Effect of post-mortem delay on density of tachykinin receptors in rat peripheral tissues

The effect of post-mortem delay on the affinity and density of tachykinin NK1 and NK2 receptors was examined in the rat submandibular gland and gastric fundus, respectively, using saturation binding studies with the radioligands [125I]Bolton-Hunter [Sar9, Met(O2)11]SP and [125I][Lys5, Tyr(I2)7, MeLeu9, Nle10]NKA(4-10). For NK1 receptors, no significant changes were seen in either Kd (control 375 +/- 35 pM, n = 5; 32 h post-mortem 390 +/- 59 pM, n = 5) or Bmax (control 96 +/- 16 fmol/mg protein, n = 5; 32 h post-mortem 62 +/- 10 fmol/mg protein, n = 5). For NK2 receptors, no alterations were seen up to 16 h post-mortem. However, significant (p < 0.001) changes were seen at 32 h post-mortem (n = 4), where values for Kd were increased (3.0 +/- 0.2 nM) and those for Bmax were reduced (42 +/- 5.9 fmol/mg protein), relative to control (Kd = 1.3 +/- 0.2 nM; Bmax = 208 +/- 30 fmol/mg protein, n = 5). These changes are probably related to observed histological deterioration. This study demonstrates the stability of tachykinin receptors in these peripheral tissues and indicates the suitability of post-mortem tissue as a valid control in future tachykinin receptor studies.