The 5-hydroxytryptamine content and synthesis of normal and denervated pineal gland

Abstract

The bioassay the 5-HT content of the pineal gland was determined in normal rats and after 5 to 30 days of bilateral extirpation of the superior sympathetic ganglia. The normal 5-HT content varied between 10 and 20 ng of 5-HT base per pineal with a mean of 14.5 ± 1.3 which corresponds to 11.1 μg/g. In brain the normal content was approximately 0.28 μg/g. Denervation produces a decrease in 5-HT of 73 per cent after 5 days, which stabilizes at about ▪ per cent, between 10 to 30 days. The injection of 25 mg/kg 5-HTP increased the 5-HT content of the normal gland by 400 per cent in 30 minutes. In brain the increase was 200 per cent. In the denervated gland the synthetic capacity for 5-HT is reduced to about 1/5 of the normal. The injection of 25 mg/kg of 5-HT showed no uptake by the normal pineal glands and by brain after 10 minutes. However the denervated gland increased the 5-HT content above the control level. The existence of two pools of 5-HT in the pineal gland, one in nerves and the other in the pinealocytes is demonstrated and some of their properties are discussed.