Plasticity of the frog monocular OKN: involvement of pretectal GABAergic and cholinergic systems.
The frog horizontal monocular optokinetic nystagmus (OKN) is asymmetrical, the temporal-nasal (T-N) stimulation being the sole stimulation efficient to evoke the reflex, the nasal-temporal (N-T) component being almost absent. Coil recordings showed that, in adult animals, prolonged monocular visual deprivation by unilateral eyelid suture provoked the appearance of the N-T component. The OKN became symmetrical, reacting for both directions of stimulation. Microinjection of either gamma-aminobutyric acid (GABAA) agonist 4,5,6,7-tetrahydroisoxazolo (5,4-C) Pyridin-3-ol (THIP) or muscarinic cholinergic antagonist atropine into the nucleus lentiformis mesencephali, the pretectal mesencephalic structure involved in OKN, transiently abolished the presence of N-T component. This result suggests that the phenomenon of visual plasticity, occurring after a week of monocular deprivation, can be due, at least partially, to reduction in pretectal GABAergic inhibition, and to concomitant activation of cholinergic muscarinic receptors.
Jardon
B
B
Centre de Neurochimie du C.N.R.S. Strasbourg, France.
Bonaventure
N
N
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D007555:Isoxazoles / Q000494:pharmacology; D008845:Microinjections; D009760:Nystagmus, Physiologic / Q000502:physiology*; D010275:Parasympathetic Nervous System / Q000502:physiology*; D011893:Rana esculenta; D015349:Vision, Monocular / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D007555:Isoxazoles; D005680:gamma-Aminobutyric Acid; D001285:Atropine; C015542:gaboxadol