The brain nicotinic acetylcholine receptor gene family.
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Amino Acid Sequence↗
Biomedical subjects
J Patrick
Publications and source records attributed to J Patrick.
Nicotine receptors in the mammalian brain.
Nicotine is a drug of abuse that presumably exerts its psychoactive effect through its interactions with nicotine binding sites in the central nervous system. Among its potential sites of action are the neuronal nicotinic acetylcholine receptors and the neuronal alpha-bungarotoxin binding sites. In this review we focus on the neuronal nicotinic acetylcholine receptors, their diversity, distribution, and functions as nicotine receptors or as mediators of synaptic transmission in the mammalian brain. We find that the complexity characteristic of the gene family encoding the subunits of these receptors is reflected both in the pattern of expression of the genes and in the pharmacological diversity of the expressed receptors.
Animals↗
Neurotoxins distinguish between different neuronal nicotinic acetylcholine receptor subunit combinations.
Neuronal and muscle nicotinic acetylcholine receptor subunit combinations expressed in Xenopus oocytes were tested for sensitivity to various neurotoxins. Extensive blockade of the alpha 3 beta 2 neuronal subunit combination was achieved by 10 nM neuronal bungarotoxin. Partial blockade of the alpha 4 beta 2 neuronal and alpha 1 beta 1 gamma delta muscle subunit combinations was caused by 1,000 nM neuronal bungarotoxin. The alpha 2 beta 2 neuronal subunit combination was insensitive to 1,000 nM neuronal bungarotoxin. Nearly complete blockade of all neuronal subunit combinations resulted from incubation with 2 nM neosurugatoxin, whereas 200 nM neosurugatoxin was required for partial blockade of the alpha 1 beta 1 gamma delta muscle subunit combination. The alpha 2 beta 2 and alpha 3 beta 2 neuronal subunit combinations were partially blocked by 10,000 nM lophotoxin analog-1, whereas complete blockade of the alpha 4 beta 2 neuronal and alpha 1 beta 1 gamma delta muscle subunit combinations resulted from incubation with this concentration of lophotoxin analog-1. The alpha 1 beta 1 gamma delta muscle subunit combination was blocked by the alpha-conotoxins G1A and M1 at concentrations of 100 nM. All of the neuronal subunit combinations were insensitive to 10,000 nM of both alpha-conotoxins. Thus, neosurugatoxin and the alpha-conotoxins distinguish between muscle and neuronal subunit combinations, whereas neuronal bungarotoxin and lophotoxin analog-1 distinguish between different neuronal subunit combinations on the basis of differing alpha subunits.
Animals↗
Effects of hypoxia on release of amino acid neurotransmitters from fetal lamb brain in vitro.
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Amino Acids↗
Indomethacin reversal of ethanol-induced suppression of ovine fetal breathing movements and relationship to prostaglandin E2.
The effects of indomethacin on the ethanol-induced suppression of fetal breathing movements and fetal arterial plasma and cerebrospinal fluid (CSF) PGE2 concentrations and maternal arterial plasma PGE2 concentration were determined in the near-term fetal lamb. Eight conscious instrumented pregnant ewes (between 130 and 133 days of gestation; term, 147 days) received 1-h maternal intravenous infusion of 1 g ethanol/kg total body weight, and the fetus received 6-h intravenous infusion of indomethacin (1 mg/h per kg fetal body weight) commencing 30 min later. Serial fetal and maternal arterial blood samples (n = 8) and fetal CSF samples (n = 5) were collected at selected times throughout the 12-h study for the determination of PGE2 concentration. Fetal breathing movements were monitored continuously throughout the experimental period. Maternal ethanol infusion resulted in initial suppression (P less than 0.05) of fetal breathing movements for 2 h below pretreatment value, followed by a rapid increase in the incidence of fetal breathing movements after the onset of fetal indomethacin treatment. Fetal and maternal plasma PGE2 concentrations and fetal CSF PGE2 concentration were increased (P less than 0.05) above the pre-infusion value during the administration of ethanol and 1 h thereafter. Fetal indomethacin treatment suppressed (P less than 0.05) to undetectable levels fetal plasma and CSF PGE2 concentrations, which then became similar (P greater than 0.05) to pretreatment by 12 h. There was a positive correlation between fetal plasma and CSF PGE2 concentrations. There was an inverse correlation between the incidence of fetal breathing movements and fetal CSF PGE2 concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The absence of adapted sodium and potassium transport in erythrocytes of cerebral palsied children with secondary malnutrition.
