Abstract P198: Biphasic And Sex-dependent Roles Of The Prorenin Receptor In The Rostral Ventrolateral Nucleus In Mice Subjected To Deoxycorticosterone Acetate-salt Hypertension

The brain renin angiotensin system (RAS) regulates blood pressure (BP) and autonomic function. However, it remains unclear how and where angiotensin II (Ang II) is generated in conditions eliciting brain RAS overactivation including deoxycorticosterone acetate (DOCA)-salt hypertension (HT). In several tissues, the activation of prorenin requires its binding to the prorenin receptor (PRR). New evidence from this study indicates that prorenin and PRR are co-expressed in the proximity to the rostral ventrolateral nucleus (RVL), an anatomical brain region that controls sympathetic nerve activity. Therefore, we hypothesized that selective ablation of PRR targeting the RVL attenuates BP increase due to DOCA-salt. PRR ablation was targeted to the RVL by stereotactic microinjections of adeno-associated virus (AAV) expressing Cre recombinase-mCherry in PRR-flox mice (PRR RVL-KO ). AAV mCherry was used as control virus (WT). A pressor response to L-glutamate in the injection site served as confirmatory stereotactic target hit. RVL-targeted ablation of PRR resulted in lower BP responses to DOCA-salt in females (WT=115±3 vs KO=104±4 mmHg; p <0.05; n=8), but not males (n=5-8), only during the first 3 days of DOCA-salt treatment. However, at day 13 of DOCA-salt treatment, female PRR RVL-KO unexpectedly exhibited exaggerated increase in systolic BP (WT=149±3 vs KO=163±3 mmHg; p =0.004; n=8) and pulse pressure (WT=31±4 vs KO=45±4 mmHg; p =0.02; n=8) when compared to control. Next, mice were challenged with an intraperitoneal hypertonic saline injection equivalent to 10% of their body weight followed by 4 hours of urine collection. Urinary sodium excretion in female PRR RVL-KO was significantly lower when compared to WT ( p <0.05). These data indicate that the role of PRR in the RVL is sex-dependent and biphasic. That is, PRR contributes to the pressor response during the initial stage of DOCA-salt HT in females, presumably by facilitating the generation of angiotensin peptides in the RVL, while it plays a protective role by promoting renal sodium excretion and preventing elevation of systolic BP during the maintenance stage of DOCA-salt HT. This study suggests that distinct PRR expressing cell populations might elicit diverging physiological functions within the RVL.

Resting-State Functional Connectivity of the Thalamus in Complete Spinal Cord Injury

Background. Neuroimaging studies of spinal cord injury (SCI) have mostly examined the functional organization of the cortex, with only limited focus on the subcortical substrates of the injury. However, thalamus is an important modulator and sensory relay that requires investigation at a subnuclei level to gain insight into the neuroplasticity following SCI. Objective. To use resting-state functional magnetic resonance imaging to examine the functional connectivity (FC) of thalamic subnuclei in complete SCI patients. Methods. A seed-based connectivity analysis was applied for 3 thalamic subnuclei: pulvinar, mediodorsal, and ventrolateral nucleus in each hemisphere. A nonparametric 2-sample t test with permutations was applied for each of the 6 thalamic seeds to compute FC differences between 22 healthy controls and 19 complete SCI patients with paraplegia. Results. Connectivity analysis showed a decrease in the FC of the bilateral mediodorsal nucleus with right superior temporal gyrus and anterior cingulate cortex in the SCI group. Similarly, the left ventrolateral nucleus exhibited decreased FC with left superior temporal gyrus in SCI group. In contrast, left pulvinar nucleus demonstrated an increase in FC with left inferior frontal gyrus and left inferior parietal lobule in SCI group. Our findings also indicate a negative relationship between postinjury durations and thalamic FC to regions of sensorimotor and visual cortices, where longer postinjury durations (~12 months) is associated with higher negative connectivity between these regions. Conclusion. This study provides evidence for reorganization in the thalamocortical connections known to be involved in multisensory integration and affective processing, with possible implications in the generation of sensory abnormalities after SCI.

c-Fos and FosB/ΔFosB colocalizations in selected forebrain structures after olanzapine, amisulpride, aripiprazole, and quetiapine single administration in rats preconditioned by two different mild stressors sequences

Objective. Olanzapine (OLA), amisulpride (AMI), aripiprazole (ARI), and quetiapine (QUE) belong to antipsychotics, which administration represents still most reliable way for the treatment of schizophrenic and bipolar disorders. The intention of the present study was to explore whether the acute administration of a particular antipsychotic, indicated by the presence of c-Fos, will: a) stimulate neurons already activated by a long lasting homogeneous or heterogeneous stress preconditioning, indicated by the FosB/ΔFosB (ΔFosB) expression, or b) have a stimulatory effect only on a not activated, so called silent neurons. The pattern of ΔFosB and c-Fos spatial relationship was investigated in three forebrain structures, including the septal ventrolateral nucleus (seVL), the striatal dorsolateral area (stDL), and the shell of the nucleus accumbens (shell).Methods. The rats were divided into 10 groups and exposed to two types of stressors. Half of them was exposed to a sequence of homogeneous stressor – handling (HDL) and the other half to a heterogeneous stressor (CMS) daily for 20 days. CMS consisted of five types of stressors: crowding, air-puff, wet bedding, predator stress, and forced swimming applied in an unexpected order. On the 21st day of the experiment, the rats were free of the stress exposure and on the 22nd day, both groups of animals receive a single intraperitoneal injection of vehicle (4% DMSO in saline, 0.1 ml/100 g) or OLA (5 mg/kg), AMI (20 mg/kg), ARI (10 mg/kg), and QUE (15 mg/kg). 90 min after the drugs administration the animals were transcardially perfused, brains removed, cut into 30 µm thick coronal sections, and double stained: first with ΔFosB antibody linked with Alexa488 fluorescent dye and second with c-Fos antibody linked to Alexa596 one. Quantitative evaluation of ΔFosB and c-Fos colocalizations was performed on fluorescence photomicrographs transformed into a final picture containing only yellow, green, and red colored circles.Results. The data of this investigation demonstrate that ΔFosB and c-Fos colocalizations occurred in each of the three areas investigated, i.e. seVL, stDL, and shell ones, in both HDL as well as CMS preconditioned rats. The levels of ΔFosB and c-Fos colocalizations varied in the individual forebrain areas studied. From the total 22 areas measured, level of c-Fos colocalization prevailed over ΔFosB in 18 ones. However, neither c-Fos nor ΔFosB reached 100% level of colocalization in any of the forebrain areas investigated.Conclusion. The present findings indicate that ΔFosB and c-Fos colocalizations occurred in each of the three areas investigated, i.e. seVL, stDL, and shell, in both HDL and CMS preconditioned rats, whereas the parallel occurrence of free c-Fos as well as c-Fos colocalized with ΔFosB might speak out for a possible involvement of the c-Fos activated by antipsychotics applied in dual, i.e. short- and long-lasting, functions.