Nicotine-treated Animals Research Articles

Effect of chronic nicotine delivery on the proliferation rate of endothelial and smooth muscle cells in experimentally induced vascular wall plaques

To study the effect of nicotine, cholesterol feeding, and their combination on endothelial and smooth muscle cells in vascular wall plaques an experimental method was established which allows the immunohistochemical detection and quantification of the fractions of endothelial and smooth muscle cells in DNA synthesis under the effect of these stimuli. For this purpose standardized fibromuscular plaques were produced by electrostimulation in the common carotid arteries of rabbits. The animals received either nicotine via implanted osmotic minipumps or a cholesterol diet or both. Plaque size was determined at the end of the experiments after 7 or 14 days as well as the fraction of endothelial and smooth muscle cells in DNA synthesis during exposure to bromodeoxyuridine (BrdU). The BrdU labeling index of endothelial cells clearly increased under chronic nicotine administration for either 7 days or 14 days compared to controls. The combination of nicotine and cholesterol diet led to a more significant increase. In contrast, the BrdU labeling index of smooth muscle cells was not increased under nicotine delivery. The combination of nicotine and cholesterol, however, led to a significant increase of the BrdU labeling index of smooth muscle cells in the plaques compared to cholesterol feeding. Measurement of the plaque size revealed no difference between controls and nicotine-treated animals after 14 days of nicotine delivery, whereas the combination of cholesterol and nicotine produced increased plaque formation compared to a group of animals which received a cholesterol diet alone.

Chronic nicotine ingestion improves radial arm maze performance in rats

Effects of chronic nicotine treatment on spatial memory were studied in rats. After 3 weeks of administration of 2.5mg/kg/day in drinking water, the rats were submitted to a spatial learning task in an eight-arm radial maze, during which time the treatment was maintained. Chronic nicotine treatment improved daily spatial memory performance after the animals reached an asymptotic level. Nicotine-treated animals showed significantly better performance than control animals regarding the first error and the total correct path choices.

The chronic infusion of nicotine into the developing chick embryo does not alter tensity of (−)-[ 3H]nicotine-binding sites or vestibular function

(−)-Nicotine (1.2 mg/day) or saline was infused into chick embryos ( Gallus domesticus) for 10 days beginning 12 h beyond the eight day of incubation (E8 + 12h). Twelve h beyond the eightenenth day if incubation (E8 + 12h), the eggs were opened to access the embryos and subcutaneous skull electrodes placed. Short latency vestibular thresholds and input/output fure determined to assess neurophysiological consequences of chronic nicotine administration. Samples of serum extraembryonic (amniotic and albumen) fluid were analyzed by gas chromatography-mass spectrometry to determine the levels of nicotine and its major metabolite, cotinine. The brains were removed and divided into diencephalon and mesencephalon and the density of (−)-[ 3H]nicotine binding sites in each brain area was measured. Nicotine and cotinine were found in the serum and extraembryonic fluid, but nicotinic receptors were not up-regulated in the brains of animals infused with nicotine in comparison to controls. Vestibular response thresholds also did not differ between nicotine-treated and control animals.

Tolerance to nicotine following chronic treatment by injections: a potential role for corticosterone.

