Journal of Neuroscience, Vol 4, 1653-1661, Copyright © 1984 by Society for Neuroscience
A single class of neurotensin receptors with high affinity in neuroblastoma X glioma NG108-15 hybrid cells that mediate facilitation of synaptic transmission
Y Nakagawa, H Higashida and N Miki
Receptor binding of [3H]neurotensin was examined on membrane preparations
derived from neuroblastoma X glioma NG108-15 hybrid cells. The specific
binding was saturable and reversible, and a dissociation constant (Kd) was
calculated to be about 0.24 nM from the rate constants. Scatchard analysis
of neurotensin binding at equilibrium revealed a single class of binding
sites with a Kd of 0.86 nM and a maximal binding capacity (Bmax) of 250
fmol/mg of protein (7700 receptor sites/cell). [D-Arg9]-Neurotensin had a
high affinity (IC50 = 0.5 nM) for the neurotensin receptors, but
[D-Phe11]-neurotensin had a lower affinity (IC50 = 280 nM), while
angiotensin II and bradykinin had almost no affinity for
[3H]neurotensin-binding sites. Under similar conditions [3H]neurotensin
binding to mouse and rat brain synaptosomal fractions showed two binding
sites with high (0.86 and 0.44 nM) and low (13 and 19 nM) affinities. We
have examined several possible physiological consequences of neurotensin
receptor binding. Neurotensin (10 microM) exhibited no influence on
adenylate cyclase activity, 45Ca uptake, or 32Pi incorporation into
phosphatidylinositol fractions of NG108-15 cells. Electrophysiological
study of isolated NG108-15 cells revealed neurotensin-induced transient
hyperpolarization followed by sustained depolarization with enhanced
membrane excitability. Application of neurotensin to NG108-15 cells that
had formed synapses with cultured striated muscle cells caused a
considerable increase in frequency of miniature endplate potentials from
the muscle cells. These data show that NG108-15 cells possess a single
class of neurotensin receptors similar to a high affinity site of
synaptosomal membranes from the murine brains.(ABSTRACT TRUNCATED AT 250
WORDS)