Mediation of the photoperiodic effect on grooming reflexes by glucocorticoid hormones and serotonin
Abstract
Investigated 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 in cats with pontile lesions. 19 adult male cats with pontile lesions were divided among 4 groups. One group was adrenalectomized, another received 5,7-dihydroxytryptamine (5,7-DHT) injections in the superior colliculi, and the other 2 groups were used to provide the baseline response to photoperiod. For all 4 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 im injections of hydrocortisone and 5-HTP in abolishing the receptive fields was demonstrated. Data indicate a modulatory effect of serotonergic neurons on the photoperiodic regulation of glucocorticoid hormones. Comparisons of this study with previous photoperiodic studies establish that a complex seasonal rhythm exists that is controlled by the annual rhythm in photoperiod. (55 ref)