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: Intraperitoneal injection of thioperamide (30 mg/kg) produced a significant (P < 0.05) decrease in VO2 for a two hour period in SAP-treated hamsters but not in the hamsters that had been lesioned with OXSAP (Fig. 6). No parameters of food intake nor locomotor activity were significantly altered by thioperamide treatment in either group (data not shown). At necropsy 22 weeks after the initial OXSAP/SAP infusion, there were no significant differences between the groups in the wet weight of the intra-scapular brown adipose tissue, testes or epididymides (Table 1), however the epididymal fat pad weight was significantly lower in OXSAP-treated hamsters (Table 1), consistent with the lower overall body weight (Fig. 3, Table 1).
Affiliation: Biology Department, Washington and Lee University, Lexington, VA, USA.