Effect of surgical stress on benzodiazepine receptors as a consequence of placebo pellet implantation in rat: An autoradiographic study

This paper reports modifications in benzodiazepine (BZ) receptors induced b y minimally invasive surgery, such as pellet implantation, a widely used su rgical process for chronic drug administration. The intrinsic stress induce d by this manipulation on BZ receptors was analysed in an autoradiographic saturation study determining the affinity (K-D) and total number (B-max) of binding sites of a number of brain areas from the mesencephalon, cerebral cortex, hippocampus, and cerebellum, The radioligand used for the study was [H-3]flunitrazepam, which permitted overall characterization of BZ binding sites. Use of the specific BZ1 agonist zolpidem as an inhibitor of this ra dioligand permitted the direct characterization of subtype 2 (BZ2) and the indirect characterization of subtype 1 receptor (BZ1). Significant increase s in B-max and K-D values were observed in pellet-implanted animals with re spect to those not implanted. The results support the notion of an upregula tion of these receptors, mainly in BZ1 receptors, following sustained desen sitization as a result of the surgical stress induced by pellet implantatio n. (C) 1999 Elsevier Science Inc.