Nicotine-mediated activation of α2 nAChR-expressing OLM cells in developing mouse brains disrupts OLM cell-mediated control of LTP in adolescence.

Early postnatal nicotine exposure, a rodent model of smoking during pregnancy, affects hippocampal synaptic plasticity and memory. Here, we investigated the role of α2 nAChR-expressing OLM (α2-OLM) cells in LTP in unexposed and postnatal nicotine-exposed mice. We found that reduced α2 nAChR-dependent activation of OLM cells in α2 heterozygous knockout mice prevented LTP, whereas enhanced α2 nAChR-dependent activation of OLM cells in heterozygous knockin mice expressing hypersensitive α2 nAChRs facilitated LTP. Both optogenetic and chemogenetic activation of α2-OLM cells facilitated LTP as nicotine did. However, in postnatal nicotine-exposed mice, expressing chemogenetic hM3Dq receptors in α2-OLM cells, LTP was facilitated and both nicotinic and chemogenetic activation of α2-OLM cells prevented rather than facilitated LTP. These results demonstrate a critical role of α2-OLM cell activation in LTP as well as altered α2-OLM cell function in postnatal nicotine-exposed mice. To determine whether nicotine-mediated α2 nAChR activation in developing brains causes facilitated LTP and altered nicotinic modulation of LTP in adolescence, we used homozygous knockin mice expressing hypersensitive α2 nAChRs as a way to selectively activate α2-OLM cells. In the knockin mice, postnatal exposure to a low dose of nicotine, which had no effect on LTP in wild-type mice, is sufficient to cause facilitated LTP and altered nicotinic modulation of LTP as found in wild-type mice exposed to a higher dose of nicotine. Thus, the nicotine-mediated activation of α2 nAChRs on OLM cells in developing brains disrupts the α2-OLM cell-mediated control of LTP in adolescence that might be linked to impaired memory.

Long-term effects of early postnatal nicotine exposure on cholinergic function in the mouse hippocampal CA1 region.

In rodent models of smoking during pregnancy, early postnatal nicotine exposure results in impaired hippocampus-dependent memory, but the underlying mechanism remains elusive. Given that hippocampal cholinergic systems modulate memory and rapid development of hippocampal cholinergic systems occurs during nicotine exposure, here we investigated its impacts on cholinergic function. Both nicotinic and muscarinic activation produce transient or long-lasting depression of excitatory synaptic transmission in the hippocampal CA1 region. We found that postnatal nicotine exposure impairs both the induction and nicotinic modulation of NMDAR-dependent long-term depression (LTD). Activation of muscarinic receptors decreases excitatory synaptic transmission and CA1 network activity in both wild-type and α2 knockout mice. These muscarinic effects are still observed in nicotine-exposed mice. M1 muscarinic receptor activity is required for mGluR-dependent LTD. Early postnatal nicotine exposure has no effect on mGluR-dependent LTD induction, suggesting that it has no effect on the function of m1 muscarinic receptors involved in this form of LTD. Our results demonstrate that early postnatal nicotine exposure has more pronounced effects on nicotinic function than muscarinic function in the hippocampal CA1 region. Thus, impaired hippocampus-dependent memory may arise from the developmental disruption of nicotinic cholinergic systems in the hippocampal CA1 region.

Volatile anesthetic sevoflurane pretreatment alleviates hypoxia-induced potentiation of excitatory inputs to striatal medium spiny neurons of mice.