Previous studies of erythrocyte ion (potassium and sodium) transport during marasmus and kwashiorkor have indicated increased passive permeation to both ions in both syndromes, and increased Na,K pump activity in kwashiorkor and reduced activity in marasmus. Children with severe cerebral palsy (CP) frequently suffer secondary protein energy malnutrition (PEM). Unlike marasmus and kwashiorkor, this PEM is uncomplicated by micronutrient deficiency, parasitism and infections. Because of deformities classification of PEM cannot be performed in these children by stature-based anthropometry, therefore we used triceps skinfold thicknesses less than the fifth percentile and absence of weight gain in the previous year as criteria for malnutrition. K influx data from well- and malnourished CP children, and from well-nourished controls reveal that ouabain-sensitive K influx is highest in malnourished CP, followed by well-nourished CP (P = 0.02), and lowest in controls (P less than 0.001, vs. malnourished). Determinations of ouabain-sensitive Na efflux, though less precise and therefore more variable, were consistent with this finding of no decrease of Na,K pump activity occurring during the development of this malnutrition. There were no statistically significant differences in ouabain-insensitive fluxes of either Na or K. Ion transport in undernourished CP children thus resembles that found in kwashiorkor rather than in marasmus; but oedema is rarely seen in this form of secondary PEM.
Adolescent↗
Effect of ethanol on ovine fetal and maternal plasma prostaglandin E2 concentrations and fetal breathing movements.
The effect of maternal administration of ethanol on fetal and maternal plasma prostaglandin E2 (PGE2) concentrations and fetal breathing movement was determined in the near-term pregnant ewe. Six conscious instrumented pregnant ewes (between 129 and 134 days of gestation; term, 147 days) were studied on two successive days (day 1 and day 2). On each of the two days of the experiment, there was a 1-h period of maternal infusion of ethanol (1 g ethanol/kg total body weight) or an equivalent volume of normal saline. Animals were assigned to two groups with one group (n = 3) receiving ethanol on day 1 and saline on day 2, and the other group (n = 3) receiving saline on day 1 and ethanol on day 2. Fetal and maternal blood samples were collected at selected times for blood ethanol determination (n = 2), and plasma was obtained for the determination of PGE2 concentration (n = 6). Fetal breathing movements were monitored continuously during the experimental periods. Maternal saline infusion had no effect (P greater than 0.05) on fetal breathing movement and fetal and maternal plasma PGE2 concentrations (187 +/- 25 (SEM) pg/ml and 196 +/- 32 pg/ml, respectively). Maternal ethanol infusion suppressed (P less than 0.05) fetal breathing movement below preinfusion levels for 8 h and increased (P less than 0.05) both fetal and maternal plasma PGE2 concentrations to 314 +/- 55 pg/ml and 306 +/- 25 pg/ml, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Acid-Base Equilibrium↗
Cerebral palsy diplegia: improvements for walking.
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Cerebral Palsy↗
Distribution of alpha 2, alpha 3, alpha 4, and beta 2 neuronal nicotinic receptor subunit mRNAs in the central nervous system: a hybridization histochemical study in the rat.
Previous studies have revealed the existence of a gene family that encodes a group of neuronal nicotinic acetylcholine receptor (nAChR) subunits. Four members of this family have been characterized thus far; three of these subunits (alpha 2, alpha 3, and alpha 4) are structurally related to the ligand binding subunit expressed in muscle and form functional nAChRs when combined with the beta 2 gene product in Xenopus oocytes. In addition, the alpha 4 gene appears to encode two different products (alpha 4-1 and alpha 4-2) that have been proposed to arise by alternative mRNA splicing. Nine different [35S]-complementary ribonucleic acid (cRNA) probes were used in the present study to map the distribution of these nAChR subunit mRNAs throughout the central nervous system (CNS) of the rat. It was found that the beta 2 gene is expressed in most regions of the CNS, as are the alpha subunit genes as a group. However, each alpha gene is expressed in a unique, although partly overlapping, set of neuronal structures. Alpha 4 is the most widely expressed alpha gene, and the evidence suggests that mRNAs for the alpha 4-1 and alpha 4-2 products are virtually always found in the same regions, in approximately the same ratios (alpha 4-2 greater than alpha 4-1). In addition, there are several examples of cell groups that express beta 2 but none of the alpha subunit mRNAs examined here (particularly in the hypothalamus), as well as all groups that express the converse, thus suggesting that additional neuronal nAChR subunits remain to be characterized. Finally, the extensive expression of multiple alpha subunits in certain regions, particularly for alpha 3 and alpha 4 in the thalamus, suggests that there is microheterogeneity in a small population of cells or that some neurons may express more than one alpha subunit. This problem needs to be examined directly with double labeling methods but raises the possibility that some neuronal nAChRs may be composed of more than one kind of alpha subunit. The wide expression of these receptor genes suggests that nAChRs constitute major excitatory systems in the CNS.
