| Objective: Insulin-like growth factor-1(IGF-1)is a potent neuroendocrine regulator in the development,maturation,and nutritional support of central nervous system.IGF-1 has great therapeutic value for some growth and development disorders,diabetes and metabolic disorders,neurological or skeletal muscle lesions,as well as neuropsychiatric diseases.In recent year,many researches are focus on the effects of IGF-1 on aging,hippocampal synaptic plasticity and neurodegenerative changes.Currently,there is no published paper on the effects of IGF-1 on synaptic transmission of spinal cord motor neurons(MNs).The purpose of this study was to observe the effect of IGF-1 on synaptic transmission in spinal motor neurons.Methods: By using intracellular recording techniques and 7-14-day-old neonatal SD rat spinal cord slices,cell electrophysiological parameters of excitatory postsynaptic potentials(iVLF-EPSPs and iDR-EPSP)evoked by ipsilateral ventrolateral funiculus(iVLF)and ipsilateral dorsal roots(i DR)simultaneous stimulation(monopulse,0.1 to 0.3ms,10 times per minutes,10 to 100V)were observed from MNs,then effects of IGF-1(300 nmol/L)bath on MNs were evaluated.Results:(1)We recorded 62 stable and healthy MNs,the resting potential of-66.71 ± 4.59 mV,amplitude of 74.98 ± 7.25 mV and overshoot of 10.77 ± 5.65 mV were measured.(2)Amplitude of iVLF-EPSPs evoked by iVLF threshold stimulation was observed to be 4.47 ±1.83 mV,duration 65.62 ± 19.89 ms,and area under curve 112.75 ± 50.99 mV· ms in 49 MNs;and amplitude of iDR-EPSPs evoked by iDR threshold stimulation was observed to be 2.49 ± 1.00 mV,duration 51.78 ± 12.95 ms,and area under curve 51.00 ± 33.83 mV· ms in the same MNs.(3)In 5 tested MNs,IGF-1(300 nmol/L)bath induced a membrane hyperpolarization(p < 0.05)and the membrane resistance decreased.(4)A fter IGF-1(300 nmol/L)bathing,5 MNs increased area under curve,duration and half-width of iVLFEPSPs,while increased amplitude,duration and shortened latency of i DR-EPSP(all P<0.05).(5)In 2 cells of 5 tested MNs bathed IGF-1(300 nmol/L)with iVLF-EPSPs and iDR-EPEPs,the tetanic electrical stimulation(100Hz,50pulse/train,duration 0.4~1.0ms,6 trains,main interval 10 s,10~100V)on iVLF and i DR,enhanced the amplitude of iVLFEPSPs to 120% of the basicline and enlargement lasted longer than 30 minutes in 1 MNs,which could be referred as long-term potential(i VLF-LTP),whilethe other MN's amplitude and area under the curve had increased continuously more than 120% of the basicline for 23 minutes and then lost unexpectedly,with a iVLF-LTP trend.Conclusion: These primary results suggest that:(1)IGF-1 can induce depolarization of motor neurons,enhance synaptic transmission and produce excitatory effects on spinal cord.(2)IGF-1 may be involved in the iVLF-LTP induction of spinal motor neuron.(3)IGF-1 may modulate final motor outputs by regulating the descending activation and dorsal roots afferent signals in the rat spinal cord. |
PDF Full Text Request