Brain TRF immunoreactivity during various physiological and stress conditions in the rat.

Methanol extracts of several rat tissues (hypothalamus, amygdala, the rest of the forebrain, brain stem and pancreas) were partially purified in SP-cation exchange chromatography and measured in TRF radioimmunoassay. It was found that hypothalamic and amygdaloid TRF contents were highest during the light period of the day, but brain stem TRF had an opposite rhythm. Hypothalamic TRF content rose after 10 min by 14% (p less than 0.05) when the rats were exposed to transfer stress. During short-time immobilization stress tests, hypothalamic TRF rose by 41% (p less than 0.05) after a 10-sec immobilization. Cold exposure did not produce any changes in hypothalamic TRF contents within 45 min. Handling stress and time of day appear to be the most important factors influencing the hypothalamic TRF content and have to be taken into account when measuring TRF.