L-arginine-nitric oxide system in submandibular glands of rats chronically exposed to constant light..

Saliva secretion is mediated by activation of both branches of the autonomous nervous system. It has been suggested that the L-Arginine/Nitric Oxide System (L-Arg/NO) plays a modulatory role in the parasympathetic control of saliva secretion. Previous works in our laboratory shows that chronic exposure of rats to Constant Light increase sympathetic control and decrease parasympathetic control of submandibular gland secretory responses. The purpose of this work was study the involvement of L-Arg-NO system in submandibular gland of rats exposed (20 days) to constant light (LL). As control were used rats maintained under photoperiod. Total tissue activity of the enzyme nitric oxide synthase (NOS) was measured and the effect of NOS activity inhibitor, Nj nitro L- Arginine Methyl Ester (L-NAME 30mg/Kg, iv ­), upon the in vivo secretory response to the cholinergic agonist metacholine was determined. 

Results: a) The total activity of NOS in submandibular gland was significantly higher in LL  as compared to control rats and the levels remained without changes after the addition of aminoguanidine (500mM),  an inhibitor of inducible NOS activity. b) Secretory response to metacholine administration (10mg/Kg, iv) was similarly inhibited by L-NAME   in both groups. c) The inhibitor effect of L-NAME upon the secretory responses was totally reverted by the administration of NOS substrate, L-Arginine (300mg/Kg, iv).

Our results suggest that the increase of L-Arginine/Nitric Oxide System could participate in the change of parasympathetic nervous control of saliva secretion observed in constant light exposed rats.

 

Key words: constant light, NOS, salivary secretion.

This work was supported by the Agencia Cordoba Ciencia and SECyT.

rgallara@biomed.uncor.edu