Sevoflurane, a commonly used anesthetic in surgery, has drawn attention because of its preconditioning effects in hypoxic conditions. To investigate the preconditioning effects in the striatum, a common site for ischemic stroke, we collected whole-cell current-clamp recordings from striatal medium spiny neurons. In our in vitro brain slice experiments, deprivation of oxygen and glucose depolarized the striatal neurons to subthreshold potentials, and the pre-administration of sevoflurane (4%, 15 min) prolonged the time to depolarization. Furthermore, transient hypoxia induced the potentiation of excitatory postsynaptic potentials, which play a part in post-ischemic excitotoxicity. Glibenclamide, a KATP channel inhibitor, reversed the prolonged time to depolarization and the prevention of the pathological potentiation of excitatory responses, indicating that the short exposure to sevoflurane likely participates in neuroprotection against hypoxia via activation of KATP channels. A monocarboxylate transporter blocker, 4-CIN, also depolarized striatal neurons. Interestingly, the blockade of monocarboxylate transporters that supply lactate to neurons caused the pathological potentiation, even in the presence of enough oxygen and glucose. In this case, sevoflurane could not prevent the pathological potentiation, suggesting the involvement of monocarboxylate transporters in the sevoflurane-mediated effects. These results indicate that sevoflurane protects striatal neurons from hypoxic damage and alleviates the pathological potentiation. Under these conditions, sevoflurane may become an effective intervention for patients undergoing surgery.

Modulation of hyperpolarization-activated cation current Ih by volatile anesthetic sevoflurane in the mouse striatum during postnatal development.

Volatile anesthetics have been reported to inhibit hyperpolarization-activated cyclic-nucleotide gated channels underlying the hyperpolarization-activated cation current (Ih) that contributes to generation of synchronized oscillatory neural rhythms. Meanwhile, the developmental change of Ih has been speculated to play a pivotal role during maturation. In this study, we examined the effect of the volatile anesthetic sevoflurane, which is widely used in pediatric surgery, on Ih and on functional Ih activation kinetics of cholinergic interneurons in developing striatum. Our analyses showed that the changes in Ih of cholinergic interneurons occurred in conjunction with maturation. Sevoflurane application (1-4%) caused significant inhibition of Ih in a dose-dependent manner, and apparently slowed Ih activation. In current-clamp recordings, sevoflurane significantly decreased spike firing during the rebound activation, which is essential for responses to the sensory inputs from the cortex and thalamus. The sevoflurane-induced inhibition of Ih in striatal cholinergic interneurons may lead to alterations of the acetylcholine-dopamine balance in the neural circuits during the early postnatal period.

α2* Nicotinic acetylcholine receptors influence hippocampus-dependent learning and memory in adolescent mice.

The absence of α2* nicotinic acetylcholine receptors (nAChRs) in oriens lacunosum moleculare (OLM) GABAergic interneurons ablate the facilitation of nicotine-induced hippocampal CA1 long-term potentiation and impair memory. The current study delineated whether genetic mutations of α2* nAChRs (Chrna2L9'S/L9'S and Chrna2KO) influence hippocampus-dependent learning and memory and CA1 synaptic plasticity. We substituted a serine for a leucine (L9'S) in the α2 subunit (encoded by the Chrna2 gene) to make a hypersensitive nAChR. Using a dorsal hippocampus-dependent task of preexposure-dependent contextual fear conditioning, adolescent hypersensitive Chrna2L9'S/L9'S male mice exhibited impaired learning and memory. The deficit was rescued by low-dose nicotine exposure. Electrophysiological studies demonstrated that hypersensitive α2 nAChRs potentiate acetylcholine-induced ion channel flux in oocytes and acute nicotine-induced facilitation of dorsal/intermediate CA1 hippocampal long-term potentiation in Chrna2L9'S/L9'S mice. Adolescent male mice null for the α2 nAChR subunit exhibited a baseline deficit in learning that was not reversed by an acute dose of nicotine. These effects were not influenced by locomotor, sensory or anxiety-related measures. Our results demonstrated that α2* nAChRs influenced hippocampus-dependent learning and memory, as well as nicotine-facilitated CA1 hippocampal synaptic plasticity.

Impaired function of α2-containing nicotinic acetylcholine receptors on oriens-lacunosum moleculare cells causes hippocampus-dependent memory impairments.