C57BL/6 male mice were injected intraperitoneally with nicotine (2.0 mg/kg) or saline three times each day (0800 h, 1300 h and 1800 h) for a period of 12 days and then tested for nicotine tolerance using a series of behavioral and physiological tests. For each of these tests, animals that received chronic nicotine treatment were significantly less sensitive to nicotine challenge than were animals that received chronic saline treatment, as indicated by shifts to the right of dose-response curves. Animals were retested for nicotine sensitivity 2 weeks following cessation of chronic nicotine injections. Tolerance to acute nicotine challenge persisted in nicotine-treated animals. Chronic nicotine treatment by injections did not alter the binding of L-[3H]-nicotine or alpha-[125I]-bungarotoxin in any of eight brain regions. Plasma corticosterone (CCS) levels were determined in animals prior to the initiation of the injection series (day 0), and on days 4, 8 and 12 of chronic treatment, immediately before the first injection of the day. CCS levels in nicotine-treated animals were elevated as compared to saline-injected controls by day 12 of treatment. Nicotine-treated animals also had elevated CCS levels 2 weeks after the last chronic injection. Nicotine-treated animals were, however, tolerant to nicotine-induced CCS release. Since previous studies from our laboratory have demonstrated that plasma CCS levels are inversely correlated with sensitivity to nicotine, it is possible that the tolerance to nicotine measured following chronic treatment by injections is due, at least in part, to the elevation in plasma CCS levels.

Effects of Topical and Systemic Nicotine on Gingival Blood Flow in Dogs

It has been suggested that due to its vasoconstrictive action, nicotine may have a deleterious effect on the periodontium. This study examined the effects of topical and systemic nicotine administration on gingival blood flow. Eighteen young adult dogs were divided into three groups receiving the following treatments for 28 days; topical nicotine in orabase, systemic nicotine via osmotic mini-pumps, and topical orabase or systemic saline via osmotic mini-pumps. Blood flow to the gingiva was measured (at days 0 and 28) by the radiolabeled microsphere method. Blood flow was consistently increased from day 0 to day 28 in the nicotine-treated animals. Comparison of days 0 and 28 blood-flow values demonstrated a statistically significant change (p less than 0.05) in the anterior regions of the topical-nicotine group as compared with the control group. The increased flow may be a reflection of the mode of nicotine delivery and timing of the blood-flow determination procedures.

Postnatal Effects of Nicotine on First Molar Development in the CD-1 Mouse

Young CD-1 mice, 4 days old, exposed to 0.1% nicotine sulfate on gestational days 6-20 were compared with untreated pups of the same age to determine its effect on the development of mandibular first molars. Pregnant mice were given intraperitoneal injections of nicotine at a dose of 1.67 mg/kg/day. Pups were then decapitated, their entire mandibles were excised, routinely prepared and embedded in paraffin, sectioned in the frontal plane and stained with hematoxylin and eosin for histological examination of developing lower first molars. The results demonstrated that the process of odontogenesis appears retarded in nicotine-treated animals while the molars of the control group revealed dentin and enamel formation. It was concluded that nicotine has a detrimental effect on molar development. Nicotine may interfere with cellular maturation of the tooth germ indicating that this effect is prenatal and extends postnatally.

Chronic Nicotine Treatment Enhances the Depressor Responses to Arachidonic Acid in the Rat

The depressor responses to intravenous injections of arachidonic acid, prostacyclin (PGI2), prostaglandin E2 (PGE2) and sodium nitroprusside were studied in chronically nicotine-treated rats. Arachidonic acid, PGI2, PGE2 and sodium nitroprusside decreased the diastolic blood pressure dose-dependently in the control animals. The vasodepressor effect of arachidonic acid was significantly enhanced in rats given nicotine 5 and 25 micrograms/ml in their drinking water for 10 days but remained unchanged in the animals treated with 1 microgram/ml nicotine for 10 days or given 1 mg/kg i.v. nicotine 10 min before administration of arachidonic acid. Indometacin abolished arachidonic-acid-induced depressor responses in both the control and nicotine-treated rats. Hypotension induced by PGI2, PGE2 and sodium nitroprusside was of similar magnitude in the control and nicotine-treated animals. It is suggested that the enhancement by chronic nicotine treatment of depressor responses to arachidonic acid could be due to changes in the formation and/or removal of its vaso-active metabolites (i.e. prostacyclin and/or thromboxane A2).

