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M J Marks

Publications and source records attributed to M J Marks.

At least 73 records · Page 4Linked to original sources
PubMed1988

Genetic influences on acute responses to nicotine and nicotine tolerance in the mouse.

Nineteen inbred mouse strains were tested for their relative sensitivity to nicotine's effects on respiratory rate, acoustic startle response, heart rate, Y-maze activity (crosses and rears) and body temperature. Separate animals were tested for their sensitivity to nicotine-induced seizures following IP injection or IV infusion. Dose-response curves were constructed for each measure. Large strain differences were obtained for all of these measures. Nicotine's effects on heart rate, Y-maze activity and body temperature segregated together into the various mouse strains whereas seizure sensitivity segregated independently which suggests that these responses are under separate genetic control. Evidence was obtained which suggests that nicotine-induced seizures are regulated, in part, by the number of hippocampal nicotinic receptors measured with alpha-bungarotoxin (BTX). Strain differences in the development of tolerance to nicotine were also observed. Four mouse strains were tested and one of these strains (C3H) did not exhibit tolerance to nicotine. The binding of (3H)nicotine and (125I)BTX increased in the brains of all four mouse strains. These changes may relate to tolerance in some mouse strains, but since C3H mice did not exhibit tolerance even though brain nicotinic receptors changed following chronic treatment, other explanations for the role of receptor changes in tolerance to nicotine must be sought.

Animals↗
PubMed1988

Sulfhydryl modification of two nicotinic binding sites in mouse brain.

Two distinct binding sites with properties corresponding to those expected for nicotinic cholinergic receptors can be identified in brain by the specific binding of nicotine (or acetylcholine) and alpha-bungarotoxin. The effects of modification of these binding sites by treatment with the disulfide-reducing agent dithiothreitol were examined in tissue prepared from DBA mouse brains. Treatment with dithiothreitol reduced the binding measured with either ligand, and reoxidization of the disulfides fully restored binding. The effects of dithiothreitol treatment appeared to be due to a reduction in the maximal binding of nicotine and to a decrease in the binding affinity for alpha-bungarotoxin. Agonist affinity for the alpha-bungarotoxin binding site was reduced by treatment with low concentrations of dithiothreitol. The nicotine binding sites remaining after disulfide treatment displayed rates of ligand association and dissociation similar to those of unmodified tissue, but treatment of previously unmodified tissue with dithiothreitol accelerated the rate of nicotine dissociation. After reduction, both binding sites could be selectively alkylated with bromoacetylcholine. The results suggest that both putative nicotinic receptors in brain respond similarly to disulfide reduction and that their responses resemble those known for the nicotinic receptor of electric tissue.

Alkylation↗
PubMed1987

Genetic influences on tolerance development with chronic oxotremorine infusion.

Mice of four inbred strains (BALB, C57BL, DBA and C3H) were administered either saline or oxotremorine, a muscarinic agonist, at a dose of 0.5 mg/kg/hr by constant infusion through cannulas implanted in the right jugular veins. Chronic treatment resulted in the development of tolerance to the effects of oxotremorine both on rotarod performance and on body temperature. For drug-treated BALB mice, the dose-response curves for both measures were parallel to those for saline-treated mice, while for DBA and C3H mice the slopes of the dose-response curves were significantly less for treated mice than they were for controls. The equi-effective doses for the drug-treated animals were at least 8-fold greater than those for saline-treated mice. Drug treatment resulted in a significant decrease in the total number of muscarinic receptors in cortex as measured by the binding of [3H]quinuclidinyl benzilate (QNB) without effect on the KD for this ligand. Similarly, drug treatment did not affect the affinity of carbamylcholine as an inhibitor of QNB binding, but did significantly decrease the levels of both the high- and low-affinity agonist binding sites in cortex. The number of M1 muscarinic receptors measured by high affinity [3H]pirenzepine (PZ) binding was also significantly decreased in cortex without effect on the KD. The experiments were extended to five other brain regions. Full saturation curves were not constructed, however. Oxotremorine treatment significantly reduced QNB binding in every brain region. While the binding to agonist affinity states measured by carbamylcholine inhibition of QNB binding and M1 receptor levels measured by high affinity PZ binding tended to decrease with oxotremorine treatment not all changes were statistically significant. The changes in muscarinic receptor subtype levels induced by oxotremorine infusion did not differ among the strains. The results demonstrate that chronic treatment with a muscarinic agonist results in substantial tolerance to the effects of the drug in all four mouse strains. Although some differences in tolerance development exist, these differences are not readily explained by differences in the number or affinity states of brain muscarinic receptors.

