Immunohistochemistry as a technique in the studies on the neuroendocrine control of hydromineral balance: the legacy of José Antunes-Rodrigues.

Several forebrain and brainstem neurochemical circuitries interact with peripheral, neural, and humoral signals to collaboratively maintain both the volume and osmolality of extracellular fluids. Over the past decades, much progress has been made in understanding the complex mechanisms underlying the neuroendocrine control of hydromineral homeostasis. Classical experiments performed by Dr. Antunes-Rodrigues in the early 1960s, such as lesions of hypothalamic and extra-hypothalamic areas and drug microinfusions, associated with behavioral analysis and electrolytes/hormones measurements, were crucial to elucidate several aspects of the regulation of hydromineral balance. Fifty years after this pioneering research, the use of immunohistochemistry shifted methodological efforts to the central nervous system, in an attempt to elucidate how neurons (and lately, also glial cells) receive and interpret sensory signals originating from the periphery. This report focuses on the main findings obtained by Dr. Antunes-Rodrigues and colleagues using immunohistochemistry as an important tool in the first two decades of this century to elucidate the brain specific neurochemical circuits underlying functional mechanisms by which osmotic and volume challenges could impact hormonal and behavioral responses.