Neuroprotective effects of cannabidiol in spinal motoneurons and dorsal root ganglion sensory neurons after sciatic nerve crush in neonatal rats: role of CB 1 and CB 2 receptors

Author(s)

Matheus Perez

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2018-02-16

Examining board members

Alexandre Leite Rodrigues de Oliveira; Fabrício Alano Pamplona; Fabrício de Araújo Moreira; Renata Frazão; Catarina Raposo Dias Carneiro

• Advisor: Alexandre Leite Rodrigues de Oliveira

Abstract

Sciatic nerve crush in neonatal rats mimics the obstetric axonotmesis, leading to an extensive death or motor and sensory neurons, enabling the evaluation of neuroprotective effects of new molecules, such as the ones related to endocannabinoid system, which is spontaneously activated in response to injury. Thus, it is possible that cannabidiol (CBD), through activation of the endocannabinoid system, leads to increased regenerative response. The present work investigated the neuroprotective effect of CBD and its action through endocannabinoid receptors after peripheral nerve lesion in neonatal rats. For this, 2days-old Wistar rats were divided into the following experimental groups: sciatic nerve crush (SNC) +Vehicle treatment (Vehicle group); SNC + CBD treatment (CBD group); SNC + CBD + AM 251 (Cb1 inhibitor) treatment (CBD + AM 251 group); SNC + CBD + AM 630 (CB2 inhibitor) treatment (CBD + AM 630 group); SNC + AM 251 treatment (AM 251 group); SNC + AM 630 treatment (AM 630 group) and SNC + AM 251 + AM 630 treatment (AM 251 + AM 630 group). Motoneuron survival, 5 days and 8 weeks after injury, showed that CBD enhances in about 54% neuronal survival, both 5 days and 8 weeks after injury. The other experimental groups showed higher motoneuron preservation than the vehicle group, but when both Cb1 and CB2 receptors were blocked, the motoneuron survival was the same then after CBD treatment. In long term, only CB1 blockade reversed the CBD positive effect. The blockade of cannabinoid receptors increases the sensory neuron death as a result of apoptosis or lesion. Although CBD treatment did not protect sensory neurons of death, it attenuates the death caused by cannabinoid receptors blockade. CBD treatment also preserved 35% of synapses in the ventral horn and this effect was partially reversed by CB 2 inactivation. Antagonists-only treatments showed synaptic preservation equivalent to Vehicle group. Corroborating with this, the microglial reaction in the acute phase was also reduced by CBD in 62%, being higher in the experimental groups that were treated only with cannabinoid receptors antagonists. Additionally, CBD or AM 251 + AM 630 treatment decreased the reactive astrogliosis 5 days after lesion. Gene transcripts expression for CB1 was higher in Vehicle group. Both CBD alone or combined with CB1 and CB2 receptors antagonists resulted in higher CB2 expression, when compared to control, being even lower when compared to Vehicle. In the dorsal root ganglia (DRG), CBD + AM 630 treatment increased CB1 levels, while CBD + AM 251 decreased it. Still, we did not detect statistical differences in neurotrophins expression in the spinal cord, both 5 days or 8 weeks after lesion, in the experimental groups that received CBD. However, CB1 and CB2 antagonists administration, alone or together, reduced BDNF expression. In DRG, CBD + AM 630 increased and CBD + AM 251 decreased BDNF expression, and 15 days after lesion, only GDNF had elevated levels, especially on CBD group. Lastly, functional motor recovery revealed that, 8 weeks after lesion, CBD group presented improved recovery when compared to CBD + AM 251 group. In general, the data herein shows that CBD is neuroprotective, enhancing neuronal survival and decreasing the glial reaction induced by axotomy. In the same way, the selective action of cannabinoid receptors can also result in neuroprotection, even in the absence of CBD (AU)

• FAPESP's process: 12/22751-5 - Neuroprotective effects of cannabidiol in spinal neurons and dorsal root ganglion sensory neurons after sciatic nerve transection in neonatal rats: role of CB1 and CB2 receptors
• Grantee: Matheus Perez
• Support Opportunities: Scholarships in Brazil - Doctorate