AIMTo investigate whether formalin inflammatory pain can induce hippocampal neuronal apoptosis of rats or not.

METHODSRats were subcutaneously injected with 0.2 ml 0.5% formalin into the ventral surface of right hind paw to induce periphery inflammatory pain. The flinches of rats were counted to observe their painful reaction. Flow cytometry was used to assay the ratio of apoptosis of hippocampal neurons. The immunohistochemistry was used to observe the expression of p53 protein in hippocampal subregions.

RESULTSCompared with control group, the apoptotic ratio of hippocampal neurons was significantly increased in rats with inflammatory pain, and formalin inflammatory pain induced upregulation of p53 protein expression in all hippocampal subregions. Both the apoptotic ratio and the p53 protein expression peaked on the third day after the formalin injection. The twice injection of formalin into the hind paws of rats resulted in an enhancement of painful reaction and increase in apoptotic ratio of hippocampal neurons compared with the rats of injection formalin once group.

CONCLUSIONFormalin inflammatory pain can induce the hippocampal neuronal apoptosis in rats with a certain time course. Neuronal apoptosis is relevant to the intensity of pain. The up-regulation of p53 protein expression may implicate in the induction of hippocampal neuronal apoptosis in rats with inflammatory pain.

Animals ; Apoptosis ; Formaldehyde ; Hippocampus ; pathology ; physiopathology ; Inflammation ; chemically induced ; physiopathology ; Male ; Neurons ; pathology ; Pain ; chemically induced ; physiopathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Tumor Suppressor Protein p53 ; metabolism

OBJECTIVETo observe whether formalin inflammatory pain can induce neuron apoptosis in rats spinal cord or not and the effects of nitric oxide on the spontaneous pain reaction and neuron apoptosis in the spinal cord of rats with formalin inflammatory pain.

METHODSFormalin-induced paw licking time was used to reflect the degree of spontaneous pain of rats, and the flow cytometry was used to detecte neuron apoptosis rate of spinal cord.

RESULTSCompared with control group, the apoptosis ratio of spinal neuron was increased in the rats with formalin inflammatory pain, and peaked at 3d after formalin injection. Pre-intrathecal injection of NOS inhibitor L-NAME inhibited the nociceptive behavioural response in double phases induced by fonnrmalin injection and cut down the neuron apoptosis ratio of spinal cord of rats with formalin inflammatory pain. Nociceptive behavioural response and incraesed neuron apoptosis in the spinal cord were induced by intrathecal injection of L-Arg in normal rats.

CONCLUSIONThe results indicated that formalin inflammatory pain could induce the apoptosis of spinal neurons. The neurons apoptosis was the most significant on the third day after formalin injection. The increased pruduction of NO in spinal cord could promote the transmit of nociceptive information and participate the induction of neuronal apoptosis during the formalin inflammatory pain.

Animals ; Apoptosis ; drug effects ; Formaldehyde ; Male ; NG-Nitroarginine Methyl Ester ; pharmacology ; Neurons ; pathology ; Nitric Oxide ; metabolism ; physiology ; Nitric Oxide Synthase ; antagonists & inhibitors ; Nociceptors ; physiology ; Pain ; chemically induced ; physiopathology ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; pathology ; physiopathology

AIMTo study the effect of intrathecal injection of MK-801, a NMDA receptor antagonist, on the NOS activity and NO content of hippocampus in rat during the process of formalin-induced inflammatory pain as well as the pain behavior of rat.

METHODSThe degree of pain was determined by observing the time of licking and biting the injected paw. NOS expression in the hippocampus was determined by using NADPH-d histochemical staining. NO content of hippocampus was determined by assaying NO3; and NO2.

RESULTSSubcutaneous injection of formalin elicited a characteristic pain behavioural response consisting of licking and biting the injected paw, etc. Intrathecal injection of MK-801 could shorten obviously the time of licking and biting representing pain behavioural response in phase 2. It is suggested that intrathecal injection of MK-801 could block the pain behavioural response induced by formalin (P < 0.05). The number and staining degree of NADPH-d positive neurons in formalin group significantly increased at 12 h after the formalin injection in CA1, CA2-3 and DG of hippocampus compared with control group as well as NO content, however, the number and staining degree of NADPH-d positive neurons in formalin + MK-801 group significantly decreased in contrast to those of formalin 12 h group as well as the NO content (P < 0.01).

CONCLUSIONIntrathecal injection of NMDA receptor antagonist MK-801 could inhibit the NOS activity and NO production in hippocampus of rat, which showed the increase of hippocampal NO production was mainly induced by the peripheral nociceptive information input.

Animals ; Dizocilpine Maleate ; administration & dosage ; pharmacology ; Formaldehyde ; Hippocampus ; metabolism ; physiopathology ; Inflammation ; chemically induced ; Injections, Spinal ; Male ; Nitric Oxide ; metabolism ; Nitric Oxide Synthase Type I ; metabolism ; Pain ; chemically induced ; physiopathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; antagonists & inhibitors

OBJECTIVE: To evaluate the prospective association between cumulative resting heart rate (cumRHR) and rapid renal function decline (RRFD) in a cohort of individuals aged 60 and older. METHODS: In the Tianjin Chronic Kidney Disease Cohort Study, the individuals who underwent three consecutive physical examinations between 2014 and 2017, with estimated glomerular filtration rate (eGFR) greater than 60 mL/min per 1.73 m² and aged 60 years or older were enrolled. A total of 27,564 patients were prospectively followed up from January 1, 2017 to December 31, 2020. The 3-year cumRHR was calculated. The primary outcome was RRFD, defined as an annualized decline in eGFR of 5 mL/min per 1.73 m² or greater. Logistic and restricted spline regression models and subgroup analysis were used to investigate the association of cumRHR with RRFD after adjusting for all confounders. RESULTS: During a median follow-up of 3.2 years, a total of 4,347 (15.77%) subjects developed RRFD. In fully-adjusted models, compared with the lowest quartile of cumRHR, the odds ratio (OR) for the highest was 1.44 (1.28-1.61), P < 0.001. Furthermore, each 1-standard deviation (27.97 beats/min per year) increment in cumRHR was associated with a 17% (P < 0.001) increased risk of RRFD, with a linear positive correlation (P for non-linear = 0.803). Participants with a 3-year cumRHR ≥ 207 (beats/min) * year (equivalent to ≥ 69 beats/min per year in 3 years) were found to be at a higher risk of RRFD. CONCLUSIONS The cumRHR is significantly associated with a higher risk of RRFD among older adults. These results might provide an effective goal for managing and delaying the decline of renal function in the older adults.