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Associative recognition memory depends on a network of brain regions, which in cludes: the hippocampus (HPC), medial prefrontal cortex (mPFC) and nucleus reuniens (NRe). How noradrenaline modulates these brain regions during asso ciative recognition memory has not been thoroughly characterised. In addition, little is known about the anatomical organisation of the noradrenergic (as well as dopaminergic) systems in the NRe. This thesis aims to characterise the anatomy of the catecholaminergic system in the NRe as well as explore the functional role of noradrenaline originating from the locus coeruleus (LC), in the NRe, HPC and mPFC, in long-term associative recognition memory. The first results chapter employs anatomical techniques, revealing that the entire rostral-caudal axis of the NRe is innervated with catecholaminergic-positive fibers. The chapter further demonstrates that the NRe receives its dopaminergic input from the A13 cell group and noradrenergic input from the LC. The second results chapter utilises a pharmacological approach to explore the functional role of noradrenergic neurotransmission in the NRe, HPC and mPFC in long-term object-in-place memory. It revealed that antagonism of α1- and agonism of α2- adrenoceptors in the NRe impaired the retrieval but not encoding of object in-place memory. In contrast, in the HPC, agonism of α2- and antagonism of β- adrenoceptors impaired memory encoding but not retrieval, while in the mPFC manipulation of the adrenergic receptors were without effect on memory performance. The third results chapter employs an optogenetic approach to explore whether inputs from the LC to the NRe and HPC are critical for recognition memory. In line with the pharmacology results, it is revealed that LC to NRe inputs are critical for the retrieval but not encoding of object-in-place memory while LC to HPC inputs are critical for the encoding but not retrieval of object-in-place memory. Together, the results of this thesis indicate that the NRe is more extensively innervated with catecholaminergic fibers than previously characterised. Further, the data also demonstrates that noradrenaline originating from the LC, has dissociable effects at different stages of associative memory processing in the NRe, HPC and mPFC.