Bromocriptine Administration Lowers Serum Prolactin and Disrupts Parental Responsiveness in Common Marmosets (Callithrix j. jacchus)

The influence of prolactin on parental responsiveness was investigated in eight unpaired, parentally inexperienced common marmosets (Callithrix jacchus; 6 female, 2 male). The marmosets were prescreened with infants (1–10 days of age) and required to exhibit short latency retrieval and infant carrying in at least three consecutive pretests as criterion for inclusion in this study. The marmosets were then administered the dopamine agonist bromocriptine (0.5 mg/0.5ml vehicle subcutaneously) and the vehicle alone (0.5 ml 10% ethanol solution) twice daily for 3 consecutive days in random order. Bromocriptine treatment reduced circulating prolactin to nondetectable levels. Bromocriptine treatment eliminated infant retrieval in four of the eight marmosets and was associated with significantly increased retrieval latencies and significantly reduced carrying durations in the four monkeys that continued to retrieve following bromocriptine treatment. When given the vehicle alone, the marmosets retrieved infants significantly faster than during pretests, suggesting a handling effect of the injection series. Bromocriptine treatments were associated with significantly increased movement during the tests. The results of this study indicate that prolactin and/or its regulatory neurotransmitters are involved in the control of the spontaneous display of parental responsiveness in common marmosets.