Role of presynaptic 5-HT1A and 5-HT3 receptors in modulation of synaptic GABA transmission in dissociated rat basolateral amygdala neurons.
Serotonin (5-HT) is considered to play a significant role in anxiety-related behaviors in animals through actions on the amygdaloid complex. To evaluate this role from the point of neurotransmitter release regulation, nystatin-perforated patch recording was employed on mechanically dissociated basolateral amygdala neurons containing functional synaptic boutons. GABAAergic miniature inhibitory postsynaptic currents (mIPSCs) were pharmacologically separated. In subsets of neurons, 8-OH-DPAT (1 microM), a specific 5-HT1A agonist, continuously inhibited mIPSC frequency without effects on mIPSC amplitude. By comparison, mCPBG (1 microM), a specific 5-HT3 agonist, transiently facilitated mIPSC frequency without effects on mIPSC amplitude. Together these results suggest the presynaptic existence of both 5-HT receptor subtypes. In these neurons, application of 8-OH-DPAT and its subsequent removal still suppressed mCPBG-induced responses on mIPSCs. This suppression was not caused by a reduction of presynaptic 5-HT3 receptor affinities to mCPBG and was completely eliminated by pretreatment with N-ethylmaleimide, a pertussis toxin sensitive GTP-binding protein inhibitor. In the neurons exhibiting presynaptic modulation with mCPBG but not 8-OH-DPAT, such suppression by exposure to 8-OH-DPAT was not observed. In conclusion, activation of presynaptic 5-HT1A receptors inhibited mIPSC frequency and at the same time suppressed, via a G-protein-mediated mechanism, the transient facilitation of mIPSC frequency produced by activation of presynaptic 5-HT3 receptors.
Koyama
Susumu
S
Cellular and System Physiology, Graduate School of Medical Sciences Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Matsumoto
Nozomu
N
Murakami
Nobuya
N
Kubo
Chiharu
C
Nabekura
Junichi
J
Akaike
Norio
N
D000679:Amygdala / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D044263:Receptors, Serotonin, 5-HT1; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000502:physiology*
D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D005680:gamma-Aminobutyric Acid