Children of mothers who smoked during pregnancy are at significantly greater risk for cognitive impairments including memory deficits, but the mechanisms underlying this effect remain to be understood. In rodent models of smoking during pregnancy, early postnatal nicotine exposure results in impaired long-term hippocampus-dependent memory, functional loss of α2-containing nicotinic acetylcholine receptors (α2∗ nAChRs) in oriens-lacunosum moleculare (OLM) cells, increased CA1 network excitation, and unexpected facilitation of long-term potentiation (LTP) at Schaffer collateral-CA1 synapses. Here we demonstrate that α2 knockout mice show the same pattern of memory impairment as previously observed in wild-type mice exposed to early postnatal nicotine. However, α2 knockout mice and α2 knockout mice exposed to early postnatal nicotine did not share all of the anomalies in hippocampal function observed in wild-type mice treated with nicotine during development. Unlike nicotine-treated wild-type mice, α2 knockout mice and nicotine-exposed α2 knockout mice did not demonstrate increased CA1 network excitation following Schaffer collateral stimulation and facilitated LTP, indicating that the effects are likely adaptive changes caused by activation of α2∗ nAChRs during nicotine exposure and are unlikely related to the associated memory impairment. Thus, the functional loss of α2∗ nAChRs in OLM cells likely plays a critical role in mediating this developmental-nicotine-induced hippocampal memory deficit.

Phosphoproteomics of the Dopamine Pathway Enables Discovery of Rap1 Activation as a Reward Signal In Vivo.

Dopamine (DA) type 1 receptor (D1R) signaling in the striatum presumably regulates neuronal excitability and reward-related behaviors through PKA. However, whether and how D1Rs and PKA regulate neuronal excitability and behavior remain largely unknown. Here, we developed a phosphoproteomic analysis method to identify known and novel PKA substrates downstream of the D1R and obtained more than 100 candidate substrates, including Rap1 GEF (Rasgrp2). We found that PKA phosphorylation of Rasgrp2 activated its guanine nucleotide-exchange activity on Rap1. Cocaine exposure activated Rap1 in the nucleus accumbens in mice. The expression of constitutively active PKA or Rap1 in accumbal D1R-expressing medium spiny neurons (D1R-MSNs) enhanced neuronal firing rates and behavioral responses to cocaine exposure through MAPK. Knockout of Rap1 in the accumbal D1R-MSNs was sufficient to decrease these phenotypes. These findings demonstrate a novel DA-PKA-Rap1-MAPK intracellular signaling mechanism in D1R-MSNs that increases neuronal excitability to enhance reward-related behaviors.

Early postnatal nicotine exposure disrupts the α2* nicotinic acetylcholine receptor-mediated control of oriens-lacunosum moleculare cells during adolescence in rats.

Maternal cigarette smoking during pregnancy and maternal nicotine exposure in animal models are associated with cognitive impairments in offspring. However, the underlying mechanism remains unknown. Oriens-lacunosum moleculare (OLM) cells expressing α2* nicotinic acetylcholine receptors (nAChRs) are an important component of hippocampal circuitry, gating information flow and long-term potentiation (LTP) in the CA1 region. Here we investigated whether early postnatal nicotine exposure alters the normal role of α2*-nAChR-expressing OLM cells during adolescence in rats. We found that early postnatal nicotine exposure significantly decreased not only the number of α2-mRNA-expressing interneurons in the stratum oriens/alveus, but also α2*-nAChR-mediated responses in OLM cells. These effects of nicotine were prevented by co-administration with the nonselective nAChR antagonist mecamylamine, suggesting that nicotine-induced activation, but not desensitization, of nAChRs mediates the effects. α2*-nAChR-mediated depolarization of OLM cells normally triggers action potentials, causing an increase in spontaneous inhibitory postsynaptic currents in synaptically connected pyramidal cells. However, these α2*-nAChR-mediated effects were profoundly reduced after early postnatal nicotine exposure, suggesting altered control of CA1 circuits by α2*-nAChR-expressing OLM cells. Furthermore, these effects were associated with altered excitatory neural activity and LTP as well as the loss of normal α2*-nAChR-mediated control of excitatory neural activity and LTP. These findings suggest the altered function of α2*-nAChR-expressing OLM cells as an important target of further study for identifying the mechanisms underlying the cognitive impairment induced by maternal smoking during pregnancy.

