Pharmacology, biochemistry, and behavior
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Pharmacol. Biochem. Behav. · Mar 1998
Comparative StudyDifferential involvement of opioid receptors in intrathecal butorphanol-induced analgesia: compared to morphine.
The present experiments were performed to investigate the differential involvement of the opioid receptor subtypes in the antinociception of intrathecal (IT) butorphanol compared to IT morphine. A single dose (26 nmol) of IT nor-binaltorphimine (nor-BNI), beta-funaltrexamine (beta-FNA), and naltrindole (NTI) demonstrated a significant attenuation in the overall antinociception of IT butorphanol (52 nmol) or IT morphine (26 nmol). However, IT butorphanol elicits thermal antinociceptive effect through kappa > delta > or = mu, whereas morphine acts on mu >delta > kappa. These results indicate that the antinociceptive effect of both IT butorphanol and IT morphine are mediated through mu, delta, and kappa opioid receptors in different relative orders.
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Pharmacol. Biochem. Behav. · Mar 1998
Effects of chlordiazepoxide on opioid-induced antinociception and respiratory depression in restrained rats.
This study investigates the influence of possible stress due to housing in Bolman cages on antinociception and on respiratory depression following opioid administration. To evaluate the functional role of this stressor and to modulate it, rats were subcutaneously pretreated with the anxiolytic chlordiazepoxide (CDP; 10 mg/kg) or saline (SAL) before the immobilization in the Bolman cages and before the intravenous administration of small doses of morphine (MOR), sufentanil (SUF), or vehicle (VEH). Antinociception, respiratory impairment and stress were evaluated by means of the tail-flick latency, blood gas analysis, and serum corticosterone (CS), adrenocorticotropic hormone (ACTH), and prolactin (PRL) determinations. ⋯ Also, MOR without CDP prevented the increases in CS, but the opioid intrinsically increased ACTH. These results indicate that restraint in Bolman cages in the present setup, with animals recovering for several hours in these cages after being equipped with an arterial catheter, is stressful but without any significant effect on the opioid-induced antinociception. Pretreatment with an anxiolytic benzodiazepine only minimally affected the outcome of the opioids on respiratory depression and pointed to a stress-reducing effect of low doses of the opioids, especially sufentanil.