Cholinergic muscarinic binding by rat lymphocytes: effects of antagonist treatment, strain and aging.

Cholinergic muscarinic binding by viable peripheral lymphocytes was assessed by measuring specific binding of the muscarinic antagonist [3H]quinuclidinyl benzylate. After atropine treatment maximal lymphocyte muscarinic binding was increased by about 30%, as it did in the hippocampus of the same rats. Strain-dependent differences in muscarinic binding by peripheral lymphocytes were correlated with similar differences in selective brain regions. Higher muscarinic binding was observed in lymphocytes derived from aged (24 months old) rats. We conclude: atropine treatment causes an increase in lymphocyte muscarinic binding as it does in the brain; strain differences in brain muscarinic binding are paralleled by similar differences in lymphocytes; and in aged rats muscarinic binding capacity by lymphocytes is elevated. The results indicate that circulating lymphocytes may serve as a useful peripheral marker reflecting induced alterations or inherent differences in muscarinic binding.