Microsatellite analysis of genetic diversity and population structure of Chinese mitten crab （Eriocheir sinensis）

Chinese mitten crab (Eriocheir sinensis) has higher commercial value as food source than any other species of Eriocheir in China.To evaluate the germplasm resources and characterize the genetic diversity and population structure of the crabs in different water systems,two stocks and two farming populations were assessed with 25 polymorphic microsallite loci available in public GenBank.Basic statistics showed that the average observed heterozygosity (Ho) amongst populations ranged from 0.5789 to 0.6824.However,a remarkable presence of inbreeding and heterozygote deficiencies were observed.To analyze population structure,pairwise FST coefficients explained only ～10.3% variability from the subdivision of mitten crab populations,the remaining variability stems from the subdivision within subpopulations.Although the four populations had slight differentiation,different allelic frequencies resulted in distinct population structures.Two stocks and one farming population were clustered together to the phylogenetic branch of Yangtze crab,with an approximate membership of 95%.Whereas,another fanning population was clustered singly to the phylogenetic branch of the Liaohe crab,with a membership of 97.1%.The tests for individual admixture showed that Yangtze crab had probably been contaminated with individuals from other water systems.Genetic relationships between populations also supported the conclusion that Yangtze crab and Liaohe crab had different gene pools in spite of the origins of the same species.     

Microsatellite analysis of variation among wild,domesticated,and genetically improved populations of blunt snout bream(Megalobrama amblycephala)

In the present study,the genetic diversity of one selected strain(Pujiang No.1),two domesticated populations(GA and HX)and four wild populations(LZ,YN,SS and JL)of blunt snout bream(Megalobrama amblycephala)was analyzed using 17microsatellite markers.The results showed that an average of 4.88-7.65 number of alleles(A);an average of 3.20-5.33 effective alleles(Ne);average observed heterozygosity(Ho)of 0.6985-0.9044;average expected heterozygosity(He)of 0.6501-0.7805;and the average polymorphism information content(PIC)at 0.5706-0.7226.Pairwise FST value between populations ranged from0.0307-0.1451,and Nei’s standard genetic distance between populations was 0.0938-0.4524.The expected heterozygosities in the domesticated populations(GA and HX)were significantly lower than those found in three wild populations(LZ,SS and JL),but no difference was detected when compared with the wild YN population.Likewise,no difference was found between the four wild populations or two domesticated populations.The expected heterozygosity in Pujiang No.1 was higher than the two domesticated populations and lower than the four wild populations.Regarding pairwise FST value between populations,permutation test P-values were significant between the GA,HX and PJ populations,but not between the four wild populations.These results showed that the expected heterozygosity in the selected strain of blunt snout bream,after seven generations of selective breeding,was lower than that of wild populations,but this strain retains higher levels of genetic diversity than domesticated populations.The genetic differences and differentiation amongst wild populations,domesticated populations and the genetically improved strain of blunt snout bream will provide important conservation criteria and guide the utilization of germplasm resources.     

Additive and Over-dominant Effects Resulting from Epistatic Loci Are the Primary Genetic Basis of Heterosis in Rice

A set of 148 F9 recombinant inbred lines （RILs） was developed from the cross of an indica cultivar 93-11 and japonica cultivar DTI13, showing strong F1 heterosis. Subsequently, two backcross F1 （BCFI） populations were constructed by backcrossing these 148 RILs to two parents, 93-11 and DT713. These three related populations （281BCF1 lines, 148 RILs） were phenotyped for six yield-related traits in two locations. Significant inbreeding depression was detected in the population of RILS and a high level of heterosis was observed in the two BCF1 populations. A total of 42 main-effect quantitative trait loci （M-QTLs） and 109 epistatic effect QTL pairs （E-QTLs） were detected in the three related populations using the mixed model approach. By comparing the genetic effects of these QTLs detected in the RILs, BCF1 performance and mid-parental heterosis （HMp）, we found that, in both BCF1 populations, the QTLs detected could be classified into two predominant types： additive and over-dominant loci, which indicated that the additive and over-dominant effect were more important than complete or partially dominance for M-QTLs and E-QTLs. Further, we found that the E-QTLs detected collectively explained a larger portion of the total phenotypic variation than the M-QTLs in both RILs and BCF1 populations. All of these results suggest that additive and over-dominance resulting from epistatic loci might be the primary genetic basis of heterosis in rice.     

