Sex differences in body weight gains following amygdaloid lesions in rats

Abstract

Lesions of the most posterodorsal aspects of the amygdala resulted in equal weight gains (mean = 58 g) in male and female rats during a 22-day observation period. However, the absolute weight gains in the first 5 days after lesions were greater in females (+41.4 g) than in males (+18.8 g), as were the longer-term gains relative to their respective control groups. In a second study with female rats, it was found that amygdaloid lesions had little effect on the estrous cycle and that ovariectomy resulted in additional excessive weight gains in both rats with sham lesions and those with amygdaloid lesions. The weight gains produced by amygdaloid lesions and ovariectomy were additive. It is concluded that there is a sex difference in weight gains after amygdaloid lesions, but that the lesion-induced obesity is independent of estrogen levels. Similarities to lesions of the ventromedial hypothalamus are noted, and an amygdaloid-ventromedial hypothalamic pathway for the regulation of feeding behavior is proposed.

Glutamate Microinjected in the Posterodorsal Medial Amygdala Induces Subtle Increase in the Consumption of a Three‐Choice Macronutrient Self‐Selection Diet in Male Rats

“…As evidenced by electrophysiological recordings, not all hypothalamic neurons sampled responded to MeA stimulation but, when it occurred, both excitatory and inhibitory responses were evoked in different target areas (Carrer et al, 1978;Choi et al, 2005;Bian et al, 2008). It is also conceivable that lesions involving the ''posterodorsal amygdala'' and that induced hyperphagia (King et al, 1998(King et al, , 1999(King et al, , 2003Rollins and King, 2000;Grundmann et al, 2005) have affected other amygdaloid nuclei or transition areas besides the MePD (Rollins and King, 2000;King et al, 2003;Moscarello et al, 2009). In effect, excessive weight gains in lesioned females might be more related to damage the intra-amygdaloid division of the bed nucleus of the ST than to the MePD itself (King et al, 1998).…”

“…Rats received saline (sterile NaCl 0.9%, pH 7.4; 0.3 lL, n ¼ 8) or glutamate (45 nM or 45 mM/0.3 lL of saline, n ¼ 5 and 8, respectively) in the MePD. The ''hit rate'' for MePD microinjections reflects the rigorous including criteria and the small size of this brain subnucleus (see also King et al, 1999;Grundmann et al, 2005). The doses of glutamate were adapted from previous reports, that is, the lowest dose of glutamate is close to the physiological values obtained by brain microdialysis in various amygdaloid nuclei and the highest dose is a pharmacological one (Fillenz, 1995;Kaura et al, 1995;Ferreira et al, 2005).…”

“…Previous reports involved the ''posterodorsal region'' of the amygdala with feeding behavior in rats (King et al, 1998(King et al, , 1999(King et al, , 2003Rollins and King, 2000;Grundmann et al, 2005). This wide area is neither an anatomical nor a functional unit; rather, it involves different amygdaloid components, such as the medial nucleus of the amygdala (MeA), the stria terminalis (ST), and the bed nucleus of the ST among others.…”

“…This wide area is neither an anatomical nor a functional unit; rather, it involves different amygdaloid components, such as the medial nucleus of the amygdala (MeA), the stria terminalis (ST), and the bed nucleus of the ST among others. Unilateral or bilateral electrolytic lesions of this ''posterodorsal region'' led Long-Evans adult female rats to display a marked preference for carbohydrate consumption, hyperphagia, and an abnormal increase in body weight (King et al, 1998(King et al, , 1999(King et al, , 2003. Lesions also promoted anterograde degeneration in the ipsilateral hypothalamic ventromedial nucleus (Rollins and King, 2000;Grundmann et al, 2005), an integrated area for the central control of food intake and energy balance (Berthoud, 2002).…”

Body weight is regulated by the brain: a link between feeding and emotion

“…For example, amygdala lesions produce hyperphagia and obesity in rodents. 136 Bilateral microinjections of a selective MC4-R antagonist HS014 into the CeA increase food intake. 137 Within the CeA (Figure 1b), a subnucleus of the amygdala, a-MSH-or AgRPpositive axons are accumulated preferentially in the medial region 107 in which MC4-R-positive cells populate.…”