Clomipramine increases the incidence and duration of spike-wave discharges in freely moving WAG/Rij rats

Information Transmission in Delay-Coupled Neuronal Circuits in the Presence of a Relay Population

Synchronization between neuronal populations is hypothesized to play a crucial role in the communication between brain networks. The binding of features, or the association of computations occurring in spatially segregated areas, is supposed to take place when a stable synchronization between cortical areas occurs. While a direct cortico-cortical connection typically fails to support this mechanism, the participation of a third area, a relay element, mediating in the communication was proposed to overcome this limitation. Among the different structures that could play the role of coordination during the binding process, the thalamus is the best placed region to carry out this task. In this paper we study how information flows in a canonical motif that mimics a cortico-thalamo-cortical circuit composed by three mutually coupled neuronal populations (also called the V-motif). Through extensive numerical simulations, we found that the amount of information transferred between the oscillating neuronal populations is determined by the delay in their connections and the mismatch in their oscillation frequencies (detuning). While the transmission from a cortical population is mostly restricted to positive detuning, transmission from the relay (thalamic) population to the cortical populations is robust for a broad range of detuning values, including negative values, while permitting feedback communication from the cortex at high frequencies, thus supporting robust bottom up and top down interaction. In this case, a strong feedback transmission between the cortex to thalamus supports the possibility of robust bottom-up and top-down interactions in this motif. Interestingly, adding a cortico-cortical bidirectional connection to the V-motif (C-motif) expands the dynamics of the system with distinct operation modes. While overall transmission efficiency is decreased, new communication channels establish cortico-thalamo-cortical association loops. Switching between operation modes depends on the synaptic strength of the cortico-cortical connections. Our results support a role of the transthalamic V-motif in the binding of spatially segregated cortical computations, and suggest an important regulatory role of the direct cortico-cortical connection.

Absence epileptic activity in Wistar Albino Glaxo Rijswijk rat mothers

Absence epileptic activity was analyzed during pregnancy, the postpartum period and after weaning to establish alterations of seizures throughout the reproductive cycle. Wistar Albino Glaxo Rijswijk (WAG/Rij) rats were used in the study as a model of absence epilepsy and because their seizures do not interfere with rearing offspring. The number of spike-wave discharges (SWDs) was gradually elevated from the 19th pregnancy day to delivery. Meanwhile, the characteristics of individual SWDs did not change suggesting that SWD generation remained the same. In the postpartum and postweaning periods, the number of SWDs was not increased in the absence of pups. However, returning the pups to mothers resulted in a markedly elevated number of SWDs for 1h. If pups were taken away after 30min, the number of SWDs dropped immediately suggesting that the presence of pups increased the SWD number. The time mothers spent with the litter and in kyphosis suckling posture were in correlation with their SWD number further suggesting the importance of interaction with pups in SWD induction. Suckling elevates prolactin levels but surprisingly, its intracerebroventricular injection markedly reduced SWD number in suckled WAG/Rij mothers suggesting that the SWD-inducing effect of suckling is not mediated by prolactin. Rather, the elevated prolactin level may provide some protection against pro-epileptic effects of suckling. In conclusion, we first identified periods within the reproductive cycle with increased absence epileptic activity, implying that more attention should be devoted to epileptic activity changes in mothers.

Sleep-related epilepsy in a Long-Evans hooded rat model of depression

INTRODUCTION

Neonatal treatment with clomipramine (CLI) has been shown to have reliable behavioral and biological changes that mimic major symptomatic and biochemical changes found in depression. This paper further explores a common feature of depression, the comorbidity of seizure activity and depressive behaviors in this mode.

METHODS

Rat pups were neonatally treated with 40 mg/kg/day of CLI from postnatal day 8 through 21. In adulthood, they were instrumented with electroencephalographic (EEG) and electromyographic (EMG) electrodes for 24 h of polysomnogram (PSG) recordings. PSG data were analyzed for: (1) sleep-wake cycle; (2) spectral power; and (3) epileptiform activity, including NREM-to-REM transition (NRT) bursts.

RESULTS

Neonatal treatment with CLI reliably produces enhanced levels of REM (p < 0.01) and reduced sexual activity (p < 0.05). Theta power was enhanced during NREM sleep in the CLI group (p = 0.02). CLI-treated animals experienced increased frequency at the NRT (p < 0.01), as well as additional epileptiform activity of continuous (CTS; p < 0.05) and petite-continuous (P-CTS; p < 0.01) types, across the sleep-wake cycle. There is a strong temporal correlation with increased REM sleep duration, increased frequency of NRT bursts, and increased theta power during NREM sleep in CLI-treated animals.

DISCUSSION

Neonatal CLI-treated animals experienced significantly more epileptiform activity as a whole, in addition to comorbid features of depression in adulthood. Neonatal exposure to CLI will not only produce depressive phenotype but may also enhance risk for epilepsy in some individuals. This warrants further investigation into currently acceptable medicinal use in humans.

Neonatal tricyclic antidepressant clomipramine treatment reduces the spike-wave discharge activity of the adult WAG/Rij rat

Recently it was revealed that the absence-like epileptic activity of the WAG/Rij (Wistar Albino Glaxo/Rijswijk) rat is associated with depression-like behavioural symptoms. Whether these depressive-like symptoms are accompanying epileptic activity (manifested in spike-wave discharges, SWDs, in the EEG) or whether they are causative for each other are open questions. Neonatally administered tricyclic antidepressant clomipramine is a well characterized animal model of major depression. It evokes behavioural symptoms of depression and changes sleep pattern in normal adult rats. We investigated whether in the WAG/Rij rat the neonatally administered clomipramine would aggravate the depression-like behavioural symptoms and the SWD activity. Male WAG/Rij pups from postnatal day 8 (PD8) to PD21 were treated with clomipramine (20mg/kg) or saline (control animals) twice daily intraperitoneally (i.p.). In the 8 months old rats, sleep parameters and sucrose solution intake (as hedonic index) as well as the SWD activity were measured. While the neonatal clomipramine treatment significantly increased the rapid eye movement sleep (REM) amount and decreased the sucrose preference score, it surprisingly attenuated the adult (8 months old) SWD activity. We concluded that neonatal clomipramine treatment produced aggravation of depression-like symptoms while decreased the SWD activity in the adult (8 months old) WAG/Rij rat.