choline (150 microg), but the response was only partially attenuated by pre-treatment with the nicotinic receptor antagonist, mecamylamine (20 microg, i.c.v.). Pirenzepine (25 microg), a muscarinic M1 receptor antagonist, or hexahydro-siladifenidol (HHSD) (100 microg), a muscarinic M3 receptor antagonist, also blocked choline-induced hypothermia when injected centrally. Unlike the other muscarinic receptor antagonists, M2-selective 11-[[2-[(diethylamino)methyl]-1-piperidinyl]acetyl]-5,11-dihydro-6H-pyri do[2,3-b][1,4]benzodiazepin-6-one (AF-DX116) (10 microg), did not affect choline-induced hypothermia. We also found that choline-induced hypothermia was very sensitive to the ambient temperature. Similar to its effect at room temperature, choline produced dose-dependent hypothermia at 4 degrees C, but this effect was abolished at 32 degrees C. These data suggest that choline produces hypothermia and this effect is mediated by muscarinic receptors.

Effect of intracerebroventricularly injected choline on plasma ACTH and beta-endorphin levels in conscious rats.

In the present study, we examined the effect of intracerebroventricularly injected choline on plasma ACTH (adrenocorticotrophin) and beta-endorphin levels in conscious rats. The intracerebroventricularly injection of choline (50-150 micrograms) elevated plasma ACTH levels in a dose-dependent manner. Plasma beta-endorphin levels were also significantly increased. Pretreatment of rats with mecamylamine (50 micrograms; intracerebroventricularly), the nicotinic receptor antagonist, completely inhibited the ACTH and beta-endorphin response to choline (150 micrograms; intracerebroventricularly). An antagonist of the muscarinic receptor, atropine (10 micrograms; intracerebroventricularly), failed to alter these effects. Pretreatment of rats with hemicholinium-3 (20 micrograms; intracerebroventricularly), a drug which inhibits the uptake of choline into cholinergic neurons, abolished the choline-induced increases in both plasma ACTH and beta-endorphin levels. These results indicate that choline can increase plasma concentrations of ACTH and beta-endorphin through the activation of central nicotinic acetylcholine receptors.

3,4-Diaminopyridine and choline increase in vivo acetylcholine release in rat striatum.

We investigated the effects of choline, 3,4-diaminopyridine and their combination on acetylcholine release from the corpus striatum of freely moving rats which were treated or not with atropine. Intraperitoneal administration of choline or intrastriatal administration of 3,4-diaminopyridine increased acetylcholine levels in striatal dialysates in a dose-dependent manner. When 3,4-diaminopyridine treatment was combined with choline, the observed effect was considerably greater than the sum of the increases produced by choline or 3,4-diaminopyridine alone. Administration of atropine (1 microM) in the dialysing medium was also found to be effective to stimulate striatal acetylcholine levels. 3,4-Diaminopyridine did not affect acetylcholine levels under these conditions. Whereas the choline-induced increase in acetylcholine release was significantly potentiated by atropine, co-administration of 3,4-diaminopyridine with choline failed to produce a further significant increase in the presence of atropine. These results suggest that a highly effective means for increasing acetylcholine release involves two concurrent treatments that increase neuronal choline levels and inhibition of the negative feedback modulation of acetylcholine release.

Cardiovascular effects of centrally injected tetrahydroaminoacridine in conscious normotensive rats.

