A novel choline-sensitive nicotinic receptor subtype that mediates enhanced GABA release in the chick ventral lateral geniculate nucleus

Nicotinic acetylcholine receptors modulate the release of GABA, glutamate, acetylcholine and dopamine in the brain. Here we describe a novel choline-sensitive nicotinic acetylcholine receptor that mediates enhanced GABA release in the chick ventral lateral geniculate nucleus. Whole-cell recordings in slices demonstrated that choline (0.03–10 mM), generally considered an α7-selective agonist, and carbachol (3–300 μM), a non-selective cholinergic agonist, both increased the frequency of spontaneous GABAergic events in ventral lateral geniculate nucleus neurons. Tetrodotoxin (0.5 μM) partially reduced responses to carbachol, but eliminated responses to choline. During long-term (5 min) exposure to choline the GABA enhancement was maintained until choline was washed out. Choline (300 μM) enhanced the frequency of spontaneous GABAergic events by 4.28-fold in control artificial cerebrospinal fluid. This choline-mediated enhancement was significantly reduced by the following nicotinic acetylcholine receptor antagonists: 1 μM dihydro-β-erythroidine (1.49-fold increase, P