New neostigmine-based behavioral mouse model of abdominal pain

BACKGROUND

Animal models of visceral pain have gained much attention as an important tool to elucidate the possible mechanisms underlying functional gastrointestinal (GI) disorders. Here we report the development of a new, minimally invasive behavioral model of abdominal pain induced by ip administration of neostigmine in mice.

METHODS

Spontaneous behavioral responses evoked by ip injection of neostigmine were compared to pain-related behaviors induced by acetic acid solution (ip), mustard oil (MO) and capsaicin (both ic). Pain behaviors were quantified by assessment of defined postures (licking of the abdomen, stretching, squashing of the abdomen and abdominal contractions). Neuronal activation of spinal cord was measured by determining the number of c-Fos-positive cells.

RESULTS

Neostigmine (2.5 μg/kg, ip), acetic acid solution (ip), MO and capsaicin (both ic) induced spontaneous behavioral responses in mice, which were blocked by morphine (3 mg/kg, ip), suggesting the involvement of pain signaling pathways. Injection of neostigmine enhanced c-Fos expression in spinal cord neurons.

CONCLUSION

The neostigmine model represents a new minimally invasive mouse model to study visceral pain. Based on the neuronal activation pattern in the spinal cord we suggest that this model may be used to study abdominal pain signaling pathways in the GI tract.

Zebrafish keratin 8 is expressed at high levels in the epidermis of regenerating caudal fin

Cytokeratins are structural proteins of the intermediate filament family and are mainly expressed in epithelial cells. In several vertebrates it has been shown that keratin 8 is expressed in simple epithelial tissues, some non-epithelial tissue and in hyper-proliferative tissues during development and tumor transformation. We previously cloned and characterised the zebrafish (Danio rerio) homologous cytokeratin 8 cDNA (zfk8) which was described as an epidermal marker during zebrafish development. It has been found that the zfk8 gene is normally expressed in simple epithelia in embryonic and mature zebrafish. Using whole-mount in situ hybridisation, we show in this report that expression of zfk8 is tightly linked to the regeneration of caudal fin and exclusively observed in epidermal cells. It is strongly expressed in the epidermis overlaying the inter-rays zone of regenerating caudal fin. Our results indicate that in zebrafish, cytokeratin 8 is a suitable epidermal marker during regeneration.