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Review
. 1998 Mar 15;18(6):2108-17.
doi: 10.1523/JNEUROSCI.18-06-02108.1998.

Comparison of plasticity in vivo and in vitro in the developing visual cortex of normal and protein kinase A RIbeta-deficient mice

T K Hensch  1 , J A Gordon, E P Brandon, G S McKnight, R L Idzerda, M P Stryker
Affiliations
Review

Comparison of plasticity in vivo and in vitro in the developing visual cortex of normal and protein kinase A RIbeta-deficient mice

T K Hensch et al. J Neurosci. .

Abstract

Developing sensory systems are sculpted by an activity-dependent strengthening and weakening of connections. Long-term potentiation (LTP) and depression (LTD) in vitro have been proposed to model this experience-dependent circuit refinement. We directly compared LTP and LTD induction in vitro with plasticity in vivo in the developing visual cortex of a mouse mutant of protein kinase A (PKA), a key enzyme implicated in the plasticity of a diverse array of systems. In mice lacking the RIbeta regulatory subunit of PKA, we observed three abnormalities of synaptic plasticity in layer II/III of visual cortex in vitro. These included an absence of (1) extracellularly recorded LTP, (2) depotentiation or LTD, and (3) paired-pulse facilitation. Potentiation was induced, however, by pairing low-frequency stimulation with direct depolarization of individual mutant pyramidal cells. Together these findings suggest that the LTP defect in slices lacking PKA RIbeta lies in the transmission of sufficient net excitation through the cortical circuit. Nonetheless, functional development and plasticity of visual cortical responses in vivo after monocular deprivation did not differ from normal. Moreover, the loss of all responsiveness to stimulation of the originally deprived eye in most cortical cells could be restored by reverse suture of eyelids during the critical period in both wild-type and mutant mice. Such an activity-dependent increase in response would seem to require a mechanism like potentiation in vivo. Thus, the RIbeta isoform of PKA is not essential for ocular dominance plasticity, which can proceed despite defects in several common in vitro models of neural plasticity.

