Diabetes mellitus and impaired fasting glucose in Alaska Eskimos: the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study.

AIMS/HYPOTHESIS: We aimed to: (1) define the prevalence of type 2 diabetes and IFG in Eskimos in Norton Sound, Alaska; (2) determine correlates of prevalent diabetes in this population; and (3) compare the prevalence of diabetes in the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) Study with other samples of Eskimos, Inuit, American Indians and US blacks, whites and Mexican Americans. METHODS: The GOCADAN Study enrolled 1,214 participants >or=18 years who were members of extended pedigrees from the Norton Sound region of Alaska. Diagnosed type 2 diabetes was based on reported use of insulin or hypoglycaemic medications and a medication inventory. Fasting glucose measurements were obtained to ascertain IFG status and undiagnosed diabetes according to American Diabetes Association (ADA) criteria. OGTTs were performed to ascertain diabetes according to the World Health Organization (WHO) definition. We used logistic regression analysis to model factors that were significantly associated with odds of prevalent ADA diabetes. RESULTS: The prevalences of ADA diabetes and IFG were 3.8% (5.0% of women; 2.2% of men) and 15.6% (13.9% of women; 17.7% of men), respectively. In the subset of 787 participants who took the OGTT, the prevalences of ADA and WHO diabetes were 5.1 and 6.9%, respectively. The adjusted odds of ADA diabetes was 2.8 times higher in participants meeting Adult Treatment Panel III criteria for abdominal obesity than in those who did not. The statistically significant sex-related difference in diabetes prevalence did not persist in multivariable analyses. CONCLUSIONS/INTERPRETATION: Alaska Eskimos have a low prevalence of type 2 diabetes. The high prevalence of IFG indicates that diabetes may become increasingly problematic in this population. Abdominal obesity in women may help explain why diabetes prevalence differs according to sex.

Overweight and obesity among Alaskan Eskimos of the Bering Straits Region: the Alaska Siberia project.

OBJECTIVE: To document the height, weight, BMI and prevalence of obesity for Eskimo residents of four villages of the Bering Straits Region of Alaska. DESIGN AND SUBJECTS: 454 Non-pregnant residents over 24 y of age, with at least one Eskimo grandparent participated in one cross sectional survey within each village. MEASUREMENTS: Height, weight, calculation of BMI (kg/m2), proportion of 'overweight' (BMI 25-29.9), and proportion of 'obese' (BMI>/=30). RESULTS: For women and men, respectively, mean heights were 153.4 and 165.2 cm; weights were 64.2 and 71.6 kg; and BMI were 27.2 and 26.2 kg/m2 after age standardization. For women, 27.9% were overweight, and 32.8% were obese compared with 36.2% and 15.6%, respectively, for men. Alaskan Eskimo participants of the Alaska Siberia Project had a significantly lower proportion of total overweight (BMI>/=25, 54.9% for women, and 32.0% for men) compared with the three sites of the Strong Heart Study, which ranged from 65.9 to 80.2% for women and 53.6 to 66.7% for men. Compared with American men of all races, the proportion of overweight and obese participants was similar for Eskimo men. The proportion of obese was significantly higher for Eskimo women compared with American women of all races, but the proportion of overweight was similar. CONCLUSION: Although the prevalence of obesity among the Alaskan Eskimos is lower than for American Indians, the high proportion of overweight observed in this study is of concern for Alaskan Eskimo adults, especially for women.

Body fat distribution in Alaskan Eskimos of the Bering Straits region: the Alaskan Siberia Project.

OBJECTIVE: To describe the body fat content and distribution of adult Alaska Natives of the Bering Straits Region. DESIGN: Cross-sectional screening in the spring of 1994. SUBJECTS: 454 non-pregnant native residents from four rural Alaskan villages. MEASUREMENTS: Height, weight, waist, hip and thigh circumference, bioelectrical impedance, sagittal abdominal diameter, and triceps, biceps, suprailiac, subscapular and thigh skinfolds. RESULTS: Mean height, weight and subscapular-to-triceps ratio were higher in men than women. The women had larger waist, hip and thigh circumferences, higher body fatness, as well as larger skinfolds than the men. There were no demonstrable differences between men and women in measures of body fat distribution. The proportions of women and men with high waist-to-hip ratio (>/=0.8 for women, >/=0.9 for men) for low (<25 kg/m2), medium (25-30 kg/m2) and high (>30 kg/m2) body mass index (BMI) groups were compared with a Canadian study of all races. 1 In the lowest BMI subgroup (<25 kg/m2) a much higher proportion of Eskimo women exhibited a high waist-to-hip ratio (91%) than Eskimo men (42%) or Canadian women (29%) or men (51%). In the highest BMI subgroup (>30 kg/m2) Eskimo women were similar in proportion of high waist-to-hip ratio (99%) compared to Eskimo men (100%), but still demonstrated a much greater proportion of subjects with high waist-to-hip ratio than either Canadian men (90%) or women (76%). CONCLUSIONS: The large abdominal fat depots found in Eskimo women were similar to men, and may indicate that future increases in diabetes mellitus and other metabolic alterations can be anticipated. International Journal of Obesity (2000) 24, 171-179

