Reliable assessment of pollen quality in Chrysanthemum × morifolium: comparative evaluation of viability tests and germination media.

Amylin belongs to the calcitonin gene-related peptide (CGRP) family. Members of the family include calcitonin, salmon calcitonin, calcitonin gene-related peptides (α-CGRP and β-CGRP), adrenomedullin and AM2 (also known as intermedin). Amylin is co-secreted with insulin by pancreatic β-cells and exerts various biological functions such as glucose homeostasis, the sensation of satiety and the control of food intake. This peptide has also been reported to cross the blood-brain barrier (BBB) and is supposedly able to bind to its receptors in several brain areas to produce effects such as anorexia. Beyond its metabolic role, amylin is also expressed in the nervous system primarily within CGRP peptidergic neurons of the dorsal root ganglia (DRG) that project to the spinal dorsal horn, indicating a potential involvement in nociceptive signaling. Amylin receptors consist of a calcitonin-receptor (CTR) core associated with a receptor activity-modifying protein (RAMP). Amylin acts at the spinal cord, where CTR and RAMP are expressed in rats. Studies suggest that amylin may be involved in nociceptive processing; however, its effects vary depending on the pain model and the route of administration. For instance, Intrathecal (i.t.) administration of amylin suppresses the spinal expression of c-fos, a neuronal protein typically upregulated in response to painful stimuli. This downregulation of c-fos in the spinal cord correlates with a reduction in pain induced by acetic acid or by formalin. Amylin administered via intracerebroventricular (ICV) injection markedly increased paw withdrawal latency (PWL) in the hot plate test, but did not alter responses in the tail flick assay. The antinociceptive effects of amylin were shown to be inhibited by amylin antagonists such as salmon calcitonin. Furthermore, results from our laboratory have also revealed that i.t. amylin, when co-administered with morphine from days 6 to 10, reversed morphine tolerance in rats. Chronic administration of opioids such as morphine results in enduring behavioral alterations, including opioid-induced hyperalgesia (OIH), the development of tolerance, and physical dependence. These phenomena restrict the therapeutic use of morphine as a potent painkiller. Tolerance is a state of reduced analgesic effect of morphine in which an increase in dose is required to maintain its primary analgesic effects. It is highly desirable to avoid or at least attenuate the development of tolerance. A number of spinal signaling molecules including neuropeptides, cyclooxygenase inhibitors, excitatory amino acids, neurotrophins and endogenous opioids have been reported to modulate pain sensitivity and opioid tolerance. Consistent with this, molecules like brain- derived neurotrophic factor (BDNF) and prodynorphin (PDYN) are involved in the control of opioid tolerance. The gene encodes a precursor protein that, upon processing yields, multiple active peptides of the opioid family, including dynorphin A, dynorphin B, and α- and β-neo-endorphin. In addition to their antinociceptive effects, mediated through kappa opioid receptors, these peptides also exert non-opioid effects mainly through NMDA receptors. The non opioid effects of dynorphins appear to be relevant to several pathophysiological processes including chronic neuropathic pain and spinal cord injury. Thus, spinal cord levels of mRNA and dynorphin immunoreactivity are elevated in cases of peripheral nerve injury and spinal cord trauma. A recent study has demonstrated that chronic opioid exposure and hind paw incision interact through spinal epigenetic mechanisms to up-regulate and which are well-established pain related- genes. Specifically, chromatin immunoprecipitation assays revealed that the and promoters were associated with acetylated histone H3K9 after morphine exposure combined with incision.