P. Schmidt et al., Numerical density of mu opioidreceptor expressing neurons in the frontal cortex of drug related fatalities, FOREN SCI I, 115(3), 2001, pp. 219-229
In animal and cell culture experiments, chronic morphine treatment has been
followed by 'up'- as well as 'down-regulation' of the mu opioidreceptor (m
u OR) number. The present postmortem morphometric study of morphine-related
fatalities of drug addicts (n = 12 and 22-35 years old, with blood unconju
gated morphine levels from 27.1 to 458 ng/ml, m.v. 198.5 ng/ml) versus a no
n-addicted control group (n = 13 and 10-44 years old) was intended to exami
ne whether chronic opiate exposure affects the numerical density of mu OR e
xpressing neurons in the human neocortex (area 10 according to Brodmann). F
or the immunohistochemical procedure, thick (100 mum) vibratome sections we
re incubated with a monoclonal antibody against the mu OR [Arvidsson et al.
, J. Neurosci. 15 (1995) 3328] and immunoreactive sites were visualized usi
ng an immunoperoxidase protocol. The numerical densities of mu OR-expressin
g and Nissl-stained neurons were assessed morphometrically (camera lucida-d
rawings). In both collectives, the anti-mu OR immunoreactivity was mainly f
ound in pyramidal neurons of layers (L) II/III and V and in multiform neuro
ns of L VI. In the drug-related fatalities and the control group, the densi
ty of neurons expressing mu OR protein was similar, amounting for 2698 +/-
153 and 2688 +/- 172/mm(3), respectively. These findings extend the binding
studies of opioid ligands in postmortem brains of heroin addicts [Gabilond
o ct al., Psychopharmacology 115 (1994) 135] revealing similar receptor den
sities and affinities by showing no difference in the density of mu OR-posi
tive neurons. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.