Animals↗
PubMed1987

Influence of kinetics of nicotine administration on tolerance development and receptor levels.

Nicotine was administered intravenously to DBA mice through cannulae implanted in the jugular veins. Five groups of animals were treated: a control group which received saline and four nicotine treatment groups. All of the nicotine treatment groups received a dose of 4.0 mg/kg/hr. The first group received continuous infusion, the second group received 1 mg/kg pulses four times an hour, the third group received 2 mg/kg pulses twice an hour, and the fourth group received 4 mg/kg pulses once an hour. After a 10-day treatment period, the animals were tested for tolerance to an acute intraperitoneal administration of nicotine. Tolerance was measured using a test battery composed of the following tests: respiratory rate, acoustic startle response, Y-maze crosses and rears, heart rate, and body temperature. Mice from each of the four nicotine treatment groups were tolerant to the acute effect of nicotine, but the extent of tolerance varied among the groups as follows: continuous infusion less than 1 mg/kg pulses four times/hr less than 2 mg/kg pulses twice/hr less than 4 mg/kg pulse once/hr. Chronic nicotine infusion resulted in significant increases in the binding of L-[3H]nicotine in all six brain regions assayed and in significant increases in the binding of alpha-[125I]bungarotoxin binding in cerebral cortex and hippocampus. All increases in binding resulted from increases in Bmax for these ligands. In contrast to the effects observed for tolerance development, the increases in [3H]nicotine binding were not significantly affected by the kinetics of nicotine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Postnatal development of cholinergic enzymes and receptors in mouse brain.

The developmental profiles for the cholinergic enzymes acetylcholinesterase and choline acetyltransferase, and the muscarinic and nicotinic receptors were determined in whole mouse brain. The enzyme activities (per milligram of protein) increased steadily from birth, reaching adult levels at 20 days of age. These increases were primarily due to increases in Vmax. Muscarinic receptor numbers, measured by [3H]quinuclidinyl benzilate binding, also increased from birth to 25 days of age. Brain nicotinic receptors were measured with the ligands L-[3H]nicotine and alpha-[125I]-bungarotoxin. Neonatal mouse brain had approximately twice the number of alpha-bungarotoxin binding sites found in adult mouse brain. Binding site numbers rose slightly until 10 days of age, after which they decreased to adult values, which were reached at 25 days of age. The nicotine binding site was found in neonatal brain at concentrations comparable to those at the alpha-bungarotoxin site followed by a steady decline in nicotine binding until adult values were reached. Thus, brain nicotinic and muscarinic systems develop in totally different fashions; the quantity of muscarinic receptors increases with age, while the quantity of nicotinic receptors decreases. It is conceivable that nicotinic receptors play an important role in directing the development of the cholinergic system.

Acetylcholinesterase↗
PubMed1986

Mecamylamine blockade of nicotine responses: evidence for two brain nicotinic receptors.

Mice of two inbred strains, DBA and C3H, were pretreated with mecamylamine before challenge with nicotine. Mecamylamine blocked nicotine-induced seizures, enhanced startle, and alterations in respiratory rate, Y-maze activity, heart rate and body temperature. Mecamylamine blocked nicotine-induced seizures and enhanced startle with IC50 values of less than 0.1 mg/kg. The other nicotine effects were blocked by mecamylamine with IC50 values between 0.8 and 2.3 mg/kg. Strain differences in sensitivity to mecamylamine blockade were also detected. These results suggest that nicotine elicits its effects at two receptors, which may be those labeled with [125I]-alpha-bungarotoxin and with [3H]-nicotine.

Animals↗
PubMed1986

A genetic analysis of nicotine effects on open field activity.

The genetics of the effects of nicotine on the open field activity of mice were studied using a 5 by 5 diallel cross. The five inbred strains used were: A, BALB, C57BL, DBA, and C3H. These strains differ both in basal open field activity as well as activity after injection of nicotine. Analysis of the results of baseline activity indicated that both additive and dominance variance affected the activity of the animals. The dominance was non-directional. Likewise, the responses observed after injection of 0.75 mg/kg nicotine displayed both additive and dominance components. However, after correcting the results for differences in basal activity, the dominance item was primarily directional. This directional dominance was towards a more intense response to the effects of the drug, that is, a decrease in open field activity.