Genetic Variation and Clonal Diversity of the Two Divergent Types of Clonal Populations of Leymus chinensis Tzvel on the Song Liao Steppe in the West of Northeastern China

The genetic variation and clonal diversity of two divergent types (grey-green and yellow-green) of clonal populations of Leymus chinensis Tzvel at 14 loci were compared. Total gene diversity (HT) and the coefficient of genetic differentiation (GST) were all higher for the yellow-green type (HT = 0.270; GST =0.186) than for the grey-green type (HT = 0.250; GST = 0.157) of L. chinensis. Rare alleles usually occurred as heterozygotes rather than homozygotes and significant deviations from Hardy-Weinberg equilibrium were found only at a few loci. This indicated that these two types of populations were mainly out-crossing. Clonal diversity, evenness of clones, and mean clone size were not significantly different between the two types. We found that differences between the clone size and genetic variation of the yellow-green type of populations occurred with different climate and habitat population groups. However, for the grey-green type of populations, these genetic variations decreased under conditions of different climate and habitat population groups.     

Aphid populations showing differential levels of virulence on Capsicum accessions

The green peach aphid,Myzus persicae,is one of the most threatening pests in pepper cultivation and growers would benefit from resistant varietices.Previously,we identified two Capsicum acessions as susceptible and three as resistant to M.persicae using an aphid population originating from the Netherlands(NL).Later on we identified an aphid population originating from a diferent gcographical region(Switserland,SW)that was virulent on all tested Capsicum acessions.The objeetive of the current work is to describe in detail diferent aspects of the interaction between two aphid populations and two sclected Capsicum acessions(one that was susceptible[PB2013046]and one that was resistant[PB2013071]to population NL),including biochemical processes involved.Electrical penetration graph(EPG)recordings showed similar feeding activities for both aphid populations on PB2013046.On acession PB2013071 the aphid population sw was able to devote significantly more time to phloem ingestion than population NL.We also studied plant defense response and found that plants of acession PB2013046 could not induce an accumulation of reactive oxygen species and callose formation after infestation with either aphid population.However,plants of PB2013071 induced a stronger defense response after infestation by population NL than after infestation by population SW.Based on these results,population SW of M.persicae seems to have overcome the resistance of PB2013071 that prevented feeding of aphids from NL population.The potential mechanism by which SW population overcomes the resistance is discussed.     

The Statistical Power of Inclusive Composite Interval Mapping in Detecting Digenic Epistasis Showing Common F2 Segregation Ratios

Epistasis is a commonly observed genetic phenomenon and an important source of variation of complex traits,which could maintain additive variance and therefore assure the long-term genetic gain in breeding.Inclusive composite interval mapping（ICIM） is able to identify epistatic quantitative trait loci（QTLs） no matter whether the two interacting QTLs have any additive effects.In this article,we conducted a simulation study to evaluate detection power and false discovery rate（FDR） of ICIM epistatic mapping,by considering F₂ and doubled haploid（DH） populations,different F₂ segregation ratios and population sizes.Results indicated that estimations of QTL locations and effects were unbiased,and the detection power of epistatic mapping was largely affected by population size,heritability of epistasis,and the amount and distribution of genetic effects.When the same likelihood of odd（LOD） threshold was used,detection power of QTL was higher in F₂ population than power in DH population;meanwhile FDR in F₂ was also higher than that in DH.The increase of marker density from 10 cM to 5 cM led to similar detection power but higher FDR.In simulated populations,ICIM achieved better mapping results than multiple interval mapping（MIM） in estimation of QTL positions and effect.At the end,we gave epistatic mapping results of ICIM in one actual population in rice（Oryza sativa L.）.     

Elevation-related variation in the population characteristics of distylous Primula nivalis affects female fitness and inbreeding depression

