Neurohormones on Brain Adenyl Cyclase Activity <Emphasis Type="Italic">in vivo</Emphasis>

CYCLIC adenosine 3′,5′-monophosphate (cyclic AMP) has been suggested to be the receptor site for neurotransmitters as well as a second messenger which mediates the action of a variety of hormones and neurohormones in animals and human tissues. Cyclic AMP is derived from adenosine triphosphate (ATP) by the activity of adenyl cyclase and it is metabolized into adenosine monophosphate (AMP) by phosphodiesterase. Beta receptor and adenyl cyclase may be the same in the peripheral tissues¹. In vitro activation of adenyl cyclase activity by various putative neurotransmitters such as noradrenaline (NA), 5-hydroxytryptamine (5-HT), acetylcholine (ACh) and histamine in preparations from brain homogenates and slices is well established². The in vivo effect, however, of these neurohormones on adenyl cyclase has not been studied.