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

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.