Alterations in γ-aminobutyric acid content in the rat superior cervical ganglion and pineal gland

Abstract

The endogenous γ-aminobutyric acid (GABA) content of the rat pineal gland and superior cervical ganglion (SCG) was measured by high pressure liquid chromatography. It was found that GABA levels in both tissues increased after decapitation of the animals. The GABA content of tissues frozen within 20 seconds after decapitation was the same as that of tissues removed from animals killed by microwave irradiation. Amino-oxyacetic acid, a GABA-transaminase inhibitor, increased the endogenous GABA content of both of these tissues. Dimethylphenylpiperizinium or isoniazid administration did not alter GABA levels in these tissues. Isoproterenol increased the GABA content of the SCG but did not change the pineal gland GABA levels. The ability of the pineal gland to take up and accumulate 3H-GABA was significantly reduced in rats that had been ganglionectomized. A fluctuation in endogenous GABA levels in the pineal gland was seen to occur when measures were taken at different times of the day. These results tend to suggest that GABA may have some functional role in the pineal gland and the superior cervical ganglion.