In freely moving rats, intracerebroventricularly (i.c.v.) injected tetrahydroaminoacridine (10, 25, 50 microg) increased blood pressure and decreased heart rate in a dose- and time-dependent manner. Intravenous (i.v.) tetrahydroaminoacridine (1 and 3 mg/kg) also increased blood pressure. Atropine sulphate (10 microg; i.c.v.) pretreatment greatly attenuated the blood pressure response to i.c.v. tetrahydroaminoacridine while mecamylamine (50 microg; i.c.v.) failed to change the pressor effect. Neither atropine sulphate nor mecamylamine pretreatment affected the bradycardia induced by tetrahydroaminoacridine. However, the bradycardic response was completely blocked by atropine methylnitrate (2 mg/kg; i.p.) pretreatment. The pressor response to i.c.v. tetrahydroaminoacridine was associated with a several-fold increase in plasma levels of vasopressin, adrenaline and noradrenaline, but not of plasma renin. Pretreatment with prazosin (0.5 mg/kg; i.v.) attenuated the pressor effect without changing the bradycardia. Vasopressin V1 receptor antagonist [beta-mercapto-beta,beta-cyclopentamethylenepropionyl1,O-Me-Tyr2-A rg8]vasopressin (10 microg/kg; i.v.) pretreatment also partially inhibited the pressor response to i.c.v. tetrahydroaminoacridine and abolished the bradycardia. Tetrahydroaminoacridine's cardiovascular effects were completely blocked when rats were pretreated with prazosin plus vasopressin antagonist. The data show that tetrahydroaminoacridine increases blood pressure in normotensive freely moving rats by activating central muscarinic cholinergic transmission. Increases in plasma catecholamines and vasopressin are both involved in this response. The tetrahydroaminoacridine-induced reduction in heart rate appears to be due to the increase in vagal tone and plasma vasopressin.

Centrally administered choline increases plasma prolactin levels in conscious rats.

Intracerebroventricular (i.c.v.) administration of choline, a precursor of acetylcholine (ACh) increased plasma prolactin levels in a time and dose-dependent manner in conscious rats. Pretreatment of rats with the cholinergic muscarinic antagonist, atropine (10 microg, i.c.v.), blocked the increase in plasma prolactin level. The increase was not influenced by pretreatment with the cholinergic nicotinic antagonist, mecamylamine (50 microg, i.c.v.). Pretreatment with hemicholinium-3 (HC-3; 20 microg, i.c.v.), a high affinity choline uptake inhibitor, attenuated the choline-induced increase of plasma prolactin levels. These results show that choline increases plasma prolactin levels by activating muscarinic receptors via presynaptic mechanisms.

Effects of neuronotrophic factors on adrenal medulla grafts implanted into adult rat brains.

The effects of neuronotrophic factors (NFs) on adult adrenal medulla grafts transplanted into the rat caudate nucleus after the destruction of the nigrostriatal dopaminergic pathways were investigated. Two months after implantation, all of the adrenal medulla grafts treated with NFs, but only 45% of the untreated grafts, had survived. The levels of tyrosine hydroxylase activity in the caudate nucleus however, were not significantly different between the sham-operated control and either NF-treated or untreated grafted groups. These results indicate that treatment with NFs significantly enhances the survival rate of the grafts.

Caffeine potentiates the enhancement by choline of striatal acetylcholine release.

We investigated the effect of peripherally administered caffeine (50 mg/kg), choline (30, 60, or 120 mg/kg) or combinations of both drugs on the spontaneous release of acetylcholine (ACh) from the corpus striatum of anesthetized rats using in vivo microdialysis. Caffeine alone or choline in the 30 or 60 mg/kg dose failed to increase ACh in microdialysis samples; the 120 mg/kg choline dose significantly enhanced ACh during the 80 min following drug administration. Coadministration of caffeine with choline significantly increased ACh release after each of the choline doses tested. Peak microdialysate levels with the 120 mg/kg dose were increased 112% when caffeine was additionally administered, as compared with 54% without caffeine. These results indicate that choline administration can enhance spontaneous ACh release from neurons, and that caffeine, a drug known to block adenosine receptors on these neurons, can amplify the choline effect.

Central injection of captopril inhibits the blood pressure response to intracerebroventricular choline.

In the present study, we investigated the involvement of the brain renin-angiotensin system in the effects of central cholinergic stimulation on blood pressure in conscious, freely moving normotensive rats. In the first step, we determined the effects of intracerebroventricular (icv) choline (50, 100 and 150 microg) on blood pressure. Choline increased blood pressure in a dose-dependent manner. In order to investigate the effects of brain renin-angiotensin system blockade on blood pressure increase induced by choline (150 microg, icv), an angiotensin-converting enzyme inhibitor, captopril (25 and 50 microg, icv), was administered 3 min before choline. Twenty-five microg captopril did not block the pressor effect of choline, while 50 microg captopril blocked it significantly. Our results suggest that the central renin-angiotensin system may participate in the increase in blood pressure induced by icv choline in normotensive rats.