Metabolic and Pathologic Effects of Nicotine on Gastrointestinal Tract and Pancreas of Rats

We examined in male Sprague-Dawley rats the effects of nicotine at doses of 50 (0.31 mM) and 200 mg/L (1.23 mM) given for a period of 16 weeks on body weight gain, food and fluid intake, plasma CCK, glucose and insulin levels, amylase secretory responses of isolated pancreatic acinar cells to CCK-8 and carbachol, and histopathology (gross and light microscopy) of stomach and pancreas. These parameters were re-examined further in animals treated with nicotine at doses of 200 mg/L (1.23 mM) for 12 weeks and given tap water for an additional 4 weeks to evaluate the effects of nicotine withdrawal. Metabolic data suggest that decreases in body weight gain, food and fluid intake, and plasma levels of glucose and insulin by nicotine are dose dependent. Endocrinological studies showed that the plasma levels of CCK were significantly increased with nicotine but the amylase secretory response of pancreatic acinar cells was inhibited in response to CCK-8 and carbachol. Histopathologic data revealed that treatment of animals with a high dose of nicotine enhanced the appearance of numerous vacuoles in the pancreatic acinar cell cytoplasm. When the pancreatic acinar cell morphology was closely examined, it showed evidence of pyknotic nuclei and fusion of vacuoles. Prominent loss of gastric mucosal surface was found in nicotine-treated animals with gross microscopic evidence of bleeding ulcers. All of the metabolic parameters except body weight gain were reversed upon nicotine withdrawal. In addition, plasma CCK levels and pancreatic enzyme secretion were reversed upon nicotine withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic nicotine treatment eliminates asymmetry in striatal glucose utilization following unilateral transection of the mesostriatal dopamine pathway in rats

Partial hemitransection was performed through a knife lesion at the meso-diencephalic level in rats to sever the mesostriatal dopamine system. During the subsequent 2 weeks the animals received 0.125 mg/kg/h of nicotine continuously via an osmotic minipump implanted s.c. To achieve prompt high nicotine levels, 4 i.p. injections of 0.5 mg/kg nicotine were, in addition, given during the first 2 h following the lesion. The total treatment corresponded to a mean plasma level of 50 ng/ml nicotine, measured at the end of the experiment. Control animals received corresponding volumes of 0.9% saline. Quantitative autoradiographic analysis of the glucose utilization in the caudate nucleus using Sokoloff's [ 14C]2-deoxyglucose method demonstrated a 16% side-to-side difference in the lesioned control animals, whereas the asymmetry was counteracted by the nicotine treatment. Although there was an overall tendency to a lower rate of glucose utilization (by 6%) in the nicotine-treated animals compared to the controls receiving saline only, the difference was not statistically significant. The eliminated asymmetry probably reflects an increased survival of the dopamine neurons and/or of striatal nerve cells on the lesioned side due to protective effects of nicotine resulting from desensitization of nicotinic-type cholinergic receptors following continuous administration of the drug.

Inhibition of Platelet Aggregation Following Chronic In Vivo Treatment of Rats with Nicotine

Platelet aggregability is known to be enhanced and platelet-survival time shortened in smokers when compared with nonsmokers. Up to now it is unknown which of the substances in tobacco smoke are responsible for these effects. To evaluate a possible role of nicotine, rats were chronically treated with the alkaloid (10 mg/kg/day), continuously released from subcutaneously implanted osmotic minipumps. Surprisingly, after 8 weeks, platelet sensitivity toward the aggregating stimulus adenosine 5'-diphosphate (ADP) was markedly reduced. The mean ADP concentration required to induce half the maximum rate of aggregation (EC50) was 0.88 mumol/L in nicotine-treated animals, as compared with 0.67 mumol/L in controls (p less than 0.002). Platelet aggregability remained normal when the rats were treated simultaneously with nicotine and the beta blocker propranolol (3.5 mg/kg/day); for these animals, the mean EC50 for ADP was 0.73 mumol/L. These results are suggestive of a catecholamine-mediated action of nicotine. However, neither the basal levels of cAMP in platelet-rich plasma, nor the cAMP levels attained after stimulation of platelet adenylate cyclase with prostaglandin E1 (PGE1), were affected by 8 weeks of treatment with nicotine or nicotine plus propranolol. No effect on platelet aggregation was observed when the rats were treated with nicotine for only 2 weeks, or when nicotine or nicotine plus cotinine were added to platelet-rich plasma in vitro in concentrations equal to those attained in vivo after 8 weeks. Thus, prolonged application of nicotine in vivo caused an inhibition of ADP-induced rat platelet aggregation presumably mediated by beta-catecholaminergic stimulation of platelets.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of nicotine pretreatment on striatal dopaminergic system in rats.

