Powerful anticonvulsant action of IL-1 receptor antagonist on intracerebral injection and astrocytic overexpression in mice.

IL-1beta and its endogenous receptor antagonist (IL-1Ra) are rapidly induced by seizures in the rodent hippocampus. Exogenously applied IL-1beta prolongs seizures in an IL-1R type I-mediated manner. This effect depends on N-methyl-d-aspartate receptor activation. We report here that intrahippocampal application of recombinant IL-1Ra or its selective endogenous overexpression in astrocytes under the control of glial acidic fibrillary protein promoter potently inhibits motor and electroencephalographic seizures induced by bicuculline methiodide in mice. Accordingly, transgenic mice show a reduced seizure-related c-fos mRNA expression in various forebrain areas compared with their wild-type littermates. Recombinant IL-1Ra was ineffective in mice deficient in IL-1R type I, having per se a delayed onset to generalized convulsions. These results demonstrate that IL-1Ra mediates potent anticonvulsant effects acting on IL-1R type I and suggest that the balance between brain IL-1beta and IL-1Ra represents a crucial mechanism to control seizure generalization.

Identification of the spinal degradation products and inhibition of adenylate cyclase by recombinant rat galanin message-associated peptide.

In rat preprogalanin, galanin is C-terminally flanked by a 60 amino acid long peptide: galanin message-associated peptide (GMAP). GMAP sequences in different species show high degree of homology, suggesting a biological role. However, the study of the physiological and pharmacological actions of this peptide have been hampered by lack of availability of this large peptide, its fragments and well-characterized antibodies to GMAP. This study report the production of GMAP in Escherichia coli and the use of the recombinant peptide to define its degradation products in the spinal cord. The GMAP fragments formed upon incubation of GMAP with membranes of lumbar spinal cord were identified by sequencing and were also produced by solid phase synthesis for studies on second messenger systems. Furthermore, the study demonstrates that GMAP inhibits forskolin stimulated adenylate cyclase activity in a concentration dependent manner, while GMAP and its synthetic fragments did not affect cGMP level.

The effect of naturally occurring fragments of galanin message-associated peptide on spinal cord excitability in rats.

Galanin message-associated peptide (GMAP), a 60 amino acid fragment of galanin precursor protein, is present in dorsal root ganglion cells and upon intrathecal (i.t.) administration influences the spinal nociceptive flexor reflex in rat in a complex manner. The present study assessed the effects on spinal cord excitability of N-terminal fragment GMAP (1-30) and C-terminal fragments GMAP (34-60) or GMAP (35-60), which were formed from GMAP following enzymatic degradation. The effect of the fragments was compared with the effects of the complete peptide sequence. The GMAP fragments slightly facilitated the flexor reflex and dose-dependently blocked hyperexcitability following C-fiber conditioning stimulation. The potency of the blocking effect of GMAP (1-30) was comparable to GMAP (1-60) and was one order of magnitude higher than the potency of the C-terminal fragments. The results indicated that both naturally formed N- and C-terminal fragments of GMAP are pharmacologically active and produce effects which are similar to the full peptide sequence.

Nociceptive responses in interleukin-6-deficient mice to peripheral inflammation and peripheral nerve section.

The cutaneous nociceptive response threshold to mechanical and thermal stimulation, the development of hyperalgesia and plasma extravasation after subcutaneous injection of carrageenan and the development of autotomy behaviour after nerve section were assessed in interleukin-6-deficient (IL-6-/-) and age-matched wild-type (IL-6+/+) mice. IL-6-/- mice had significantly lower response threshold to both mechanical and thermal stimulation in comparison to IL-6+/+ controls. Both IL-6-/- and IL-6+/+ mice developed hyperalgesia to mechanical and thermal stimulation after localized carrageenan injection, but the magnitude of the hyperalgesia was less in the IL-6-/- than in the IL-6+/+ controls. IL-6-/- mice also exhibited less plasma extravasation after carrageenan injection. No difference was noted between males and females in basal nociception and inflammatory hyperalgesia. However, female IL-6-/- mice exhibited autotomy behaviour, a sign of neuropathic pain, significantly more frequently and after a shorter interval following peripheral nerve injury than male IL-6-/- or male and female IL-6+/+ mice. It is suggested that IL-6-/- mice exhibited numerous changes in nociceptive responses compared to controls, some of which are sex related. The mechanisms of these changes in relation to null-mutation of the IL-6 gene and the influence of genetic background are discussed. 1997 Academic Press Limited.