Diabetes is related to fatty acid imbalance in Eskimos.

The reasons for the rapidly increasing prevalence of diabetes (NIDDM) among Alaskan Eskimos are only partly understood. This study examines the association of fatty acid metabolism in 68 Alaskan Eskimos with NIDDM or impaired glucose tolerance (IGT) and 386 with normal glucose tolerance > 24 years old. The prevalence of NIDDM was 12% and IGT was 18% in those > 54 years of age and in those < 55 years of age was 3.7% and 3.0%, respectively. Those with abnormal glucose tolerance had lower concentrations of some omega-3 fatty acids (FAs 18:3 omega-3, 20:5 omega-3) and some omega-6 FAs (18:3 omega-6, 20:3 omega-6, 22:4 omega-6) and higher concentrations of palmitic acid (16:0) and oleic acid (18:1 omega-9) than the normo-glycemic participants. These data provide evidence that glucose intolerance and insulin resistance are associated with a deviation from a traditional diet of fish and marine mammals (high in omega-3 FAs and low in saturated fats) to commercial foods (low in omega-3 FAs and high in saturated fats). The low plasma concentrations of the long-chain omega-6 FAs in the glucose impaired may reflect a defect in desaturase activity.

Associations between dietary factors and plasma lipids related to cardiovascular disease among Siberian Yupiks of Alaska.

The diet of northern Native people has been postulated to protect against cardiovascular disease. We asked whether nutrient and food intakes of Eskimos were correlated with their plasma cholesterol, LDL, HDL, triglycerides and LDL-HDL ratio. Frequency of consumption of 91 foods among 64 Siberian Yupik adults was measured during home-based interviews. Intake of monounsaturated fat by men was negatively correlated with LDL. Foods and nutrients that contribute to the LDL-HDL ratio explained 42% of its variation among all subjects. Inclusion of the body mass index (BMI) explained 59% of the variation in the LDL-HDL ratio. Coefficients were negative for alpha-tocopherol, fresh bird, evaporated milk and cheese, and positive for BMI, syrup and pizza. BMI had a positive effect on the LDL-HDL ratio among younger adults, women and the entire sample, but did not contribute to explaining the variation among older adults or men. This emphasizes the importance of weight control among younger Siberian Yupik women. While coefficients were both positive and negative for traditional and western foods, the presence of traditional foods that were negatively correlated in the regression supports the hypothesis that consumption of traditional foods is important for maintaining cardiovascular health among Siberian Yupiks.

Low fasting insulin levels in Eskimos compared to American Indians: are Eskimos less insulin resistant?

The prevalence of diabetes is relatively low among Eskimo people in contrast to that in other Native American populations. The reasons for this may be partially explained by differences in the occurrence of insulin resistance. In this report we compare fasting insulin levels, which correlate with insulin resistance, in Alaskan Eskimo subjects to those among American Indians. After adjusting for age, gender, and body mass index, and using identical laboratory methods, we found significantly lower insulin levels among Eskimo compared with Indian participants with normal glucose tolerance. Among Eskimos insulin levels increased with increasing body mass index, were higher for women than men, and did not appreciably change with age. Our data suggest that among Eskimo people insulin resistance may be less prevalent or severe than among American Indians, but that obesity is associated with increased insulin resistance. Future analyses will examine the association between insulin levels and other correlates of the insulin resistance syndrome. We hope that by further characterizing insulin resistance or sensitivity among Eskimo people, specific recommendations can be made that will lead to cardiovascular risk factor reduction.

Dietary intakes among Siberian Yupiks of Alaska and implications for cardiovascular disease.

