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A brief review of hormonal and behavioral aspects of reproduction in the aging avian male
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THE INFLUENCE OF STEROIDS ON SEXUAL IMPRINTING IN MALE ZEBRA FINCHES. Ekkehard Prove*, Universitat Bielefeld. The phenomenon of imprinting provides an excellent tool to study the interplay of endo- and exogenous factors during behavioural development because of its clear-cut species-specific sensitive phases and the stability of the acquired information. From the ethological point of view imprinting phenomena are well studied. The knowledge about physiological mechanisms underlying imprinting processes is scarce. Immelmanns investigations on sexual imprinting in male Zebra Finches provide an excellent basis to investigate the sexual imprinting process from a physiological point of view. One of the physiological sets of factors which may be responsible for the occurrence of specific sensitive phases during early ontogeny are steroid hormones. They are well known to possess organizational abilities in the CNS during early ontogeny. Based on the hypothesis (1) that changes in neuronal connectivity of certain areas of the brain are involved, and (2) that steroids take part in the control of these changes, a series experiments were designed. Findings on the hormonal development indicated that steroid titers in developing Zebra Finch males are not only correlated with increasing age. For were found in testosterone development and the time example , correlations Both, onset and end scale of the sensitive phase for sexual imprinting. of the sensitive phase coincide with maxima in testosterone production. Results from various experiments including a treatment with different steroids during the sensitive phase support the hypothesis that steroids take part in the control of sexual imprinting.
A BRIEF REVIEW OF HORMONAL AND BEHAVIORAL ASPECTS OF REPRODUCTION IN THE AGING AVIAN MALE. M. A. Ottinger, J. Balthazart*and J. H. Soares, Jr. Department OF Poultry Science, University of Maryland, College Park, MD 20742 and University of Liege, Liege, Belgium. Reproduction capability, as reflected in egg production and fertility, declines with age. This decline aopears to be due to alterations that In broiler occur in both endocrine and behavioral aspects of reproduction. breeders housed in floor pens, fertility progressively decreased after 50 Levels of plasma testosterone declined and frequency of weeks of age. mating behavior simultaneously decreased in these birds coincident with the Experiments in Japanese quail have shown that a similar drop in fertility. decline in fertility occurs by 56 weeks of age in quail maintained under stimulatory photoperiod (16L:8D). By this age males had decreased or ceased courtship and mating behavior. Plasma levels of testosterone fell with age, even in males that continued to show reproductive behavior. As might be expected plasma LH was elevated in older, behaviorally active males. However, males that were behaviorally inactive had lower plasma concentrations of both testosterone and LH. Testosterone implants in intact behaviorally inactive males restored behavior indicating that additional testosterone could restimulate behavior. In old or young castrated males, testosterone implants restimulated behavior; however, older males had a longer lag time for their response. Finally, there is evidence that metabolism of testosterone becomes altered with age, resulting in changes in the availability of physiologically active metabolites. These results implicate gonadal as well as hypothalamic alterations in the aging avian male which can then affect reproductive capability.
THE INFLUENCE OF STEROIDS ON SEXUAL IMPRINTING IN MALE ZEBRA FINCHES. Ekkehard Prove*, Universitat Bielefeld. The phenomenon of imprinting provides an excellent tool to study the interplay of endo- and exogenous factors during behavioural development because of its clear-cut species-specific sensitive phases and the stability of the acquired information. From the ethological point of view imprinting phenomena are well studied. The knowledge about physiological mechanisms underlying imprinting processes is scarce. Immelmanns investigations on sexual imprinting in male Zebra Finches provide an excellent basis to investigate the sexual imprinting process from a physiological point of view. One of the physiological sets of factors which may be responsible for the occurrence of specific sensitive phases during early ontogeny are steroid hormones. They are well known to possess organizational abilities in the CNS during early ontogeny. Based on the hypothesis (1) that changes in neuronal connectivity of certain areas of the brain are involved, and (2) that steroids take part in the control of these changes, a series experiments were designed. Findings on the hormonal development indicated that steroid titers in developing Zebra Finch males are not only correlated with increasing age. For were found in testosterone development and the time example , correlations Both, onset and end scale of the sensitive phase for sexual imprinting. of the sensitive phase coincide with maxima in testosterone production. Results from various experiments including a treatment with different steroids during the sensitive phase support the hypothesis that steroids take part in the control of sexual imprinting.
A BRIEF REVIEW OF HORMONAL AND BEHAVIORAL ASPECTS OF REPRODUCTION IN THE AGING AVIAN MALE. M. A. Ottinger, J. Balthazart*and J. H. Soares, Jr. Department OF Poultry Science, University of Maryland, College Park, MD 20742 and University of Liege, Liege, Belgium. Reproduction capability, as reflected in egg production and fertility, declines with age. This decline aopears to be due to alterations that In broiler occur in both endocrine and behavioral aspects of reproduction. breeders housed in floor pens, fertility progressively decreased after 50 Levels of plasma testosterone declined and frequency of weeks of age. mating behavior simultaneously decreased in these birds coincident with the Experiments in Japanese quail have shown that a similar drop in fertility. decline in fertility occurs by 56 weeks of age in quail maintained under stimulatory photoperiod (16L:8D). By this age males had decreased or ceased courtship and mating behavior. Plasma levels of testosterone fell with age, even in males that continued to show reproductive behavior. As might be expected plasma LH was elevated in older, behaviorally active males. However, males that were behaviorally inactive had lower plasma concentrations of both testosterone and LH. Testosterone implants in intact behaviorally inactive males restored behavior indicating that additional testosterone could restimulate behavior. In old or young castrated males, testosterone implants restimulated behavior; however, older males had a longer lag time for their response. Finally, there is evidence that metabolism of testosterone becomes altered with age, resulting in changes in the availability of physiologically active metabolites. These results implicate gonadal as well as hypothalamic alterations in the aging avian male which can then affect reproductive capability.