Increased coherence among striatal regions in the theta range during attentive wakefulness

The striatum, the largest component of the basal ganglia, is usually subdivided into associative, motor and limbic components. However, the electrophysiological interactions between these three subsystems during behavior remain largely unknown. We hypothesized that the striatum might be particularly active during exploratory behavior, which is presumably associated with increased attention. We investigated the modulation of local field potentials (LFPs) in the striatum during attentive wakefulness in freely moving rats. To this end, we implanted microelectrodes into different parts of the striatum of Wistar rats, as well as into the motor, associative and limbic cortices. We then used electromyograms to identify motor activity and analyzed the instantaneous frequency, power spectra and partial directed coherence during exploratory behavior. We observed fine modulation in the theta frequency range of striatal LFPs in 92.5 ± 2.5% of all epochs of exploratory behavior. Concomitantly, the theta power spectrum increased in all striatal channels (P < 0.001), and coherence analysis revealed strong connectivity (coefficients >0.7) between the primary motor cortex and the rostral part of the caudatoputamen nucleus, as well as among all striatal channels (P < 0.001). Conclusively, we observed a pattern of strong theta band activation in the entire striatum during attentive wakefulness, as well as a strong coherence between the motor cortex and the entire striatum. We suggest that this activation reflects the integration of motor, cognitive and limbic systems during attentive wakefulness.

A link between the hippocampal and the striatal memory systems of the brain

Ao longo dos anos, têm-se identificado dois sistemasprincipais de memória (Squire 1992): o sistema das memórias declarativas, que está sob o controle do hipocampo e estruturas relacionadas do lobo temporal e o sistema das memórias procedimentais ou memórias para hábitos, que está sob controle do corpo estriado e suas conexões. Porém, quase todas as tarefas de aprendizado utilizadas para estudar a formação de memórias em animais envolvem a realização ou a supressão de movimentos e, se bem aprendidas poderia interpretar-se que essas memórias se converteram em um hábito. Sabe-se que os processos envolvidos na formação de memórias mudam na medida em que a associação original torna-se fortalecida através do treinamento. Será que esta mudança também envolve a passagem de um sistema de memória para outro? Aqui nós iremos comentar a respeito 1) do aprendizado reverso na tarefa do labirinto aquático de Morris (LAM), na qual o componente declarativo da tarefa muda, mas o componente procedimental (nadar para um lugar seguro) persiste e precisa ser re-associado a um grupo distinto de dicas espaciais e 2) a respeito de uma série de observações relacionadas com a tarefa de esquiva inibitória que indicam que os sistemas neurais envolvidos no processamento mnemônico mudam na medida em que o aprendizado original é reforçado.

Role of striatal dopamine in the lordosis behaviour.

Effects of intrastriatal injections of haloperidol (Dopamine antagonist) and D-amphetamine (Dopamine agonist) on lordosis behaviour were studied in ovariectomized female albino rats, after priming with subcutaneous injections of estrogen and progesterone. The lordosis quotient (LQ) significantly increased after haloperidol, and decreased following D-amphetamine treatment. However, the inhibitory effect of D-amphetamine was transient and could be reversed by haloperidol in the same animal when given one hour after the D-amphetamine injection. The ovarian hormones probably act centrally to suppress the DA system in the striatum thereby enhancing the tonic and dorsal immobility responses associated with lordosis.

Homogenous fetal dopaminergic cell transplantation in rat striatum by cell suspension methods

The transplantation of dopaminergic neurons in the brain has been attempted in experimental animals and humans as the new treatment modality of Parkinson's disease. Before the trial of dopaminergic neuronal transplantation in human, the authors proceeded with the animal experiment of fetal dopaminergic cell transplantation in a rat Parkinson's disease model. The aims of this experiment were to confirm the availability of fetal mesencephalic cells as the donor, to compare the viability of cells according to different cell manipulation methods, and to follow up the functional recovery in the transplanted Parkinson's disease model. As a result, the authors concluded that the simple enzyme digestion method had a better cell survival rate than the multiple enzyme digestion method. Also, the transplanted mesencephalic cells could not only survive in the host animal but also promote functional recovery.

The action of prolyl-leucyl-glycinamide (PLG) on the nigrostriatal pathway of the rat

No intuito de estudar a via nigroestriatal, produzimos uma lesäo na regiäo hipotalâmica lateral de ratos Wistar. Os animais passavam a apresentar comportamento rotatório para o mesmo lado da lesäo. A administraçäo isolada do PLG näo induziu o comportamento rotatório. Entretanto, com doses baixas do composto, concomitantemente à administraçäo de apomorfina em animais previamente submetidos à privaçäo de sono REM, observou-se aumento no número de rotaçöes quando comparado ao grupo controle e aos grupos que receberam doses altas de PLG. Estes achados sugerem que o PLG age como um modulador sobre os receptores dopaminérgicos do estriado

Central monoamine dysfunction in diabetes: psychotherapeutic implications; electroanalysis by voltammetry

Se examinaron en ratas, mediante voltametría, los efectos de la diabetes inducida por estreptozotocina o de la hiperglucemia, sobre la liberción de dopamina y serotonina en el estriado in vivo. En el estado diabético agudo se observó un incremento del 67% en la liberación de dopamina, mientras que el incremento observado en la diabetes crónica fue menor (19%). En las ratas a los 3 días de inducida la diabetes la señal electroquímica correspondiente a serotonina aumentó en un 62%, efecto que desapareció en la diabetes crónica. Luego de la inyección de L-triptófano en ratas normales, se detectó una disminución del 45% en la dopamina estriatal liberada y un aumento del 25% en la liberación de serotonina. Este incremento fue máximo a los 90 min más. Los animales crónicamente diabéticos mstraron una disminución significativa en la liberación de dopamina y serotonina estriatal luego de inyectar triptófano. Los efectos de la hiperflucemia en ratas no diabéticas fueron una disminución (52%) de la liberación de dopamina, y un incremento (304%) de la liberación de serotonina. Estos cambios indican que el estado diabético no tratado se asocia con una disminución progresiva de la liberación de neurotrasmisor, y que las modificaciones emocionales observadas en la disponibilidad de dopamina y serotonina en sinapsis centrales