Mariana Zancan and Alberto A. Rasia-Filho136
hypothalamic arcuate nucleus of estrus females relevant for GnRH surge and
ovulation”. In contrast, males show no difference between hemispheres for the
density of dendritic spines (Arpini et al., 2010) or dendritic shaft and spines
synapses (Brusco et al., 2014).
These dendritic spines, somatic spines, and direct axonal contacts on
dendritic shafts and perikarium are important sites for the integration of
information coming from different, but overlapping networks in the MePD.
Spatial and temporal processing in spines affect the impact of each circuit for
the ultimate display of neuroendocrine secretion and behavioral display. A
robust example of this synaptic organization was provided recently. According
to Keshavarzi et al. (2015), “The MeA is a central hub in the olfactory neural
network. It receives vomeronasal information directly from the accessory
olfactory bulb (AOB) and main olfactory information largely via odor-
processing regions such as the olfactory cortical amygdala (CoA)... Using the
GAD67-GFP mouse, we show that MeA principal neurons receive convergent
AOB and CoA inputs. Somatically recorded AOB synaptic inputs had slower
kinetics than CoA inputs, suggesting that they are electrotonically more
distant. Field potential recording, pharmacological manipulation, and Ca+2
imaging revealed that AOB synapses are confined to distal dendrites and
segregated from the proximally located CoA synapses. Moreover,
unsynchronized AOB inputs had significantly broader temporal summation
that was dependent on the activation of NMDA receptors. These findings show
that MeA principal neurons process main and accessory olfactory inputs
differentially in distinct dendritic compartments... suggesting that this
dendritic segregation leads to distinct input integration and impact on neuronal
output; hence, dendritic mechanisms control olfactory processing in the
amygdala”.
Finally, sex steroids actions in the MePD are not restricted to the
modulation of reproductive behavior. For example, ER-α in the MeA prevents
stress-induced elevations in blood pressure in female mice (Hinton et al.,
2016). Previously, it was reported that “the MePD modulates the occurrence of
sexual and aggressive behaviors in both males and females (Newman, 1999),
for which blood pressure has to be concomitantly regulated. In this sense, it is
an interesting working hypothesis to consider that... the MePD might be
changing baroreceptor- and chemoreceptor-reflex responses, broadening their
ranges, to make homeostatic responses intentionally adjusted for the proper
execution of an intended behavior... it is likely that the MePD might be
coordinating sympathetic/parasympathetic responses with ongoing behavior.
This would provide the animal with a dynamic mechanism of cardiovascular