The effects of castration on histamine levels and 24-hour rhythm in the male rat hypothalamus.
Holtzman male rats were castrated or sham-operated at 22 days of age and raised in a 12 h light: 12 h dark illumination cycle. At age 63 days they were sacrificed by decapitation at six different times during the light:dark (L:D) cycle, and hypothalamic histamine (H) concentrations were measured using a modified single isotope-enzyme microassay. Hypothalamic H was significantly elevated in the castrated rats at all but two of the six times sampled during the L:D cycle, when compared with the sham-operated controls. Both surgical groups had similar 24-h rhythms of hypothalamic H concentrations, with the peak concentration occurring during the light phase followed by a rapid drop to the minimum 2-3 h later. However, the castrated rats appeared to attain both maximal and minimal concentrations somewhat earlier in the day. These results provide circumstantial evidence that hypothalamic H may have a role in the hypothalamo-hypophyseal-gonadal axis in the male rat.
D000375:Aging; D000818:Animals; D002369:Castration; D002940:Circadian Rhythm; D006632:Histamine / Q000378:metabolism*; D007031:Hypothalamus / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D051381:Rats; D013737:Testis / Q000502:physiology; D013997:Time Factors
D006632:Histamine