Pituitary-Adrenal Function after Small and Large Lesions in the Lateral Septal Area in Food-Deprived Rats

Abstract

Either partial or near-total electrolytic destructionof the lateral septal area was performed on male rats, half of which were then subjected to food deprivation. Compared to either fed or deprived control animals there was no blockade of starvation-induced ACTH release in either lesioned group, as determined by thymus atrophy and plasma corticosterone levels; there was some evidence of an increased pituitary-adrenal function relative to controls. It is postulated that the quality and severity of the stress, and possibly the exact locus of the septal lesion may influence the degree of resultant interference with corticosteroid feedback systems. Evidence is presented that the resting level of plasma corticosterone is raised in animals with bilateral septal lesions.

The Modulatory Role of the Lateral Septum on Neuroendocrine and Behavioral Stress Responses

“…In support of this, we observed increased neuronal activation (indicated by an enhancement of c-Fos-positive cells) in the mpPVN, the key region of HPA axis regulation that contains the main neuropeptidergic adrenocorticotropin secretagogues, such as CRF and arginine vasopressin (Antoni, 1986; Whitnall, 1993). Thus, our data suggest an inhibitory role of LS neurons on stress-induced HPA axis activity, and extend previous findings demonstrating higher corticosterone levels after electrolytic lesioning of the whole septum in rats (Brown et al , 1974; Usher et al , 1974; Dobrakovova et al , 1982; Seggie, 1987). In contrast to previous studies, in which only corticosterone levels were measured, our study provides information on HPA axis activity at different levels from hypothalamus, pituitary to adrenal level.…”

“…However, the exact role of the LS in HPA axis regulation is presently obscure, because of inconsistent findings from previous studies. For example, basal plasma corticosterone levels following septal lesions are elevated in some studies (Usher et al , 1974; Dobrakovova et al , 1982) but not in others (Seggie and Brown, 1971; Seggie et al , 1974; Uhlir et al , 1974; Dobrakovova et al , 1982; Seggie, 1987). Moreover, the impact of LS neurons on the expression of anxiety-related behaviors are similar controversial as both reduced (Pesold and Treit, 1992; Menard and Treit, 1996) as well as increased anxiety levels (Albert and Chew, 1980; Yadin et al , 1993) were found after septal lesions.…”

Functional Subsets of Serotonergic Neurones: Implications for Control of the Hypothalamic‐Pituitary‐Adrenal Axis

“…Many neural targets of the ventral subiculum have been implicated in inhibition of neuroendocrine, autonomic or behavioural responses to cognitive stressors, including the medial prefrontal cortex (cingulate gyrus) (95, 96) [but see also (97)], olfactory tubercle (98, 99), ventral subdivision of the lateral septum (86, 100–105), medial or ventral BNST (106), posterior intermediate and/or posterior medial BNST (93, 107), habenula (108), medial mammillary nucleus (109), medial preoptic area (93, 110), anterior hypothalamic area (93, 111), dorsomedial hypothalamic nucleus and adjacent posterior hypothalamic area (93, 111, 112), peri‐PVN zone and perifornical nucleus (93). In many cases, lesions of these structures result in enhanced corticosterone secretion following exteroceptive, but not interoceptive, stressors (88, 89, 95, 113, 114).…”

The Hippocampus

“…On the other hand, Usher et al (1967) and Usher and Lamble (1969) reported that the pituitary-adrenal response to mild neurogenie stressors such as intermittent air blast or shuttle-box avoidance was completely blocked by lateral septaliesions. Later, they suggested that the quantity and severity of stress may he of importance, because ACTH release due to food deprivation was not blocked but even slightly enhanced by the same septal lesions (Usher et al, 1974). Available data on the plasma corticosterone level under resting conditions in septally damaged rats are also rather conflicting.Both increased (Usher et al, 1974) and not changed baseline levels Uhlir et al, 1974) have been reported.…”

“…Later, they suggested that the quantity and severity of stress may he of importance, because ACTH release due to food deprivation was not blocked but even slightly enhanced by the same septal lesions (Usher et al, 1974). Available data on the plasma corticosterone level under resting conditions in septally damaged rats are also rather conflicting.Both increased (Usher et al, 1974) and not changed baseline levels Uhlir et al, 1974) have been reported.…”