Abstract

A subcutaneous injection of an oil suspension of l-epinephrine (270 mumol/kg), dopamine (270 mumol/kg) or l-norepinephrine (270 mumol/kg), when administered with phenoxybenzamine (32 mumol/kg i.p.) to blocl alpha adrenergic effects, increases the cyclic 3', 5'-adenosine monophosphate (cAMP) content in superior cervical ganglia (SCG) of rats. The increase is highest after l-epinephrine and dopamine and is barely detectable after l-norepinephrine; it lasts longer than 2 hours after l-epinephrine, about 30 minutes after dopamine and is fleeting after l-norepinephrine. The duration of the increase in cAMP elicited by l-epinephrine in SCG of rats is dose-related. Furthermore, when the cAMP increase lasts longer than 90 minutes, 48 hours later the tyrosine hydroxylase (TH) activity in SCG is increased. l0Epinephrine (150 mol/kg s.c.) induces TH in decentralized ganglia. One injection of l-isoproterenol (77 mol/kg i.p.) increases cAMP concentrations in intact and decentralized SCG. This increase lasts only 30 minutes and fails to induce TH 48 hours later. However, if the increase of cAMP concentration is prolonged by four successive injections of l-isoproterenol (15 30-minute intervals) the TH activity of intact and decentralized SCG is increased 48 hours later.l-Isoproterenol (four injections of 77 mumol/kg, each) and l-epinephrine (270 mumol/kg) fail to induce TH in the adrenal medulla. dl-Propranolol (125 mumol/kg i.p.) injected 30 minutes before l-isoproterenol blocks the increase of cAMP content and the delayed induction of TH activity in SCG. The elevation of TH activity elicited in SCG by beta adrenergic receptor agonists is always preceded by an increase of cAMP concentration lasting 90 minutes or longer. However, the induction of TH elicited by cold exposure or by reserpine administration can occur without an apparent increase in ganglionic cAMP concentration.