IntroductionThe Onset of Maternal Behaviour in the Rat
Hormonal events at the time of parturition in mammals are believed to initiate the onset of maternal behaviour. In the rat, the medial preoptic area (MPOA) of the brain is considered to be the primary site that mediates the onset of maternal behaviour. Since some of the hormones associated with parturition are known, in other systems and cell types, to stimulate an intracellular increase in calcium levels, it is likely that CaM and its CaMBPs might mediate some of the events during the onset of maternal behaviour. This idea is strengthened by the fact that c-Fos levels increase specifically in the MPOA during the onset of rat maternal behaviour and certain CaMBPs have been shown to lie upstream of c-Fos expression in other cell types. Our research has shown that the levels of certain CaMBPs decrease specifically in the MPOA during the onset of maternal behaviour while other signaling pathways remain unchanged or increase in amounts. One CaMBP, calcineurin, which is known to be expressed at high levels in other brain regions, is low in the MPOA of virgin females and becomes undetectable after parturition. Could the loss of calcineurin be the trigger to the onset of parturition-induced maternal behaviour?
h Subsequent to this published work, my lab has examined the expression patterns of other signalling components and the scaffold protein RACK1. These are shown in the following image.
Expression of PKC isoforms and RACK1 in the Rat Brain
(click to enlarge)
The proteins were probed for the antibodies directed against isoforms of protein kinase C, PKCα and PK(ε and RACK1 as detailed previously (O'Day et al, 2001a; unpublished).
Thus, as in other mammalian cell types and neurons, it is possible that RACK1 acts as a scaffold for the appropriate signaling components in MPOA neurons. The following graphic shows how these signaling components would be organized in post-synaptic neurons in the MPOA of virgin vs. maternal rats.
Theorettical Model of AKAP79 Scaffolding in the Virgin and Primiparous Maternal MPOA
(click to enlarge)
References
Fleming, A.S., D.H. O'Day and G. Kraemer, 1999. Neurobiology of Mother-Infant Interactions: Central Nervous System Plasticity across Development and Generations. Neuroscience & Biobehavioral Reviews 23: 673-685.
Fleming, A.S. and O'Day, D.H., 1999. Understanding maternal behavior: Analyses of behavior, c-fos expression and calmodulin binding proteins in the medial preoptic area and other areas of the rat brain. In: Molecular Genetic Techniques for Brain & Behavior Research (W.E. Crusio & R. Gerlai, eds), Chaper 13, pp. 722- 737; In: Techniques for Behavioral & Neural Research (J.P. Huston, ed.)
O'Day, Danton H., Lori-Ann Payne, Irene Drmic, Alison S. Fleming, 2001. Loss of Calcineurin from the Medial Preoptic Area of Primiparous Rats. Biochemical and Biophysical Research Communications 281: 1037-1040.
O'Day, Danton H., M. A. Lydan, J. Watchus, & A. S. Fleming, 2001. Decreases in Calmodulin Binding Proteins and Calmodulin Dependent Protein Phosphorylation in the Medial Preoptic Area at the Onset of Maternal Behavior in the Rat. J. Neuroscience Research 64: 599-605.
Last update June, 2005. Unless otherwise stated the information and graphics that are presented are the sole property of Danton H. O'Day, copyright 1998(c), 1999(c), 2000(c), 2001(c), 2002(c), 2003(c), 2004(c), 2005(c). If you would like permission to use any of the information contained in this website please contact Professor O'Day (doday@utm.utoronto.ca).