Differences in GABAergic transmission between two inputs into the perirhinal cortex.
We have investigated properties of GABAergic synaptic transmission in perirhinal cortex evoked by stimulation of temporal and entorhinal cortex sides. GABAA IPSCs were isolated by blockade of glutamatergic transmission in slices of adult perirhinal cortex; IPSC decay was best fitted with two exponentials. Interestingly, temporal IPSCs had a larger slow component of decay (P < 0.05) compared to entorhinal IPSCs. Depression of IPSCs by the GABAB receptor agonist baclofen was greater (P < 0.05) in the temporal input (79 +/- 4% depression) than the entorhinal input (65 +/- 3% depression). Furthermore, baclofen abolished the slow component of IPSC decay in both inputs. Activity-dependent depression of IPSCs at 5 Hz was greater (P < 0.05) in the temporal input [paired pulse ratio (PPR) 0.5 +/- 0.04] compared to that in the entorhinal input (PPR 0.67 +/- 0.02, n = 10). The differences in paired pulse depression between the inputs were removed by the GABAB receptor antagonist CGP55845A. This study demonstrates several differences in GABA transmission between temporal and entorhinal inputs including the differential activation of presynaptic GABAB receptors and differential regulation of inhibitory synaptic transmission. These properties may be important in the control of neuronal activity within perirhinal cortex.
MRC Centre for Synaptic Plasticity, Department of Anatomy, University of Bristol, Bristol BS8 1TD, UK.
Derek L F
DL
Garden
Nicola
N
Kemp
Zafar I
ZI
Bashir
D000344:Afferent Pathways / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D004558:Electric Stimulation; D018728:Entorhinal Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018755:GABA Agonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D020534:Parahippocampal Gyrus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D018080:Receptors, GABA-B / Q000187:drug effects / Q000378:metabolism*; D013570:Synaptic Membranes / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018755:GABA Agonists; D018756:GABA Antagonists; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D005680:gamma-Aminobutyric Acid