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Higher intrinsic network excitability in ventral compared with the dorsal hippocampus is controlled less effectively by GABAB receptors.

Papatheodoropoulos C - BMC Neurosci (2015)

Bottom Line: Importantly, blockade of GABAB receptors produced a stronger effect in enhancing the probability of generation of spfps and spfps-nmda in the dorsal compared with the ventral hippocampal slices and increased spfps-nmda only in dorsal slices.These results demonstrate a higher intrinsic neuronal excitability of the ventral compared with the dorsal local circuitry with the considerable contribution of NMDA receptors.It is proposed that NMDA and GABAB receptors significantly contribute to differentiate local network dynamics between the dorsal and the ventral hippocampus with important implications in the information processing performed along the long hippocampal axis.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Physiology, Department of Medicine, School of Health Sciences, University of Patras, Rion, 26504, Patras, Greece. cepapath@upatras.gr.

ABSTRACT

Background: Elucidating specializations of the intrinsic neuronal network between the dorsal and the ventral hippocampus is a recently emerging area of research that is expected to help us understand the mechanisms underlying large scale functional diversification along the hippocampus. The aim of this study was to characterize spontaneous network activity between the dorsal and the ventral hippocampus induced under conditions of partial or complete blockade of GABAergic inhibition (i.e. disinhibition).

Results: Using field recordings from the CA3 and CA1 fields of hippocampal slices from adult rats I found that ventral compared with dorsal hippocampus slices displayed higher propensity for and higher frequency of occurrence of spontaneous field potentials (spfps) at every level of disinhibition. Also NMDA receptor-depended spfps (spfps-nmda) occurred with higher probability more frequently and were larger in the ventral compared with the dorsal hippocampus. Importantly, blockade of GABAB receptors produced a stronger effect in enhancing the probability of generation of spfps and spfps-nmda in the dorsal compared with the ventral hippocampal slices and increased spfps-nmda only in dorsal slices.

Conclusion: These results demonstrate a higher intrinsic neuronal excitability of the ventral compared with the dorsal local circuitry with the considerable contribution of NMDA receptors. Furthermore, the GABAB receptors control the total and the NMDA receptor-dependent excitation much less effectively in the ventral part of the hippocampus. It is proposed that NMDA and GABAB receptors significantly contribute to differentiate local network dynamics between the dorsal and the ventral hippocampus with important implications in the information processing performed along the long hippocampal axis.

No MeSH data available.


Related in: MedlinePlus

GABABRs control the likelihood of spfps generation in DH but not VH. a Example recordings illustrating that blockade of GABABRs by CGP 35348 (200 μM) induced spfps in a previously silent dorsal slice without affecting the rate of ongoing spfps in another ventral slice. b Cumulative results on the incidence and the rate of spfps are shown. Asterisk indicate statistically significant drug effect at p < 0.05 (Wilcoxon test)
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Fig4: GABABRs control the likelihood of spfps generation in DH but not VH. a Example recordings illustrating that blockade of GABABRs by CGP 35348 (200 μM) induced spfps in a previously silent dorsal slice without affecting the rate of ongoing spfps in another ventral slice. b Cumulative results on the incidence and the rate of spfps are shown. Asterisk indicate statistically significant drug effect at p < 0.05 (Wilcoxon test)

Mentions: In addition to GABAARs, the GABABR-mediated transmission plays an important role in controlling neuronal activity and network excitability [35]. Thus, I examined whether blockade of GABABRs could further enhance excitability in DH and VH by applying CGP 35348 (200 μM) in slices already perfused with 10 μM SR 95531. I found that blockade of GABABRs induced a considerable increase in the incidence of spfps in DH (from 45.9 ± 10.5 to 89.6 ± 4.0 %, n = 24, Wilcoxon test and χ2 test, p < 0.05) but not in VH (from 79.4 ± 12.4 to 95.3 ± 4.8 %, n = 9, Wilcoxon test and χ2 test, p > 0.05), (Fig. 4). Regarding VH, the blockade of GABABRs could not have considerable effect since the incidence of spfps in VH slices was already very high under SR 95531. CGP 35348 did not significantly change the rate of spfps either in DH (from 0.7 ± 0.1 to 0.6 ± 0.1 spfsp/min, n = 11) or VH (from 15.0 ± 4.3 to 16.2 ± 5.7 spfsp/min, n = 7), (Fig. 4b). In order to examine whether there is any difference in spfps between DH and VH under blockade of only GABABRs, a population of ten dorsal and eight ventral slices taken from three animals were bathed with CGP 35348 alone. However, the drug did not induce any detectable synchronous field activity in any of the slices studied.Fig. 4


Higher intrinsic network excitability in ventral compared with the dorsal hippocampus is controlled less effectively by GABAB receptors.

