["Push-pull" perfusion technic in neuroendocrinology]

In this article the author reviews the different models of push-pull cannula device used in neuroendocrinology, mainly those applied to the study of neurohormones release from median eminence (ME). At present, three technical details might explain some disagreements resulting from application of push-pull perfusion (PPP) in neuroendocrinology, concerning for instance, the SRIF release: firstly, the tissue damage connected with the diameter of the cannulas utilized (guide and perfusion), secondly, the perfusion flow which can vary from 15 to 40 microliter/min according to the authors, and finally, the means of implanting the cannula in the ME (between 8 days and 1 hour before perfusion). The author compares the values of SRIF, TRH and CRF releases measured by portal cannula with those obtained by PPP. It would seem that the application of a physiological stimulus triggers a response measured in the perfusate whose amplitude as compared to basal levels, is more important than the amplitude measured in portal blood. In conclusion, in despite of its limits--reproductiveness and yield--, at the present time PPP may be considered one of the major methodological tools affording the physiologist optimum conditions for in vivo studies.