Animals↗
Beta 3: a new member of nicotinic acetylcholine receptor gene family is expressed in brain.
Screening of a rat brain cDNA library with a radiolabeled probe made from an alpha 3 cDNA (Boulter, J., Evans, K., Goldman, D., Martin, G., Treco, D., Heinemanns, S., and Patrick, J. (1986) Nature 319, 368-374) resulted in the isolation of a clone whose sequence encodes a protein, beta 3, which is homologous (40-55% amino acid sequence identity) to previously described neuronal nicotinic acetylcholine receptor subunits. The encoded protein has structural features found in other nicotinic acetylcholine receptor (nAChR) subunits. Two cysteine residues that correspond to cysteins 128 and 142 of the Torpedo nAChR alpha subunit are present in beta 3. Absent from beta 3 are 2 adjacent cysteine residues that correspond to cysteines 192 and 193 of the Torpedo subunit. In situ hybridization histochemistry, performed using probes derived from beta 3 cDNAs, demonstrated that the beta 3 gene is expressed in the brain. Thus, beta 3 is the fifth member of the nAChR gene family that is expressed in the brain. The pattern of beta 3 gene expression partially overlaps with that of the neuronal nAChR subunit genes alpha 3, alpha 4, or beta 2. These results lead us to propose that the beta 3 gene encodes a neuronal nAChR subunit.
Amino Acid Sequence↗
Vibratory acoustic stimulation in 26- to 32-week, small-for-gestational-age fetus.
Seven pregnant women with early-onset (less than 32 weeks' gestation) intrauterine growth retardation were studied to examine fetal heart rate and fetal activity patterns after vibratory acoustic stimulation. All studies were done between 26 and 32 weeks' gestation. All fetuses but one were not acidotic at birth. There was a reduced time during which accelerations (50% less), long-term fetal heart rate variability (25% less), and body movements (60% less) occurred in small-for-gestational-age fetuses compared with these times in age-matched normally grown fetuses. Fetal heart rate and fetal activity patterns were not significantly altered after stimulation with the electronic artificial larynx. We hypothesized that severe, early-onset (less than 32 weeks' gestation), chronic nutritional deprivation of human fetuses is associated with a delay in the functional maturation of fetal sensory receptors.
Acoustic Stimulation↗
Effects of low-frequency vibration on human term fetuses.
Thirteen healthy pregnant women between 37 and 41 weeks' gestational age were studied to examine effects of a 5-second external vibratory stimulus (100 Hz, square wave) on fetal heart rate, fetal breathing, and gross fetal body movement patterns. All fetuses were stimulated during an episode of low fetal heart rate variability (mean minute range less than or equal to 32 milliseconds for greater than or equal to 5 minutes) lasting at least 5 minutes. There was an immediate and sustained increase in long-term FHR variability, number of FHR accelerations, and gross fetal body movements after stimulation. Fetuses made breathing movements more irregularly after vibratory stimulus. We hypothesize that external low-frequency vibratory stimulus, applied during episodes of low fetal heart rate variability, causes a change from a state of quiet sleep to a state of rapid-eye-movement sleep in healthy term fetuses.
Acoustic Stimulation↗
The functional diversity of the neuronal nicotinic acetylcholine receptors is increased by a novel subunit: beta 4.
A new nicotinic acetylcholine receptor (nAChR) subunit, beta 4, was identified by screening a rat genomic library. In situ hybridization histochemistry revealed expression of the beta 4 gene in the medial habenula of adult rat brains. The primary structure of this subunit was deduced from a cDNA clone isolated from a PC12 cDNA library. Functional nAChRs were detected in Xenopus oocytes injected in pairwise combinations with in vitro synthesized RNAs encoding beta 4 and either the alpha 2, alpha 3, or alpha 4 subunit. Unlike the alpha 3 beta 2 receptor, the alpha 3 beta 4 receptor is not blocked by bungarotoxin 3.1, indicating that the beta subunit can affect the sensitivity of neuronal nAChRs to this toxin. These results extend the functional diversity of nicotinic receptors in the nervous system.
Amino Acid Sequence↗
Single-channel currents of rat neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes.