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Figures

Fig. 1.
Fig. 1.
Characteristic morphology and synaptic responses in the visual cortex of PKA RIβ− mutant mice.A, Six distinct laminae are identifiable in Nissl-stained coronal sections through the binocular zone of primary visual cortex taken from animals at the peak of the critical period. Scale bar, 100 μm. B, Visual responses are retinotopically organized in RIβ− cortex. A series of evenly spaced microelectrode penetrations were made across a portion of the lateromedial extent of V1 in each animal. Receptive field (RF)-center azimuths are plotted versus electrode position relative to the vertical meridian (n = 3–7 cortical cell RFs per penetration). The correlation coefficients for three RIβ− and four WT regressions were 0.92 ± 0.04 and 0.91 ± 0.03, respectively. C, Neurons filled with biocytin in the supragranular layers exhibit pyramidal morphology with a long apical dendrite extending to the pial surface and profuse basal processes. Numerous postsynaptic spines are readily visible (inset). Scale bar (shown in A): 45 μm; inset, 6 μm. D, Synaptic responses to underlying layer IV stimulation consist of fast non-NMDA-R and slower NMDA-R-mediated components in supragranular pyramidal cells. Whole-cell voltage-clamp recordings were first made at −90mV, and then fast non-NMDA and GABAA receptors were blocked using CNQX and bicuculline methiodide (10 μm each) to reveal slow NMDA-R currents when membrane potential was set to +50 mV. Finally, NMDA-Rs were blocked by 50 μm D-APV at +50 mV (middle trace). Calibration: 50 pA, 10 msec.
Fig. 2.
Fig. 2.
TBS-induced LTP of extracellular field responses via NMDA-R activation in mouse visual cortex. Theta-burst stimulation (TBS) to layer IV in the binocular zone of wild-type mouse visual cortex (left arrow) fails to potentiate supragranular field responses in the presence of D-APV (50–100 μm). The ability to generate LTP by TBS along this pathway (right arrow) is restored after washing out (40–60 min) the NMDA-R antagonist from the slice (n = 6 slices from 5 mice). Responses are normalized to the baseline period just before each TBS, and grouped data are shown as the average of all slices (± SEM), with one trial per slice.
Fig. 3.
Fig. 3.
Defective LTP of extracellular field responses in the visual cortex of PKA RIβ− mice. TBS (arrow) applied (A) to the white matter (n = 6 and 5 slices from 4 and 3 mice, WT and RIβ−, respectively) or (B) directly to layer IV (n = 8 and 11 from 7 and 6 mice, WT and RIβ−, respectively) potentiates supragranular field response amplitudes in WT (○) but not RIβ− (•) mice recorded blind to genotype.C, More powerful tetani (four 1 sec bursts of 100 Hz;arrow) fail to induce LTP in both WT and mutant slices (n = 5 slices from 3 mice each). Representative traces 5 min before and 25 min after conditioning stimuli are shownabove each graph. Sample traces during post-tetanic potentiation are also indicated in C. Except for the experiments in B, which were continued to examine depotentiation (compare Fig. 6A), glutamate receptor antagonists CNQX (10 μm) and D-APV (50 μm) were routinely bath-applied to determine the synaptic nature of the field response. Calibration: 0.3 mV, 20 msec for each.
Fig. 4.
Fig. 4.
Preservation of postsynaptic LTP mechanisms in PKA RIβ− mice. A, Direct postsynaptic depolarization of supragranular pyramidal cells (from −70 to 0 mV) induces LTP in mutant visual cortex when paired with synaptic stimulation (100 pulses at 1 Hz to layer IV). B, Robust LTP is similarly induced by pairing at Schaeffer collateral synapses studied as a control within the same slice. Nine cells from each region were recorded in slices from a total of seven mice. Sample traces 5 min before and 20 min after pairing are shown above each graph. Calibration: 100 pA, 20 msec.
Fig. 5.
Fig. 5.
Disrupted net depolarization and paired-pulse facilitation in the visual cortex of PKA RIβ− mice.A, Whereas TBS produces a prolonged depolarization in wild-type pyramidal cells, a decrementing response is observed in the knockout cells (n = 10 of 10 cells). Whole-cell current-clamp responses to the first bursts in five episodes of TBS to layer IV are shown superimposed. Arrows indicate the four stimulus pulses delivered at 10 msec intervals. Calibration: 5 mV, 20 msec. B, Paired-pulse facilitation (PPF) is perturbed in RIβ− visual cortex but not in the hippocampus. Pairs of stimuli to layer IV elicit a prominent PPF only at 10 msec interpulse intervals in WT supragranular pyramidal cells voltage-clamped to −70 mV. In contrast, mutant V1 exhibits no PPF along this pathway, whereas it is pronounced at all intervals tested in RIβ− CA1 (n = 8 cells each; **p < 0.01, * p < 0.05;t test WT vs RIβ− cortex). Calibration: 40 pA, 20 msec.
Fig. 6.
Fig. 6.
Absence of synaptic depression after low-frequency stimulation in PKA RIβ− mice. Extracellular field potential amplitude was monitored in layer II/III after low-frequency stimulation (900 pulses at 1 Hz) to layer IV of visual cortex (•, RIβ−; ○, WT). A, Renormalized responses after an earlier TBS (compare Fig. 3B) were depotentiated in wild-type (n = 8 slices from 7 mice) but unchanged in RIβ− mice (n= 11 slices from 6 animals). B, Low-frequency stimulation was similarly ineffective at naïve RIβ− synapses (n = 5 slices from 3 mice). Bath application of CNQX (10 μm) and D-APV (50 μm) terminated each experiment to confirm the synaptic nature of the field response. Representative traces 5 min before and 20 min after LFS are shown superimposed to the right of each graph. Calibration: 0.3 mV, 10 msec.
Fig. 7.
Fig. 7.
Loss of deprived-eye responses after monocular deprivation in PKA RIβ− mice. Ocular dominance distributions were recorded blind to genotype from the binocular zone of two nondeprived adults each (left panels) of wild-type (hollow bars; n = 77 cells) and RIβ− mice (hatched bars;n = 75 cells). Both distributions shifted significantly and similarly (right panels) in response to monocular deprivation of the contralateral eye for 4 d beginning at P25–27 (n = 76 and 78 cells from 3 mice each, WT and RIβ−, respectively). Numbers of cells are indicated above each bar, and contralateral bias indices are shown in the top right-hand corner of each graph.
Fig. 8.
Fig. 8.
Potentiation of initially deprived eye responses by reverse suture in PKA RIβ− mice. A, Ocular dominance distribution of cells recorded ipsilateral to an eye deprived of vision for 5 d beginning at P20–22 (“Left” Hemisphere). A nearly complete dominance of the RIβ− cortex by the contralateral eye occurs because of the innate bias toward contralateral eye dominance in nondeprived animals (n = 85 cells in 3 hemispheres). Numbers of cells are indicated above each bar, and contralateral bias indices are shown in the top right-hand corner of each graph. B, The shift in ocular dominance is typically less dramatic in the opposite “Right” Hemisphere (n = 41 cells in 3 mice) (see also Fig. 7, or Gordon and Stryker, 1996). C, Ocular dominance distribution of cells in RIβ− visual cortex recorded ipsilateral to the initially deprived eye (“Left” Hemisphere) reveals a strengthening of previously lost inputs after suture reversal for an additional 4–8 d (P26–34;n = 106 cells from 4 mice). D, Individually calculated CBIs of ipsilaterally deprived (○, same animals as in A) and reverse-sutured animals (•, same animals as in C) demonstrate the gradual recovery of response, similar to WT (□) with increasing duration of suture reversal.
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References

    1. Abel T, Nguyen PV, Barad M, Deuel TAS, Kandel ER, Bourtchouladze R. Genetic demonstration of a role for PKA in the late phase of LTP and in hippocampus-based long-term memory. Cell. 1997;88:615–626. - PubMed
    1. Amieux PS, Cummings DE, Motamed K, Brandon EP, Wailes LA, Le K, Idzerda RL, McKnight GS. Compensatory regulation of RIα protein levels in protein kinase A mutant mice. J Biol Chem. 1997;272:3993–3998. - PubMed
    1. Andreasen M, Hablitz JJ. Paired-pulse facilitation in dentate gyrus: a patch-clamp study in rat hippocampus in vitro. J Neurophysiol. 1994;72:326–336. - PubMed
    1. Artola A, Singer W. Long-term potentiation and NMDA receptors in rat visual cortex. Nature. 1987;330:649–652. - PubMed
    1. Bannerman DM, Good MA, Butcher SP, Ramsay M, Morris RGM. Distinct components of spatial learning revealed by prior training and NMDA receptor blockade. Nature. 1995;378:182–186. - PubMed

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