JOURNAL ARTICLE

Role of spinal 5-HT(1A) receptors in morphine analgesia and tolerance in rats

Laurent Bardin, Francis C Colpaert
European Journal of Pain: EJP 2004, 8 (3): 253-61
15109976
We here studied the involvement of spinally located 5-HT(1A) and opioid receptors, in the paradoxical effects that their activation can produce on nociception. Intrathecal (i.t.) injection of the 5-HT(1A) receptor agonist 8-hydroxy-2-[di-n-propylamino] tetralin (8-OH-DPAT) (1-10 microg) induced analgesic effects in the formalin model of tonic pain whereas in the paw pressure test, it decreased the vocalization threshold. In this latter test, i.t. 8-OH-DPAT also markedly reduced the analgesic effect of systemic morphine (5-10 mg/kg, s.c.). At 10 microg, 8-OH-DPAT totally abolished the effect of 5 mg/kg of morphine; this inhibitory effect was antagonized by pre-treatment with 0.63 mg/kg of the 5-HT(1A) antagonist WAY-100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]-ethyl]-N-(2-pyridinyl)-cyclohexanecarboxamide-trihydrochloride). In contrast, the i.t. injection of WAY-100635 (1-10 microg) dose-dependently potentiated the antinociceptive activity of a dose of morphine (2.5 mg/kg, s.c.). Furthermore, WAY-100635 (10 microg, i.t.) potentiated morphine analgesia in morphine-tolerant rats. These findings demonstrate that 5-HT(1A) receptor agonists can act in the spinal cord to produce both hyper- and hypo-algesic effects and play a major role in the opioid analgesia and tolerance.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read
15109976
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"