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Analgesic doses of morphine do not reduce noxious stimulus‐evoked release of immunoreactive neurokinins in the dorsal horn of the spinal cat
Author(s) -
Lang C.W.,
Duggan A.W.,
Hope P.J.
Publication year - 1991
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1991.tb12344.x
Subject(s) - morphine , analgesic , noxious stimulus , dorsum , medicine , anesthesia , stimulus (psychology) , nociception , neuroscience , anatomy , psychology , receptor , psychotherapist
1 Antibody microprobes were used to detect immunoreactive neurokinin A release in the dorsal spinal cord of barbiturate‐anaesthetized spinal cats. 2 Noxious mechanical stimulation of the ipsilateral hind paw and electrical stimulation (suprathreshold for unmyelinated primary afferent fibres) of the ipsilateral tibial nerve evoked immunoreactive neurokinin A release. 3 Systemic morphine, 5 mg kg −1 , i.v., did not block immunoreactive neurokinin A release in response to these stimuli. 4 Subsequent naloxone administration, 0.5 mg kg −1 , i.v., did not alter this stimulus‐evoked release. 5 Basal levels of immunoreactive neurokinin A were unaltered by morphine or naloxone. 6 These results suggest that the analgesic effects of morphine at the spinal cord level are not brought about by activation of presynaptic opiate receptors on neurokinin A containing afferent terminals.