The effects of neonatal maternal deprivation and chronic unpredictable stresses on migraine-like behaviors in adult rats.

BACKGROUND: Stress is known to cause migraine. This study investigates the effects of neonatal maternal deprivation (MD) and chronic unpredictable stress (CUS) on migraine in rats. METHODS: Seventy rats were randomly divided into ten groups (five groups of each sex, and seven rats/group). The groups included: untreated intact, nitroglycerin (NTG) only, NTG + MD, NTG + CUS (10 weeks after birth), and NTG + MD + CUS. For the induction of MD, pups were separated from their mothers from postnatal day 2 to day 14. The CUS was conducted by daily exposure to different stressors for 2 weeks. For the induction of migraine after stress, NTG (5 mg/kg/IP) was administered every second day for 9 days. Afterward, NTG-related symptoms, including climbing behavior, facial rubbing, body grooming, freezing behavior, and head-scratching, were recorded for 90 min. Statistical differences between the groups were analyzed by one-way and two-way ANOVA followed by the Newman-Keuls test. RESULTS: Migraine symptoms, including increased head-scratching, facial rubbing, and decreased climbing behavior, were more significant in females than in males. Head scratching and facial rubbing increased in stressed females, but not in males as compared to NTG-treated rats. Body grooming was significantly decreased in MD males compared to the NTG group. The effects of NTG in MD + CUS on the rats did not differ from those in the MD or CUS groups. CONCLUSIONS: MD and CUS had a sex-related aggravating effect on the development of migraine, while the combination of MD and CUS had no additive migraine-aggravating effect.

Mode of delivery alters dental pulp nociception and pain-induced changes in cognitive performance in adults male rats.

This study examined the effects of delivery mode on the response to inflammatory pulpal pain and pain-induced changes in cognitive performance in adult rats. Experiments were done on rats born by vaginal or caesarean section (C-section) delivery. Dental pulp was irritated by intradental capsaicin (100 µg) application and then nociceptive scores were recorded for 40 min. Spatial and passive avoidance learning and memory were assessed using the Morris water maze (MWM) and shuttle box tools, respectively. Additionally, in vivo recording of field excitatory postsynaptic potential (fEPSP) in the CA1 of the hippocampus was used to verify synaptic plasticity. Capsaicin produced more significant nociceptive behavior in vaginally delivered rats compared to C-section rats (P < 0.01). C-section-delivered rats show better performance in both MWM and shuttle box tests. Likewise, C-section rats had greater fEPSP slopes compared to the vaginally delivered group (P < 0.05). Capsaicin impairs cognitive performance in rats born by each delivery route. However, capsaicin effects were more significant in rats delivered vaginally than by C-section. Overall, C-section-delivered rats show lower sensitivity to capsaicin-evoked pulpal nociception and better cognitive performance than vaginally delivered rats. These effects are in part mediated by reduced neuroinflammation and enhanced neuronal synaptic plasticity following C-section delivery.