Title:
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Methodological approaches for investigating noradrenergic neuromodulation within the accessory olfactory bulb of BALB/c female mice
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The formation of mate recognition memory in female mice is dependent on
enhanced noradrenaline release within the accessory olfactory bulb (AOB),
stimulated by mating, and the exposure to the mating male's pheromonal signals.
Memory formation is associated with an enhancement of inhibition at a reciprocal
dendrodendritic synapse between excitatory mitral/tufted cells and inhibitory
granule cells, however the exact mechanism by which noradrenaline facilitates the
formation of memory is unknown. This thesis aimed to further investigate the
noradrenergic modulation of the AOB in the context of mate recognition memory
using electrophysiological recording from anaesthetised female mice.
Artificial vaginocervical stimulation caused heterogeneous short- and long-term
changes in the firing rate of spontaneously active mitral/tufted cells, consistent with
the enhanced neuromodulation of the AOB during mating. However, inconsistent
responses observed across multiple exposures to different types of dilute urine in
combination with unexpected responses to control solutions following application
of stimulus solution to the nose and electrical stimulation of the sympathetic nerve
trunk suggested that stimulus-evoked mitral/tufted cell activity could not be driven
reliably. Therefore, despite the apparent success in developing a model of mating in
anaesthetised female mice, further attempts to develop an experimental protocol
for the induction of mate recognition memory were hindered.
Immunohistochemical staining showed a potentially distinct distribution of the 6 aadrenoceptor
subtypes throughout the laminar structure of the AOB and the
application of the a2-adrenoceptor agonist, cionidine, to the recording probe
craniotomy above the olfactory bulb caused an unexpected decrease in
mitral/tufted cell firing rate. These findings suggest a possible action of
noradrenaline in different layers of the AOB aside from the previously reported
modulation of the mitral/tufted cell:granule cell synapse and emphasise the need
for more targeted approaches for investigating the contribution of different aadrenoceptor
subtypes in the modulation of neuronal network activity within the
AOB
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