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Tachykinins may be involved in reproduction. A reverse transcription-polymerase chain reaction assay was used to analyze the expression of tachykinins and tachykinin receptors in different types of reproductive cells from mice. The preprotachykinin (PPT) genes, PPT-A, PPT-B and PPT-C, that encode substance P/neurokinin A, neurokinin B, and hemokinin-1, respectively, and the genes that encode the tachykinin NK1, NK2, and NK3 receptors were all expressed, at different levels, in the uterus of superovulated, unfertilized mice. The mRNA of neprilysin (NEP), the main enzyme involved in tachykinin metabolism, was also expressed in the uterus. Isolated cumulus granulosa cells expressed PPT-A, PPT-B, PPT-C, and NEP and low levels of the tachykinin NK1 and NK2 receptors. Mouse oocytes expressed PPT-A and -B mRNA transcripts. A low expression of the three tachykinin receptors was observed but PPT-C and NEP were undetectable. Two- and 8- to 16-cell mouse embryos expressed only a low-abundance transcript corresponding to the NK1 receptor. However, the mRNAs of PPT-B, PPT-C and NEP appeared in blastocyst-stage embryos. A low-abundance transcript corresponding to the NK2 receptor was the only target gene detected in mice sperm. Female mice or rats treated neonatally with capsaicin showed a reduced fertility. A reduction in litter size was observed in female rats treated in vivo with the tachykinin NK3 receptor antagonist SR 142801. These data show that tachykinins of both neuronal and nonneuronal origin are differentially expressed in various types of reproductive cells and may play a role in female reproductive function.

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Background and purpose:The activation of CB2 receptors induces analgesia in experimental models of chronic pain. The present experiments were designed to study whether the activation of peripheral or spinal CB2 receptors relieves thermal hyperalgesia and mechanical allodynia in two models of bone cancer pain. Experimental approach: NCTC 2472 osteosarcoma or B16-F10 melanoma cells were intratibially inoculated to C3H/He and C57BL/6 mice. Thermal hyperalgesia was assessed by the unilateral hot plate test and mechanical allodynia by the von Frey test. AM1241 (CB2 receptor agonist), AM251 (CB1 receptor antagonist), SR144528 (CB2 receptor antagonist) and naloxone were used. CB2 receptor expression was measured by Western blot. ) abolished thermal hyperalgesia and mechanical allodynia in both tumour models. The antihyperalgesic effect was antagonized by subcutaneous, intrathecal or peri-tumour administration of SR144528. In contrast, the antiallodynic effect was inhibited by systemic or intrathecal, but not peri-tumour, injection of SR144528. The effects of AM1241 were unchanged by AM251 but were prevented by naloxone. No change in CB2 receptor expression was found in spinal cord or dorsal root ganglia. Conclusions and implications: Spinal CB2 receptors are involved in the antiallodynic effect induced by AM1241 in two neoplastic models while peripheral and spinal receptors participate in the antihyperalgesic effects. Both effects were mediated by endogenous opiates. The use of drugs that activate CB2 receptors could be a useful strategy to counteract bone cancer-induced pain symptoms.

Endothelin receptors have been involved in inflammatory, neuropathic and tumoral pain. In the case of inflammatory hyperalgesia, some previous papers have pointed towards the involvement of ETB receptors, although the stimulation of ETA receptors seems to participate in the development of the inflammatory reaction. We have studied the effect of ETA and ETB receptor antagonists in the thermal and mechanical hyperalgesia induced in a model of acute (induced by carrageenan) and chronic (induced by complete Freund's adjuvant, CFA) inflammation in mice. The i.pl. administration of the selective ETA antagonist BQ-123 (1-10 nmol) antagonized the thermal hyperalgesia detected by the unilateral hot plate test, observed in both inflammatory models, whereas the i.pl. administration of the ETB selective antagonist BQ-788 (17.7 nmol) failed to modify this. In contrast, both BQ-123 (3-17.7 nmol) and BQ-788 (3-17.7 nmol) antagonized the mechanical hyperalgesia, as assessed by the Randall-Selitto test in carrageenan- and CFA-treated mice. Both BQ-123 and BQ-788 were able to antagonize the mechanical hyperalgesia induced by ET-1 (200 pmol; i.pl.) in the same dose range. Thus, ETA receptors are involved in both thermal and mechanical hyperalgesia whereas ETB receptors are only involved in mechanical hyperalgesia in these inflammatory models. In conclusion, the role of ETB receptors in inflammatory pain is further supported and new insights into the participation of ETA receptors in inflammatory hyperalgesia are given.

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