Early postnatal nicotine exposure causes hippocampus-dependent memory impairments in adolescent mice: Association with altered nicotinic cholinergic modulation of LTP, but not impaired LTP.

Fetal nicotine exposure from smoking during pregnancy causes long-lasting cognitive impairments in offspring, yet little is known about the mechanisms that underlie this effect. Here we demonstrate that early postnatal exposure of mouse pups to nicotine via maternal milk impairs long-term, but not short-term, hippocampus-dependent memory during adolescence. At the Schaffer collateral (SC) pathway, the most widely studied synapses for a cellular correlate of hippocampus-dependent memory, the induction of N-methyl-D-aspartate receptor-dependent transient long-term potentiation (LTP) and protein synthesis-dependent long-lasting LTP are not diminished by nicotine exposure, but rather unexpectedly the threshold for LTP induction becomes lower after nicotine treatment. Using voltage sensitive dye to visualize hippocampal activity, we found that early postnatal nicotine exposure also results in enhanced CA1 depolarization and hyperpolarization after SC stimulation. Furthermore, we show that postnatal nicotine exposure induces pervasive changes to the nicotinic modulation of CA1 activity: activation of nicotinic receptors no longer increases CA1 network depolarization, acute nicotine inhibits rather than facilitates the induction of LTP at the SC pathway by recruiting an additional nicotinic receptor subtype, and acute nicotine no longer blocks LTP induction at the temporoammonic pathway. These findings reflect the pervasive impact of nicotine exposure during hippocampal development, and demonstrate an association of hippocampal memory impairments with altered nicotinic cholinergic modulation of LTP, but not impaired LTP. The implication of our results is that nicotinic cholinergic-dependent plasticity is required for long-term memory formation and that postnatal nicotine exposure disrupts this form of plasticity.

Endogenous ACh suppresses LTD induction and nicotine relieves the suppression via different nicotinic ACh receptor subtypes in the mouse hippocampus.

AIMS: Studying the normal role of nicotinic cholinergic systems in hippocampal synaptic plasticity is critical for understanding how cholinergic loss in Alzheimer's disease (AD) and tobacco use affect cognitive function. However, it is largely unknown how nicotinic cholinergic systems regulate the induction of long-term depression (LTD). MAIN METHODS: Extracellular field potential recordings were performed in hippocampal slices prepared from wild-type, α2, α7, and ß2 knockout (KO) mice. Effects of nicotine and nicotinic antagonists on LTD induction in wild-type, α2, α7, and ß2 KO mice were compared. KEY FINDINGS: Activation of α7 nicotinic acetylcholine receptors (nAChRs) occurs during LTD-inducing stimulation to suppress LTD induction at CA3-CA1 synapses. Nicotine relieves this suppression, causing larger LTD. This nicotine effect was mediated by the activation of non-α7 nAChR subtypes, which were not activated by ACh released during LTD-inducing stimulation, and requires the presence of endogenous ACh-induced α7 nAChR activation. Furthermore, the effect of nicotine was prevented in the presence of mecamylamine, but not dihydro-ß-erythroidine, and was still observed in both α2 KO and ß2 KO mice. SIGNIFICANCE: This is the first report to evaluate the involvement of different nAChR subtypes in LTD induction. Findings indicate the involvement of unique non-α7 nAChR subtypes, which have not been considered in the nicotinic modulation of hippocampal long-term potentiation, in the control of LTD induction. The implication of our results is that the loss of cholinergic projections to the hippocampus, which reduces ACh release as seen in AD patients, and nicotine from tobacco smoking can differentially affect LTD induction.

