Presynaptic 5-HT1B receptor-mediated synaptic suppression to the subplate neurons in the somatosensory cortex of neonatal rats.
Serotonin (5-HT), the target of numerous psychiatric medicines, plays important roles in neural development. In this study we examined the direct effects of 5-HT on the physiological properties of neurons in the cortical subplate, a structure that develops early in life and is important for the maturation of cortical circuits. Acute brain slices were prepared from neonatal rats and the intrinsic and synaptic properties of subplate neurons (SPns) were evaluated before and after 5-HT bath-application. In all concentrations tested, 5-HT did not affect the intrinsic properties of SPns. However, thalamus-evoked excitatory postsynaptic currents (eEPSCs) in SPn were significantly suppressed by 5-HT in a dose-dependent manner. Because 5-HT did not affect AMPA- or NMDA-induced currents, it is unlikely that a 5-HT-mediated postsynaptic mechanism reduced EPSCs. Subsequent to 5-HT application, increased paired-pulse ratios and decreased MK-801 blocking rates were noted, indicating the presence of a presynaptic 5-HT receptor-mediated suppressive effect in the thalamocortical afferent (TCA)-SPn synapses. To elucidate the type(s) of 5-HT receptor involved in this process, various 5-HT receptor agonists and antagonists were tested. CP93129, a 5-HT(1B) receptor agonist, mimicked the effect of 5-HT and in the contrary, the 5-HT(1B) receptor antagonist SB224289 prevented 5-HT-mediated synaptic suppression. Our cumulative data demonstrated the presynaptic 5-HT(1B) receptor-mediated suppressive effect on the excitatory synapses between TCAs and SPns in the somatosensory cortex of neonatal rats. Early exposure to drugs that might interrupt 5-HT homeostasis should be considered.
Graduate Institute of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan. Electronic address: ntujj@yahoo.com.tw.
Chun-Chieh
CC
Liao
Graduate Institute of Anatomy and Cell Biology, National Taiwan University, Taipei, Taiwan; Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan; Neurobiology and Cognitive Science Center, National Taiwan University, Taipei, Taiwan. Electronic address: ljlee@ntu.edu.tw.
Li-Jen
LJ
Lee
D000818:Animals; D000831:Animals, Newborn; D004305:Dose-Response Relationship, Drug; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D010881:Piperidones / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D044302:Receptor, Serotonin, 5-HT1B / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013003:Somatosensory Cortex / Q000187:drug effects* / Q000378:metabolism; D013141:Spiro Compounds / Q000494:pharmacology
D010881:Piperidones; D011725:Pyridines; D011758:Pyrroles; D044302:Receptor, Serotonin, 5-HT1B; C108518:SB 22489G; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013141:Spiro Compounds; C065046:3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo(3,2-b)pyrid-5-one; D012701:Serotonin
Brain development; Serotonin receptor; Synaptic transmission; Thalamocortical afferent