Role of 5-HT1A and 5-HT2 receptors in the aversion induced by electrical stimulation of inferior colliculus.
In addition to being a relay station for auditory pathways in the brainstem, the inferior colliculus may also be part of a brain system commanding defensive behavior. In the present work, we present evidence for the serotonergic modulation of the neural substrate of aversion in this structure. Rats implanted with an electrode-cannula in the inferior colliculus were placed inside a shuttle-box and submitted to a switch-off paradigm. Microinjections of zimelidine, a 5-HT uptake blocker, caused dose-dependent increases in latency and reductions in the frequency of switch-off responses to the inferior colliculus electrical stimulation. The 8-OH-DPAT, a classical 5-HT1A agonist, and alpha-methyl-5-hydroxytryptamine, a highly selective 5-HT2 agonist, injected directly into th e inferior colliculus also produced clear antiaversive effects in a dose-dependent manner. The antiaversive effect produced by alpha-methyl-5-hydroxytryptamine was attenuated by the systemic administration of ketanserin, a preferential 5-HT2 receptor antagonist. These results suggest that serotonergic mechanisms modulate the neural substrates commanding defensive behavior in the inferior colliculus, probably through a cooperative mechanism with the activation of 5-HT1A and 5-HT2 receptors.
Melo
L L
LL
Laboratório de Psicobiologia, FFCLRP, Ribeirão Preto, SP Brasil.
Brandão
M L
ML
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D007245:Inferior Colliculi / Q000502:physiology*; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000008:administration & dosage / Q000494:pharmacology; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D015031:Zimeldine / Q000494:pharmacology
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D007650:Ketanserin; D011985:Receptors, Serotonin; D012701:Serotonin; D017366:Serotonin Receptor Agonists; D017367:Selective Serotonin Reuptake Inhibitors; D015031:Zimeldine; C042390:alpha-methylserotonin