Endogenous material in brain inhibiting [3H]nicotine and [3H]acetylcholine binding

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Abstract
The supernatant obtained from mouse brain homogenates contains material that inhibits the saturable binding of [3H]nicotine in mouse cerebral cortex. This inhibitory material was further purified by heat denaturation, ultrafiltration through an Amicon PM‐10 membrane filter, and gel chromatography on Sephadex G‐10. The material inhibited the binding of [3H]acetylcholine with the same potency as it did that of [3H]nicotine. It also had some affinity for the sites that specifically bind [3H]D‐Ala, D‐Leu enkephalin, but had much lower affinity for the binding sites for [3H]quinuclidinyl benzilate (QNB), [3H]spiroperidol, [3H]naloxone, or [3H]imipramine. Acid hydrolysis destroyed the activity. These preliminiary results suggest the presence in brain of “nicotinelike” substances, one of which may be the endogenous ligand for the sites that specifically bind [3H]nicotine.