Determination of mRNA levels of specific genes is becoming increasingl
y important as a measure of gene expression. With the recent advent of
RT-PCR, the sensitivity for mRNA determination has been increased dra
matically, and this technique is becoming widely used in neuroendocrin
e studies which involve small tissue samples and/or isolated nuclei. N
evertheless, the exact procedure for reliable quantification of RT-PCR
has been widely debated. This minireview attempts to assimilate the a
vailable literature on the RT-PCR technique and discuss the various ap
proaches commonly used to obtain quantitative results using the techni
que. An example from our laboratory of the use of RT-PCR for the measu
rement of several gene products in the same sample using exogenous int
ernal standards is also provided. Particular attention is paid to the
choice of endogenous vs. exogenous internal standards, the length of t
he transcript of the standard and its relationship to the target seque
nce being amplified, the amplification pattern of the target gene and
internal standard, the reproducibility of the method, and the overall
usefulness and suitability of RT-PCR for neuroendocrine studies.