GABAA-benzodiazepine receptors in the dorsomedial (Dm) telencephalon modulate restraint-induced antinociception in the fish Leporinus macrocephalus.
The possibility that fish experience pain has been denied based on the absence of the neural substrates to support this "experience". In this context, the identification of brain regions involved in nociception modulation could provide important insights regarding the processing of nociceptive information in fish. Our study evaluated the participation of the GABAA-benzodiazepine receptor in the dorsomedial (Dm) telencephalon in restraint-induced antinociception in the fish Leporinus macrocephalus through the microinjection of the anxiolytic drug midazolam. The microinjection of midazolam in the Dm did not alter the nocifensive response; however, this drug did block the inhibition of the nocifensive response to formaldehyde promoted by restraint stress. The fish that received midazolam (40nmol) microinjection prior to restraint (3 or 5min), followed by subcutaneous injection with formaldehyde presented a higher distance traveled than the fish that received saline microinjection. This effect might reflect the specific action of midazolam on benzodiazepine receptors in the Dm telencephalon, as pre-treatment with flumazenil, a benzodiazepine receptor antagonist, inhibited the effects of this drug. In the present study, we present the first evidence demonstrating a role for the dorsomedial telencephalic region in the modulation of stress-induced antinociception in fish, revealing new perspectives in the understanding of nociceptive information processing in this group.
Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida dos Bandeirantes, 3900 Ribeirão Preto, SP, Brazil. Electronic address: carlawolkers@yahoo.com.br.
Carla Patricia Bejo
CP
Wolkers
Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida dos Bandeirantes, 3900 Ribeirão Preto, SP, Brazil.
Augusto
A
Barbosa Junior
Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida dos Bandeirantes, 3900 Ribeirão Preto, SP, Brazil.
Leda
L
Menescal-de-Oliveira
Departamento de Fisiologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Avenida dos Bandeirantes, 3900 Ribeirão Preto, SP, Brazil.
Anette
A
Hoffmann
D000704:Analysis of Variance; D000818:Animals; D005399:Fishes; D005442:Flumazenil / Q000494:pharmacology; D005557:Formaldehyde / Q000009:adverse effects; D018757:GABA Modulators / Q000494:pharmacology; D008124:Locomotion / Q000187:drug effects; D008845:Microinjections; D008874:Midazolam / Q000494:pharmacology; D059225:Nociception / Q000502:physiology*; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology*; D010147:Pain Measurement; D011963:Receptors, GABA-A / Q000378:metabolism*; D012149:Restraint, Physical / Q000379:methods*; D013687:Telencephalon / Q000187:drug effects / Q000378:metabolism*
D018757:GABA Modulators; D011963:Receptors, GABA-A; D005557:Formaldehyde; D005442:Flumazenil; D008874:Midazolam
Formaldehyde test; Midazolam; Nociception; Pain evolution