Facilitation of affiliation and pair-bond formation by vasopressin receptor gene transfer into the ventral forebrain of a monogamous vole.

Behaviors associated with monogamy, including pair-bond formation, are facilitated by the neuropeptide vasopressin and are prevented by a vasopressin receptor [V1a receptor (V1aR)] antagonist in the male prairie vole. The neuroanatomical distribution of V1aR dramatically differs between monogamous and nonmonogamous species. V1aR binding is denser in the ventral pallidal region of several unrelated monogamous species compared with nonmonogamous species. Because the ventral pallidum is involved in reinforcement and addiction, we hypothesize that V1aR activation in this region promotes pair-bond formation via a mechanism similar to conditioning. Using an adeno-associated viral vector to deliver the V1aR gene, we increased the density of V1aR binding in the ventral pallial region of male prairie voles. These males exhibited increased levels of both anxiety and affiliative behavior compared with control males. In addition, males overexpressing the V1aR in the ventral pallidal region, but not control males, formed strong partner preferences after an overnight cohabitation, without mating, with a female. These data demonstrate a role for ventral pallidal V1aR in affiliation and social attachment and provide a potential molecular mechanism for species differences in social organization.

Low socioeconomic class is a risk factor for upper and lower gastrointestinal symptoms: a population based study in 15 000 Australian adults.

BACKGROUND: The association of social class with health has been extensively studied, yet relationships between social class and gastrointestinal symptoms remain almost unexplored. AIMS: To examine relationships between social class and gastrointestinal symptoms in a population sample. METHODS: The prevalence of 16 troublesome gastrointestinal symptoms was determined by a postal questionnaire sent to 15 000 subjects (response rate 60%) and compared with a validated composite measure of socioeconomic status (index of relative socioeconomic disadvantage). Comparisons across social class were explored for five symptom categories (oesophageal symptoms; upper dysmotility symptoms; bowel symptoms; diarrhoea; and constipation). Results are reported as age standardised rate ratios with the most advantaged social class as the reference category. RESULTS: There were clear trends for the prevalence rates of all gastrointestinal symptoms to increase with decreasing social class. These trends were particularly strong for the five symptom categories. Lower social class was associated with a significantly (p<0.0001) higher number of symptoms reported overall and with a higher proportion of individuals reporting 1-2 symptoms and more than five symptoms. In both sexes, the most pronounced effects for subjects in the lowest social class were found for constipation (males: rate ratio 1.83 (95% confidence intervals (CI) 1.16-2.51); females: rate ratio 1.68 (95% CI 1.31-2.04)) and upper dysmotility symptoms (males: rate ratio 1.45 (95% CI 1.02-1.88); females: rate ratio 1.35 (95% CI 1.07-1.63)). Oesophageal symptoms and diarrhoea were not associated with social class. CONCLUSIONS: Troublesome gastrointestinal symptoms are linked to socioeconomic status with more symptoms reported by subjects in low socioeconomic classes. Low socioeconomic class should be considered a risk factor for both upper and lower gastrointestinal symptoms.

Increased affiliative response to vasopressin in mice expressing the V1a receptor from a monogamous vole.

Arginine vasopressin influences male reproductive and social behaviours in several vertebrate taxa through its actions at the V1a receptor in the brain. The neuroanatomical distribution of vasopressin V1a receptors varies greatly between species with different forms of social organization. Here we show that centrally administered arginine vasopressin increases affiliative behaviour in the highly social, monogamous prairie vole, but not in the relatively asocial, promiscuous montane vole. Molecular analyses indicate that gene duplication and/or changes in promoter structure of the prairie vole receptor gene may contribute to the species differences in vasopressin-receptor expression. We further show that mice that are transgenic for the prairie vole receptor gene have a neuroanatomical pattern of receptor binding that is similar to that of the prairie vole, and exhibit increased affiliative behaviour after injection with arginine vasopressin. These data indicate that the pattern of V1a-receptor gene expression in the brain may be functionally associated with species-typical social behaviours in male vertebrates.

Gene targeting approaches to neuroendocrinology: oxytocin, maternal behavior, and affiliation.

Transgenic technology affords exciting new opportunities in the field of behavioral neuroendocrinology. We have extended our research into the behavioral function of oxytocin in maternal and social behavior using two transgenic approaches: (i) targeted deletion of the oxytocin gene in mice and (ii) augmented oxytocin receptor expression in the brain. Mice genetically deficient in oxytocin can mate, give birth, and display normal maternal behavior; however, milk ejection and certain aspects of social behavior are affected. Comparative studies of oxytocin receptors have led to the observation that species differences in social organization are associated with differences in receptor distribution. Specifically, monogamous prairie voles and nonmonogamous, asocial montane voles exhibit different patterns of OT receptor expression in the brain. Transgenic mice have been created with a reporter gene driven by the prairie vole oxytocin receptor gene promoter. Analysis of the expression pattern suggests that it should be possible to manipulate receptor expression in the vole brain in order to examine the effects of receptor distribution on behavior.