The compulsive-like aspect of the head dipping emission in rats with chronic electrolytic lesion in the area of the median raphe nucleus

Abstract

Head dipping (HD) is a behavioral pattern considered to have a risk assessment or an exploratory role and is used as a complementary parameter to evaluate anxiety in experimental animals. Since rats with electrolytic lesion in the area of the median raphe nucleus displayed high frequencies of HD in a previous study, the present investigation was undertaken to confirm this observation and to determine its anxiety-related origin. HD episodes were counted in adult male Wistar rats (270-350 g) with electrolytic lesion (N = 11) and sham-lesioned controls (N = 12). When HD was measured for 60 min on an elevated open platform, lesioned rats emitted 13 times more HD than controls (264.7 ± 93.3 vs 20.3 ± 7.6 episodes), with the difference being statistically significant (P < 0.05). HD counts during 10-min sessions held 7, 14, 21, 27, and 63 days after lesion showed significantly higher means (range: 28.14 ± 5.38 to 62.85 ± 9.48) compared to shamlesioned controls (range: 7.37 ± 1.13 to 8.5 ± 1.45). Normal rats stepped down into their home cages when the vertical distance between them and the cage was short (16 cm), and the step-down latencies increased with increasing depths (36.7 ± 7.92 to 185.87 ± 35.44 s). Lesioned rats showed a similar behavior when facing the shortest depth, but had a significantly increased number (23.28 ± 2.35 episodes) and latency (300 ± 0.00 s) of HD compared to normal rats (9.25 ± 1.37 episodes and 185.87 ± 35.44 s) when facing the greatest depth (30 cm). This suggests that HD may be a depth-measuring behavior related to risk assessment.

Translational approaches to obsessive‐compulsive disorder: from animal models to clinical treatment

“…Knock‐down of the dopamine transporter in mice (DAT KD mice) produces ‘sequential super‐stereotypy’ with the perseverative performance of complex chains of grooming behaviour (Berridge et al ., 2005). Likewise, a knock‐down of the 5‐HT 2C receptor leads to perseverative ‘head‐dipping’ or the excessively orderly chewing of screen material (Chou‐green et al ., 2003), a compulsive behaviour which – together with stereotypic locomotion and excessive self‐aggressive grooming – has also been shown in rats following chronic lesions of the median raphé nucleus (Hoshino et al ., 2004). However, the data obtained from this genetic preparation do not match with other data investigating the same receptor, possibly because of unspecified compensatory processes that may develop in the transgenic preparation, as recent pharmacological data indicate the opposite finding that 5‐HT 2C receptor activation is associated with increased compulsivity (Tsaltas et al ., 2005; Boulougouris et al ., 2008).…”

Changes in Emotional Behavior of Mice in the Hole-Board Test After Olfactory Bulbectomy

“…Bilkei-Gorzo and Gyertyan (24) reported that brighter lighting, which was highly aversive environment, increased the head-dipping behavior of rats. Hoshino et al (25) also reported that the higher frequency of head-dipping behavior was observed in the rats with chronic electrolytic lesion of the raphe nucleus, which was produced higher anxiety levels in rats. Tsuji et al (26) also reported that the mouse exposure to chronic mild stress for 1 week produced a significant increase in the head-dipping behavior.…”

Efeitos comportamentais da lesão eletrolítica da região do núcleo mediano da rafe como modelo experimental de mania no rato e no camundongo

“…Os parâmetros do procedimento de lesão eletrolítica utilizado nos experimentos do Capítulo I (eletrodo, tempo de passagem da corrente, posição de inserção) foram definidos com base nos estudos anteriores realizados por Hoshino e colaboradores (Hoshino & Sugizaki, 1986;Hoshino et al, 2004;Leite, Hoshino, & De Paula, 2004;Pezzato & Hoshino, 2004. Ao longo de diversos anos tais parâmetros se mostraram efetivos na indução da hiperatividade locomotora e outras alterações comportamentais que incitaram a hipótese da correspondência do quadro decorrente deste procedimento com a mania.…”

“…Diversas pesquisas realizadas nos últimos anos no Laboratório de Neurobiologia da UNESP/Bauru por Hoshino e colaboradores (Hoshino & Sugizaki, 1986;Hoshino, Uga, & de Paula, 2004;Pezzato, de Paula, Bosqueiro, & Hoshino, 2003;Pezzato & Hoshino, 2004 exploraram os efeitos da lesão eletrolítica do núcleo mediano da rafe (MnR).…”

“…A exarcebação adicional da atividade locomotora decorrente do procedimento de lesão eletrolítica do MnR, juntamente com outros efeitos comportamentais induzidos exclusivamente as por este tipo de procedimento -como déficits de aprendizagem (Asin et al, 1985), alteração na frequências de exposição ao risco e estereotipia (Andrade & Graeff, 2001;Hoshino et al, 2004) -justificam a escolha pela inativação por eletrocoagulação não específica da região estudada nesta pesquisa. A investigação da ocorrência do conjunto de efeitos comportamentais decorrentes de um único procedimento experimental pode ser considerada como ponto de partida necessário à comparação com quadro maníaco humano -o estabelecimento da validade de face justificaria então a identificação de diferentes mecanismos responsáveis por efeitos específicos.…”