Animals↗
PubMed1986

Nicotinic binding sites in rat and mouse brain: comparison of acetylcholine, nicotine, and alpha-bungarotoxin.

The properties of the binding sites for radiolabeled acetylcholine (measured in the presence of atropine), nicotine, and alpha-bungarotoxin were compared in brain tissue prepared from both rat and mouse. These three binding sites were tested for the following properties: affinity and density of ligand binding, effects of competitive inhibitors, regional distribution, effects of treatment with dithiothreitol and the reversal of these effects by treatment with 5,5'-dithiobis(2-nitrobenzoic acid), thermal lability, effects of protease treatment, and response to chronic administration of nicotine in vivo. The binding sites for acetylcholine and nicotine were affected identically for all measurements, whereas the binding site for alpha-bungarotoxin was affected in a manner different from that for the other two ligands. Although the regional distribution of nicotine and acetylcholine binding differed between rat and mouse brain, other properties of this binding site were very similar between the two species. The results are consistent with the proposal that acetylcholine and nicotine bind to the same sites in both rat and mouse brain, whereas alpha-bungarotoxin binds to different sites.

Acetylcholine↗
PubMed1986

Nicotine-induced tolerance and receptor changes in four mouse strains.

The effects of chronic infusion of 3.0 mg/kg/hr of nicotine on the behavioral responses of four mouse strains (C3H, C57BL, BALB and DBA) to challenge doses of nicotine and on the levels of cholinergic receptors and enzymes were determined. Mice of the C57BL, BALB and DBA strains developed tolerance to the effects of nicotine on Y-maze activity, Y-maze rearing and body temperature. The C3H mice did not exhibit any evidence of tolerance to the effects of nicotine on these measures, but this strain did show tolerance to the effects of nicotine on acoustic startle response. None of the strains developed tolerance to the effects of nicotine on respiration rate, and only the BALB mice demonstrated tolerance to nicotine-induced bradycardia. Chronic nicotine treatment also elicited changes in putative brain nicotinic receptors. Increased binding of L-[3H]nicotine was seen in six brain regions in all four mouse strains. The changes in binding were similar for all the strains. The binding of alpha-[125I]bungarotoxin was also elevated in the four mouse strains, and modest differences among the strains were evident in this measure, with the C3H strain showing the smallest increases in four of the six brain regions. Chronic nicotine treatment did not alter brain muscarinic receptors, as measured with L-[3H]quinuclidinyl benzilate binding, nor were the activities of acetylcholinesterase or choline acetyltransferase altered, except that a small change in hippocampal choline acetyltransferase activity may have occurred. These results indicate that tolerance to nicotine is regulated by genetic factors and that changes in brain nicotinic receptor numbers are not sufficient to explain the development of tolerance.

Acetylcholinesterase↗
PubMed1986

Dose-response analysis of nicotine tolerance and receptor changes in two inbred mouse strains.

Mice of two inbred strains, DBA and C3H, were infused i.v. with saline, or 2, 4 or 6 mg/kg/hr of nicotine for 10 days. Two hours after termination of infusion the mice were challenged with one of several nicotine doses and the effects on respiration rate, Y-maze activity and rears, acoustic startle response, heart rate and body temperature were measured. Saline-infused C3H mice were less responsive than were DBA mice for all these tests with the exception of the acoustic startle response test. Nicotine-treated DBA mice developed a dose-related tolerance for most measures, whereas C3H mice did not appear to develop tolerance to any measure until the infusion dose reached 4 mg/kg/hr. The two mouse strains did not differ in the number of [3H] nicotine binding sites in six brain regions, and chronic nicotine treatment elicited similar changes in the binding of this ligand in the two strains. C3H mice had greater concentrations of alpha-[125I] BTX binding in hippocampus, midbrain and hypothalamus than did DBA mice. Chronic nicotine treatment resulted in an identical increase in bungarotoxin binding in the two mouse strains such that the initial strain differences were maintained. These results indicate that a threshold in drug response must be surpassed before a mouse develops tolerance to nicotine. In addition, mechanisms other than differences in receptor numbers must be invoked to explain differences in response to nicotine.

