Selective breeding of rats differing in sensitivity to the effects of acute ethanol administration.

Selective breeding of rats for sensitivity to the anesthetic effects of ethanol is being carried out with rats derived from the genetically heterogeneous N/Nih stock. Thirteen generations of within family selection have been achieved with replicate high (HAS), low (LAS) and control alcohol sensitive (CAS) lines. Significant separation between lines on sleep time and blood ethanol concentration (BEC) at awakening following ethanol administration has been achieved. In general, the results obtained so far replicate the findings with short (SS) and long (LS) sleep mice. One exception is that the high alcohol sensitivity rats (HAS) also appear more sensitive to pentobarbital relative to LAS rats. This finding is opposite to that which occurs with SS and LS mice where the low ethanol sensitive SS mice appear more sensitive to pentobarbital than the LS mice.

Genetic covariation in low alcohol-sensitive and high alcohol-sensitive selected lines of rats: behavioral and electrophysiological sensitivities to the depressant effects of ethanol and the development of acute neuronal tolerance to ethanol in situ at generation eight.

Phenotypic differences in behavioral and initial neuronal sensitivities to acute ethanol (EtOH) administration were examined and compared among replicate lines of rats, which were selectively bred for low and high EtOH sensitivity. The eighth generation of HAS (EtOH-sensitive) and LAS (EtOH-insensitive) rats were significantly different in terms of sensitivity both to EtOH-induced loss of righting response (sleep time) and to EtOH-induced depressions of cerebellar Purkinje neuron firing rates. This study provides the first evidence for a significant correlation between behavioral and electrophysiological EtOH sensitivities among individual animals and between replicate selected rodent lines. These data support the hypothesis that a genetic correlation exists between these two phenotypes. In addition, the LAS rats expressed a significantly higher incidence of acute cellular tolerance to the depressant neuronal effects of repeated local applications of EtOH over a period of a few minutes. We have characterized this response and concluded that it may contribute to EtOH sensitivity. However, our data also suggest that the EtOH insensitivity of cerebellar Purkinje neurons in LAS rats is not only a consequence of acute neuronal tolerance to EtOH, but also due to low initial EtOH sensitivity of these neurons. Both behavioral and electrophysiological EtOH phenotypes of LAS and HAS rats have diverged with the application of selection pressure for behavioral EtOH sensitivity; these data suggest that the mechanisms underlying neuronal sensitivity and acute neuronal tolerance to EtOH are important in determining the behavioral EtOH sensitivities of these animals.

gamma-Aminobutyric acid-activated chloride channels: relationship to genetic differences in ethanol sensitivity.

We demonstrated recently that low concentrations of ethanol enhanced the muscimol-stimulated chloride influx in cerebellar membranes from long sleep (LS-ethanol sensitive) mice, but had no effect on membranes from short sleep (SS-ethanol resistant) mice. The LS and SS were selected from a heterogeneous stock (HS) of mice for differential sensitivity to the hypnotic effects of ethanol as measured by the duration of the loss of the righting reflex (sleep time). In the present study, we tested 100 HS for ethanol sleep time. The mice with the shortest sleep time (HS-SS) and the mice with the longest sleep time (HS-LS) were selected and tested for the effect of ethanol and muscimol on chloride flux in cerebellum. The effects of ethanol and muscimol on both cerebellar and cortical chloride flux were also examined in rats from the 7th generation selected for differential sensitivity to the hypnotic effects of ethanol (high acute ethanol sensitive rats-HAS and low acute ethanol sensitive rats-LAS). Low concentrations of ethanol (10-30 mM) potentiated muscimol stimulation of 36Cl- uptake in both cortical and cerebellar membranes prepared from ethanol-sensitive animals (HS-LS and HAS). None of the ethanol concentrations tested altered stimulated chloride uptake in ethanol-resistant animals (HS-SS and LAS). No differences in muscimol stimulation of chloride uptake were observed between the pairs of selected lines. These findings strongly suggest that genetic differences in ethanol hypnosis are related to differences in the sensitivity of gamma-aminobutyric acid-operated chloride channels to ethanol.

Genetic risk for recombinant 8 syndrome and the transmission rate of balanced inversion 8 in the Hispanic population of the southwestern United States.

