Postsynaptic actions of neurotensin on preoptic-anterior hypothalamic neurons in vitro

This study examines the effects of neurotensin (NT) on single neurons in explants of the preoptic-anterior hypothalamus (POAH) in vitro. Standard in vitro electrophysiological techniques were employed. Cultures were prepared from newborn rats and maintained in roller tubes for 3-4 weeks. NT was administered either through the superfusion fluid or via micropressure ejection (0.5-10 psi). Pressure ejection of NT produced a consistent, dose-related, excitatory effect on 71% of the cells studied. The remaining cells were either unresponsive to NT or inhibited by it. In addition, the excitatory effects of microiontophoretically applied glutamate (10-100 nA) were markedly enhanced by NT applied at concentrations that did not alter spontaneous rate. The effects of NT at higher concentrations were additive with glutamate. The effects of NT persisted in Ca2+-free medium when synaptic activity was suppressed. These data indicate that NT exerts a potent excitatory effect on single neurons in the POAH in vitro. Moreover, this effect proved to be additive with that of glutamate. The persistence of these effects in Ca2+-free medium suggests that the actions of NT are postsynaptic in nature.