Involvement of opioid and non-opioid mechanisms in footshock-induced enhancement of brain histamine turnover in mice.
Naloxone (1-10 mg/kg, i.p.) dose-dependently inhibited the footshock-induced elevation in levels of tele-methylhistamine (t-MH), a predominant metabolite of brain histamine (HA), although this compound had no effect on the HA dynamics in the non-shocked control mice. Footshock significantly enhanced the HA depletion induced by alpha-fluoromethylhistidine, a specific inhibitor of histidine decarboxylase. However, in mice treated with naloxone (5 mg/kg, i.p.) footshock did not significantly facilitate the alpha-fluoromethylhistidine-induced HA depletion. In mice which had been rendered morphine-tolerant following an s.c. implantation of a pellet containing 50 mg of morphine base 3 days before, footshock produced no significant elevation of the t-MH level. The treatment with alpha-methyl-p-tyrosine, p-chlorophenylalanine or atropine had no significant influence on the footshock-induced t-MH elevation. The t-MH elevation was the most marked in the midbrain. In the hypothalamus and pons-medulla oblongata, no significant change in the t-MH level was produced by footshock. These results suggest that footshock increases the HAergic activity in the mouse brain partly through activation of opioid-related mechanisms and that alterations in HA dynamics differ with region of the brain.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004597:Electroshock; D010134:Fenclonine / Q000494:pharmacology; D005528:Foot; D006632:Histamine / Q000378:metabolism*; D008297:Male; D008761:Methylhistamines / Q000378:metabolism; D008781:Methyltyrosines / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D010293:Pargyline / Q000494:pharmacology; D019805:alpha-Methyltyrosine
D008761:Methylhistamines; D008781:Methyltyrosines; D009270:Naloxone; D019805:alpha-Methyltyrosine; D009020:Morphine; D001285:Atropine; D006632:Histamine; D010293:Pargyline; C020404:tele-methylhistamine; D010134:Fenclonine