Spinal beta-endorphin analgesia involves an interaction with local monoaminergic systems.
Male; Animals; Rats; Adrenergic alpha-Antagonists/pharmacology; Injections; Serotonin Antagonists/pharmacology; Naltrexone/pharmacology; Spinal Cord/*drug effects; Biogenic Monoamines/*physiology; Analgesics/administration & dosage/antagonists & inhibitors/*pharmacology; beta-Endorphin/administration & dosage/antagonists & inhibitors/*pharmacology; Norepinephrine/physiology; Serotonin/physiology; Inbred Strains; Spinal
beta-Endorphin administered intrathecally (i.t.) in rats produced a dose-dependent elevation in tail-flick latency. Naltrexone administered i.t. as a pretreatment reversed the spinal antinociceptive action of beta-endorphin, suggesting that the opioid interacts directly with spinal opiate receptors. Spinal administration of the alpha 1-adrenoceptor antagonist WB-4101 failed to alter the analgesic effects of the opioid, whereas the alpha 2-adrenoceptor antagonist yohimbine completely blocked beta-endorphin-induced elevations in tail-flick latency. Thus, there is an apparent specificity for the alpha
Crisp T; Stafinsky J L; Hess J E; Uram M
European journal of pharmacology
1989
1989-01
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Serotonin contributes to the spinal antinociceptive effects of morphine.
Adrenergic alpha-Antagonists/pharmacology; Adrenergic Antagonists; Analgesics/*pharmacology; Animals; Biogenic Monoamines/physiology; Dose-Response Relationship; Drug; Inbred Strains; Injections; Male; Morphine/*pharmacology; Naltrexone/pharmacology; Nerve Endings/drug effects; Opioid/drug effects; Rats; Reaction Time; Receptors; Serotonin Antagonists/pharmacology; Serotonin/*physiology; Spinal; Spinal Cord/*drug effects
This study was designed to determine if morphine administered intrathecally (IT) interacts with serotonergic or noradrenergic nerve terminals in the spinal cord to produce analgesia on the spinally mediated tail-flick test. Male Sprague-Dawley rats were fitted with IT catheters. One week later, animals were spinally pretreated with receptor antagonists selective for opioid, serotonin or alpha-adrenoceptors, and the ability of these agents to alter spinal morphine-induced antinociception was assessed. Morphine dose-dependently elevated tail-flick latency in a naltrexone-reversible manner. The serotonin receptor antagonists spiroxatrine (5-HT1A), pindolol (5-HT1B), ritanserin (5-HT2) and ICS
Crisp T; Stafinsky J L; Uram M; Perni V C; Weaver M F; Spanos L J
Pharmacology, biochemistry, and behavior
1991
1991-07
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/0091-3057(91)90133-m" target="_blank" rel="noreferrer noopener">10.1016/0091-3057(91)90133-m</a>
A lack of supersensitivity to opioid receptor agonists following chronic spinal opioid receptor antagonist administration in the rat.
5)-; Ala(2)-MePhe(4)-Gly(5)-; Animals; D-Penicillamine (2; Dose-Response Relationship; Drug; Enkephalin; Enkephalins/*pharmacology; Male; Naltrexone/analogs & derivatives/pharmacology; Narcotic Antagonists/*pharmacology; Opioid/*drug effects; Rats; Receptors; Somatostatin/analogs & derivatives/pharmacology; Species Specificity; Spinal Cord/*drug effects; Sprague-Dawley
1. Male Sprague-Dawley rats were chronically tested with intrathecal (i.t.) receptor selective opioid antagonists to determine if antinociceptive supersensitivity developed to selective i.t. opioid receptor agonists. 2. A subcutaneously implanted osmotic minipump was used to deliver the mu-opioid receptor antagonist CTOP (0.3 nmol) or the delta-opioid receptor antagonist naltrindole (5.5 nmol) for 7 days. 3. Following a 24 hr washout period, rats received a single i.t. dose (ED50) of either DAMPGO (for CTOP-treated animals) or DPDPE (for naltrindole-treated animals) and the antinociceptive effects of the agents were tested on the tail-flick test. 4. Our findings revealed that chronic spinal treatment with selective opioid receptor antagonists did not induce an antinociceptive supersensitivity to selective opioid receptor agonists. 5. Perhaps this lack of supersensitivity is reflective of difficulties inherent to opioid receptor antagonists that do not possess negative intrinsic activity.
Keck B J; Stafinsky J L; Uram M; Crisp T
General pharmacology
1995
1995-01
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/0306-3623(94)00154-f" target="_blank" rel="noreferrer noopener">10.1016/0306-3623(94)00154-f</a>