The action of neurotensin on single myenteric neurones

The action of neurotensin was studied on single myenteric neurones within ganglia of the myenteric plexus isolated from the guinea-pig ileum. Drugs were applied by adding them to the perfusing Krebs solution. Extracellular recording with glass suction electrodes indicated that neurotensin (100 pM-300 nM) caused a dose-dependent excitation of about 50% of myenteric neurones; the remaining neurones were unaffected. This effect persisted in calcium-free solutions. Intracellular recording showed that a similar proportion of Type 1 myenteric neurones were depolarized by neurotensin: this was associated with an increase in membrane resistance. Type 2 cells were either depolarized or hyperpolarized by neurotensin. The depolarization persisted in calcium-free solutions. The hyperpolarization disappeared in calcium-free solutions, suggesting either that the potential change itself is calcium-dependent or that it was due to release by neurotensin of a hyperpolarizing substance.