Lack of function of histamine H₁ and muscarinic acetylcholine receptors of mouse neuroblastoma cells grown in serum-free medium

Mouse neuroblastoma cells (Clone N1E-115) were grown in serum-free (defined) medium, defined medium supplemented with serum, and control medium to determine whether serum-free medium could substitute for serum-containing medium in our studies of the histamine H₁ and muscarinic acetylcholine receptors of these cells. The function of these receptors as determined by measurement of receptor-mediated cyclic [³H]GMP formation was absent in cells grown in serum-free medium and increased as the percentage of serum was increased in the defined medium, but never attained the levels found with control cells. Muscarinic receptor number for cells grown in defined medium was 60% above that found for control cells with no change in the affinity of the receptor for the radioligand (−)[³H]quinuclidinyl benzilate. Guanylate cyclase and acetylcholinesterase activities for cells grown in defined medium were 23 and 66% of those found in control cells, respectively. This marked reduction of guanylate cyclase activity in large part explains the lack of function of these receptors.