A specific antiserum recognizes clonidine-displacing substance: implications for the structure of the brain's own clonidine

Neurosci Lett. 1988 Jan 11;84(1):84-90. doi: 10.1016/0304-3940(88)90342-4.


A polyclonal antiserum was raised in rabbit against the clonidine analog p-aminoclonidine (PAC) coupled to hemocyanin. The antiserum (anti-PAC3) exhibited high affinity for unconjugated [3H]PAC (Kd 0.32 +/- 0.07 nM) in a rapid-filtration radioimmunoassay. Competition experiments showed that PAC, clonidine, and naphazoline cross-reacted with the anti-PAC3 antiserum, whereas a number of other structurally related compounds did not. An endogenous clonidine-displacing substance (CDS) partially purified from bovine brain also inhibited specific [3H]PAC binding to anti-PAC3 in a dose-dependent manner. Thus, (a) anti-PAC3 antiserum is specific for clonidine and closely related compounds, and (b) CDS may structurally resemble clonidine since it is recognized by this highly specific antiserum.

MeSH terms

  • Animals
  • Brain / metabolism*
  • Cattle
  • Chemical Phenomena
  • Chemistry
  • Clonidine / antagonists & inhibitors*
  • Clonidine / immunology
  • Clonidine / metabolism*
  • Cross Reactions
  • Immune Sera / immunology*
  • Radioimmunoassay


  • Immune Sera
  • clonidine-displacing substance
  • Clonidine