EXPRESSION OF BRAIN NITRIC-OXIDE SYNTHASE IN THE DEVELOPING RAT PINEAL-GLAND COINCIDES WITH THE APPEARANCE OF THE ADRENERGIC CYCLIC GUANOSINE 3'5'-MONOPHOSPHATE RESPONSE

In the developing rat pineal gland, norepinephrine (NE)-stimulated cyc lic guanosine 3',5'-monophosphate (cGMP) formation appears 2 weeks lat er than that of cyclic adenosine 3',5'-monophosphate (cAMP) formation. Since NE-stimulated cGMP formation requires formation of nitric oxide (NO) in the adult rat pineal, we investigated the developmental appea rance of the NO-forming enzyme brain NO-synthase (NOS) to find out whe ther the delayed cGMP response results from the late appearance of NOS . In this study, we investigated pineal glands of rats aged 8-21 days and 8 weeks. Western blot analysis revealed that NOS-immunoreactivity (NOS-TR) was barely detectable until day 12. On day 15 NOS-IR exhibite d the same intensity as in adult rats. Expression of NOS at this postn atal stage appears to be responsible for the developmental appearance of the adrenergic cGMP response.