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The lateral septum (LS) is implicated in behavioral defense. We tested whether bilateral infusions of the GABAA receptor agonist muscimol into the LS suppress rats' defensive responses to cat odor. Rats received intra-LS infusions of either saline or muscimol (40 ng/rat) and were exposed to either a piece of a cat collar that had been previously worn by a cat or to a control (cat odor free) collar. Rats exposed to the cat odor collar displayed more head-out postures, while intra-LS application of muscimol reduced the number of head-out postures. However, this reduction was also present in rats exposed to a control (cat odor free) collar. This latter finding suggests that despite its involvement in other defensive behaviors (e.g., open arm avoidance in the elevated plus maze), the LS does not selectively regulate rats' receptor defensive responding to the olfactory cues present in our cat odor stimulus., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

The neural histaminergic system is involved in a wide range of physiological processes, including anxiety. Histaminergic neurons are localized in the tuberomammillary nucleus of the posterior hypothalamus and share bidirectional connections with the lateral septum, an area well implicated in anxiety. The current study examined whether the histaminergic system of the lateral septum regulates rats' defensive behaviors in two animal models of anxiety, the elevated plus maze (EPM) and novelty-induced suppression of feeding paradigm (NISF). We found that bilateral infusions of histamine (1.0 μg and 5.0 μg) into the lateral septum selectively decreased rats' defensive behaviors in the EPM (both doses) and NISF (1.0 μg only). Follow-up studies found that pre-infusions of the H1 and H2 antagonists, pyrilamine (20 μg) and ranitidine (20 μg) respectively, reversed the anxiolytic-like effects of intra-LS histamine (1.0 μg) in the NISF but not in the EPM, while pre-infusions of the H3 antagonist ciproxifan (200 pg) attenuated the anxiolytic-like effects of intra-LS histamine in the EPM but not in the NISF. This double dissociation suggests that H1 and H2 receptors in the lateral septum, likely via a post-synaptic mechanism, mediate the anxiolytic-like effects of histamine in the NISF but not in the EPM. In contrast, lateral septal H3 receptors mediate, likely pre-synaptically, the anxiolytic-like effects of histamine in the EPM but not in the NISF. Our findings indicate that these receptors differentially contribute to rats' specific defensive behaviors in the EPM and NISF, that is, avoidance of open spaces and neophagia respectively., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Past studies have shown that the lateral septum is involved in anxiety. Here, we tested whether the dorsal lateral septum contributes to neophagia by using the novelty induced suppression of feeding (NISF) paradigm. We found that while lesions of the dorsal lateral septum did not affect home or novel cage responding in the NISF test, they did decrease open arm avoidance in the elevated plus maze and burying in the shock probe burying test. Our results suggest that the dorsal lateral septum does not regulate neophagia in the NISF, but further experiments are needed to determine if the same is true for the intermediate and ventral lateral septum., (Copyright © 2011 Elsevier B.V. All rights reserved.)