| Substance P (SP), belong to the tachykinin neuropeptide-family likely to function as a neurotransmitter and/or neuromodulator in the mammalian nervous system. SP play a dual role in pain and acupuncture analgesia that transfer "pain"sigals as neurotransmitter in the spinal cord and have an analgesic effect in brain. The highest concentration of SP found in the subcortex of the brain, such as the substatia nigra hypothalamus, globus pallidus, caudate nucleus and central gray. Radioimmunoassay or immunohistochemistry was used to study SP in central nerves system in rats and found the highest levels of SP in the midbrain, hypothalamus and preoptic area while it is very low contents in the cerebellum. SP immuno-reaction (IR) positive cells increased significantly in both low-frequency and high-frequency EA groups, particularly in low frequency. EA can cause up-regulation of SP expression in the caudate putamen, hypothalamic paraventricular nucleus, anterior hypothalamic area, amygdaloid nucleus and periaqueduct grey matter in rats. But in the spinal cord,15Hz is the best frequency that can increase the content of SP in rats.The widely distribution of SP in the brain of rats indicated SP may play an importance roles to the body, and function of EA may regulate SP. However, veterinary experience had showed that the optimal for the ruminant are high frequency (30-300Hz) while that for the small laboratory animals and people are low frequency (2-15Hz).Whether the mechanism effect about ruminant are same as the small laboratory animals are still unclear. The aim of the present experiments was to study small animal but the ruminant. We choose goats as object because goats are smaller and cheaper than other ruminants. This study was designed to detect the expressing and the distribution of SP induced by different frequencies in goats, to determine the optimal analgesic frequency for goats, to elucidate the mechanism of SP participating in the ruminant's acupuncture analgesia, and to provide a theoretical basis for the application of the acupuncture analgesia in veterinary practice.Thirty-five male hybridism-goats weight (25±2) kg, provided by The Experimental Animal Center, were fed for two week in the room with ample water and food, free-running. These goats were randomly divided into five group (including normal control,2 Hz,40 Hz,60 Hz and 100 Hz), and there were 7 goat in each of the above-mentiond 5 groups.The goat was put in the fixer. When calmed, the goats in EA groups were stimulated at two groups of "baihui-qijia" and "ergen-sanyangluo" with needle. The pain threshold value was tested by potassiumion penetration method at the beginning of EA and after treatment of EA for 30 min. Goats were deeply anesthesia, and then transcardially perfuse with saline followed by the paraformaldehyde in phosphate buffer and the brains were removed and were made Paraffin section. The distribution and expressing levels of SP were observed in mainly analgesic nuclei (septal area, caudate nucleus, supraoptic nucleus, hypothalamie paraventricular nucleus, ventromedial hypothalamic nucleus, amygdale, PAG, red nucleus, locus ceruleus, parabrachial nucleus, nucleus raphes magnus, nucleus tractus solitary, gigantocellular reticular nucleus, spinal cord dorsal horn) by SABC immunohistochemistry.The analgesic effects of EA were expressed based on the pain threshold.60Hz increased greasted and improved by 84% compared with the basic pain threshold, and had significant difference from 2Hz but 40Hz and 100Hz. The pain threshold elicited by 100 Hz was secondery to that by 60Hz, increased by 54% of the pain threshold, and had significant difference from that by 2Hz, and was not different from that by 40Hz. The pain threshold induced by 40Hz, improved by 54%, was had significant difference from that by 2Hz (improved by 35%).The immunohistochemistry result exhibited that after EA stimulation for 30 min that SP have an expression level in some nuclei significantly higher than the control groups including septal area, caudate nucleus, supraoptic nucleus, hypothalamic paraventricular nucleus, amygdale, red nucleus, parabrachial nucleus, nucleus raphes magnus, gigantocellular reticular nucleus, spinal cord dorsal horn. High frequency (40Hz,60Hz and 100Hz) increased the release of SP in septal area, PAG, red nucleus and parabrachial nucleus greater compared by the control did and 2Hz and septal area. And there was significant different in red nucleus and parabrachial nucleus between high frequency and 2Hz (P<0.05).60Hz induce the expressing of SP in caudate putame nucleus, supraoptic nucleus, amygdale, nucleus raphes magnus and gigantocellular reticular nucleus higher than other groups (P<0.05).100Hz increased the SP releasing in hypothalamic paraventricular nucleus greater than other groups (P<0.05).2Hz EA stimulation increased SP releasing in locus ceruleus and solitary nucleus more than other groups. |
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