RESUMO
The electroencephalographic sleep patterns recorded during short periods of time (3 h) of a neurological mutant rat (taiep) were studied. This rat exhibits, among other signs, immobility episodes that are similar to those observed in narcolepsy-cataplexy. We describe findings of long term (6 months) electroencephalographic studies done in 9 mutant and 5 control rats. The mutant rats present electroencephalographic and behavioral disorders consisting of: (a) bursts of cortical waxing and waning waves occurring during the drowsy state; in some animals this activity represents up to 25% of the total drowsiness time; (b) shortened sleep time; (c) fragmented paradoxical sleep; (d) immobility episodes when the animals are subjected to an emotional excitement; and (e) electrographic activity of paradoxical sleep without atonia during the immobility episodes. These findings show that the taiep mutant shows several aspects of narcolepsy-cataplexy and it may represent an experimental model for the study of this pathology.
Assuntos
Cataplexia/fisiopatologia , Modelos Animais de Doenças , Eletroencefalografia , Transtornos dos Movimentos/fisiopatologia , Narcolepsia/fisiopatologia , Animais , Cataplexia/genética , Feminino , Masculino , Transtornos dos Movimentos/genética , Narcolepsia/genética , Ratos , Ratos Mutantes , Sono/fisiologia , Fases do Sono , Sono REM/fisiologia , VigíliaRESUMO
We previously found that the opiate antagonist, naloxone, partially blocks stimulation-produced analgesia (SPA) elicited from ventral but not dorsal regions of the medial midbrain in rats. The present study compares the effects of n. raphe magnus (NRM) lesions on SPA from these same two midbrain areas. SPA thresholds were measured with the tail-flick method and compared before and for up to two weeks after NRM lesions. A high positive correlation was found between percent NRM destruction and percent increase in SPA threshold for rats with ventral but not dorsal electrode placements. Damage to brain areas other than NRM seemed not to contribute to these effects. We conclude that n. raphe magnus is a critical relay in the pain-suppressive path from that area of the rat midbrain mediating an opioid form of stimulation-produced analgesia.
Assuntos
Tronco Encefálico/fisiologia , Mesencéfalo/fisiologia , Nociceptores/fisiologia , Núcleos da Rafe/fisiologia , Transmissão Sináptica , Animais , Estimulação Elétrica , Gânglios Espinais/fisiologia , Masculino , Naloxona/farmacologia , Substância Cinzenta Periaquedutal/fisiologia , Ratos , Ratos Endogâmicos , Receptores Opioides/fisiologia , Limiar Sensorial , Transmissão Sináptica/efeitos dos fármacosRESUMO
This study compares stimulation-produced analgesia (SPA) elicited from two different midline regions of the midbrain of the rat. Dorsal electrode placements were in the caudal periaqueductal gray matter; ventral placements lay within or subjacent to the dorsal raphe n. SPA thresholds were measured by the tail-flick method both during and immediately after the period of brain stimulation. Thresholds were consistently higher in the post-stimulation test. SPA from dorsal and ventral regions differed in the following ways: (1) Post-stimulation analgesia was significantly more difficult to obtain in ventral than in dorsal regions, whereas during-stimulation analgesia did not vary as a function of electrode location; (2) Although a continuous distribution of thresholds was seen for ventral placements, thresholds for dorsal placements tended to be either high or low on both during- and post-stimulation tests; (3) Naloxone (0.01--10 mg/kg) reliably elevated SPA thresholds for ventral but not dorsal stimulation placements. We conclude that different substrates of SPA lie in close proximity to one another in the medial midbrain of the rat. This portion of the midbrain appears to mediate both opioid and non-opioid mechanisms of analgesia.