The population characteristics of distylous species are highly sensitive to stochastic natural selection pressure.Therefore,populations growing under different environmental conditions may vary in floral morph ratios,potentially affecting female fitness and leading to inbreeding depression.However,the variation in offspring quality among populations as a result of inbreeding depression is poorly understood in distylous species.This study investigates variations in plant density,seed mass,seed viabilityfemale fitness,and post-dispersal inbreeding depression in both sexual morphs(long-styled and shortstyled plants)of the distylous Primula nivalis that were subjected to different pollination treatments along an elevational gradient from 1657 to 2704 m a.s.l.Population characteristics(morph plant density and ratio)and fruit set were significantly affected by sexual morph and elevation.Plant density and fruitset frequencies were lower for short-styled than for long-styled plants at 2704 m a.s.l.The seeds from the cross-pollinated flowers of both morphs were higher in quality than those of self-pollinated flowers.The female fitness of seeds from cross-pollinated flowers of both morphs was higher than that of seeds from open-pollinated and self-pollinated flowers.The female fitness of seeds from long-styled flowers was higher than that of seeds from short-styled flowers at all elevations.Inbreeding depression increased with elevation among plants with short-styled flowers but not among those with long-styled flowers.Variation in the elevation-dependent mating system might influence female fitness and affect inbreeding depression in both floral morphs.In conclusion,the low quality of seeds from short-styled flowers at high elevations might decrease short-styled flower frequency,affecting population characteristics.     

Analysis of genetic diversity in the endangered Hucho taimen from China

Hucho taimen are listed as endangered in China. The population size has declined recently, prompting an increase in the level of listing from grade three in 2002 to grade five in 2006. We analyzed the genetic diversity of wild populations using 17 microsatellite markers to establish a scientific basis for conservation of this species. We collected tissue samples from four populations in the Heilongjiang River basin: Huma River (HM), Hutou (HT), Haiqing (HQ), and Zhuaji (ZJ). A total of 21 loci were amplified, 18 of which were polymorphic. The number of alleles per locus ranged from 2 to 9 (mean: 4.1905). There were 13 highly polymorphic loci and 5 moderately polymorphic loci. Analysis of five genetic diversity parameters (Na, Ne, Ho, He, and PIC) suggested moderate levels of diversity within the populations. The populations were ranked HT > HQ > ZJ > HM, but the differences in diversity were not statistically significant (P > 0.05). A comparison of variation among all four populations suggested Hardy–Weinberg disequilibrium at 20% of the loci. Genetic differentiation (Fst) was 0.0644 and the gene flow among populations was estimated at 3.36 individuals per generation. The majority of diversity (93.88%) occurred among individuals within a population. In contrast, relatively little (6.12%) of the genetic diversity was distributed between the populations. An analysis of genetic differentiation and genetic distance between pairs of populations revealed that both parameters were higher in comparisons of the HM population to the HT, HQ, and ZJ populations than among the three latter populations. This suggests that the HM population has a distinct genetic structure. We hypothesize that habitat degradation and excessive fishing, not low genetic diversity, has caused the decline in H. taimen populations. However, this species should be protected from further declines in genetic diversity.     

Analysis of genetic diversity in the endangered Hucho taimen from China

Hucho taimen are listed as endangered in China. The population size has declined recently, prompting an increase in the level of listing from grade three in 2002 to grade five in 2006. We analyzed the genetic diversity of wild populations using 17 microsatellite markers to establish a scientific basis for conservation of this species. We collected tissue samples from four populations in the Heilongjiang River basin: Huma River (HM), Hutou (HT), Haiqing (HQ), and Zhuaji (ZJ). A total of 21 loci were amplified, 18 of which were polymorphic. The number of alleles per locus ranged from 2 to 9 (mean: 4.1905). There were 13 highly polymorphic loci and 5 moderately polymorphic loci. Analysis of five genetic diversity parameters (Na, Ne, Ho, He, and PIC) suggested moderate levels of diversity within the populations. The populations were ranked HT > HQ > ZJ > HM, but the differences in diversity were not statistically significant (P > 0.05). A comparison of variation among all four populations suggested Hardy–Weinberg disequilibrium at 20% of the loci. Genetic differentiation (Fst) was 0.0644 and the gene flow among populations was estimated at 3.36 individuals per generation. The majority of diversity (93.88%) occurred among individuals within a population. In contrast, relatively little (6.12%) of the genetic diversity was distributed between the populations. An analysis of genetic differentiation and genetic distance between pairs of populations revealed that both parameters were higher in comparisons of the HM population to the HT, HQ, and ZJ populations than among the three latter populations. This suggests that the HM population has a distinct genetic structure. We hypothesize that habitat degradation and excessive fishing, not low genetic diversity, has caused the decline in H. taimen populations. However, this species should be protected from further declines in genetic diversity.     

