gamma-Aminobutyric acid enhances the light response of ganglion cells in the trout pineal organ.
Electrical recordings from achromatic second order neurons of intact superfused pineal organs of the rainbow trout were used to investigate the role of gamma-aminobutyric acid (GABA) in the transmission of photoreceptor signals onto centrally projecting ganglion cells. Bath-applied GABA decreased the spike discharge rate of 98% of achromatic ganglion cells in a dose-dependent manner. GABA was also active if applied during synaptic blockade, demonstrating the presence of GABAergic receptors at the ganglion cell level. Responsiveness of ganglion cells to light was reversibly enhanced by GABA. The light response curve of ganglion cells, which was obtained by plotting spike rate versus light intensity, was significantly shifted to lower frequencies by GABA, indicating that GABA is an important inhibitory modulator of ganglion cell activity in the trout pineal organ.
Brandstätter
R
R
Department of Animal Physiology, University of Salzburg, Austria. brandst@edvz.sbg.ac.at
Hermann
A
A
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003623:Dark Adaptation / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D005724:Ganglia / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D017686:Oncorhynchus mykiss / Q000502:physiology*; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000187:drug effects; D010870:Pineal Gland / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D005680:gamma-Aminobutyric Acid