Histaminergic regulation of seasonal metabolic rhythms in Siberian hamsters.
Bottom Line: A ribosomal toxin (saporin) conjugated to orexin-B was infused into the ventral tuberomammillary region of the hypothalamus, since most histaminergic neurons express orexin receptors.This caused not only 75-80% loss of histaminergic neurons in the posterior hypothalamus, but also some loss of other orexin-receptor expressing cells e.g. MCH neurons.In summary, ablation of orexin-responsive cells in the posterior hypothalamus blocks the short-day induced decline in body weight by preventing seasonal hypophagia, evidence consistent with the hypothesis that central histaminergic mechanisms contribute to long-term regulation of body weight.
Affiliation: Biology Department, Washington and Lee University, Lexington, VA, USA.Show MeSH
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Mentions: Hamsters in both groups lost weight following surgery, however, there were generally no signs of stress or trauma in the animals during this period and recovery was rapid in both groups in terms of eating, grooming and activity levels. After one week of weight loss, the control hamsters infused with SAP began to gain weight, and continued on a positive growth trajectory (Fig. 3, top). In contrast, hamsters infused with OXSAP continued to lose weight for up to 3 weeks post-surgery, thereafter they gradually regained weight (Fig. 3, top), but were significantly lighter than the SAP-treated controls throughout the study (Fig. 3, top). Maintenance of a lower body weight in the OXSAP-treated hamsters occurred despite their actual food intake in the home cage being similar to that of the SAP-treated hamsters (Fig. 3, bottom).
Affiliation: Biology Department, Washington and Lee University, Lexington, VA, USA.