Rats were pretreated with saline or nicotine (1.5 mg/kg/day) by subcutaneously implanting each animal with an Alzet osmotic minipump for 1 or 14 days. Short-term (1-day) administration of nicotine to rats reduced the stimulatory effect of (+)-amphetamine on locomotor activity. This was correlated with an attenuation in the ability of (+)-amphetamine to stimulate [3H]dopamine formation from [3H]tyrosine in rat striatal slices of these nicotine-treated animals. In long-term (14-day) nicotine-pretreated animals, both the apomorphine- and (+)-amphetamine-induced locomotor activity were potentiated. This behavioral potentiation was associated with an increase in the total number of postsynaptic dopaminergic receptor binding sites in the striatum. The development of striatal dopamine receptor supersensitivity may be caused by a decrease in the rate of dopamine turnover in the striatum.

Effect of continuous administration of nicotine on urinary histamine and Nτ-methylhistamme levels in the guinea pig

The effect of continuous subcutaneous administration of S-(−)- and R-(+)-nicotines on urinary excretion levels of histamine and N τ -methylhistamine in guinea pigs, over a 23-day period, has been studied. Urinary levels of these endogenous compounds were measured utilizing paired-ion reversed-phase high performance liquid chromatography with flow-through electrochemical detection. Urinary histamine levels of animals that had been administered either of these nicotine isomers were not significantly different from control values. Initial levels of urinary N τ -methylhistamine (days 2–3) in R-(+)- and S-(−)-nicotine-treated animals were, 2-fold and 8-fold higher, respectively than control levels but in both cases these levels returned to control values over the remainder of the time course examined (days 6–23). These results suggest that exposure to S-(−)-nicotine results in initial histamine release and/or inhibition of histamine uptake. However, longer term exposure to S-(−)-nicotine may not result in significantly altered levels of circulating histamine.

Chronic ethanol or nicotine treatment results in partial cross-tolerance between these agents.

Female DBA/2Ibg mice were treated chronically (21 days) with ethanol- or dextrin-containing liquid diets or infused chronically with nicotine (8 mg/kg/h) or saline for 10 days. The responses of these animals to challenge doses of ethanol (2.5 g/kg) or nicotine (1 or 2 mg/kg) were measured using a test battery consisting of respiration rate, acoustic startle response, Y-maze crosses and rears, heart rate and body temperature. Chronic ethanol-treated animals were tolerant to the effects elicited by a challenge dose of ethanol on four of the six measures and were cross-tolerant to nicotine's effects on the acoustic startle test. Chronic nicotine-treated animals were tolerant to nicotine's effects on five of the six measures and cross-tolerant to ethanol's effects on heart rate and body temperature. Thus, partial cross-tolerance between ethanol and nicotine exists. Chronic nicotine treatment resulted in significant increases in L-[3H]-nicotine binding in six of seven brain regions and in alpha-[125I]-bungarotoxin binding in three of seven brain regions. Chronic ethanol treatment failed to alter the binding of either ligand. Therefore, the cross-tolerance that develops between ethanol and nicotine is not totally dependent on alterations in the number of brain nicotinic receptors.