Differences of Cu uptake and acid phosphatase activities of two Elsholtzia haichowensis Sun populations

Two Elsholtzia haichowensis Sun populations, one from Cu mine sites (Tonglushan) and the other from uncontaminated sites (Hong'an) in Hubei Province, China, were investigated in hydroponic experiments for the differences of Cu accumulation and ecophysiological responses to Cu under Cu treatment. The results showed that a significant increase in malondialdehyde (MDA) concentration in roots was observed in Hong'an population, whereas no significant change was observed in Tonglushan population. The root pressure exudates (ml) decreased significantly in Hong'an population, but increased significantly in Tonglushan population at high Cu concentration (≥ 20 μ mol/L) treatment. Cu concentration in roots of Hong'an population was significantly higher than that in Tonglushan population. For example, Cu concentration in Hong'an population was 3 times and 4 times higher than that in Tonglushan population after 20 μ mol/L Cu treatment for one day and three days, respectively. Cu concentration in Hong'an population was 20 times and 5 times higher than that in Tonglushan population after 80 μ mol/L Cu treatment for one day and three days, respectively. The intracellular and secreted acid phosphatase (APase) activities in roots were significantly higher in Tonglushan population than in Hong'an one. The intracellular APase activities in Tonglushan population were 3 times higher than those in Hong'an population after 80 μ mol/L Cu treatment for three days and five days, respectively. The root-secreted APase activities in Tonglushan population were 1.6 times and 1.8 times higher than those in Hong'an population after 80 μ mol/L Cu treatment for three days and five days, respectively. In conclusion, excessive Cu caused serious oxidative damage in roots of Hong'an population, but not in Tonglushan population. The high intracellular and root-excreted APase activities in Tonglushan population might play an important role in reducing Cu accumulation in roots and maintaining normal phosphorus physiological metabolism in root cells under Cu stress.     

中华稻蝗两地理种群酯酶特性的比较研究

对采自江苏徐州和山西临猗两个种群中华稻蝗进行了马拉硫磷敏感性的生物测定,同时对两个种群的酯酶特性进行了比较研究。生物测定结果表明,徐州种群的LD₅₀值（13.00 μg/g虫重）是临猗种群（4.64 μg/g虫重）的2.8倍;用对氧磷、马拉氧磷、西维因及毒扁豆碱等四种抑制剂对该两个种群的酯酶的体外抑制研究表明,两个种群所含酯酶大都为B型酯酶;酯酶动力学研究结果表明,徐州种群动力学参数米氏常数（K_m值）和最大反应速度（V_max值）均较临猗种群为高;用α-乙酸萘酯（α-NA）、α-丁酸萘酯（α-NB）和β-乙酸萘酯（β-NA）三种底物测定酯酶活性,在雌性稻蝗中,徐州种群比临猗种群分别高2.02、1.58和1.28倍,雄性中则分别高2.71、1.67和1.33倍;对两个种群酯酶活性频率分布进行比较,徐州种群中酯酶活性高的个体数远大于临猗种群。我们推测徐州种群酯酶的生化特性可能不同于临猗种群,这可能与地理分布、生态环境和食物条件不同有关,杀虫剂选择压力不同可能也起一定的作用。     

Comparisons of malathion susceptibility, target sensitivity, and detoxification enzyme activity in nine field populations of Oxya chinensis (Orthoptera: Acrididae)

The malathion susceptibility, acetylcholinesterase (AChE) sensitivity, and the activity of selected detoxification enzymes including general esterase (EST) and glutathione S-transferase (GST) were compared among field populations of the grasshopper Oxya chinensis (Thunberg) (Orthoptera: Acrididae) collected from nine regions of China. Bioassay results showed that these populations had various levels of the susceptibility to malathion with the LDo values ranging from 1.4- to 22.6-fold compared with the most susceptible population (Xiangyuan or XY). The Jinnan (JN) population seemed to be malathion resistant (22.6-fold), whereas other populations exhibited 1.4- to 6.8-fold reduced malathion susceptibility with a rank order of Changan > Baodi > Hanzhong > Xinxiang > Yinchuan > Beidagang > Jinyuan. It seemed that the observed malathion resistance in the JN population was attributed to at least two resistance mechanisms, including increased EST activity (2.2-fold) and reduced sensitivity of AChE to inhibition by malaoxon (4.6-fold) compared with those of the XY population. In contrast, differential malathion susceptibilities in other populations may be due to increased activities of certain detoxification enzymes (e.g., EST and GST), reduced sensitivity of AChE, or other factors, which were not consistent across the populations examined. Such differential susceptibilities to malathion were likely due to different population habitats (e.g., grasslands, rice [Oryza sativa L.]-producing regions) with very different insecticide application histories and pest management practices.     

