Neurotensin selectively alters ethanol-induced anesthesia in LS/Ibg and SS/Ibg lines of mice

Abstract

Neurotensin (NT) differentially altered ethanol-induced anesthesia as measured by duration of loss of righting response or by blood ethanol levels producing loss of righting response in mice (LS and SS) which were selectively bred for differences in response to ethanol. At dose of 5–500 ng i.c.v., NT increased ethanol sensitivity in SS mice, but not in LS mice, as measured by blood ethanol concentrations at loss of righting response. At higher doses, 0.5–10 μg i.c.v., NT enhanced the sensitivity of both SS and LS mice to ethanol-induced anesthesia. The hypothermic effect of ethanol determined at loss of righting response was not altered in either LS or SS mice at low doses of NT, but at higher doses NT enhanced ethanol-induced hypothermia in both lines of mice. The altered anesthetic sensitivity was specific for ethanol in that NT did not alter pentobarbital-induced sleep time in either LS or SS mice and halothane anesthesia was altered slightly on ly in LS mice. NT analogues, N-acetyl-NT 8−13, and [ d-Trp 11]-NT but not NT 1−8 enhanced the anesthetic action of ethanol in SS mice. Bombesin, cholecystokinin sulfate, substance P, [ d-Trp 8, d-Cys 14]-somatostatin and corticotropin releasing hormone (CRF) were not effective in enhancing ethanol-induced anesthesia in LS or SS mice. CRF appeared to decrease ethanol sensitivity in LS but not in SS mice. β-Endorphin (β-END) markedly increased the ethanol sensitivity of SS and to a lesser extent of LS mice at relatively high doses, e.g. 0.5–1.0 μg i.c.v. The results of the present study indicate that differences in brain sensitivity of LS and SS mice to ethanol may be mediated by genetic differences in NT systems. Likewise, NT, and probably β-endorphin, may interact with other neurochemical processes that are involved in the mechanism of ethanol-induced anesthesia and that differ genetically in LS and SS mice.