Saliva secretion stimulated by alpha adrenergic beta adrenergic and muscarinic cholinergic neurotransmitters was evaluated in young adult and old rats. Parotid saliva was collected following methoxamin (METH) (6 mg/kg), isoproterenal (ISO) (30 mg/kg), or pilocarpin (PILO) (7.5 mg/kg) as secretory stimuli. The flow rate and the concentrations of protein, Na+ and K+ were measured. Saliva flow rate was 40%-50% lower (P < 0.01) in old rats following METH and PILO, but there was no difference following ISO stimulation. Saliva of old rats stimulated by METH or PILO contained about 30%-40% more (P < 0.01) protein, Comparable protein levels were in saliva stimulated by ISO. No changes were found in Na+ and K+ concentrations in all saliva samples. These results suggest that the age-related alteration in flow rate is not a general phenomenon, but rather specific and limited to the high flow rate stimulants (alpha-adrenergic and muscarinic-cholinergic). Transport alteration from the circulatory system into the parotid gland may be the underlying mechanism.