Endogenously released ACh and exogenous nicotine differentially facilitate long-term potentiation induction in the hippocampal CA1 region of mice.

We examined the role of α7- and ß2-containing nicotinic acetylcholine receptors (nAChRs) in the induction of long-term potentiation (LTP). Theta-burst stimulation (TBS), mimicking the brain's naturally occurring theta rhythm, induced robust LTP in hippocampal slices from α7 and ß2 knockout mice. This suggests TBS is capable of inducing LTP without activation of α7- or ß2-containing nAChRs. However, when weak TBS was applied, the modulatory effects of nicotinic receptors on LTP induction became visible. We showed that during weak TBS, activation of α7 nAChRs occurs by the release of ACh, contributing to LTP induction. Additionally, bath-application of nicotine activated ß2-containing nAChRs to promote LTP induction. Despite predicted nicotine-induced desensitization, synaptically mediated activation of α7 nAChRs still occurs in the presence of nicotine and contributed to LTP induction. Optical recording of single-stimulation-evoked excitatory activity with a voltage-sensitive dye revealed enhanced excitatory activity in the presence of nicotine. This effect of nicotine was robust during high-frequency stimulation, and was accompanied by enhanced burst excitatory postsynaptic potentials. Nicotine-induced enhancement of excitatory activity was observed in slices from α7 knockout mice, but was absent in ß2 knockout mice. These results suggest that the nicotine-induced enhancement of excitatory activity is mediated by ß2-containing nAChRs, and is related to the nicotine-induced facilitation of LTP induction. Thus, our study demonstrates that the activation of α7- and ß2-containing nAChRs differentially facilitates LTP induction via endogenously released ACh and exogenous nicotine, respectively, in the hippocampal CA1 region of mice.

Nicotine facilitates long-term potentiation induction in oriens-lacunosum moleculare cells via Ca2+ entry through non-alpha7 nicotinic acetylcholine receptors.

Hippocampal inhibitory interneurons have a central role in the control of network activity, and excitatory synapses that they receive express Hebbian and anti-Hebbian long-term potentiation (LTP). Because many interneurons in the hippocampus express nicotinic acetylcholine receptors (nAChRs), we explored whether exposure to nicotine promotes LTP induction in these interneurons. We focussed on a subset of interneurons in the stratum oriens/alveus that were continuously activated in the presence of nicotine due to the expression of non-desensitizing non-alpha7 nAChRs. We found that, in addition to alpha2 subunit mRNAs, these interneurons were consistently positive for somatostatin and neuropeptide Y mRNAs, and showed morphological characteristics of oriens-lacunosum moleculare cells. Activation of non-alpha7 nAChRs increased intracellular Ca(2+) levels at least in part via Ca(2+) entry through their channels. Presynaptic tetanic stimulation induced N-methyl-D-aspartate receptor-independent LTP in voltage-clamped interneurons at -70 mV when in the presence, but not absence, of nicotine. Intracellular application of a Ca(2+) chelator blocked LTP induction, suggesting the requirement of Ca(2+) signal for LTP induction. The induction of LTP was still observed in the presence of ryanodine, which inhibits Ca(2+) -induced Ca(2+) release from ryanodine-sensitive intracellular stores, and the L-type Ca(2+) channel blocker nifedipine. These results suggest that Ca(2+) entry through non-alpha7 nAChR channels is critical for LTP induction. Thus, nicotine affects hippocampal network activity by promoting LTP induction in oriens-lacunosum moleculare cells via continuous activation of non-alpha7 nAChRs.

Concurrent observations of astrocytic Ca(2+) activity and multisite extracellular potentials from an intact cerebral cortex.

