Presynaptic interneuron subtype- and age-dependent modulation of GABAergic synaptic transmission by beta-adrenoceptors in rat insular cortex.
beta-Adrenoceptors play a crucial role in the regulation of taste aversion learning in the insular cortex (IC). However, beta-adrenergic effects on inhibitory synaptic transmission mediated by gamma-aminobutyric acid (GABA) remain unknown. To elucidate the mechanisms of beta-adrenergic modulation of inhibitory synaptic transmission, we performed paired whole cell patch-clamp recordings from layer V GABAergic interneurons and pyramidal cells of rat IC aged from postnatal day 17 (PD17) to PD46 and examined the effects of isoproterenol, a beta-adrenoceptor agonist, on unitary inhibitory postsynaptic currents (uIPSCs). Isoproterenol (100 microM) induced facilitating effects on uIPSCs in 33.3% of cell pairs accompanied by decreases in coefficient of variation (CV) of the first uIPSC amplitude and paired-pulse ratio (PPR) of the second to first uIPSC amplitude, whereas 35.9% of pairs showed suppressive effects of isoproterenol on uIPSC amplitude obtained from fast spiking (FS) to pyramidal cell pairs. Facilitatory effects of isoproterenol were frequently observed in FS-pyramidal cell pairs at > or =PD24. On the other hand, isoproterenol suppressed uIPSC amplitude by 52.3 and 39.8% in low-threshold spike (LTS)-pyramidal and late spiking (LS)-pyramidal cell pairs, respectively, with increases in CV and PPR. The isoproterenol-induced suppressive effects were blocked by preapplication of 100 microM propranolol, a beta-adrenoceptor antagonist. There was no significant correlation between age and changes of uIPSCs in LTS-/LS-pyramidal cell pairs. These results suggest the presence of differential mechanisms in presynaptic GABA release and/or postsynaptic GABA(A) receptor-related assemblies among interneuron subtypes. Age- and interneuron subtype-specific beta-adrenergic modulation of IPSCs may contribute to experience-dependent plasticity in the IC.
Koyanagi
Yuko
Y
Department of Pharmacology, Nihon University School of Dentistry, Tokyo, Japan.
Yamamoto
Kiyofumi
K
Oi
Yoshiyuki
Y
Koshikawa
Noriaki
N
Kobayashi
Masayuki
M
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000375:Aging / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D007395:Interneurons / Q000187:drug effects / Q000502:physiology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D011433:Propranolol; D017966:Pyramidal Cells / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D051381:Rats; D055647:Rats, Transgenic; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D005680:gamma-Aminobutyric Acid; D011433:Propranolol; D007545:Isoproterenol