Evidence That the Periaqueductal Gray Matter Mediates the Facilitation of Panic-Like Reactions in Neonatally-Isolated Adult Rats

Plenty of evidence suggests that childhood separation anxiety (CSA) predisposes the subject to adult-onset panic disorder (PD). As well, panic is frequently comorbid with both anxiety and depression. the brain mechanisms whereby CSA predisposes to PD are but completely unknown in spite of the increasing evidence that panic attacks are mediated at midbrain's dorsal periaqueductal gray matter (DPAG). Accordingly, here we examined whether the neonatal social isolation (NSI), a model of CSA, facilitates panic-like behaviors produced by electrical stimulations of DPAG of rats as adults. Eventual changes in anxiety and depression were also assessed in the elevated plus-maze (EPM) and forced-swimming test (FST) respectively. Male pups were subjected to 3-h daily isolations from post-natal day 2 (PN2) until weaning (PN21) allotting half of litters in individual boxes inside a sound-attenuated chamber (NSI, n = 26) whilst siblings (sham-isolated rats, SHAM, n = 27) and dam were moved to another box in a separate room. Non-handled controls (CTRL, n = 18) remained undisturbed with dams until weaning. As adults, rats were implanted with electrodes into the DPAG (PN60) and subjected to sessions of intracranial stimulation (PN65), EPM (PN66) and FST (PN67-PN68). Groups were compared by Fisher's exact test (stimulation sites), likelihood ratio chi-square tests (stimulus-response threshold curves) and Bonferroni's post hoc t-tests (EPM and FST), for P<0.05. Notably, DPAG-evoked panic-like responses of immobility, exophthalmus, trotting, galloping and jumping were markedly facilitated in NSI rats relative to both SHAM and CTRL groups. Conversely, anxiety and depression scores either did not change or were even reduced in neonatally-handled groups relative to CTRL, respectively. Data are the first behavioral evidence in animals that early-life separation stress produces the selective facilitation of panic-like behaviors in adulthood. Most importantly, results implicate the DPAG not only in panic attacks but also in separation-anxious children's predispositions to the late development of PD.Fundacao de Amparo a Pesquisa do Espirito Santo (FAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Associacao Fundo de Incentivo a Pesquisa (AFIP)Universidade Federal do Espirito Santo (UFES)FAPESUFES/AFIPUniv Fed Espirito Santo, Dept Physiol Sci, Vitoria, ES, BrazilUniv Fed Espirito Santo, Dept Sports, Vitoria, ES, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, São Paulo, BrazilFAPES: 38.413.280/2007CNPq: 55203345/11UFES/AFIP: 23068020409/2010-43Web of Scienc

ON THE VERGE OF A RESPIRATORY-TYPE PANIC ATTACK: SELECTIVE ACTIVATIONS OF ROSTROLATERAL AND CAUDOVENTROLATERAL PERIAQUEDUCTAL GRAY MATTER FOLLOWING SHORT-LASTING ESCAPE TO A LOW DOSE OF POTASSIUM CYANIDE

Intravenous injections of potassium cyanide (KCN) both elicit escape by its own and facilitate escape to electrical stimulation of the periaqueductal gray matter (PAG). Moreover, whereas the KCN-evoked escape is potentiated by CO2, it is suppressed by both lesions of PAG and clinically effective treatments with panicolytics. These and other data suggest that the PAG harbors a hypoxiasensitive alarm system the activation of which could both precipitate panic and render the subject hypersensitive to CO2. Although prior c-Fos immunohistochemistry studies reported widespread activations of PAG following KCN injections, the employment of repeated injections of high doses of KCN (> 60 mu g) in anesthetized rats compromised both the localization of KCN-responsive areas and their correlation with escape behavior. Accordingly, here we compared the brainstem activations of saline-injected controls (air/saline) with those produced by a single intravenous injection of 40-mu g KCN (air/KCN), a 2-min exposure to 13% CO2 (CO2/saline), or a combined stimulus (CO2/KCN). Behavioral effects of KCN microinjections into the PAG were assessed as well. Data showed that whereas the KCN microinjections were ineffective, KCN intravenous injections elicited escape in all tested rats. Moreover, whereas the CO2 alone was ineffective, it potentiated the KCNevoked escape. Compared to controls, the nucleus tractus solitarius was significantly activated in both CO2/saline and CO2/KCN groups. Additionally, whereas the laterodorsal tegmental nucleus was activated by all treatments, the rostrolateral and caudoventrolateral PAG were activated by air/KCN only. Data suggest that the latter structures are key components of a hypoxia-sensitive suffocation alarm which activation may trigger a panic attack. (C) 2017 IBRO. Published by Elsevier Ltd. All rights reserved.CAPESCNPqConselho Nacional de Desenvolvimento Cientifico e Tecnologico/Fundacao de Amparo a Pesquisa do Espirito Santo (CNPq/FAPES)Universidade Federal do Espirito Santo/Associacao Fundo de Incentivo a Pesquisa (UFES/AFIP)Univ Fed Espirito Santo, Dept Physiol Sci, Vitoria, ES, BrazilUniv Fed Sao Paulo, Dept Psychobiol, Sao Paulo, SP, BrazilUniv Fed Espirito Santo, Dept Pharmaceut Sci, Vitoria, ES, BrazilUniv Sao Paulo, Inst Biomed Sci, Dept Anat, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Psychobiol, Sao Paulo, SP, BrazilCNPq/FAPES: 55203345/11UFES/AFIP: 23068.020409/2010-43Web of Scienc

