title: The role of Cx36 and Cx43 in 4-aminopyridine-induced rhythmic activity in the spinal nociceptive dorsal horn: an electrophysiological study in vitro.
abstract: Connexin (Cx) proteins and gap junctions support the formation of neuronal and glial syncytia that are linked to different forms of rhythmic firing and oscillatory activity in the CNS. In this study, quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to profile developmental expression of two specific Cx proteins, namely glial Cx43 and neuronal Cx36, in postnatal lumbar spinal cord aged 4, 7, and 14 days. Extracellular electrophysiology was used to determine the contribution of Cx36 and Cx43 to a previously described form of 4-aminopyridine (4-AP)-induced 4-12 Hz rhythmic activity within substantia gelatinosa (SG) of rat neonatal dorsal horn (DH) in vitro. The involvement of Cx36 and Cx43 was probed pharmacologically using quinine, a specific uncoupler of Cx36 and the mimetic peptide blocker Gap 26 which targets Cx43. After establishment of 4-12 Hz rhythmic activity by 4-AP (25 μmol/L), coapplication of quinine (250 μmol/L) reduced 4-AP-induced 4-12 Hz rhythmic activity (P < 0.05). Preincubation of spinal cord slices with Gap 26 (100 μmol/L), compromised the level of 4-AP-induced 4-12 Hz rhythmic activity in comparison with control slices preincubated in ACSF alone (P < 0.05). Conversely, the nonselective gap junction "opener" trimethylamine (TMA) enhanced 4-12 Hz rhythmic behavior (P < 0.05), further supporting a role for Cx proteins and gap junctions. These data have defined a physiological role for Cx36 and Cx43 in rhythmic firing in SG, a key nociceptive processing area of DH. The significance of these data in the context of pain and Cx proteins as a future analgesic drug target requires further study.
authors.affiliation: School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom.
authors.forename: Christopher W P
authors.initials: CW
authors.lastname: Kay
authors.affiliation: Eli Lilly & Co., Lilly Research Centre Erl Wood Manor, Windlesham, Surrey, GU20 6PH, United Kingdom.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ursu
authors.affiliation: Eli Lilly & Co., Lilly Research Centre Erl Wood Manor, Windlesham, Surrey, GU20 6PH, United Kingdom.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Sher
authors.affiliation: School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom a.e.king@leeds.ac.uk.
authors.forename: Anne E
authors.initials: AE
authors.lastname: King
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D018031:Connexin 43 / Q000235:genetics / Q000502:physiology*; D017630:Connexins / Q000235:genetics / Q000502:physiology*; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D008159:Lumbar Vertebrae; D008297:Male; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017208:Rats, Wistar; D066148:Spinal Cord Dorsal Horn / Q000187:drug effects / Q000378:metabolism*; D013376:Substantia Gelatinosa / Q000187:drug effects / Q000378:metabolism; D046509:Tissue Culture Techniques; D000097004:Gap Junction delta-2 Protein
chemical_list: D015761:4-Aminopyridine; D018031:Connexin 43; D017630:Connexins; D026902:Potassium Channel Blockers; D000097004:Gap Junction delta-2 Protein; C580592:Gja1 protein, rat
keywords: Connexins; pain; rhythmic firing; substantia gelatinosa