We describe dietary intake for 65 Siberian Yupik residents of Gambell, AK using 24-h recalls and annual food frequencies collected in October 1992. The objectives were to describe dietary characteristics important in risk of cardiovascular disease, determine the extent that their diet differs from the diet of general US and northern populations, assess how the diet met national guidelines for the prevention of cardiovascular disease, and propose dietary recommendations. Compared to US intakes in general (NHANES III), intakes of Siberian Yupiks expressed as percent of energy were: 8-10% higher in fat, 6% higher in protein, 5-7% higher in monounsaturated fats and 12-15% lower in carbohydrate. Energy from saturated and polyunsaturated fats was similar (11% and 8% respectively). Cholesterol intakes were not significantly different. Mean intakes of selenium, a-topocopherol, folacin (men), and vitamin C (men) met Recommended Dietary Allowances, which may contribute to cardiovascular health. Mean intake of n-3 fatty acids (7.0 g/d), twice the 3 g/d associated with favorable effects, was comparable with intake of Greenlandic Eskimos. Dietary risk factors included high intakes of % energy from fat and saturated fat, and low intakes of fiber. Native foods were important sources of monounsaturated fats, n-3 fatty acids and selenium.

Diabetes and impaired glucose tolerance in three Alaskan Eskimo populations. The Alaska-Siberia Project.

OBJECTIVE: The objectives of this study were to determine the prevalence of diabetes and impaired glucose tolerance (IGT) in three Alaskan Eskimo populations, using standardized diagnostic criteria, and to evaluate family history and obesity as risk factors. RESEARCH DESIGN AND METHODS: This cross-sectional study involved men and women > or = 25 years of age from three Eskimo ethnic groups (Siberian Yupik, Central Yupik, and Inupiat) residing in northwestern Alaska. Glucose tolerance status was defined by World Health Organization criteria and was based on a 75-g oral glucose tolerance test. Data on age, family history of diabetes, and degree of Eskimo ancestry were obtained from a personal interview. Obesity was assessed using BMI. RESULTS: A total of 454 of 899 (50.5%) eligible participants were examined for diabetic status (239 Siberian Yupik, 106 Central Yupik, and 109 Inupiat participants). The prevalence of diabetes was more than twice as high among the Siberian Yupik (9.6%) as among the Central Yupik (2.8%) and Inupiat participants (3.7%). Diabetes was more prevalent in women than men (8.8 vs. 4.2%). IGT was found in an additional 11.7% of the women and 4.7% of the men. The combined prevalence of diabetes and IGT in the population > or = 55 years of age was 30.4% (diabetes 12.0%, IGT 18.4%). Of the people identified with diabetes, 47% had not been previously diagnosed. Age-specific prevalences were similar to those found in U.S. whites in the National Health and Nutrition Examination Survey II. After adjustment for age, family history of diabetes was associated with diabetes in study participants with an odds ratio of 4.4, while obesity was associated with diabetes with an odds ratio of 2.6. CONCLUSIONS: These prevalences of diabetes are the highest yet reported among Eskimo populations. Obesity and family history of diabetes are associated with increased odds of developing diabetes. These data underscore the need to further examine risk factors and to design effective interventions.

Glucose tolerance and insulin-resistance syndrome among St. Lawrence Island Eskimos.

OBJECTIVES: Non-insulin-dependent diabetes mellitus (NIDDM) prevalence in Alaska Natives is rising but remains lower than the U.S. average. We conducted a screening study for diabetes mellitus and cardiovascular disease in a remote Yup'ik Eskimo community in Alaska. RESEARCH DESIGN AND METHODS: The study population included Siberian Yup'ik Eskimo residents of Gambell, Alaska, > or = age 40 years who underwent a 2 h 75 gm oral glucose tolerance test interpreted by WHO criteria. Other measurements included fasting serum insulin and lipid levels, bioimpedance body fat %, body-mass-index (BMI), waist-to-hip ratio (WHR), and blood pressure. RESULTS: Of 114 eligible subjects, 65 (57%) participated. These subjects had lower mean systolic or diastolic blood pressure, lower triglyceride, and higher mean HDL cholesterol levels compared to a similarly aged U.S. all races sample. The mean fasting insulin level of 50.9 pmol/L appeared low given the high mean BMI (27.2). Six subjects had NIDDM (9%, 95% CI 2%-16%) and eight had impaired glucose tolerance (IGT) (12%, 95% CI 4%-20%). Compared to normoglycemic subjects, diabetic subjects were more frequently female (83% vs 53%) and had higher mean systolic BP (138 mm Hg vs 117 mm Hg) than normoglycemic subjects. We used multiple regression to analyze associations between fasting insulin and either blood pressure or serum lipids, while adjusting for % body fat, WHR, age, sex, and antihypertensive medication use. Fasting insulin was significantly related to both diastolic blood pressure (p = .0430) and fasting serum triglyceride (p = .0182) but not to systolic BP, total cholesterol, or LDL and HDL subfractions. CONCLUSIONS: Although NIDDM prevalence was not high compared to non-Native U.S. residents, elements of the insulin-resistance syndrome exist in this subarctic population.

