Journal of neuroscience research
-
The bed nucleus of the stria terminalis (BST) is a limbic structure involved in regulating the hypothalamic-pituitary-adrenal axis as well as in central cardiovascular control. We report here on cardiovascular effects caused by microinjection of noradrenaline (NA) in the BST of the rat brain and the peripheral mechanisms involved in their mediation. Injection of NA (3, 7, 10, 15, 30, or 45 nmol in 100 nl) in the BST of unanesthetized rats caused long-lasting dose-related pressor and bradycardiac responses. ⋯ The pressor response was potentiated by i.v. pretreatment with the ganglion blocker pentolinium and blocked by i.v. pretreatment with the selective V(1)-vasopressin antagonist dTyr(CH(2))(5)(Me)AVP, suggesting its mediation by vasopressin release into circulation. The bradycardiac response to NA microinjected into the BST was also abolished by pretreatment with the vasopressin antagonist, indicating its reflex origin. In conclusion, results indicate that microinjection of NA into the BST evokes pressor responses, which are mediated by acute vasopressin release.
-
Despite a large body of literature on the nociceptin (NC) opioid system in pain modulation, the mechanism of action of NC remains largely unexplored. Here, we investigated the role and mode of action of the spinal NC system in inflammatory pain. Preemptive intrathecal administration of NC attenuated thermal hyperalgesia and mechanical allodynia in rats with intraplantar complete Freund's adjuvant (CFA) injection. ⋯ Real-time reverse transcription-polymerase chain reaction showed that NC reduced the up-regulation of inducible nitric oxide synthase mRNA but not that of neuronal nitric oxide synthase mRNA in spinal cord segments after CFA. Furthermore, [Nphe1]NC(1-13)NH2, a selective opioid receptor-like 1 (ORL1) receptor antagonist, significantly antagonized the effects of NC on pain modulation and on the expression of inflammatory mediators, indicating a specific NC action through the ORL1 receptor. Together, these findings reveal novel mechanisms by which the NC system produces analgesia.
-
Dorsal root ganglia (DRG) neurons connect the spinal cord and uterine cervix, and are activated at parturition with subsequent stimulation of secondary neurons in the spinal dorsal horn and autonomic areas. Neuropeptide neurotransmitters and receptors have been studied in these areas, but amino acid transmitters, e.g., glutamate, an excitatory neurotransmitter involved in sensory and nociceptive processing, have not been characterized. To determine if glutamate is involved in innervation of the cervix, rats were examined for markers of glutamatergic neurons in the L6-S1 spinal cord, DRG and cervix. ⋯ Fos-positive neurons were present among mGluR5-immunoreactivity in the spinal dorsal horn. Parturition-induced Fos-positive neurons in the spinal cords were abundant in control rats, but were reduced by 70% in MPEP-treated animals. These results suggest that glutamate is likely involved in the transmission of sensory signals, possibly pain, from the cervix to the spinal cord at parturition.