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Morphine, capsaicin and K+ release purines from capsaicin-sensitive primary afferent nerve terminals in the spinal cord.
J Pharmacol Exp Ther. 1989 Jan; 248(1):447-54.JP

Abstract

In the present study the neuronal source of adenosine released by K+, morphine and norepinephrine (NE) from the spinal cord was investigated. Intrathecal pretreatment with 5,7-dihydroxytryptamine and 6-hydroxydopamine reduced spinal 5-hydroxytryptamine and NE levels, respectively, but had no effect on adenosine release from dorsal spinal cord synaptosomes evoked by K+ or morphine. NE-evoked release of adenosine was unaffected by 5,7-dihydroxytryptamine but increased by 6-hydroxydopamine. Subcutaneous pretreatment of neonatal or intrathecal pretreatment of adult rats with capsaicin increased nociceptive thresholds and reduced the release of adenosine evoked by K+ and morphine but not NE from dorsal spinal cord synaptosomes. Intrathecal capsaicin also inhibited morphine-evoked release of adenosine in vivo. K+ and morphine released only small amounts of adenosine from ventral spinal cord synaptosomes whereas NE released significant amounts. Exposure of dorsal, but not ventral, spinal cord synaptosomes to capsaicin produced a dose- and Ca++-dependent release of adenosine, which was reduced by capsaicin pretreatment (neonatal and adult) and inhibition of ecto-5'-nucleotidase. Capsaicin also released endogenous ATP from dorsal spinal cord synaptosomes. These results suggest that primary afferent nerve terminals in the dorsal horn of the spinal cord release adenosine in response to morphine and K+, and a nucleotide (possibly ATP) in response to capsaicin. Adenosine does not appear to be released from the terminals of descending aminergic pathways. The source of purines released by NE is less certain.

Authors+Show Affiliations

Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

2492344

Citation

Sweeney, M I., et al. "Morphine, Capsaicin and K+ Release Purines From Capsaicin-sensitive Primary Afferent Nerve Terminals in the Spinal Cord." The Journal of Pharmacology and Experimental Therapeutics, vol. 248, no. 1, 1989, pp. 447-54.
Sweeney MI, White TD, Sawynok J. Morphine, capsaicin and K+ release purines from capsaicin-sensitive primary afferent nerve terminals in the spinal cord. J Pharmacol Exp Ther. 1989;248(1):447-54.
Sweeney, M. I., White, T. D., & Sawynok, J. (1989). Morphine, capsaicin and K+ release purines from capsaicin-sensitive primary afferent nerve terminals in the spinal cord. The Journal of Pharmacology and Experimental Therapeutics, 248(1), 447-54.
Sweeney MI, White TD, Sawynok J. Morphine, Capsaicin and K+ Release Purines From Capsaicin-sensitive Primary Afferent Nerve Terminals in the Spinal Cord. J Pharmacol Exp Ther. 1989;248(1):447-54. PubMed PMID: 2492344.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Morphine, capsaicin and K+ release purines from capsaicin-sensitive primary afferent nerve terminals in the spinal cord. AU - Sweeney,M I, AU - White,T D, AU - Sawynok,J, PY - 1989/1/1/pubmed PY - 1989/1/1/medline PY - 1989/1/1/entrez SP - 447 EP - 54 JF - The Journal of pharmacology and experimental therapeutics JO - J. Pharmacol. Exp. Ther. VL - 248 IS - 1 N2 - In the present study the neuronal source of adenosine released by K+, morphine and norepinephrine (NE) from the spinal cord was investigated. Intrathecal pretreatment with 5,7-dihydroxytryptamine and 6-hydroxydopamine reduced spinal 5-hydroxytryptamine and NE levels, respectively, but had no effect on adenosine release from dorsal spinal cord synaptosomes evoked by K+ or morphine. NE-evoked release of adenosine was unaffected by 5,7-dihydroxytryptamine but increased by 6-hydroxydopamine. Subcutaneous pretreatment of neonatal or intrathecal pretreatment of adult rats with capsaicin increased nociceptive thresholds and reduced the release of adenosine evoked by K+ and morphine but not NE from dorsal spinal cord synaptosomes. Intrathecal capsaicin also inhibited morphine-evoked release of adenosine in vivo. K+ and morphine released only small amounts of adenosine from ventral spinal cord synaptosomes whereas NE released significant amounts. Exposure of dorsal, but not ventral, spinal cord synaptosomes to capsaicin produced a dose- and Ca++-dependent release of adenosine, which was reduced by capsaicin pretreatment (neonatal and adult) and inhibition of ecto-5'-nucleotidase. Capsaicin also released endogenous ATP from dorsal spinal cord synaptosomes. These results suggest that primary afferent nerve terminals in the dorsal horn of the spinal cord release adenosine in response to morphine and K+, and a nucleotide (possibly ATP) in response to capsaicin. Adenosine does not appear to be released from the terminals of descending aminergic pathways. The source of purines released by NE is less certain. SN - 0022-3565 UR - https://www.unboundmedicine.com/medline/citation/2492344/Morphine_capsaicin_and_K+_release_purines_from_capsaicin_sensitive_primary_afferent_nerve_terminals_in_the_spinal_cord_ L2 - http://jpet.aspetjournals.org/cgi/pmidlookup?view=long&pmid=2492344 DB - PRIME DP - Unbound Medicine ER -