A rec(8) dup(q) syndrome, secondary to a pericentric inversion--inv(8)(p23q22)--has been identified in 26 probands from Hispanic kindreds in the southwestern United States. The clinical phenotype of the Hispanic rec(8) syndrome includes a dysmorphic facies, cardiovascular and urinary-tract malformations, and mental retardation. Segregation analysis utilizing pedigree and cytogenetic data from 31 kindreds including five additional kindreds from additional sources has provided computation of genetic risks for counseling. An inv(8) carrier parent has a 6.2% risk of having a rec(8) child. The transmission rate of the inv(8) was significantly higher for inv(8) carrier mothers (59%) than for carrier fathers (42%). The combined transmission rate for both sexes was 53%. Risk for spontaneous abortion or stillbirth (11.3%) was not higher than the general population frequency of 13%-15%. It is significant that all kindreds identified to date are of Hispanic background with ancestors traced to the southern Colorado/northern New Mexico region. By means of extended pedigree information, three independently ascertained kindreds have been linked through common ancestry 4 generations in ascendance. The Hispanic background, geographic localization, and common ancestry in three kindreds suggest a single founder of the Hispanic inv(8) in the Southwest.

CNS monoamine levels and the effect of DSP4 on ethanol sensitivity in LS and SS mice.

Brain area monoamine levels were determined in selectively-bred ethanol sensitive (LS) and insensitive (SS) mice. Norepinephrine, dopamine and serotonin were measured using high performance liquid chromatography coupled with electrochemical detection. Brain regions studied included cerebellum, brain stem, striatum, frontal cortex, hippocampus and hypothalamus. LS and SS mice exhibited similar regional monamine levels with the exception of differences in brain stem and cerebellar norepinephrine levels. The role of norepinephrine in regulating ethanol sensitivity of these mice was investigated using the neurotoxin, DSP4 (selectively lesions central noradrenergic pathways). Treatment with DSP4 did not alter ethanol sensitivity in the LS or SS mice, measured by duration of righting response loss and blood ethanol concentration at its recovery. Differences in brain stem and cerebellar norepinephrine levels between the LS and SS mice were considerably smaller than the large decreases in levels produced in both lines by DSP4. It is concluded that although synaptically-released monoamines may influence ethanol responses, norepinephrine probably does not directly mediate differences in behavioral sensitivity to ethanol between these mouse lines.

Genetic correlation of ethanol-induced ataxia and cerebellar Purkinje neuron depression among inbred strains and selected lines of rats.

In the present study, we compared phenotypic differences in behavioral and neurophysiological responses to acute ethanol administration among six inbred rat strains. Genetic variation was found both for ataxia, as measured by loss of righting response (sleep time) after a hypnotic dose of ethanol, and for the depressant action of ethanol on the spontaneous discharge of cerebellar Purkinje neurons. Results from an analysis of covariance of these phenotypes, measured among the inbred strains, provided strong evidence for a high genetic correlation between sleep time and inhibition of cerebellar Purkinje neuron discharge in response to acute ethanol administration. However, ethanol metabolism was also found to correlate with the behavioral sensitivity of rats to ethanol. Preliminary data from the third generation of replicate lines of rats currently being selectively bred for high and low acute sensitivity to ethanol shows a trend toward divergence of both ethanol sleep time and neuronal sensitivity to acute ethanol. The conclusion from these data supports the hypothesis that the cerebellum is an important locus of ethanol action, and suggests that neuronal sensitivity to ethanol will continue to diverge between these rat lines as selection for the sleep time phenotype progresses.

Genetic brain polypeptide variants in inbred mice and in mouse strains with high and low sensitivity to alcohol.

Twelve genetically determined brain polypeptide charge variants were identified by comparing cerebellar vermis of 7 inbred mouse strains and of mice selectively bred from 8 strains closely related to these 7 ancestral strains and one other for acute behavioral sensitivity to the sedative effects of ethanol. The selectively bred ethanol-sensitive (LS, long sleep) and insensitive (SS, short sleep) mice exhibited different allelic variants at 6 of these 12 gene loci expressed in the cerebellum. Variant polypeptide A1 (81 kdalton, pI 5.6) was shown to be associated with the membrane of synaptosomal mitochondria and to exhibit a basic variant in SS mice that is determined by a dominant allele. Other variant polypeptides showed codominant inheritance in F1 crosses. However, the phenotype of no single one of these brain polypeptides consistently correlated with the ethanol behavioral sensitivity of the 7 inbred mouse strains nor of 8 recombinant inbred (B X D, C57BL X DBA) strains. This finding supports the hypothesis that a substantial amount of inbreeding, leading to random fixation of alleles independent of selection for ethanol sensitivity, occurred during the breeding of the SS and LS mice. The present findings of a lack of a strong association between sleep time and a brain polypeptide variant do not preclude the existence of a major gene effect contributing to variation in acute sensitivity to ethanol but are consistent with reports that multiple loci are responsible for the difference in ethanol sensitivity between SS and LS mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of a high performance liquid chromatography method for screening of aldehyde dehydrogenase isozyme deficiency in hair roots from different ethnic groups.

