Accumbens-caudate-septal circuit as a system for hippocampal regulation: involvement of a GABAergic neurotransmission.
Hippocampal-based epileptiform activity may reach the basal ganglia via the nucleus accumbens. Previous data suggested that caudate nucleus is able to influence hippocampal epilepsy, probably sending a projection to the septum. In order to test the hypothesis of a retrograde activation of accumbens-caudate pathway in hippocampal regulation, we electrically stimulated both caudate nucleus and nucleus accumbens and studied modifications of hippocampal EEG in the feline focal epilepsy model. We also performed bilateral electrolytic lesion of nucleus accumbens and repeated caudate stimulation. Results showed that nucleus accumbens stimulation was ineffective in modifying hippocampal epilepsy; on the contrary, caudate stimulation caused a statistically significant decrease of hippocampal spike frequency and amplitude. On the other hand, in accumbens-lesioned animals caudate activation consistently reduced hippocampal epilepsy to a significant degree. As the caudate nucleus influences hippocampal activity and the septum may constitute a relay station of this functional relation, a possibility was tested concerning a GABAergic mediation. To this end, after a stable caudate-induced effect was reached, an intraseptal microinjection of picrotoxin (GABA receptor antagonist) was made and caudate stimulation repeated at the same parameters. Such a study showed that after intraseptal picrotoxin, caudate stimulation failed to elicit any type of modification of hippocampal activity. Experimental findings support the notion that the striatal modulation on hippocampus is mediated by an anterograde rather than a retrograde pathway, and underline the possibility of a GABAergic caudate-septal influence.
Sabatino
M
M
Istituto di Fisiologia umana dell'Università di Palermo, Italy.
Ferraro
G
G
Caravaglios
G
G
Sardo
P
P
Aloisio
A
A
Iurato
L
L
La Grutta
V
V
D000818:Animals; D002415:Cats; D002421:Caudate Nucleus / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D004569:Electroencephalography; D005917:Globus Pallidus / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D010406:Penicillins / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D010406:Penicillins; D010852:Picrotoxin; D005680:gamma-Aminobutyric Acid