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1

Participation of muscarinic receptors in memory consolidation in passive avoidance learning

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Dobryakova Y. V., Gurskaya O., Markevich V. A.
Acta Neurobiologiae Experimentalis
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2014
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tom 74
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nr 2
It is well-known that the cholinergic system and the muscarinic cholinergic receptors are associated with cognitive functions. Here we examined whether a non-selective muscarinic receptor antagonist scopolamine affects learning performance and/or synaptic plasticity during the memory consolidation period. Adult male Wistar rats (250-300 g) were injected with scopolamine (2 mg/kg) or saline immediately after training in a "passive avoidance" task. Memory retention test was conducted 24h after training. The changes in the latency of the first entry into a dark compartment of a test chamber was choosen as a criterion of learning. The efficacy of synaptic transmission was estimated by the changes in the basal level of focal potentials (fEPSP amplitude and slope ratio) before training (baseline), 90 min after the training (consolidation period), and 24 hour after the training (retention period). We found that foot-shock presentation by itself had no effect on fEPSP within the first 90 min after training, but in 24 hour fEPSPs were decreased. In untrained rats administration of scopolamine had no effect on the fEPSP amplitude within the first 90 min after the injection, but in 24 h we observed an increase in the fEPSP amplitude. In trained animals, scopolamine decreased the fEPSP amplitude in the hippocampal CA1 area during first 1.5 h after the injection. However, the drug had no effect on the memory retention in the passive avoidance task. Taken together our data suggest that scopolamine modifies the synaptic placticity of the hippocampal network but does not induce significant changes in the retention of the passive avoidance skill.
2

Administration of muscarinic antagonists induce changes in passive avoidance learning and in synaptic transmission in the CA1 area of the hippocampus

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Dobryakova Y. V., Ivanova O. Y., Merkevich V. A.
Acta Neurobiologiae Experimentalis
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2018
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tom 78
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nr 2
Muscarinic acetylcholine receptors (mAChR) are known to be related to learning and memory processes. Inactivation of mAChR by cholinergic antagonists have been shown to produce amnesia in a variety of behavioral tasks. In this study, we investigated the role of M1 and M2 AChR on passive avoidance learning and plasticity of synapses formed by Schaffer collaterals in freely moving rats. Experiments were performed using Wistar male rats. Seven days before testing, a recording electrode was lowered in the CA1 region under chloral hydrate anaesthesia to record the field excitatory postsynaptic potential (fEPSP) in response to Schaffer collateral stimulation. Selective M2 receptor antagonists methoctramine and selective M1 receptors antagonist pirenzepine were intraperitoneally injected immediately after training. The effects on memory retention were examined using passive avoidance training. We measured latency of the first entry into a dark compartment of the chamber. fEPSP amplitude and slope ratio were measured before shock presentation, 90 min after the shock, and 24 hour after the shock. Methoctramine significantly impaired behavior in the passive avoidance test but pirenzepine did not induce any changes compared to control. Our results showed that pirenzepine but not methoctramine supressed the amplitude of fEPSPs. On the other hand, intracerebroventricular methoctramine administration impaired passive avoidance learning and increased the amplitude of fEPSP.
3

Maternal behavior in a genetic animal model of absence epilepsy

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Dobryakova Y. V., Dubynin V. A., van Luijtelaar G.
Acta Neurobiologiae Experimentalis
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2008
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tom 68
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nr 4
In this study we quantified maternal behavior in genetic epileptic rats with deficiencies in the DA system known to be involved in maternal behavior in order to assess whether these rats have disturbances in maternal care. Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats, a genetic model for generalized absence epilepsy and Wistar rats were compared. Maternal behavior parameters and activity scores were quantified from post-natal day (PND) 4-6 in an open field in the presence of pups. WAG/Rij rats had less approaches to the pups and higher latencies of approaching them compared to Wistar, while locomotion showed a different pattern over days. This confirms the hypothesis that animals with absence epilepsy show more poor maternal behavior and that these effects cannot be solely attributed to differences in locomotor activity. It is proposed that the reduction in maternal care is attributed to low activity in the mesolimbic DA system.
4

The effect of haloperidol on maternal behavior in WAG/Rij rats and its consequences in the offspring

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Dobryakova Y. V., Dubynin V. A., van Luijtelaar G.
Acta Neurobiologiae Experimentalis
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2011
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tom 71
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nr 3
Haloperidol treatment during pre- and post-natal period affects maternal behavior and this may have long-term effects on the offspring. We examined whether early haloperidol administration to Wistar-Albino-Glaxo dams from Rijswijk (WAG/Rij) and in Wistar control rats would affect maternal care and as a consequence, seizure susceptibility and behavior in the WAG/ Rij's offspring at 3-4 months of age. Nursing dams of this well-validated genetic animal model of absence epilepsy and control dams were injected with haloperidol or saline at PPD 1 to 6. Maternal behavior was evaluated at PPD 7 to 9. Haloperidol-injected WAG/Rij dams showed more pup carryings compared with saline-injected mothers, this effect was not noticed in control Wistar dams. The offspring of haloperidol-treated WAG/Rij dams, tested during adulthood, showed heightened behavioral activity (time spent into the open arms, head dips) in the elevated plus-maze, as well as shorter spike- wave discharges (SWD) as measured in their electroencephalographs activity compared with saline-treated rats. Overall, it can be concluded that deviancies in the DA system as induced by haloperidol facilitates pup carrying/retrieval behavior in WAG/Rij rats and reduces seizure activity of the offspring in adulthood. Therefore, inter-individual differences in seizure properties and behavior in genetically predisposed animals may be due to differences in maternal behavior of the dams.
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