In vivo release of endogenously synthesized [3H]GABA from the cat substantia nigra and the pallido-entopeduncular nuclei.
Halothane anesthetized cats were implanted with push--pull cannulae to study the release of [3H]GABA continuously formed from [3H]glutamine in the substantia nigra (SN) and in the pallido-entopeduncular nuclei (PEP). A spontaneous release of [3H]GABA was observed from both structures and it reached a steady state level 1 h after the beginning of the superfusion with [3H]glutamine. In cats implanted with two push--pull cannulae, the local application of potassium (47 mM) in the PEP stimulated the release of [3H]GABA from the ipsilateral SN. In cats implanted with 4 push--pull cannulae, the unilateral 10 min electrical stimulation of the caudate nucleus evoked the release of [3H]GABA not only from the ipsilateral SN, but also in most cases from the contralateral structure. This stimulus also enhanced the release of [3H]GABA from PEP but the effects were mainly observed in the medio-caudal part of the ipsilateral PEP and in the latero-rostral part of the contralateral structure. In all cases, the changes in [3H]GABA release were observed during and after the electrical stimulation. The ipsilateral effects can be attributed to the direct activation of the caudato-PEP or caudato-SN GABAergic neurons. A polysynaptic neuronal loop must be involved in the symmetric contralateral effects.
D000818:Animals; D002415:Cats; D002421:Caudate Nucleus / Q000502:physiology; D004292:Dominance, Cerebral / Q000502:physiology; D004558:Electric Stimulation; D005917:Globus Pallidus / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D013378:Substantia Nigra / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005680:gamma-Aminobutyric Acid; D011188:Potassium