Social modulation of androgen levels in vertebrates - Research IBBG

Apart from the effects of androgens in reproductive biology and behaviour, in the last three decades evidence has been accumulated showing that behaviour, in particular social experience, can feed back and affect androgen levels. These results suggest a two-way type of interaction between androgens and behaviour, which have been interpreted as an adaptation for the individuals to adust their agonistic motivation to the social environment. Thus, in one hand androgens have a permissive effect on agonistic/sexual motivation and on the other hand male-male interactions stimulate the production of androgens and the levels of androgens would be a function of the stability of the social environment in which the animal is placed ("challenge hypothesis"). One of the predictions of this hypothesis is that androgen patterns during the breeding season should vary among species according to the mating system. For example, in monogamous species with high levels of parental care androgen levels should increase above the breeding baseline only when males are challenged by other males or by mating. The two-way relationship between hormones and behaviour mentioned above may apply to the case of the interaction between androgens and male mating strategy. Thus, polygynous males, that face higher levels of social challenges due to higher male-male competition regimes, are expected to have higher breeding levels of androgens than males of monogamous species.

 

Among the potential benefits of increased androgen levels at periods of social challenge one can think of androgen effects on cognitive tasks and risk taking behaviours that would promote the success of the animals in social interactions. Some evidence suggests that sex steroids have a major role on learning and memory and thus they may prepare the animal for a competitive context. There is an extensive literature showing that animals use information from previous interactions to adjust their behaviour in subsequent social interactions (e.g. winner-loser effects, eavesdropping). Elevated levels of androgens also have associated costs so that high circulating levels have to be restricted to periods of social challenge. Among the demonstrated costs are the immunosupression (i.e. an impairment of antibody production with associated higher parasite loads), energetic costs and a trade-off with male parental care.

 

The social modulation of androgen levels is not restricted to animals but it also occurs in humans. It has been shown that competitive encounters elicit changes in androgen levels also in humans. In male humans T levels raise before a sports confrontation and T levels remain high in winners and drop in losers. These results are consistent across a range of different contests including judo combats, team sports (e.g. basketball) and chess tournaments. This androgen response appears associated with mood or status changes, and thus androgen modulation by social interactions seems to be driven by the individual’s subjective perception of the situation, regardless of performance.

 

Despite the range of species for which the social modulation of androgens is available and its adaptive value the underlying mechanisms have not elucidated so far. That is, how is the key stimulus from the social interaction translated into a signal to the hypothalamus that controls GtH secretion and consequently androgen circulating levels?

 

Currently we have two research projects within this research line:

 

- “Androgen-mediated effects of social context on animal communication and cognition: an integrated analysis” POCTI 38484.

 

- “Social modulation of androgen levels: psychological mechanisms and inter-individual variation” POCTI 38496/PSI/2001.

 

A third project on this topic has recently been finished “Social modulation of androgen levels in vertebrates: the cichlid fishes as models for a comparative approach” PRAXIS P/BIA/10251/98 (September 1999-November 2001). 

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