Activation of the immune–endocrine system with lipopolysaccharide reduces affiliative behaviors in voles.

Abstract

In Experiment 1, individually housed male meadow voles (Microtus pennsylvanicus) and prairie voles (Microtus ochrogaster) were injected with lipopolysaccharide (LPS) and exhibited the expected decrease in testosterone and increase in corticosterone and interleukin-1beta concentrations 3 hr later, indicating activation of the endocrine and immune systems. In Experiment 2, LPS- and saline-injected males were tethered in a 3-chamber partner preference apparatus. The time females spent in each chamber with a male, as well as the amount of time spent in social contact, was monitored. Female prairie voles, but not meadow voles, spent more time in the chamber with saline- than with LPS-injected males. LPS-injected male prairie and meadow voles engaged in less social contact with female conspecifics than did saline-injected males. These data suggest that LPS modifies physiology and behavior in male voles and that females may use these changes to discriminate healthy from potentially infected males.

Seasonal modulation of sickness behavior in free-living northwestern song sparrows (Melospiza melodia morphna)

“…For instance, interleukin-1 treatment inhibits sexual behavior in female, but not male rats, while concomitantly decreasing locomotory activity in both sexes (Yirmiya et al, 1995). In microtine voles (Microtus), males paired with females are less responsive to LPS challenge than males housed alone (Klein and Nelson, 1999). These sex differences may allow males to optimize reproductive potential, especially if mating opportunities are limited.…”

“…These reproductive activities are suppressed in favor of increased sleep for recruitment of additional resources to combat infection (Kent et al, 1992;Dantzer, 2001). Acute phase responses also proximately inhibit the hypothalamo-pituitarygonadal axis (Rivier, 1990;Bosmann et al, 1996;Klein and Nelson, 1999), leading to a rapid decline in sex steroid levels. Furthermore, these life-history costs may persist until the animal has fully recovered from infection (Hart, 1988).…”

Parasite-augmented mate choice and reduction in innate fear in rats infected byToxoplasma gondii

“…Because of constant coevolutionary cycles between host and parasite, genes for resistance never reach equilibrium, and thus can sustain continual variation and selection. It is not yet possible to ascertain whether either of these scenarios (or both simultaneously) have played a role in mate choice of rats.Yet, it is interesting that female rodents detect and avoid males infected with a variety of parasites, including ectoparasites, protozoans, nematodes and bacteria (Ehman and Scott, 2002; Kavaliers et al, 2006; Kavaliers et al, 2005a; Kavaliers et al, 2005b; Kavaliers and Colwell, 1992; Kavaliers and Colwell, 1995; Kavaliers et al, 1998a; Kavaliers et al, 1998b; Kavaliers et al, 2003;Klein and Nelson, 1999;Willis and Poulin, 2000;Zala et al, 2008). Female rodents have evolved dedicated neural machinery that serves to detect odors emanating from infected individuals and to generate an aversive response.…”

Parental experience of a risky environment leads to improved offspring growth rate

“…One mechanism by which females can alter offspring phenotype is by producing stress-induced hormones (Spencer and Robinson, 1992). Several studies have shown that immune activation may affect corticosteroid production (Rivier et al, 1989;Klein and Nelson, 1999;Owen-Ashley et al, 2006;Adelman and Martin, 2009). Maternal corticosterone levels during development have been shown to affect offspring behaviour, morphology, growth, dispersal, sex and survival (Glickman et al, 1987;De Fraipont et al, 2000;Groothuis et al, 2005;Love et al, 2005).…”