The populations, characterization and activity of suspended bacteria in the Welsh River Dee

In a 29 month study of bacterial populations at three sites on the Welsh River Dee, the aerobic heterotrophic bacteria increased from an average basal level of about 1.2 times 10⁴ colony-forming units (cfu)/ml near the source of the river, to 2 times 10⁵ cfu/ml in the lower reaches. The ratio, total bacterial cell count: viable count, decreased from 70 in the upland reaches to 10 in the lower parts of the river. There was no apparent seasonal variation in bacterial numbers but on occasions the bacterial populations in both upland and lowland reaches of the river increased simultaneously. Fluctuations in bacterial numbers over a 50-fold range were observed in this study. Bacterial isolates from both upland and lowland sites were predominated by two groupings of bacteria, the Pseudomonas—Agrobacterium—Alcaligenes group and the Flavobacterium—Cytophaga—Flexibacter group. Results suggested that the latter group may have been part of the autochthonous population. Seasonal variation in heterotrophic potential ( V _max) for acetate uptake was shown to occur over a 30-fold range in the lowland reaches of the River Dee. Peaks in activity at the lowland site occurred during the summer months, the range of V _max values for acetate ranged from 0.2 to 30 μg/1/h. Fluctuations in V _max values from the upland site were not seasonal but were instead linked to faecal pollution, V _max values from this site range from 0.04 to 3 μg/1/h.     

INSECTICIDE RESISTANCE OF COTTON APHID IN NORTH CHINA

Abstract  The cotton aphid ( Aphis gossypii Glover) is one of the most important pests infesting cotton in the cotton areas of North China. Since 1953 organophosphorus insecticides such as parathion and systox have been used to control the aphids for keeping up good yield of cotton. After several years. the concentration and the amount of spray were increasing in the field. In the early 1980's highly effective pyrethroid insecticides such as decis and sumicidin were largely imported into China. When first used 2. 5% decis emulsion was diluted in the ratio from 1:10000 to 1: 12000. However in 1985 the resistance of cotton aphid to pyrethroids increased by 171 times in general, 3230 times in some cotton fields. Thus it has prompted us to investigate the mechanism of resistance to insecticides and to search for the strategy to control the resistant aphids.
Experiments showed that the use of synergists including SV₁ (O, O-diethyl, O-phenyl phos-phorothionate) and PB has given evidence indicating mixed function oxidases (MFO). α-NA esterases and α-NA carboxylesterase are involved in the formation of resistance. The results also showed that the sensitivity of AChE to paraoxon in resistant aphids was lower than that in susceptible aphids.
Experiments showed that SV₁ was particularly synergistic to organophosphorus or pyrethroid insecticides and had played an excellent role in overcoming the resistance of cotton aphids to insecticides.     

Identification of two Lynx proteins in Nilaparvata lugens and the modulation on insect nicotinic acetylcholine receptors

Nicotinic acetylcholine receptors (nAChRs) mediate fast cholinergic synaptic transmission in the insect brain and are targets for neonicotinoid insecticides. Some proteins, other than nAChRs themselves, might play important roles in insect nAChRs function in vivo and in vitro , such as the chaperone, regulator and modulator. Here we report the identification of two nAChR modulators (Nl-lynx1 and Nl-lynx2) in the brown planthopper, Nilaparvata lugens . Analysis of amino acid sequences of Nl-lynx1 and Nl-lynx2 reveals that they are two members of the Ly-6/neurotoxin superfamily, with a cysteine-rich consensus signature motif. Nl-lynx1 and Nl-lynx2 only increased agonist-evoked macroscopic currents of hybrid receptors Nlα1/β2 expressed in Xenopus oocytes, but not change the agonist sensitivity and desensitization properties. For example, Nl-lynx1 increased I _max of acetylcholine and imidacloprid to 3.56-fold and 1.72-fold of that of Nlα1/β2 alone, and these folds for Nl-lynx2 were 3.25 and 1.51. When the previously identified Nlα1^Y151S mutation was included (Nlα1^Y151S/β2), the effects of Nl-lynx1 and Nl-lynx2 on imidacloprid responses, but not acetylcholine response, were different from that in Nlα1/β2. The increased folds in imidacloprid responses by Nl-lynx1 and Nl-lynx2 were much higher in Nlα1^Y151S/β2 (3.25-fold and 2.86-fold) than in Nlα1/β2 (1.72-fold and 1.51-fold), which indicated Nl-lynx1 and Nl-lynx2 might also serve as an influencing factor in target-site insensitivity in N. lugens . These findings indicate that nAChRs chaperone, regulator and modulator may be of importance in assessing the likely impact of the target-site mutations such as Y151S upon neonicotinoid insecticide resistance.     

