Adipose organ nerves revealed by immunohistochemistry

Brown and white adipose tissue have recently gained prominence as key players in obesity and related health problems, such as type-2 diabetes and cardiovascular disease. Brown adipose tissue-dependent nonshivering thermogenesis significantly affects the body's energy balance. Originally considered as a passive store of lipids, white adipose tissue has recently been found to secrete a number of hormones and cytokines and to be thus involved in the control of body metabolism and energy balance at multiple sites. These findings have renewed the interest in adipose organ biology, including its innervation by the autonomic nervous system and sensory nerves. Here, we describe our protocols for detecting different types of adipose tissue nerves by light microscopy using peroxidase immunostaining and by laser scanning confocal microscopy using immunofluorescence. With these techniques, the presence, distribution, and colocalization of autonomic and sensory nerves can be effectively investigated in subcutaneous and visceral adipose depots of normal and obese animals.