In basic neuroscience, the attention has been recently focused on the role played by the protoplasmic astrocytes in modulating the activity of nearby neurons or else on assisting a long-term/sustained communication between these neurons and the surrounding microvasculature. However, to understand the physiological mechanisms underlying such a multiscale interactions in space and time, novel methodologies are required. This paper reports about an experimental setting and a procedure that was developed to obtain concurrently two-photon astrocytic Ca(2+) imaging and multisite large-scale extracellular potentials as recorded by a silicon-based probe. Solutions to several technical drawbacks (e.g. removal of photoelectric artifacts, the establishment of safety ranges for microinjection) are provided which are intrinsic to the technology and procedure utilized. Through the use of SR101 to stain protoplasmic astrocytes, it was possible to combine functional information represented by the Ca(2+) activity in individual astrocytes and the LFPs with geometrical descriptors of the astrocytic/vessel networks.

Alpha2 nicotine receptors function as a molecular switch to continuously excite a subset of interneurons in rat hippocampal circuits.

Rapid activation of nicotinic acetylcholine receptors (nAChRs) at various anatomical and cellular locations in the hippocampus differentially modulates the operation of hippocampal circuits. However, it is largely unknown how the continued presence of nicotine affects the normal operation of hippocampal circuits. Here, we used single and dual whole-cell recordings to address this question. We found that horizontally oriented interneurons in the stratum oriens/alveus continuously discharged action potentials in the presence of nicotine. In these interneurons, bath application of nicotine produced slow inward currents that were well maintained and inhibited by the non-alpha 7 antagonist dihydro-beta-erythroidine. Single-cell reverse transcription-polymerase chain reaction analysis showed that nicotine-responding interneurons were consistently positive for the alpha2 subunit mRNA. These observations suggest that in the presence of nicotine, a subset of interneurons in the stratum oriens/alveus are continuously excited due to the sustained activation of alpha2* nAChRs. These interneurons were synaptically connected to pyramidal cells, and nicotine increased inhibitory baseline currents at the synapses and suppressed phasic inhibition at the same synapses. Nicotine-induced inhibitory activity increased background noise and masked small phasic inhibition in pyramidal cells, originating from other interneurons in the stratum radiatum. Thus, the continued presence of nicotine alters the normal operation of hippocampal circuits by gating inhibitory circuits through activating a non-desensitizing alpha2 nAChR subtype on a distinct population of interneurons.

Nicotine gates long-term potentiation in the hippocampal CA1 region via the activation of alpha2* nicotinic ACh receptors.

Hippocampal CA1 pyramidal cells receive two major excitatory synaptic inputs via the Schaffer collateral (SC) and temporoammonic (TA) pathways. Nicotine promotes induction of long-term potentiation (LTP) in the SC path; however, it is not known whether the modulatory effect of nicotine on LTP induction is pathway-specific. Here we show that nicotine suppresses LTP induction in the TA path. Interestingly, these opposing effects of nicotine were absent or greatly reduced in alpha2 nicotinic acetylcholine receptor (nAChR)-knockout (KO) mice, suggesting that an alpha2-containing nAChR subtype mediates these effects. Optical imaging with a voltage-sensitive dye revealed significantly stronger membrane depolarization in the presence of nicotine in the SC path, facilitating spread of excitatory neural activity along both the somatodendritic and the CA1 proximodistal axes. These effects of nicotine were also absent in alpha2 nAChR-KO mice, suggesting that the enhanced optical signal is related to the nicotine-induced facilitation of LTP induction. In contrast, in the TA path nicotine terminated depolarization more quickly and increased the delayed hyperpolarization in the termination zone of the TA path input. These inhibitory effects of nicotine were absent in alpha2 nAChR-KO mice and, thus, most probably underlie the nicotine-induced suppression of LTP induction. Our results suggest that nicotine influences the local balance between excitation and inhibition, gates LTP, and directs information flow through the hippocampal circuits via the activation of alpha2* nAChRs. These effects of nicotine may represent the cellular basis of nicotine-mediated cognitive enhancement.

Chronic nicotine exposure affects the normal operation of hippocampal circuits.

