Behavioral effects of "vehicle" microinjected into the dorsal periaqueductal grey of rats tested in the elevated plus maze

Abstract

To investigate the behavioral effects of different vehicles microinjected into the dorsal periaqueductal grey (DPAG) of male Wistar rats, weighing 200-250 g, tested in the elevated plus maze, animals were implanted with cannulas aimed at this structure. One week after surgery the animals received microinjections into the DPAG of 0.9% (w/v) saline, 10% (v/v) dimethyl sulfoxide (DMSO), 2% (v/v) Tween-80, 10% (v/v) propylene glycol, or synthetic cerebrospinal fluid (CSF). Ten min after the injection (0.5 µl) the animals (N = 8-13/ group) were submitted to the elevated plus maze test. DMSO significantly increased the number of entries into both the open and enclosed arms when compared to 0.9% saline (2.7 ± 0.8 and 8.7 ± 1.3 vs 0.8 ± 0.3 and 5.1 ± 0.9, respectively, Duncan test, P<0.05), and tended to increase enclosed arm entries as compared to 2% Tween-80 (8.7 ± 1.3 vs 5.7 ± 0.9, Duncan test, P<0.10). In a second experiment no difference in plus maze exploration was found between 0.9% salineor sham-injected animals (N = 11-13/group). These results indicate that intra-DPAG injection of some commonly used vehicles such as DMSO, saline or Tween-80 affects the exploratory activity of rats exposed to the elevated plus maze in statistically different manners.

The anterior cingulate cortex contributes to the analgesic rather than the anxiolytic effects of duloxetine in chronic pain-induced anxiety

“…It is reported in previous studies that the intraperitoneal injection of 10% DMSO led to significant motor impairment ( Matias et al, 2018 ). Furthermore, another study discovered that local infusion to dorsal periaqueductal gray could increase the exploratory activity in the EPM test ( Matheus et al, 1997 ). Further verification should be done to rule out the potential interference of DMSO which might cause the result in our study.…”

Out of Control? Managing Baseline Variability in Experimental Studies with Control Groups

“…Castro et al (1995) examined the effects of several commonly used vehicles on locomotion in mice and found marked effects of Tween, DMSO and ethanol-containing vehicles at levels well below those indicated by Gad et al (2006) as being well-tolerated. Matheus et al (1997) looked at the effects of Tween, propylene glycol and DMSO on elevated plus-maze behaviour in rats following their injection into the dorsal periaqueductal grey. Interestingly, whereas Castro et al (1995) found DMSO to reduce locomotion, Matheus et al (1997) found it to increase arm entries.…”

“…Matheus et al (1997) looked at the effects of Tween, propylene glycol and DMSO on elevated plus-maze behaviour in rats following their injection into the dorsal periaqueductal grey. Interestingly, whereas Castro et al (1995) found DMSO to reduce locomotion, Matheus et al (1997) found it to increase arm entries. DMSO, at concentrations above 15%, has also been found to modify sleep architecture in rats (Cavas et al 2005).…”

Papel dos receptores 5-HT2a e 5-HT2c da matéria cinzenta periaquedutal nas reações de defesa em camundongos: influência da experiência prévia ao teste e do modelo empregado

“…RINALDI-CARMONA et al, 1992ASHWORTH et al, 1996) Muito embora pareça evidente que o tratamento prévio com eplivanserina tenha antagonizado o efeito antiaversivo do agonista DOI na reexposição, essa interpretação fica prejudicada pelo fato de os resultados do experimento 3.2 não terem sido reproduzidos quando o veículo foi administrado. O fato de o composto ter sido solúvel apenas em soluções contendo altas concentrações de dimetilsulfóxido (DMSO), um veículo diferente do que utilizamos para a solubilização dos demais compostos utilizados no estudo (solução fisiológica acrescida de Tween 80 à 2%), nos levou a administrar o fármaco por via sistêmica ao invés de realizar uma injeção intra-MCPd, haja vista que alguns estudos apontam que a administração intracerebral de DMSO pode produzir alterações no comportamento, na resposta farmacológica de compostos ou na atividade metabólica encefálica em animais de laboratório (MATHEUS, LACERDA, GUIMARÃES, 1997;FOSSUM et al, 2008;NASRALLAH et al, 2008). Levando-se em consideração que o aparentemente simples procedimento de injeção intraperitoneal eleva a expressão de proteína Fos em regiões Etapa B límbicas (RYABININ et al, 1999;ASANUMA;OGAWA, 1994;CECCATELLI et al, 1989;SHARP et al, 1991), é possível que a administração de veículo pré-reteste tenha exercido alguma influência sobre o comportamento dos animais.…”