The interrelationship between the olfactory bulbs and the basomedical hypothalamus in controlling food intake, obesity and endocrine functions in the chicken

Surgical removal of the olfactory bulbs (OB) in the chicken indicated an increase in thyrotropic activity followed by a compensatory increase in food intake, as shown earlier. Basomedial hypothalamic (BMH) lesions in these birds caused changes in certain parameters which strongly infer hypoactivity of the thyrotropic axis. The lesions also caused development of typical hypothalamic obesity demonstrating both dynamic and static phases. Removal of the OB in BMH lesioned birds in their static phase of obesity, caused no demonstrable physiological changes. While removal of the OB caused an increase in somatotropic activity, the opposite was found in BMH lesioned birds. Those animals in which OB were removed and BMH was destroyed, demonstrated a decrease in somatotropic activity. It is suggested that the syndrome caused by BMH lesions dominates that caused by removal of the OB. The possibility of involvement of the OB in the control of thyrotropic and somatotropic activities mediated by the basomedial hypothalamus, is discussed.