Chronic nicotine treatment counteracts the disappearance of tyrosine-hydroxylase-immunoreactive nerve cell bodies, dendrites and terminals in the mesostriatal dopamine system of the male rat after partial hemitransection

Male Sprague-Dawley rats were partially hemitransected at the mesodiencephalic junction and treated with nicotine (nicotine hydrogen (+)-tartrate) using Alzet minipumps implanted subcutaneously. Nicotine was delivered for 2 weeks in a dose of 0.125 mg/kg/h resulting in a serum nicotine level of 50.0 ± 5.1 ng/ml. Three other groups of rats were analyzed: hemitransected rats receiving saline treatment and sham-operated animals receiving nicotine and saline, respectively. The effects of hemistransection and nicotine rostrally as well as caudally to the lesion were evaluated with image analysis of tyrosine hydroxylase (TH)-immunoreactive (IR) nerve cell body and dendrite profiles in the rostral and caudal substantia nigra and of TH-IR nerve terminal profiles in the striatum. Adjacent sections were taken to Nissl staining. [ 3H]Nicotine binding in the midbrain and forebrain was studied by means of receptor autoradiography on partially hemitransected rats receiving no treatment. Catecholamine (CA) levels in the frontal cortex were measured using high-performance liquid chromatography (HPLC). Striatal dopamine (DA) function was analyzed studying apomorphine-induced (1.0 mg/kg) ipsilateral rotational behavior. The spontaneous behavior of the rats was evaluated with a hole board. Furthermore, body temperature and body weight were measured. The results demonstrated a lesion-induced disappearance of TH-IR cell body and dendrite profiles in the substantia nigra and of TH-IR nerve terminal profiles in the striatum. Similar findings were seen after Nissl staining. A significant counteraction of this disappearance was found in the nicotine-treated animals. On the lesioned animals a marked reduction of [ 3H]nicotine binding in the striatum and the substantia nigra was found. In the functional experiments an enhancement of the apomorphine-induced ipsilateral rotational behavior was demonstrated. The degree of rotation of was positivly correlated with the serum nicotine level. The study on spontaneous activity in the hole board showed a slower restoration of total activity in the hemitransected nicotine-treated rats. All these results are compatible with the hypothesis that the protective action of nicotine on the mesostriatal DA system may be due to a desensitization of excitatory nicotine cholinoceptors located on the nigral DA nerve cells, leading to a reduction of firing rate and reduced energy demands. Such an action of nicotine could be of importance for a possible anti-parkinsonian effect.

Behavioral and biochemical effects of nicotine in an MPTP-induced mouse model of Parkinson's disease

This study examined the effects of nicotine on locomotor activity and on the level of dopamine (DA) and its metabolies 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum and olfactory tubercle of mice that had been treated with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP significantly lowered the spontaneous locomotor activity 1–2 weeks and 2 months after 2 injections of MPTP (30 mg/kg SC, 24 hr apart) in young adult (3 months) and old mice (22–24 months old). The effect of nicotine on locomotion was biphasic; an initial stimulation of locomotor (0–5 min after nicotine) followed by a depressant period lasting from 5 to 20 min after injection. Tolerance to the depressant effect of nicotine developed after the 5th day of daily injections of nicotine (0.4 mg/kg SC, twice daily). Tolerance did not occur by day 8 to the initial stimulatory effect of nicotine. A similar effect of nicotine on locomotor activity was seen in mice treated with MPTP. The levels of DOPAC and HVA in the striatum were reduced by about 20% in the chronic nicotine-treated animals. The levels of DOPAC, DA, and HVA were reduced in the MPTP-treated mice; however, acuteand chronic nicotine did not cause an additional change in the amine levels. The results suggest that nicotine has an influence on locomotor activity in MPTP-treated mice and that this effect is not due to changes in DA receptor activity in the striatum caused by chronic nicotine.