The beta(3)-adrenergic receptor TRP64ARG polymorphism and obesity in Alaskan Eskimos.

OBJECTIVE: A polymorphism in the beta 3-adrenergic receptor (beta 3-AR) has been described and consists of an amino acid substitution at position 64 where tryptophan is replaced by arginine (Arg allele). This polymorphism appears to be a modest contributor to obesity and non-insulin dependent diabetes mellitus (NIDDM), and may be dependent on gender, gene dosage, ethnic background and environmental factors. We have investigated whether the Trp64Arg polymorphism of the beta 3-AR was associated with body mass index (BMI), blood pressure or the presence of NIDDM in Alaskan Eskimos. SUBJECTS: Two hundred and fifty four Alaskan Eskimos from two distinct villages (Inupiaq and Yupik). MEASUREMENTS: beta 3-AR genotypes were determined by polymerase chain reaction followed by enzymatic digestion. RESULTS: The frequency of the Arg allele in Alaskan Eskimos was 0.38 and represents the highest Arg allele frequency in any population reported to date. 13.8% of the population were homozygous for the Arg allele, 47.6% heterozygous, and 38.6% lacked the Arg allele. However, the Arg allele was not associated with BMI, blood pressure or the presence of NIDDM in Alaskan Eskimos. CONCLUSION: These data do not support a significant role for the beta-AR Arg allele as a marker for obesity (as measured by BMI) or the presence of NIDDM in Alaskan Eskimos. It is possible that other phenotypic variables, not yet available for analysis in this population, may be associated with the presence of the Arg allele

Transient alterations in neurotransmitter levels during a critical period of neural development in coho salmon (Oncorhyncus kisutch).

The time of parr-smolt transformation (PST) in salmon is a critical period of brain development during which the olfactory imprinting on the natal stream takes place. PST is associated with a surge of plasma thyroxine. We report here similar surges in the brain content of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA), norepinephrine (NE), and glutamine (Gln). Other putative neurotransmitters, such as glutamate and aspartate show no such change while gamma-amino-butyric acid (GABA) shows a minor elevation.

Lipoprotein profiles in Alaskan Siberian Yupik Eskimos.

Coronary heart disease and diabetes, once rare in Eskimos, is on the increase in some Alaskan communities. As part of a detailed assessment of the prevalence of these diseases and associated risk factors in several villages, we report here on the plasma concentrations of lipoprotein and apoprotein in a sample of Siberian Yupik Eskimos aged 40-87 years living in the village of Gambell on St. Lawrence Island. Mean cholesterol levels for females were 242 mg/dl and 223 for males. LDL levels were 161 for females and 149 for males, while HDL levels were 67 for females and 58 for males. The mean ApoB and Apo-A1 values were 112 mg/dl and 167 mg/dl for males and females. Triglycerides were 73 for females and 77 for males. The allele frequency of APOE*3 and APOE*4 were .900 and .100 respectively. There was a total absence of the APOE*2 allele in this sample. Mean total cholesterol concentrations in this sample were markedly higher than those reported in 1958 from this village and from those recently reported for closely related Yupik Eskimos living in Siberia. The cholesterol levels were higher and the triglyceride levels were lower than in U.S. Indian populations. The data suggest the possibility of recent increased risk of cardiovascular disease for this Eskimo population. The new information indicates a need for comprehensive epidemiological studies to identify and characterize cardiovascular disease risk factors in all Alaska Native populations in order to provide a database for meaningful interventions. The lipoprotein profiles reported here are significantly different from Amerind groups, a finding that may reflect both dietary and genetic differences.

Distribution and changes in mu- and kappa-opiate receptors during the midlife neurodevelopmental period of Coho salmon, Oncorhynchus kisutch.

