See‐Saw Signal Processing in Pinealocytes Involves Reciprocal Changes in the α1‐Adrenergic Component of the Cyclic GMP Response and the β‐Adrenergic Component of the Cyclic AMP Response

Abstract

Pineal cyclic AMP and cyclic GMP are regulated by norepinephrine (NE) acting through α₁-_- and β-adrenoceptors. β-Adrenergic stimulation appears to be an absolute requirement and a,-adrenergic activation amplifies β-adrenergic stimulation of the cyclic AMP response 10-fold and the cyclic GMP response 100-fold, respectively. Chronic deprivation of adrenergic stimulation, due to exposure to constant light (LL) or by surgical denervation, enhances the cyclic AMP response and diminishes the cyclic GMP response as compared to control animals in a 10:14 light/dark (LD) cycle. This phenomenon is termed see-saw signal processing. In the current study we find these changes do not reflect shifts in the time course or K_a of these responses. Dose-response studies indicate the p-adrenergic component of cyclic AMP stimulation is enhanced and the α₁-adrenergic component of cyclic GMP stimulation is diminished in LL pinealocytes. Several observations indicate these changes may reflect alterations in Ca²⁺ -sensitive postreceptor mechanisms.