Evidence suggests that dopamine hyperfunction in schizophrenia blocks direct sensory information flow to CA1 pyramidal cells via the temporoammonic path. Owing to the high prevalence of smoking in schizophrenics, we examined whether nicotine modulates synaptic transmission in the temporoammonic path. Application of nicotine suppressed temporoammonic synaptic transmission as in the case of dopamine application. The suppressive effect of nicotine, however, disappeared in chronic nicotine-exposed hippocampi, suggesting the loss of nicotinic modulation of transmission in the temporoammonic path. In addition, the dopaminergic modulation of temporoammonic synaptic transmission decreased after chronic nicotine treatment. These observations suggest that chronic nicotine exposure affects the normal operation of hippocampal circuits.

Nicotine reverses consolidated long-term potentiation in the hippocampal CA1 region.

Long-term potentiation (LTP) has a memory-like consolidation period during which it becomes progressively stabilized. However, it is unknown how the consolidation is achieved. The present study demonstrates that nicotine reverses stabilized LTP in the hippocampal CA1 region, providing the first evidence that consolidated LTP can be reversed. The nicotine-induced reversal appeared to work by reversing cellular processes involved in stabilizing LTP, as LTP was readily induced again after reversal. The effect of nicotine was mediated, in large part, via desensitization of alpha7 nicotinic acetylcholine receptors (nAChRs), as an alpha7 nAChR-selective antagonist mimicked the nicotine effect. A non-selective N-methyl-d-aspartate receptor (NMDAR) antagonist completely abolished the nicotine-induced reversal, whereas an NR2B-containing NMDAR-selective antagonist had no effect. Furthermore, both the protein phosphatase 1/protein phosphatase 2A inhibitor okadaic acid and the protein phosphatase 2B (calcineurin) inhibitor cyclosporin A blocked the nicotine-induced reversal. Taken together, our results suggest that the reversal of stabilized LTP depends on the activation of NR2A-containing NMDARs and dephosphorylation. Thus, the consolidation of LTP appears to be the interruption of signaling leading to NR2A-containing NMDAR-dependent activation of protein phosphatases, which can be circumvented by nicotine-induced signaling. LTP induced in chronic nicotine-treated hippocampi contained a component that is immune to reversal, and thus acute nicotine was no longer effective to reverse consolidated LTP. These results demonstrate the differential effects of acute and chronic nicotine exposure on the cellular processes that are potentially involved in learning and memory.

Rescue of hereditary form of dilated cardiomyopathy by rAAV-mediated somatic gene therapy: amelioration of morphological findings, sarcolemmal permeability, cardiac performances, and the prognosis of TO-2 hamsters.

The hereditary form comprises approximately 1/5 of patients with dilated cardiomyopathy (DCM) and is a major cause of advanced heart failure. Medical and socioeconomic settings require novel treatments other than cardiac transplantation. TO-2 strain hamsters with congenital DCM show similar clinical and genetic backgrounds to human cases that have defects in the delta-sarcoglycan (delta-SG) gene. To examine the long-term in vivo supplement of normal delta-SG gene driven by cytomegalovirus promoter, we analyzed the pathophysiologic effects of the transgene expression in TO-2 hearts by using recombinant adeno-associated virus vector. The transgene preserved sarcolemmal permeability detected in situ by mutual exclusivity between cardiomyocytes taking up intravenously administered Evans blue dye and expressing the delta-SG transgene throughout life. The persistent amelioration of sarcolemmal integrity improved wall thickness and the calcification score postmortem. Furthermore, in vivo myocardial contractility and hemodynamics, measured by echocardiography and cardiac catheterization, respectively, were normalized, especially in the diastolic performance. Most importantly, the survival period of the TO-2 hamsters was prolonged after the delta-SG gene transduction, and the animals remained active, exceeding the life expectancy of animals without transduction of the responsible gene. These results provide the first evidence that somatic gene therapy is promising for human DCM treatment, if the rAAV vector can be justified for clinical use.