A sensitive high performance liquid chromatography method has been used to measure aldehyde dehydrogenase (ALDH) activity in hair roots from Caucasian and Japanese subjects. Kinetic studies confirmed previous isoelectric focusing results that hair roots from Caucasians have two forms of ALDH, one low Km form and another high Km form, while hair roots from Japanese individuals who show a flushing reaction after ethanol intake lack, or have low activity of, the low Km form. By taking the ratio of the activities measured at a low (3 microM) and a high (75 microM) concentration of the substrate (3,4-dihydroxyphenylacetaldehyde), a suitable index for ALDH deficiency was obtained. The ratio varied between 1.6 and 3.5 for Caucasians and between 7 and 23 for Japanese flushers, and it was 2.5 for a Japanese nonflusher. The current method allows a more quantitative and qualitative assessment of the ALDH isozyme pattern in hair roots than that obtained with the isoelectric focusing technique.

Correlative analysis of ethanol-related phenotypes in rat inbred strains.

As a summary presentation of the ethanol-related traits in the rat inbred strains, the responses to ethanol for various traits of the eight strains were analyzed. The intercorrelations among the means of the strains were computed and the interrelationships among the strain correlations were determined further by partial correlation and factor analysis. Sources of data on strain ethanol response included measures from laboratories of Drs. Deitrich, Li, Erickson, Pohorecky, and Tabakoff, who have participated in this joint study on the development of the rat heterogeneous stock (N/Nih). Although there are problems with estimating strain correlations from data collected in different laboratories, some informative associations among the ethanol-related traits were apparent. Genetic variation for behavioral and physiological responses to ethanol was indicated by the inbred strain distribution. The strains clearly differed in response to ethanol, with the mean of the National Institutes of Health stock falling intermediate within the range of the inbred strain distribution. For the ethanol-related traits considered jointly, an association between initial behavioral sensitivity, ethanol intake, and metabolism, as well as an association between development of tolerance, initial sensitivity, and several physiological measures, was suggested. Thus, the rat heterogeneous stock, a systematically outbred population, should provide a useful animal model with which to study the physiological basis for ethanol intake and preference, response to acute ethanol, and the development of tolerance.

Effects of phencyclidine, amphetamine and related compounds on dopamine release from and uptake into striatal synaptosomes.

The ability of phencyclidine (PCP), amphetamine and other substances to stimulate dopamine release from and inhibit dopamine uptake into rat striatal synaptosomes was examined in a continuous superfusion system. Inhibition of uptake was measured by determining inhibition of [3H]dopamine displacement by unlabeled dopamine ([1H]dopamine). The displacement of [3H]dopamine by 10(-7) M [1H]dopamine was temperature- and sodium-sensitive and calcium-independent. [1H]Dopamine was an order of magnitude more potent than serotonin or norepinephrine in displacing [3H]dopamine. The concentrations of reserpine required to inhibit [3H]dopamine uptake and [3H]dopamine displacement by [1H]dopamine were similar. Nomifensine, benztropine, PCP and amphetamine also inhibited the displacement of [3H]dopamine by [1H]dopamine at concentrations which have been shown previously to inhibit the uptake of [3H]dopamine, suggesting that the mechanism behind displacement and uptake are very similar. PCP, at 10(-7) to 10(-5) M, significantly inhibited [3H]dopamine displacement by 10(-7) M [1H]dopamine, PCP was less potent than nomifensine or benztropine in inhibiting [3H]-dopamine displacement by 10(-7) M [1H]dopamine, but was equipotent to amphetamine. Superfusion of the synaptosomes for 6 min with PCP, 10(-6)M, induced increases in the spontaneous release of dopamine. In this regard, PCP was less potent than amphetamine, reserpine, flupenthixol, or benztropine. Upon initial exposure of the synaptosomes to amphetamine at 10(-7) to 10(-5) M, a substantial calcium-dependent release of dopamine was induced. In contrast, PCP did not stimulate the early calcium-dependent release of dopamine. These results indicate that PCP is less potent than amphetamine at releasing dopamine and may affect dopamine metabolism in the striatum primarily by inhibiting the reuptake of this catecholamine.

Risk of Down syndrome among second- and third-degree relatives of a proband with trisomy 21.

Previous studies indicate that parents who have had one child with trisomy 21 have an increased risk of having another affected child. To establish whether sibs, aunts, uncles, and cousins of an index case with trisomy 21 are also at increased risk for having an affected child, 219 kindreds of trisomy 21 probands were surveyed and compared with a control group of 247 kindreds. Control kindreds were ascertained through a child with a nonchromosomal disorder. Empiric risks were obtained and a risk interval calculated for each type of relationship. The results of this study suggest that for most families who have had a child with trisomy 21, the risk to second- and third-degree relatives is increased somewhat but still low (less than 1%). Analysis of those rare families who present with one or more affected second- or third-degree relative with trisomy 21 in addition to the proband suggests that they represent a small subpopulation with a markedly increased risk. Sibs and second-degree relatives in such families should be offered the option of amniocentesis, regardless of maternal age.

