In vivo evidence for an inhibitory glutamatergic control of serotonin release in the cat caudate nucleus: involvement of GABA neurons.
The local effect of L-glutamic acid (5 x 10(-5) M) on the release of [3H]serotonin continuously synthesized from [3H]tryptophan was examined in the caudate nucleus of 'encéphale isolé' unanaesthetized cats implanted with push-pull cannula. L-Glutamic acid (5 x 10(-5) M) decreased [3H]serotonin release from nerve terminals of the dorsalis raphe-striatal serotonergic neurons. The effect was antagonized by 2-amino-6-trifluoromethoxybenzothiazole (PK 26124) (10(-6) M), an antagonist of glutamatergic transmission. This effect was mimicked by N-methoxy-D-aspartic acid NMDA (5 x 10(-5) M) and prevented by DL-2-phosphono-valeric acid (APV) (5 x 10(-6) M), indicating that L-glutamic acid decreased serotonin release via a N-methoxy-D-aspartate type receptor. The superfusion of serotonergic nerve terminals in the caudate nucleus with tetrodotoxin prevented the inhibitory L-glutamic acid-induced effect on serotonin release. Furthermore, L-glutamic acid-induced inhibition of [3H]serotonin release was antagonized by bicuculline (5 x 10(-5) M). These data suggest that the glutamatergic receptors involved were not located directly on serotonin nerve terminals. The inhibitory control exerted by L-glutamic acid on serotonergic transmission could involve gamma-aminobutyric acid interneurons. Since no reduction of spontaneous [3H]serotonin release was observed in the presence of bicuculline, GABAergic neurons appeared to exert a phasic influence on serotonin release. Indirect inhibitory presynaptic control on serotonin release mediated by corticostriatal glutamatergic fibers is discussed in light of previous findings.
Becquet
D
D
Laboratoire de Neuroendocrinologie Expérimentale, Faculté de Médecine Nord, I.N.S.E.R.M. U.297, Marseille, France.
Faudon
M
M
Hery
F
F
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002415:Cats; D002421:Caudate Nucleus / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005971:Glutamates / Q000494:pharmacology / Q000502:physiology*; D018698:Glutamic Acid; D008297:Male; D016202:N-Methylaspartate; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D019782:Riluzole; D012701:Serotonin / Q000378:metabolism*; D013116:Spinal Cord / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects; D013779:Tetrodotoxin / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D005971:Glutamates; D013844:Thiazoles; D001224:Aspartic Acid; D012701:Serotonin; D018698:Glutamic Acid; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D019782:Riluzole; D001640:Bicuculline