GABAergic modulation is involved in the ventrolateral orbital cortex 5-HT 1A receptor activation-induced antinociception in the rat

Fu-Quan Huo, Chao-Ling Qu, Yun-Qing Li, Jing-Shi Tang, Hong Jia
Pain 2008 October 15, 139 (2): 398-405
The ventrolateral orbital cortex (VLO) is a component of an endogenous analgesic system consisting of an ascending pathway from the spinal cord to VLO via the thalamic nucleus submedius (Sm) and a descending pathway relaying in the periaqueductal gray matter (PAG). This study examines whether the activation of 5-HT 1A receptors in VLO produces antinociception and whether GABAergic modulation is involved in the VLO 5-HT 1A receptor activation-evoked antinociception. The radiant heat-evoked tail flick (TF) reflex was used as an index of nociceptive response in lightly anesthetized rats. Microinjection of the 5-HT 1A receptor agonist 8-OH-DPAT (1.0, 2.0, 5.0 microg) into VLO produced dose-dependent antinociception, which was reversed by the 5-HT 1A receptor antagonist (NAN-190, 20 mug). We also found that VLO application of the GABA A receptor antagonist bicuculline or picrotoxin (100 ng) enhanced the 8-OH-DPAT-induced inhibition of the TF reflex, whereas the GABA A receptor agonist muscimol (250 ng) or THIP (1.0 microg) significantly attenuated the 8-OH-DPAT-induced inhibition. These results suggest that 5-HT 1A receptors are involved in VLO-induced antinociception and that GABAergic disinhibitory mechanisms participate in the 5-HT 1A receptor-mediated effect. These findings provide support for the hypothesis that 5-HT 1A receptor activation may inhibit the inhibitory action of the GABAergic interneurons on the output neurons projecting to PAG leading to activation of the brainstem descending inhibitory system and depression of nociceptive inputs at the spinal cord level.

Full Text Links

Find Full Text Links for this Article


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

Related Papers

Remove bar
Read by QxMD icon Read

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"