In vivo hypothalamic release of thyrotropin-releasing hormone after electrical stimulation of the paraventricular area: comparison between push-pull perfusion technique and collection of hypophysial portal blood.
Unilateral electrical stimulation for 15 min of the paraventricular area of anesthetized rats induced a 2- to 3- fold increase in plasma TSH levels and caused an increased release of TRH into hypophysial stalk blood from 217 +/- 25 to 530 +/- 90 pg/15 min (n = 6). This experimental model was then used to determine the in vivo hypothalamic release of TRH by push-pull perfusion of either the mediobasal hypothalamus (MBH) or anterior pituitary (AP). Before stimulation, TRH release per 15 min was 4.2 +/- 0.7 pg from the MBH (n = 18) and 3.5 +/- 0.3 pg from the AP (n = 13). Unilateral electrical stimulation of the paraventricular area led to higher plasma TSH levels in 27 of 31 rats, and levels during stimulation increased from 0.89 +/- 0.04 to 1.86 +/- 0.10 ng/ml (n = 31). No significant increase in TRH in the perfusates was observed when push-pull perfusion was done in the MBH contralateral to the site of stimulation (n = 6). However, TRH release increased 2- to 3-fold during the perfusion of the MBH ipsilateral to the site of stimulation (15.4 +/- 4.3 pg/15 min; n = 13). In conclusion, push-pull perfusion of the MBH or AP can be used to estimate hypothalamic TRH release. However, the output of TRH by push-pull perfusion is low and varies considerably between individual rats. Thus, the practical value of push-pull perfusion for measurement of in vivo TRH release seems limited.
Rondeel
J M
JM
Department of Endocrinology, Erasmus University, Rotterdam, The Netherlands.
de Greef
W J
WJ
van der Vaart
P D
PD
van der Schoot
P
P
Visser
T J
TJ
D000818:Animals; D001800:Blood Specimen Collection / Q000379:methods; D004558:Electric Stimulation; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism* / Q000502:physiology; D010477:Perfusion / Q000379:methods; D010902:Pituitary Gland / Q000098:blood supply; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
D013973:Thyrotropin-Releasing Hormone