Effects of histamine and alpha-fluoromethylhistidine injections on circadian phase of free-running rhythms.
Sequential IP injections of alpha-fluoromethylhistidine at CT-6 and CT-18 elicited transient delay during the injection period in the onset of activity in the free-running circadian rhythms of locomotor and drinking activities. Histamine injection ICV resulted in various changes, permanent or transient, in the circadian phase of the free-running rhythms depending on the subjective time of the injection: it caused transient advance in onset of activity when injected at CT-0, 3, 6, 9, 18 or 21, whereas it caused permanent phase-delay when injected at CT-12 or 15. These permanent effects were plotted in a phase-response curve. Histamine administration at CT-6 and CT-18 resulted in transient, reciprocal changes of almost equivalent amplitude changes to those of histamine depletion at the corresponding subjective times. Although this transient shift may represent a masking effect of the drug, HA may modulate the circadian synchronization mechanism(s) during the advance sensitive phase. Moreover, HA seems to elicit phase-delay by affecting the light-relaying tract.
Itowi
N
N
Department of Pharmacology II, Faculty of Medicine, Osaka University, Japan.
Yamatodani
A
A
Nagai
K
K
Nakagawa
H
H
Wada
H
H
D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D004326:Drinking / Q000187:drug effects*; D006632:Histamine / Q000494:pharmacology*; D006639:Histidine / Q000031:analogs & derivatives*; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D008297:Male; D008762:Methylhistidines / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D008762:Methylhistidines; D006639:Histidine; C028309:alpha-fluoromethylhistidine; D006632:Histamine