c-fos expression in vasopressin and oxytocin neurons reveals functional heterogeneity within magnocellular neurons.
The c-fos protein is rapidly induced in hypothalamic magnocellular nuclei following hemorrhage. We used specific antibodies directed against c-fos and either vasopressin (AVP) or oxytocin (OT) neurophysin to investigate c-fos activation in individual AVP and OT neurons. AVP and OT neurons expressed c-fos in response to hypovolemic stimuli. Following a protocol of incremental hemorrhage, AVP and OT neurons expressed c-fos with a graded response that correlated with stimulus intensity. As the volume of hemorrhage increased, there was an increase in the number of cells expressing c-fos as well as in the amount of c-fos immunoreactivity per cell. These increases correlated with the amount of hormone released into the peripheral blood. In addition, a differential pattern of activation for AVP neurons occurred in response to hemorrhagic stimuli. AVP neurons in the supraoptic nucleus (SON) had a lower threshold for response than those in the paraventricular nucleus (PVN). For OT, activation required a greater blood loss than AVP and c-fos expression encompassed both SON and PVN neurons. We conclude that c-fos expression is proportional to stimulus intensity and reveals functional heterogeneity among magnocellular neurons.
Roberts
M M
MM
Department of Medicine, University of Pittsburgh School of Medicine, PA 15261.
Robinson
A G
AG
Fitzsimmons
M D
MD
Grant
F
F
Lee
W S
WS
Hoffman
G E
GE
D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D001921:Brain / Q000378:metabolism*; D015870:Gene Expression; D016762:Genes, fos; D006470:Hemorrhage; D008297:Male; D009474:Neurons / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013495:Supraoptic Nucleus / Q000378:metabolism
D016760:Proto-Oncogene Proteins c-fos; D001127:Arginine Vasopressin; D010121:Oxytocin