Behavioural endocrinology of mammalian paternal care: A role for prolactin in naturally biparental and uniparental mammals (Phodopus).

摘要

This thesis provides the first evidence for a causal link between hormones paternal care in a naturally paternal mammal.; An animal model consisting of two closely related species of dwarf hamsters, one species (Phodopus campbelli) is socially monogamous and expresses extensive paternal care in the lab and in the wild, while in the other (P. sungorus), females raise their young alone.; A new method of blood collection is validated for obtaining serial blood samples in hamsters following (isoflurane) anesthesia. Neither repeated blood collection, substantial blood volume reduction, nor prolonged anesthetic exposure produced increased concentrations of cortisol or decreased concentrations of prolactin (PRL).; Experiments quantified hormonal correlates of male paternal behaviour in the two species by measuring PRL, testosterone (T5) and cortisol at several times from before pairing to after the birth. Male P. campbelli were more likely to retrieve a displaced pup, and were quicker than P. sungorus to contact and return it to the nest. Elevated concentrations of PRL and decreased concentrations of T5 were seen after the birth in male P. campbelli. Prior to the birth both species of males had increases in PRL concentration, with increases on days 17 and 18 of their mates' 18 day gestation (G17, G18) in P. sungorus, and increased PRL concentrations at dusk on G17 in P. campbelli. Testosterone concentration was elevated in male P. campbelli on G17 and G18, but was unchanged in P. sungorus. Cortisol concentrations decreased significantly following pairing in both species and increased in P. campbelli, but not P. sungorus on G17.; To establish a causal link between the observed hormonal changes and paternal behaviour, PRL concentrations in paternal males were experimentally suppressed by pharmacological treatment with a dopamine agonist, bromocryptine mesylate. Treatment before or immediately after the birth resulted in deficits in paternal behaviour during a behaviour test on lactation day 3.; Results were broadly consistent with a role for PRL in the behavioural endocrinology of male mammals which naturally express paternal care, and supported the hypothesis that paternal behavioural endocrinology will involve hormonal activation of existing maternal neuroendocrine pathways.