Abstract: The neuroendocrine bag cells ofAplysiaprovide an excellent model system for exploring the roles of second-messenger pathways regulating peptide hormone secretion. Both the cAMP and diacylglycerol second-messenger systems and their associated protein kinases (PKA and PKC) are involved in regulating membrane excitability in bag-cell neurons ofAplysia.The purpose of the present set of experiments was to determine if PKA and PKC also play roles in regulating egg laying hormone (ELH) secretion from bag-cell neurons. Abdominal ganglia with attached bag-cell clusters and connective nerves were dissected from reproductively matureAplysia,and ELH secretion in response to electrically stimulated afterdischarges was measured by RIA. ELH secretion from bag cells treated with protein-kinase inhibitors (Rp-cAMPS to inhibit PKA; H-7 to inhibit PKC) was compared to that from untreated controls. Our experiments showed that 100 μM Rp-cAMPS significantly attenuated ELH secretion during the nonbreeding seasons (winter and spring) of 2 consecutive years. This suggested a role for PKA in regulating ELH secretion. However, Rp-cAMPS had no effect on ELH secretion during the breeding seasons (summer and fall) of 2 consecutive years, even when the dose of Rp-cAMPS was increased to 200 μM. These findings indicate that there is a seasonal fluctuation in responsiveness to PKA inhibition. We also investigated if there was a seasonal fluctuation in the ability of the PKC inhibitor H-7 to suppress ELH secretion. During the nonbreeding season, 10–100 μM H-7 significantly inhibited ELH secretion, but during the breeding season, only the highest dose (100 μM) of H-7 inhibited ELH release. These results confirm that PKC plays a role in regulating ELH secretion and indicate that there is a seasonal fluctuation in responsiveness to PKC inhibition. Overall, our findings suggest that both the cAMP and diacylglycerol second-messenger pathways are regulated on a seasonal basis.

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{{Explor lien
   |wiki=    Wicri/Psychologie
   |area=    BernheimV1
   |flux=    Main
   |étape=   Exploration
   |type=    RBID
   |clé=     ISTEX:39E36B3482B080ACFCD87AA71833CE43B5FC91F8
   |texte=   Seasonal Fluctuations in the Secretory Response of Neuroendocrine Cells of Aplysia californica to Inhibitors of Protein Kinase A and Protein Kinase C
}}