In vivo depletion of [formula omitted] and [formula omitted] in guinea pig lung after chronic S-(−)-nicotine administration

Guinea pig lung tissue is dramatically depleted of S- adenosyl- l-homocysteine (SAH) after chronic exposure (600 μg h s.c. for 21 days) of animals to either R-( + )- or S-(−)-nicotine enantiomers; S-(−)-nicotine decreased lung SAH levels by 60-fold, while R-( + )-nicotine caused an 11-fold reduction of SAH, relative to control values. Lung S-adenosyl- l-methionine (SAM) levels were also reduced (15-fold and 9-fold reductions with R-( + )- and S-(−) -isomers, respectively) in nicotine-treated animals, compared to controls. These depletions are more pronounced with the S-(−)-enantiomer. Liver tissue levels of SAH and SAM are less affected, in fact, a 4-fold increase in liver SAH levels was observed after exposure of animals to R-( + )-nicotine. These results indicate that chronic exposure to nicotine may perturb important endogenous methyltransferase reactions, which could be a contributory factor in the toxicological effects produced by cigarette smoking.

The Effects of Nicotine on Implantation in the Rat1

The effects of nicotine on blastocyst implantation were investigated in the rat. Flushing each uterine horn with a constant force and volume of saline at selected times during pregnancy demonstrated that, in control animals, implantation had progressed sufficiently by 1200 h of Day 5 (Day 0 = day of insemination) to prevent conceptus retrieval. In contrast, in animals receiving twice daily s.c. injections of nicotine (5 mg/kg body weight/injection), blastocysts could be retrieved as late as 2100 h of Day 5. Thus, in nicotine-treated rats, the development of blastocyst attachment sufficient to resist flushing was delayed approximately 9 h. Simultaneous entrance of fertilized ova into the uterine lumen at 1800 h of Day 3 in both control and nicotine-treated animals demonstrated that this delay could not be attributed to altered transport through the oviduct. Associated with the altered time course of implantation in nicotine-treated rats were changes in blastocyst development: the time of zona pellucida loss and the growth of the inner cell mass were delayed. However, the number of blastocysts ultimately implanting in nicotine-treated animals did not differ from that of controls.

The effect of nicotine on ascorbic acid retention by guinea pigs.

Forty-eight male guinea pigs on an ascorbic acid free diet received daily oral injections of 2 mg L-ascorbic acid/100 g body weight for 2 weeks. Simultaneous injections of nicotine were given subcutaneously at 0.66 mg per animal per day; during the second week a second nicotine dose was administered 3 h later. On an equal weight basis each injection was approximately double the nicotine intake of a smoker of 40 cigarettes per day. On the last day at 1 h after a dose of L-ascorbic acid-1-14C there was more radioactivity and ascorbic acid remaining in the gastrointestinal tract contents of nicotine-treated animals than in saline-injected control animals. There were lower concentrations of L-ascorbic acid-1-14C in adrenals, brain, kidneys, and liver of nicotine-injected animals 1 h after the dose but higher concentrations 3, 6, and 12 h after the dose when compared to saline-injected animals. At all times adrenal and liver total ascorbic acid concentrations were higher in nicotine-treated animals. Brain and kidney concentrations showed a similar trend. The results indicate that there was delayed absorption of ascorbic acid in the presence of nicotine. Possible mechanisms of this effect are considered.

Effect on nicotine on clot retraction of rat blood platelets.

Clot retraction in platelet-plasma preparations was enhanced by nicotine treatment of rats. Platelets from nicotine-treated rats retracted to a greater degree if incubated in plasma from nicotine treated rats than if incubated in control plasma. Furthermore, platelets from nontreated rats retracted to a greater degree if they were incubated in plasma of nicotine-treated rats, than in plasma of nontreated rats. The results indicate that the effects of nicotine are not directly on platelets. It is concluded that the enhanced clot retraction observed in the blood of nicotine-treated animals was due to a plasma factor and not to changes in the platelets themselves.