Atypical Synergistic<i>α</i>₁- and<i>β</i>-Adrenergic Regulation of Adenosine 3′,5′-Monophosphate and Guanosine 3′,5′- Monophosphate in Rat Pinealocytes

Abstract

The adrenergic control of cAMP and 3',5'-cyclic GMP (cGMP) in dispersed adult rat pinealocytes was investigated. Norepinephrine treatment increased cAMP and cGMP content 60- and 400-fold, respectively; both alpha- and beta-adrenoceptors had to be activated for these responses to occur. Beta-Adrenergic stimulation alone produced only about 6- and 2-fold increase in cAMP and cGMP content, respectively. Alpha-Adrenergic stimulation, which alone had no effect on either cyclic nucleotide concentration, markedly amplified the beta-adrenergic stimulation of both cAMP and cGMP. The relative potency of alpha-adrenergic agonists and antagonists indicates the alpha 1-subclass of adrenoceptors is involved. A role of alpha 1-adrenoceptors in the control of pineal cAMP is consistent with published evidence of the presence of alpha 1-adrenoceptors on pinealocytes and their role in the regulation of N-acetyltransferase activity and melatonin production.