Evidence for genetic correlation of hypnotic effects and cerebellar Purkinje neuron depression in response to ethanol in mice.

In the present study, we compared phenotypic differences in behavioral and neurophysiological responses to acute ethanol administration among eight inbred strains of mice. Genetic variation for behavioral sedation, as measured by loss of the righting reflex (sleep time) after a hypnotic dose of ethanol, was shown to be present among the inbred strain population. In addition, a large genetic component of variation in the depressant action of ethanol on the spontaneous discharge of cerebellar Purkinje neurons was found. Results from an analysis of covariance of the behavioral and electrophysiological phenotypes, measured on each mouse among the inbred strains, provided strong evidence for a high genetic correlation between sleep time and inhibition of cerebellar Purkinje neuron discharge in response to acute ethanol administration. Taken together with our previously reported data on ethanol-induced electrophysiological changes in selectively bred lines, the results described here strongly support the hypothesis that the cerebellar Purkinje neuron is one important locus for the acute soporific effects of alcohol.

Comparison of parent-offspring resemblance for specific cognitive abilities.

A battery of cognitive ability tests identical to that used in the Hawaii Family Study was administered to a set of Caucasian families who participated in the Boulder Family Study. Resemblances between parents and offspring were compared with those from the Hawaii, Korean, and other recent family studies, using the same cognitive tests. Estimates from these studies indicate that values for parent-offspring resemblance are nonzero and fall around the midrange of possible values.

Modification of response of mouse neuroblastoma cells in culture by serum type.

The effect of various types of serum on morphological and biochemical changes in mouse neuroblastoma cells (clone NBP2) in culture was studied. The extent of spontaneous morphological differentiation varied markedly depending upon the type of serum and was maximal in agammaglobulin calf serum (CS). The extent of morphological differentiation after treatment of cells with cyclic AMP-stimulating agents was also dependent upon serum type and was least pronounced in fetal calf serum. The doubling time and extent of clumping varied with the type of serum. The activity of tyrosine hydroxylase (TH) in NB cells was dependent upon serum type and it was highest in newborn CS and agammaglobulin CS. Although elevation of intracellular levels of cyclic AMP in NBP2 clone invariably stimulates neurite formation and TH activity, these functions were increased in certain sera without a significant increase in the cellular cyclic AMP levels. The present study shows that neurite formation, growth rate and TH activity are regulated by more than one mode, one of which is mediated by cyclic AMP. The above changes are independently regulated in the sense that the expression of one can be increased in the absence of others.

Response to Selection for Mating Speed and Changes in Gene Arrangement Frequencies in Descendants from a Single Population of DROSOPHILA PSEUDOOBSCURA.

Heritability estimates, based on 19 generations of selection for fast and slow mating speed, were not significantly different from zero at the 0.05 level in any replicate of selected lines in a population of flies descended from the Mather population in California. Only the combined heritability estimate of approximately 2% was significant. This indicated that very little additive genetic variance was present in the base population and that strong directional selection for rapid mating may have occurred in the previous history of the local population at Mather and/or during its many generations of laboratory propagation. Frequencies of third chromosome gene arrangements were monitored during the course of selection. Balancing selection, unrelated to that imposed for mating speed, and genetic drift appeared to be the major factors causing changes in chromosome frequencies. Present differences in adaptive value of third chromosome variants in nature may be associated with nonadditive effects on mating speed, as well as effects on other components of fitness.

Assortative marriage for cognitive abilities.

One hundred and twenty-three spouse pairs gathered as part of a family study of the genetics of special abilities were examined on a battery of ability tests. Four principal components were interpreted after rotation: Spatial, Verbal, Perceptual Speed, and Memory. In addition, the first factor from a common factor analysis (unrotated) was taken as an estimate of g. Assortive marriage was measured by the spouse correlations on the test and factor scores. Three multiple regression models were designed to determine whether phenotypic convergence during marriage occurs and whether resemblance between spouses in cognitive ability is related to fertility. The following independent variables were partialed out in the models: (1) sex and age; (2) sex, age, and length of marriage; and (3) sex, age, and number of children. Model 1 (age and sex) accounted for part of the correlation between spouses on the spatial tests, the verbal tests and the spatial and general factors. The perceptual speed and memory tests and factors were largely unaffected by partialing out the independent variables. No evidence of phenotypic convergence over years of marriage or of a relationship between fertility and resemblance in abilities was found.