Effect of glutamate intake during gestation on adenosine A(1) receptor/adenylyl cyclase pathway in both maternal and fetal rat brain

Pregnant Wistar rats were orally treated with 1 g/L l -glutamate during the entire gestational period and the status of adenosine A₁ receptor (A₁R)/adenylyl cyclase transduction pathway from maternal and fetal brain was analyzed. Glutamate consumption, estimated from the loss of water from the drinking bottles, was 110 ± 4.6 mg/kg/day. In mother brains glutamate intake did not significantly alter the B _max value, although the K _d value was significantly decreased. However in fetus brain, a significant decrease in B _max was observed, without an alteration of K _d value. Similar results were observed by western blot assays using specific A₁R antibody, suggesting a down-regulation of A₁R in fetal brain. Concerning α subunits of inhibitory G proteins (Gi), αGi₃ protein was slightly but significantly decreased in maternal brain without alterations of either Gi₁ or Gi₂. In contrast, αGi₁ and αGi₂ isoforms were increased in fetal brain. On the other hand, basal, forskolin, and forskolin plus GTPγS-stimulated adenylyl cyclase activity was significantly decreased in both maternal and fetal brain, and this was more prominent in fetal than in maternal brain. Finally, A₁R functionality was significantly decreased in mother brain whereas no significant differences were detected in fetus brain. These results suggest that glutamate administered to pregnant rats modulates A₁R signaling pathways in both tissues, showing an A₁R down-regulation in fetal brain, and desensitization in maternal brain.     

Anaerobic degradation of 3,4,5-trimethoxybenzoate by a defined mixed culture of Acetobacterium woodii, Pelobacter acidigallici, and Desulfobacter postgatei

Abstract Acetobacterium woodii was continuously grown on 3,4,5-trimethoxybenzoate as pure culture or in commensalistic combination with Pelobacter acidigallici and Desulfobacter postgatei . Under pure culture conditions the following growth parameters were determined: μ _max= 0.112 h⁻¹, K _s= 1.07 mM, Y _max= 35 g/mol, and m = 0.22 mmol·g⁻¹·h⁻¹. In coculture with P. acidigallici the affinity for the substrate increased and the K _s value was found to be 135 μM. Under batch culture conditions mixed populations of A. woodii, P. acidigallici , and D. postgatei completely mineralized 3,4,5-trimethoxybenzoate to CO₂, whereas under continuous culture conditions more than 3 mM acetate remained unused.     

Coupling of the Human Y2 Receptor for Neuropeptide Y and Peptide YY to Guanine Nucleotide Inhibitory Proteins in Permeabilized SMS-KAN Cells

Abstract: Using guanine nucleotides, pertussis toxin, and specific antisera against the COOH-terminals of the α-subunits of G_i1/2, G_i3, and G_o, the binding and biological response of the Y2 receptor (Y2R) for peptide YY (PYY) was probed in SMS-KAN neuroblastoma cells. The specific binding of radiolabeled PYY exhibited a single apparent dissociation constant, K _D = 76 p M for intact cells and K _D = 906 p M for permeabilized cells. However, other data suggested existence of multiple receptor affinity states. A shift in K _D and a decrease in apparent number of binding sites ( B _max) was observed in permeabilized cells when incubated with guanine nucleotides. By contrast, in membrane preparations guanine nucleotides induced only a decrease in B _max. In intact cells, agonist exposure inhibited the intracellular accumulation of forskolin-stimulated cyclic AMP by 80% (IC₅₀ = 420 n M ) compared with 94% inhibition (IC₅₀ = 380 n M ) in permeabilized cells. In permeabilized cells, preincubation with antisera against α_i1/2 and α_i3 blocked the functional response of PYY, with anti-α_i3 being the most potent; whereas anti-α_o failed to affect the cyclic AMP levels. These results suggest that permeabilized SMS-KAN cells serve as a good model system for analysis of Y2R binding kinetics and functional response and that the Y2R interacts directly with several different G_is (but not G_o).