ALTERATION OF MUSCARINIC ACETYLCHOLINE-RECEPTORS IN RABIES VIRAL-INFECTED DOG BRAINS

Functions of the muscarinic acetylcholine receptor (mAChR) were studie d in rabid dog brains using [H-3]quinuclidinyl benzilate (QNB) as a ra dioligand. Of various brain regions, hippocampus and brainstem were th e areas mostly affected in terms of impaired specific binding to [H-3] QNB, as compared to other regions, as well as to those of controls. Sa turation studies of the hippocampus revealed significantly elevated di ssociation equilibrium constant (K-d) values in both furious (n = 5) ( 9.80 +/- 2.77 nM) and dumb (n = 6) (6.01 +/- 1.08 nM) types of rabies as compared to 11 controls (2.15 +/- 0.31 nM), whereas the maximum num ber of receptor sites (B-max) values were comparable among all subgrou ps of normal (1.38 +/- 0.10 pmol/mg protein), dumb (1.43 +/- 0.17 pmol /mg protein) and furious (1.28 +/- 0.12 pmol/mg protein) rabies types. Hippocampal K-d values were comparable between high (fluorescent anti body test-FAT and polymerase chain reaction-PCR positive; n = 4) (7.47 +/- 3.27 nM), and low (FAT-negative and PCR-positive; n = 4) virus am ount (8.34 +/- 3.93 nM) but these were significantly higher than contr ols (n = 4) (1.58 +/- 0.17 nM). Our data suggest a functional derangem ent of mAChR at specific sites of hippocampus and brainstem which is n ot dependent on the amount of virus.