Parr-smolt transformation (PST) in coho salmon is associated with a plasma thyroid hormone (PT4) surge and a critical period of neural development that includes axonal sprouting, neurogenesis, and surges of select neurotransmitters. Here we provide a description of the selectivity, distribution, and the changes in the density of mu- and kappa-opiate receptors during PST, as revealed by quantitative in vitro autoradiography of [3H]Tyr-D-Ala-Gly-NMe-Phe-Gly-ol ([3H]DAMGO) and [3H]ethylketocyclazocine ([3H]EKC), respectively. The concentration of mu-receptors increased significantly in select cell groups in the early stages of parr-smolt transformation, until a peak was reached at the time coinciding with the peak of the PT4 surge. In other cell groups, the peaks occurred 1 or 2 weeks later. With one exception, this increase was followed by a decrease in concentration. The brain areas showing the highest concentrations are the dorsal nucleus of the ventral telencephalic area, the glomerular region, the granular layer of the valvula cerebelli, the nucleus diffuses of the inferior lobe, and the nucleus diffuses of the torus lateralis. Other regions with distinctly elevated mu-receptor concentrations are the stratum griseum centrale of the optic tectum and the preoptic area. The distribution of kappa-receptors is more diffuse, and the densities are considerably lower. The overlap in distribution of mu- and kappa-receptors is considerable, but significant exceptions are noted. For example, the dorsomedial nucleus of the dorsal telencephalic area, the habenular nucleus, and the dorsomedial nucleus of the thalamus exhibit a surge in density of kappa-receptors at the time of the PT4 surge, while the density of mu-receptors in these nuclei remain very low throughout parr-smolt transformation. The kappa-receptor containing cell groups are not identifiable until 3 weeks before the PT4 surge because of low densities. The most prominently labeled kappa-receptor regions are the ventral and dorsal nuclei of the ventral telencephalic area, the medial and dorsal zones of the dorsal telencephalic area, the optic tectum (all layers), the dorsomedial nucleus of the thalamus, the torus lateralis of the ventral hypothalamus, and the preoptic area. An increase of mu- and kappa-opiate receptor densities in specific brain regions may reflect roles in the alteration of brain organization, olfactory imprinting, neuroendocrine activity or other physiological activities. The overall distribution of these receptors are relatively more extensive in salmon than in other vertebrates so far studied.

The accessory optic system in the frog, Rana Pipiens: an electron microscopic study of the retinal afferents utilizing the anterograde tracer biocytin.

The retinal afferents to the basal optic nucleus in the frog, Rana Pipiens, were labeled anterogradely with biocytin and subsequently studied at the electron microscopic level. Labeled synaptic terminals in the nucleus varied in size from 0.5 microns to 2.0 microns and made symmetric synaptic contacts with large and small dendrites, although very rare axospinous and axosomatic contacts were also demonstrated.

Hypertension and diabetes among Siberian Yupik Eskimos of St. Lawrence Island, Alaska.

CHANGING DIETS AND LIFESTYLES contribute to an increase in the prevalence of cardiovascular disease and diabetes in Alaska Natives. To examine the problem in detail, we have begun a systematic screening of various ethnic groups by carrying out a pilot study of Siberian Yupik Eskimos ages 39 and over. Mean LDL and HDL levels were 157 mg/dl and 63 mg/dl. Mean fasting insulin was 7.0 microunits/ml; and mean BMI, 27.1. Fasting insulin level was significantly related to both diastolic blood pressure and fasting triglyceride levels, but not to systolic blood pressure, total cholesterol, LDL cholesterol, or HDL cholesterol levels. Of the 66 people screened, 27% had evidence of hypertension.

Diurnal and seasonal variations of melatonin and serotonin in women with seasonal affective disorder.

In winters 1990-1991 and 1991-1992 women with and without seasonal affective disorder, winter type, were treated by light at 2500 lux either in the morning (0800h-1000h) or afternoon (1600h-1800h). In winter before light treatment, melatonin levels in serum in daytime (1200h and 1600h) were higher in patients compared to controls (p < 0.05). This difference disappeared in the summer or after light treatment in the winter. Also, light treatment and change in season resulted in a phase advance shift of melatonin rhythm in patients. The decline in melatonin levels correlated with the decline in specific SAD symptoms of hyperphagia and carbohydrate craving. In winter, neither patients nor controls showed significant diurnal variations in levels of whole blood serotonin. In both patients and controls, levels of serotonin were higher in summer as compared with winter, especially at 2000h. Our data suggest that elevated daytime melatonin can be a state marker of winter depression, and that seasonal change of photoperiod may also affect the circadian amplitude and daytime levels of blood serotonin.

