Mediation of the photoperiodic effect on grooming reflexes by glucocorticoid hormones and serotonin.
The role of serotonin and glucocorticoid hormones in the mediation of the effect of photoperiod on the size of the receptive field for grooming reflexes was determined in cats with pontile lesions. Nineteen adult male cats with pontile lesions were used to form four groups. One group of cats with pontile lesions was adrenalectomized, another group received 5,7-dihydroxytryptamine injections in the superior colliculi, and the other two groups of cats with pontile lesions were used to provide the baseline response to photoperiod. Then, for all four groups, the receptive fields for the grooming bite, lick, and scratch reflexes were determined under different photoperiods. Both adrenalectomy and 5,7-DHT treatment blocked the effect of photoperiod. After the photoperiodic manipulations, the efficacy of intramuscular injections of hydrocortisone and 5-hydroxytryptophan in abolishing the receptive fields was demonstrated. The data indicate a modulatory effect of serotonergic neurons on the photoperiodic regulation of glucocorticoid hormones. Comparisons of this study with previous photoperiodic studies established that a complex seasonal rhythm exists which is controlled by the annual rhythm in photoperiod.
D000315:Adrenalectomy; D000818:Animals; D002415:Cats; D004837:Epinephrine / Q000494:pharmacology; D005938:Glucocorticoids / Q000502:physiology*; D006120:Grooming / Q000502:physiology*; D006854:Hydrocortisone / Q000494:pharmacology; D008027:Light; D008297:Male; D010507:Periodicity; D012018:Reflex / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology / Q000502:physiology*
D005938:Glucocorticoids; D012701:Serotonin; D006854:Hydrocortisone; D004837:Epinephrine