Animals↗
PubMed1986

Genetic analysis of nicotine-induced seizures and hippocampal nicotinic receptors in the mouse.

A classical F2 and backcross genetic design was used to examine the relationship between sensitivity to nicotine-induced seizures and hippocampal nicotinic receptors. Nicotine was administered by i.v. infusion through cannulas implanted in the right jugular veins of mice from the C3H and DBA mouse strains and their derived F1, F2 and backcross (F1 X C3H and F1 X DBA) generations. Nicotine-induced seizure sensitivity was assessed by infusing nicotine at a 2.0 mg/kg/min concentration until the onset of a clonic seizure. After seizure testing, mice were sacrificed and the binding of alpha-bungarotoxin (BTX) was determined in three brain regions: cortex, midbrain and hippocampus. The pattern of results for the six generations for seizure sensitivity was similar to that observed for hippocampal BTX binding. Genetic analyses indicate that receptor concentrations in the hippocampus and seizure sensitivity are both influenced by a relatively simple genetic system which involves one or more genes acting in an additive fashion. In addition, the genetic correlation which is indicative of the extent to which two characters are influenced by the same genes, supports the relationship between nicotine-induced seizure sensitivity and hippocampal BTX binding. The results suggest that those animals which are sensitive to nicotine-induced seizures have a greater concentration of nicotinic receptors as determined by the binding of BTX than animals which are less sensitive to the convulsant effects of nicotine.

Animals↗
PubMed1985

Relationship between nicotine-induced seizures and hippocampal nicotinic receptors.

A controversy has existed for several years concerning the physiological relevance of the nicotinic receptor measured by alpha-bungarotoxin binding. Using mice derived from a classical F2 and backcross genetic design, a relationship between nicotine-induced seizures and alpha-bungarotoxin nicotinic receptor concentration was found. Mice sensitive to the convulsant effects of nicotine had greater alpha-bungarotoxin binding in the hippocampus than seizure insensitive mice. The binding sites from seizure sensitive and resistant mice were equally affected by treatment with dithiothreitol, trypsin or heat. Thus it appears that the difference between seizure sensitive and insensitive animals may be due to a difference in hippocampal nicotinic receptor concentration as measured with alpha-bungarotoxin binding.

Animals↗
PubMed1985

Tolerance, cross-tolerance, and receptors after chronic nicotine or oxotremorine.

Saline, 8.0 mg/kg/hr nicotine, or 1.0 mg/kg/hr oxotremorine was continuously infused into the jugular veins of DBA female mice. After 10 days of treatment, respiratory rate, Rotarod performance, Y-maze crossings, Y-maze rears, heart rate, and body temperature were measured after challenge with 2.0 mg/kg nicotine or saline or 0.2 mg/kg oxotremorine. Nicotine-infused mice were tolerant to the effects of nicotine for all six tests and oxtremorine-infused mice were tolerant to the effects of oxotremorine for all six tests and to the effects of nicotine on heart rate and body temperature. Oxotremorine infusion reduced the Bmax for [3H]-L-QNB binding, but had no effect on Bmax for either [3H]-DL-nicotine or [125I]-alpha-BTX binding. Conversely nicotine infusion did not alter the Bmax for [3H]-L-QNB binding, but increased the Bmax for both [3H]-DL-nicotine and [125I]-alpha-BTX binding. These results indicate that tolerance developed to the effects of two cholinergic agents, nicotine and oxotremorine, and that some cross-tolerance to the effects of nicotine occurred in oxotremorine-treated mice. Treatment with oxotremorine caused down-regulation of muscarinic receptors, while treatment with nicotine caused up-regulation of nicotinic receptors. Although some cross-tolerance to the effects of nicotine occurred in oxotremorine-treated mice, this did not appear to result from changes in nicotinic receptors.

Animals↗
PubMed1985

A test battery for measuring nicotine effects in mice.

A test battery consisting of measurement of respiration, startle response, Y-maze activity, heart rate, and body temperature has been developed to assess the effects of nicotine on the mouse. Results obtained using the test battery were compared to those obtained with each test individually in four inbred strains of mouse (BALB, C57BL, DBA and C3H). No significant differences between the results obtained using the test battery and those obtained with individual tests were found. The results did demonstrate, however, that the genotype of the mouse strongly influenced the responses in several of the tests.

