Neurotensin release by rat hypothalamic fragments in vitro.
The release of neurotensin by hypothalami from male rats was investigated in vitro using tissue fragments incubated in Krebs-Ringer bicarbonate-glucose buffer at 37 degrees C. Neurotensin was measured by radioimmunoassay using an antibody directed toward the C-terminal portion of the peptide. Neurotensin-like immunoreactivity released into the incubation medium eluted from Sephadex G-25 in a position identical to that of the synthetic peptide and serial dilutions of incubation medium were parallel to those of synthetic neurotensin in the radioimmunoassay. Neurotensin-like immunoreactivity released into the incubation medium was degraded during the incubation period by released hypothalamic peptidases. The addition of bacitracin (0.5 mg/ml) to the medium partially prevented this degradation. Neurotensin release was stimulated by dibutyryl cyclic AMP (10(-4) M) and by depolarizing concentrations of potassium. The latter effect was shown to be Ca2+-dependent. Dopamine (10(-4)--10(-6) M) stimulated neurotensin release in a dose-dependent manner and this effect was blocked by the dopamine receptor antagonist, haloperidol. Neurotensin release was not stimulated by either norepinephrine (10(-4) M) or serotonin (10(-4) M). The results indicate that neurotensin is released by the hypothalamus in vitro; its release is stimulated by membrane depolarization in a Ca2+-dependent manner and may involve an adenylate cyclase mechanism; and dopamine appears to serve as a stimulatory neurotransmitter for neurotensin-containing neurons.
D000818:Animals; D001414:Bacitracin / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009496:Neurotensin / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D012701:Serotonin / Q000494:pharmacology
D001414:Bacitracin; D012701:Serotonin; D009496:Neurotensin; D003994:Bucladesine; D011188:Potassium; D002118:Calcium; D004298:Dopamine; D009638:Norepinephrine