A method for utilizing biocytin to study retinofugal pathways at the light and electron microscopic levels.

Numerous methods have been utilized in the past to study the retinofugal pathway at both the light and electron microscopic levels. However, many of these techniques have technical drawbacks that make them difficult to use in electron microscopic studies. We present herein a method for utilizing the anterograde tracer biocytin to study the retinal pathways at both the light and electron microscopic levels. Biocytin is an especially useful tracer since it clearly labels very small axons and boutons in addition to the larger fibers. In addition, the synaptic ultrastructure is left intact and the technique can be utilized in numerous double-labeling neuroanatomical studies.

Postsmolt change in numbers of acetylcholinesterase-positive cells in the pineal organ of the Pacific coho salmon.

We have examined the occurrence of acetylcholinesterase (AChE)-positive cells in the pineal organ of different developmental stages of the Pacific coho salmon. Large numbers of AChE cells were present in freshwater living alevins, in all stages of presmolts (n = 307-544), and in adult spawners (n = 696-1774), whereas seawater-living postmolts displayed a total lack of labeled cells. The AChE-reactive cells were evenly distributed within the pineal end-vesicle and stalk of the presmolts and adults. However, the AChE-positive cells that occurred in the pineal stalk were of a smaller type and more uniform in shape than the cells of the pineal end-vesicle. The dense populations of AChE-stained cells in the alevins were all situated in the caudal part of the pineal end-vesicle. We conclude that changes in pineal metabolism occur in postsmolt salmon that live in salt-water. It is not clear whether the observed change in pineal AChE expression is an "unspecific" change caused by the life in the sea, reflecting alterations that are related to aspects of osmoregulation, and/or is involved in the visual function of the pineal organ resulting from changes in the environmental lighting conditions, e.g., photoperiod, light-intensity, or spectral composition. This study adds to our previous findings of changes that occur in the central nervous system of the salmon during the time of the parr-smolt transformation and migration between limnic and marine environments, and indicates a possible central role of the pineal organ in the control of these events.

A morphometric study of age-related changes in serotonin-immunoreactive cell groups in the brain of the coho salmon, Oncorhynchus kisutch Walbaum.

In the coho salmon there is a transient increase in total brain concentrations of serotonin during smolt transformation which occurs midlife, just before down-stream migration to the ocean. There is also a gradual age-related increase in total brain serotonin concentrations. These increases may be due to reorganization of the central serotonergic system, changes in serotonin turnover, or both. They may be related to the specific physiological conditions during different life stages of salmon, or to ongoing growth and plastic changes of the brain. In the present study we have compared serotonin-immunoreactive (5-HTir) cell groups in 1-year-old freshwater presmolt and 2-year-old seawater postsmolt salmon. Our data indicate a continuous growth of the 5-HTir cell groups in terms of an increase in numbers of 5-HTir neurons in the cell groups of the pretectum and the brain stem, and an increase in the volumes of such neurons and cell groups. However, when related to the increase in total brain volume, i.e., the volume that may be innervated by the 5-HTir neurons, the ratio of 5-HTir neurons per mm3 decreased. The largest decreases were observed in the median raphe nucleus (P less than 0.005) and the B9 group (P less than 0.05). The ratio of volumes of the brain nuclei containing 5-HTir neurons relative to total brain volume was remarkably constant when comparing pre- and postsmolt brains: only the pretectal nucleus showed a significant decrease (P less than 0.01) in relative volume. The total volume of 5-HTir neurons increased in postsmolts (P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in ligand binding to GABAA receptor sites in pacific salmon (Oncorhynchus) brain during spawning migration and "aging".

When several years old, pacific salmon return to the site of birth, to spawn. At this time, a rapid aging process begins and the fish die within a few weeks after reproducing. Age-related changes of high and low affinity GABA binding sites were studied in salmon brains at three different phases of the spawning migration, i.e. shortly after returning to the natal stream, at the time of spawning, and thereafter. High affinity GABA binding slightly increased while the fish deteriorated. The low affinity component showed a remarkable decrease in density and a concomitant increase in affinity during this final episode of salmon life.