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This study was aimed to investigate the protective effect of Liu Wei Dihuang (LWDH) against D-galactose (D-gal)-induced brain injury in rats and the existence of sex-dependent differences in LWDH protection. Sixty-four rats evenly composed of males and females were randomly assigned into 4 groups (n = 8): normal saline (NS) + NS (N + N), NS + LWDH (N + L), D-gal + NS (D + N) and D-gal + LWDH (D + L) groups. Rats in D + N and D + L groups received daily injection of D-gal (100 mg/kg, s.c.) for six weeks to establish the aging model, while rats in N + N and N + L groups were injected with the same volume of NS. From the third week, rats in N + L and D + L groups were orally administered with a decoction of LWDH for subsequent six weeks. Rats in N + N and D + N groups were orally administered just with the same volume of NS simultaneously. Morris water maze test was employed to evaluate the ability of learning and memory of the rats in all the groups. Acetylcholine (ACh) content, activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) in visual cortex were assayed. Hematoxylin and eosin (HE) staining were used to observe the morphologic injury in hippocampus and visual cortex, and immunohistochemistry was performed to evaluate ChAT and AChE expression levels in the visual cortex. The results showed that the rats in D + N groups exhibited a longer escape latency to platform, lower swimming speed, less percent of target quadrant search time and platform crossings, compared with N + N groups, suggesting the establishment of aging model, while LWDH improved these indexes in D-gal-treated rats. Compared with D + N groups, LWDH increased ACh content and ChAT activity, and decreased AChE activity in visual cortex. Remarkable loss of neurons was found in hippocampus and visual cortex of aging rats, and the injury was significantly attenuated by LWDH. Immunohistochemistry showed D-gal-induced decreases of ChAT and AChE expressions were restored by LWDH. Furthermore, under the neural protection of LWDH, the improvement on platform crossings in male aging rats was better than that in female ones, while in ChAT expression and neuron density in visual cortex, female aging rats obtained more amelioration. These results suggest LWDH can markedly reverse the D-gal-induced cognitive impairments and neuronal damage in both hippocampus and visual cortex, which are achieved at least partly through restoring cholinergic system in central nervous system. Moreover, there is some sex difference in protective effects of LWDH against D-gal-induced impairment.

The purpose of the present study was to observe whether primary afferent Abeta-fiber is involved in the information transmission between peripheral terminals of adjacent dermatomes. The dorsal cutaneous nerve branches of spinal nerves from T(8) to T(12) segments were cut proximally. One peripheral stump end of the cut nerves was dissected into a few filaments for the examination of mechanoreceptive properties of single Abeta-fibers and their discharges were observed while the other end was stimulated antidromically. Fifty Abeta-units were recorded in forty-two intact rats. After an electrical stimulation (0.45 mA, 0.1 ms, 20 Hz, for 10 s) was delivered to the stimulated nerve, the size of the receptive field of 60.6% (n=33) Abeta-fibers extended. The mean area of receptive fields of all examined units enlarged from 8.94+/-6.51 mm(2) to 20.34+/-16.17 mm(2) (P<0.01) and the shapes of the receptive fields of 81.8% (n=20) units changed from a dot, round or ellipse with its long axis in parallel with the longitudinal axis of the body to an oblique ellipse with the longitudinal axis of the body. The mechanoreceptive threshold of 68.0% (n=50) units decreased with a reduction in mean threshold from 2.37+/-1.24 to 2.29+/-1.24 mN (P<0.05). The duration of these changes in mechano-receptive properties increased from 52.23+/-9.27 to 56.93+/-15.76 min. Meanwhile, increasing discharge was found in 50.0% (n=50) units but lasted only for 1.52+/-0.46 min. The changes in mechanoreceptive properties appeared simultaneously with discharge changes but had longer duration than that of discharge change (P<0.01). Discharges changes usually appeared in those units with the changes in mechanoreceptive properties following an antidromical electrical stimulation of adjacent spinal segment. These results suggest that low-threshold mechanoreceptive Abeta-fibers are affected by antidromical electrical stimulation of the cutaneous nerve from an adjacent spinal segment, indicating that information transmission occurs between the two endings of peripheral afferent nerves from adjacent spinal segments without any involvement of the central nervous system, and that Abeta-fibers are involved in the process of information transmission between peripheral terminals from adjacent spinal segments.

The respiratory activity of spinal cord-transected animals was reinvestigated on 71 rabbits. Under light urethane anesthesia and paralyses by gallamine, the spinal cord was transected at either C1 or C2 level, and phrenic discharges were monitored in 43 rabbits. After cordotomy, tonic phrenic discharges were observed in 25 of the 43 spinal rabbits. No spontaneous rhythmic phrenic activities appeared in any of the animal. Respiratory-like, long lasting phrenic bursts (lasting longer than 0.25s) or convulsive-like, short lasting phrenic bursts (lasting shorter than 0.1s on the average) were induced by administration of bicuculline (BCL, 20 micrograms/10 microliters-40 micrograms/20 microliters, intra-subarachnoid space, i.s.s.) in 24 spinal rabbits or picrotoxin (PIC, 20 micrograms/20 microliters, i.s.s. or 3-5 mg/kg i.v.) in 13 spinal rabbits. According to the pattern of the recruitment and de-recruitment of the phrenic discharges, the long lasting phrenic bursts may be divided into three types: Type I, average frequency 23.5 +/- 2.3 cycles/min (BCL), incidence 58.5% (BCL) or 67.7% (PIC); Type II, average frequency 33.8 +/- 4.7 cycles/min (BCL), incidence 39.3% (BCL) or 32.3% (PIC); Type III, average frequency 21.3 +/- 2.8 cycles/min (BCL), incidence 2.2% (BCL) or 3.3% (PIC). The duration of the evoked phrenic discharges was 60.0 +/- 18.9 min (BCL) or 42.0 +/- 0.8 min (PIC). The type I and type II showed respiratory-like discharges, accounting for more than 97.8% of the incidence of the long lasting phrenic bursts. It is suggested that the endogenous GABA system in spinal cord might exert a tonic inhibitory action on the spinal "respiration" activity.