Animals↗
PubMed1985

Time course study of the effects of chronic nicotine infusion on drug response and brain receptors.

The experiments reported here examined the time course of the development and loss of tolerance to nicotine as well as the time course for the up-regulation and return to basal levels of brain nicotinic receptors. Nicotine was administered by continuous i.v. infusion through cannulae implanted in the right jugular veins of DBA mice. Tolerance to the effects of nicotine on Y-maze activity and rears, body temperature and heart rate was seen accompanying the infusion of 4 mg/kg/hr of nicotine. Maximal tolerance was obtained in 4 days and was paralleled by increases in the number of brain nicotine binding sites. The binding of alpha-bungarotoxin was also increased by chronic nicotine treatment but increases in binding preceded the development of detectable tolerance to the challenge dose of nicotine. Chronic nicotine treatment had no effect on quinuclidinyl benzilate binding. Tolerance to the effects of nicotine was lost at different rates for the various tests in that base-line response was attained for the Y-maze activity and rearings test in 8 days, whereas 12 to 16 days were required to regain control response for the body temperature test. Tolerance for the heart rate test persisted throughout the 20-day withdrawal period. Brain nicotine binding sites had returned to control levels by 8 days after treatment whereas the alpha-bungarotoxin binding sites were at control levels at the earliest time of postinfusion testing (4 days). Brain quinuclidinyl benzilate binding sites were unaffected by nicotine treatment and did not change during the withdrawal period. The changes in nicotine binding in the various brain regions during the onset and offset experiments were virtually identical. These changes in binding correlated highly with the acquisition and loss of tolerance to the effects of nicotine on the Y-maze locomotor activity and body temperature tests. The correlations between changes in nicotine binding and the Y-maze rearings and the heart rate tests were lower but some association is suggested. Although changes in nicotine binding may explain some of the tolerance observed, other explanations for tolerance must be sought as well.

Animals↗
PubMed1984

Chronic scopolamine treatment and brain cholinergic function.

Scopolamine was either continuously infused or injected once daily into C3H mice. Chronic infusion resulted in mice that were supersensitive to the hypothermia and tremor produced by the muscarinic agonist, oxotremorine. Chronic scopolamine infusion did not alter brain acetylcholinesterase (AChE) or choline acetyltransferase (ChAT) activities but it did produce an increase in brain muscarinic receptors, as measured by quinuclidinyl benzilate (QNB) binding. The maximal increase in QNB binding was seen at the 0.2 mg/kg/hr dose. Further increase in dose resulted in a return to control QNB binding in all brain regions studied except cortex. These animals were still supersensitive to oxotremorine, suggesting a dissociation between receptor number and response to agonist. Animals injected once daily for 10 days with 5 mg/kg exhibited an increase in QNB binding while no increase was seen at 20 mg/kg/day. Chronic oxotremorine infusion resulted in tolerance to the hypothermia-producing effects of oxotremorine. This was accompanied by a decrease in brain QNB binding. Coinfusion of scopolamine with oxotremorine blocked both the tolerance development and receptor changes. These experiments demonstrate that chronic scopolamine treatment can elicit an increase in brain muscarinic receptors which is accompanied by supersensitivity to agonists. However, this effect is not clearly dose related, and a strict relationship between receptor number and agonist response does not exist.

Acetylcholine↗
PubMed1984

A diallel analysis of nicotine-induced hypothermia.

The hypothermic responses of mice that occur after acute injection of nicotine show genetic influences. The body temperatures of mice of all five strains tested decreased after injection of either 0.75 or 1.5 mg/kg nicotine, but mice of the C3H strain were less affected than were those of the DBA, BALB, or C57BL strains. Mice of the A strain were the most sensitive to nicotine's effects. Genetic effects on nicotine-induced hypothermia were further examined using a five-by-five diallel cross. Additive genetic variance occurred at both nicotine doses. Substantial dominance variance, including directional dominance toward a large hypothermic response induced by injection of a low dose of nicotine (0.75 mg/kg), suggested that an intense response to a low drug dose is adaptive. The directional dominance was absent after treatment with a high dose (1.5 mg/kg) of the drug. Epistatic interactions occurring in crosses involving C57BL mice were pronounced.

Alleles↗