Translational approach to studying panic disorder in rats: Hits and misses

Luiz Carlos Schenberg, Fagna Giacomin Schimitel, Rubia de Souza Armini, Cristian Setubal Bernabe, Caroline Azevedo Rosa, Sergio Tufik, Claudia Janaina Torres Muller, Jeyce Willig Quintino-dos-Santos. Translational Approach to Studying Panic Disorder in Rats: Hits and Misses. Neurosci. Biobehav. Rev. XX (X) XXX-XXX, 2014. Panic disorder (PD) patients are specifically sensitive to 5-7% carbon dioxide. Another startling feature of clinical panic is the counterintuitive lack of increments in 'stress hormones'. PD is also more frequent in women and highly comorbid with childhood separation anxiety (CSA). On the other hand, increasing evidence suggests that panic is mediated at dorsal periaqueductal grey matter (DPAG). in line with prior studies showing that DPAG-evoked panic-like behaviours are attenuated by clinically-effective treatments with panicolytics, we show here that (i) the DPAG harbors a hypoxia-sensitive alarm system, which is activated by hypoxia and potentiated by hypercapnia, (ii) the DPAG suffocation alarm system is inhibited by clinically-effective treatments with panicolytics, (iii) DPAG stimulations do not increase stress hormones in the absence of physical exertion, (iv) DPAG-evoked panic-like behaviours are facilitated in neonatally-isolated adult rats, a model of CSA, and (v) DPAG-evoked responses are enhanced in the late diestrus of female rats. Data are consistent with the DPAG mediation of both respiratory and non-respiratory types of panic attacks. (C) 2014 Elsevier B.V. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UFES/AFIPUniv Fed Espirito Santo, Dept Physiol Sci, Vitoria, ES, BrazilUniv Fed Espirito Santo, Dept Sports, Vitoria, ES, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Psychobiol, São Paulo, BrazilCNPq: 55203345/11UFES/AFIP: 23068020409/2010-43Web of Scienc

Median threshold intensities (I₅₀±SE) of neonatally-isolated rats, sham-isolated rats and non-handled controls.

<p>Symbols represent values significantly different from controls (*) and sham-isolated rats (⁺) for Bonferroni's 5% criterion (likelihood ratio χ² tests for curve location).</p

Effects of neonatal social isolation on the performance of adult rats in the elevated plus-maze (<i>n</i> = 19–27) and forced swimming test (<i>n</i> = 18–24).

<p>Columns represent mean±SEM. CTRL – controls, SHAM – sham-isolated rats, NSI – neonatally-isolated rats. EAE – number of entries in enclosed arms (mean±SEM), OAE% - percent of entries in open arms, OAT% - percent of time in open arms. * P<0.005, statistically different from CTRL.</p

Intensity-response threshold curves of panic-like behaviors evoked by electrical stimulations of the dorsal periaqueductal gray matter.

<p>Curves are the best-fitted logistic functions of threshold response accumulated proportions in function of the logarithm of the stimulus intensity (µA). The abscissa is in logarithmic scale. Dashed lines (–) indicate significant differences between groups (P<0.05, likelihood-ratio χ² test for curve location). Abbreviations: r – responders, n –number of stimulated rats.</p

Localization of stimulating electrodes.

<p>Groups symbols were plotted in the same side for the sake of clarity. Abbreviations: DGLSC and DWLSC – deep gray and white layers of superior colliculus, DMPAG, DLPAG, LPAG and VLPAG – dorsomedial, dorsolateral, lateral and ventrolateral columns of the periaqueductal gray matter, DR – dorsal raphe, IC – inferior colliculus. Numbers refer to anteroposterior coordinates in relation to bregma of coronal plates of Paxinos and Watson's (1998) rat brain atlas <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0090726#pone.0090726-Paxinos1" target="_blank">[42]</a>.</p

Brain areas stimulated in controls (CTRL), sham-isolated rats (SHAM) and neonatally-isolated rats (NSI).

<p>DMPAG, DLPAG and LPAG – dorsomedial, dorsolateral and lateral columns of periaqueductal gray matter, DLSC – deep layers of superior colliculus.</p

Protocol of neonatal social isolation (NSI).

<p>PN – postnatal day, ICS – intracranial stimulation, EPM – elevated plus-maze, FST-1 – forced swimming pretest session, FST-2 – forced swimming test session.</p