The neuronal nicotinic acetylcholine receptor subunits alpha 2, alpha 3, and alpha 4 form functional receptors with the beta 2 subunit. Each of these subunit combinations shows two distinct open states (referred to as primary and secondary). The primary open states of alpha 2 beta 2, alpha 3 beta 2, and alpha 4 beta 2 receptors were 33.6 +/- 1.8 pS, 15.4 +/- 0.8 pS, and 13.3 +/- 1.5 pS, respectively. The open times of the alpha 3 beta 2 primary open state were significantly longer than the open times of the other primary conductance states. The secondary open states of alpha 2 beta 2 and alpha 3 beta 2 were 15.5 +/- 1.3 pS and 5.1 +/- 0.4 pS, respectively. Secondary open states were seen infrequently with alpha 4 beta 2. Oocytes injected with alpha 2 RNA and a 9-fold excess of beta 2 RNA showed an enhanced expression of the secondary open state.
Amino Acid Sequence↗
Structure and function of neuronal nicotinic acetylcholine receptors deduced from cDNA clones.
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Amino Acid Sequence↗
Effect of acute, multiple-dose ethanol on maternal and fetal blood gases and acid-base balance in the near-term pregnant ewe.
The effect of ethanol on maternal and fetal blood gases and acid-base balance was determined in six conscious instrumented near-term pregnant ewes for maternal intravenous infusion of 3 g ethanol/kg total body weight administered as six doses of 0.5 g ethanol/kg total body weight over 8 h. Maternal and fetal blood ethanol concentrations, determined in two animals, were maximal at 8 h (3.74 and 3.82 mg/mL, respectively) and were virtually identical during the 24-h study. Maternal and fetal blood gases and acid-base balance were not significantly altered during and after ethanol administration compared with preinfusion values. The data demonstrate that, during near-term ovine pregnancy, the equivalent of a binge-type drinking episode does not produce fetal hypoxia or acidosis. Furthermore, these data do not support the postulated involvement of ethanol-induced fetal hypoxia in the mechanism of ethanol teratogenesis.
Acid-Base Equilibrium↗
Development of tolerance to ethanol-induced suppression of breathing movements and brain activity in the near-term fetal sheep during short-term maternal administration of ethanol.
The effect of short-term maternal ethanol administration on the ethanol-induced suppression of fetal breathing movements, electrocortical (ECoG) activity, and electroocular (EOG) activity was determined in the near-term fetal sheep. Twelve conscious instrumented pregnant ewes (between 125 and 139 days of gestation; term, 147 days) received 1-h intravenous infusion of 1 g ethanol/kg total body weight daily for six days (n = 6) or an equivalent volume of normal saline daily for six days (n = 6). On the seventh day, the ethanol- and saline-pretreated animals were administered 1 g ethanol/kg total body weight. A further six ewes received 1-h intravenous infusion of 1 g ethanol/kg total body weight (n = 3) or an equivalent volume of normal saline (n = 3) daily for thirteen days with both groups receiving 1 g ethanol/kg total body weight on day fourteen. Fetal ECoG and EOG activities, and fetal breathing movements were monitored continuously over the post- operative and experimental periods. Saline infusion had no significant effect on the parameters studied. Fetal breathing movements were suppressed for 8 h after the first ethanol dose, and were not significantly suppressed after fourteen days of once-daily, maternal ethanol administration. Low-voltage ECoG and EOG activities were suppressed for 3 h after the first ethanol dose, and were not significantly suppressed after seven days of repeated ethanol administration. Maternal and fetal blood gases and acid-base balance were not significantly affected by maternal ethanol administration. These data demonstrate that short-term maternal administration of ethanol results in the development of tolerance to ethanol in the mature fetus.
Animals↗
Indomethacin antagonizes the ethanol-induced suppression of breathing activity but not the suppression of brain activity in the near-term fetal sheep.
The effect of indomethacin on the ethanol-induced suppression of fetal breathing movements, low-voltage electrocortical (ECoG) activity, and electro-ocular (EOG) activity was studied in the near-term fetal sheep. Ten conscious instrumented pregnant ewes (between 129 and 131 days of gestation; term, 147 days) received 1-h maternal intravenous infusion of 1 g ethanol/kg total body weight and simultaneous fetal treatment with either indomethacin (2 mg/kg fetal body weight/h) (n = 5) or an equivalent volume of phosphate buffer (n = 5) intravenously for 9 h. Fetal ECoG activity, EOG activity, and fetal breathing movements were monitored continuously over the experimental periods. In animals treated with ethanol and buffer (n = 5), fetal breathing movements were suppressed for 8 h and low-voltage ECoG and EOG activity was suppressed for 2 h below preinfusion levels. In animals treated with ethanol and indomethacin (n = 5), fetal breathing movements were elevated for 13 h but low-voltage ECoG and EOG activity remained suppressed for 3 h below preinfusion levels. The data suggests that indomethacin can antagonize the ethanol-induced suppression of fetal breathing movements, but does not alter the ethanol-induced suppression of ECoG or EOG activity.
Animals↗