Involvement of the midbrain periaqueductal gray 5-HT1A receptors in social conflict induced analgesia in mice.
Recent results from our laboratory have shown that 30-bites social conflict in mice produces a high-intensity, short-term analgesia which is attenuated by systemically injected 5-HT1A receptor agonists, such as BAY R 1531 (6-methoxy-4-(di-n-propylamino)-1,3,4,5-tetrahydrobenz((c,d)indole hydrochloride) and gepirone. The present study investigated the effects of these drugs, as well as the 5-HT1A receptor antagonist WAY 100135 (N-tert-butyl-3-(4-(2-methoxyphenyl)piperazine-1-yl)-2-phenylpropanamide ) injected into the midbrain periaqueductal gray matter of mice on 30-bites analgesia. Four to five days after guide-cannula implantation, each mouse received microinjection of gepirone (30 nmol/0.2 microl), BAY R 1531 (10 nmol/0.2 microl), WAY 100135 (10 nmol/0.2 microl), saline (0.9% NaCl) or vehicle (saline + 4% Tween 80) 5 min before either an aggressive (30 bites) or a non-aggressive interaction. Nociception was assessed by the tail-flick test made before as well as 1, 5, 10 and 20 min after social interaction. The full 5-HT1A receptor agonist BAY R 1531 blocked, whereas, WAY 100135 and gepirone intensified 30-bites analgesia. Neither non-aggressive interaction, per se, nor the three compounds given after this type of social interaction significantly changed nociception. These results indicate that 5-HT1A receptors in the periaqueductal gray inhibit analgesia induced by social conflict in mice.
Canto-de-Souza
A
A
Department of Psychology, UFSCar, São Carlos, Brazil.
Nunes de Souza
R L
RL
Pelá
I R
IR
Graeff
F G
FG
D000374:Aggression / Q000187:drug effects; D000698:Analgesia; D000818:Animals; D003220:Conflict, Psychological; D007211:Indoles / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D051379:Mice; D008845:Microinjections; D010487:Periaqueductal Gray / Q000502:physiology*; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology; D011743:Pyrimidines / Q000008:administration & dosage / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012702:Serotonin Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology
D007211:Indoles; D010879:Piperazines; D011743:Pyrimidines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C081293:WAY 100135; C066665:Bay R 1531; C039979:gepirone