Intracerebroventricular Injections of Prolactin Counteract the Antagonistic Effect of Bromocriptine on Rabbit Maternal Behaviour

Abstract

To investigate the participation of prolactin in nest-building and maternal behaviour in rabbits, we administered (from pregnancy day 26 to parturition) rabbit prolactin (rbPRL; or vehicle) intracerebroventricularly (i.c.v.) to primiparous animals injected with bromocriptine subcutaneously (s.c.). Control females (given vehicle s.c. and i.c.v.) built a maternal nest (of straw and body hair) in 77% of cases. This proportion decreased to 19% in the bromocriptine-only group (P < 0.05) and increased to 93% in the group given bromocriptine plus rbPRL (P > 0.05). Maternal behaviour (i.e. the adoption of a crouching posture over the litter inside the nest box) was expressed by 77% of control rabbits, 19% of bromocriptine-only animals (P < 0.05) and 57% of females given bromocriptine plus rbPRL (P > 0.05). Values of nonmaternal activities (i.e. scent-marking, ambulation in an open field) were similar among the three studied groups. These results suggest that prolactin, acting in late pregnancy, plays a major role in the stimulation of nest-building and maternal behaviour in rabbits.

Dopaminergic activation anticipates daily nursing in the rabbit

“…This is interesting as in the rabbit also there is an increase of OT expression in the paraventricular nucleus after parturition (Caba et al ., ), which could also be related to that reported effect in the mesocorticolimbic system. Prolactin in the rabbit it is essential for the onset of maternal behavior, but after parturition does not appear to play a major role in maternal responsiveness (González‐Mariscal et al ., ). In contrast endogenous opioids may play a critical role, as their release during nursing has been associated to the duration and hedonic properties of this behavior in the rat (Byrnes et al ., ; Machin & Dunbar, ).…”

Hormonal regulation of pregnancy and related behavioral changes in rabbits

“…It has been proven that there is some antagonism between prolactin and the release of gonadotropins (28,96). Prolactin begins to be secreted in the does before birth and significantly impacts the maternal behavior (40,43). Prolactin receptors were also found in the hypothalamus (17,98).…”

Comportamiento materno y bienestar de la coneja doméstica y silvestre y su camada

“…La implantación de benzoato de estradiol 17-β en el área preóp-tica del cerebro estimula la excavación y el acarreo de paja en conejas ovariectomizadas, cuando se acompaña de la inyección subcutánea de progesterona (y posterior remoción; González-Mariscal et al, 2005). La prolactina también participa en regular la construcción del nido maternal pues: a) la inyección subcutánea de bromocriptina (droga que antagoniza la liberación de prolactina) en los úl-timos días de la gestación previene el acarreo de paja y el arrancado del pelo (González-Mariscal et al, 2000), y b) la inyección de prolactina por vía intracerebroventricular revierte los efectos provocados por la bromocriptina (González-Mariscal et al, 2004).…”

“…Sin embargo, al antagonizar la liberación pre-parto de prolactina por inyecciones de bromocriptina a finales de la gestación, sí se suprime el comportamiento maternal durante los primeros días de la lactancia (González-Mariscal et al, 2000). La co-inyección intracerebroventricular de prolactina restaura la conducta maternal (González-Mariscal et al, 2004) lo que indica que dicha hormona es esencial para el inicio de este comportamiento. Existe evidencia que sugiere que la oxitocina participa en la regulación de un aspecto particular de la conducta maternal: su temporalidad.…”