Papatheodoropoulos C - BMC Neurosci (2015)

GABABRs control the likelihood of spfps generation in DH but not VH. a Example recordings illustrating that blockade of GABABRs by CGP 35348 (200 μM) induced spfps in a previously silent dorsal slice without affecting the rate of ongoing spfps in another ventral slice. b Cumulative results on the incidence and the rate of spfps are shown. Asterisk indicate statistically significant drug effect at p < 0.05 (Wilcoxon test)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4641374&req=5

Fig4: GABABRs control the likelihood of spfps generation in DH but not VH. a Example recordings illustrating that blockade of GABABRs by CGP 35348 (200 μM) induced spfps in a previously silent dorsal slice without affecting the rate of ongoing spfps in another ventral slice. b Cumulative results on the incidence and the rate of spfps are shown. Asterisk indicate statistically significant drug effect at p < 0.05 (Wilcoxon test)
Mentions: In addition to GABAARs, the GABABR-mediated transmission plays an important role in controlling neuronal activity and network excitability [35]. Thus, I examined whether blockade of GABABRs could further enhance excitability in DH and VH by applying CGP 35348 (200 μM) in slices already perfused with 10 μM SR 95531. I found that blockade of GABABRs induced a considerable increase in the incidence of spfps in DH (from 45.9 ± 10.5 to 89.6 ± 4.0 %, n = 24, Wilcoxon test and χ2 test, p < 0.05) but not in VH (from 79.4 ± 12.4 to 95.3 ± 4.8 %, n = 9, Wilcoxon test and χ2 test, p > 0.05), (Fig. 4). Regarding VH, the blockade of GABABRs could not have considerable effect since the incidence of spfps in VH slices was already very high under SR 95531. CGP 35348 did not significantly change the rate of spfps either in DH (from 0.7 ± 0.1 to 0.6 ± 0.1 spfsp/min, n = 11) or VH (from 15.0 ± 4.3 to 16.2 ± 5.7 spfsp/min, n = 7), (Fig. 4b). In order to examine whether there is any difference in spfps between DH and VH under blockade of only GABABRs, a population of ten dorsal and eight ventral slices taken from three animals were bathed with CGP 35348 alone. However, the drug did not induce any detectable synchronous field activity in any of the slices studied.Fig. 4

Bottom Line: Importantly, blockade of GABAB receptors produced a stronger effect in enhancing the probability of generation of spfps and spfps-nmda in the dorsal compared with the ventral hippocampal slices and increased spfps-nmda only in dorsal slices.These results demonstrate a higher intrinsic neuronal excitability of the ventral compared with the dorsal local circuitry with the considerable contribution of NMDA receptors.It is proposed that NMDA and GABAB receptors significantly contribute to differentiate local network dynamics between the dorsal and the ventral hippocampus with important implications in the information processing performed along the long hippocampal axis.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Physiology, Department of Medicine, School of Health Sciences, University of Patras, Rion, 26504, Patras, Greece. cepapath@upatras.gr.

ABSTRACT

Background: Elucidating specializations of the intrinsic neuronal network between the dorsal and the ventral hippocampus is a recently emerging area of research that is expected to help us understand the mechanisms underlying large scale functional diversification along the hippocampus. The aim of this study was to characterize spontaneous network activity between the dorsal and the ventral hippocampus induced under conditions of partial or complete blockade of GABAergic inhibition (i.e. disinhibition).

Results: Using field recordings from the CA3 and CA1 fields of hippocampal slices from adult rats I found that ventral compared with dorsal hippocampus slices displayed higher propensity for and higher frequency of occurrence of spontaneous field potentials (spfps) at every level of disinhibition. Also NMDA receptor-depended spfps (spfps-nmda) occurred with higher probability more frequently and were larger in the ventral compared with the dorsal hippocampus. Importantly, blockade of GABAB receptors produced a stronger effect in enhancing the probability of generation of spfps and spfps-nmda in the dorsal compared with the ventral hippocampal slices and increased spfps-nmda only in dorsal slices.

Conclusion: These results demonstrate a higher intrinsic neuronal excitability of the ventral compared with the dorsal local circuitry with the considerable contribution of NMDA receptors. Furthermore, the GABAB receptors control the total and the NMDA receptor-dependent excitation much less effectively in the ventral part of the hippocampus. It is proposed that NMDA and GABAB receptors significantly contribute to differentiate local network dynamics between the dorsal and the ventral hippocampus with important implications in the information processing performed along the long hippocampal axis.

No MeSH data available.


Related in: MedlinePlus