CYSTEAMINE-INDUCED DEPLETION OF SOMATOSTATINERGIC SYSTEMS ALTERS POTENTIALS-EVOKED FROM THE RAT VISUAL-CORTEX

Citation
G. Fontanesi et al., CYSTEAMINE-INDUCED DEPLETION OF SOMATOSTATINERGIC SYSTEMS ALTERS POTENTIALS-EVOKED FROM THE RAT VISUAL-CORTEX, Visual neuroscience, 13(2), 1996, pp. 327-334
Citations number
43
Categorie Soggetti
Neurosciences
Journal title
ISSN journal
09525238
Volume
13
Issue
2
Year of publication
1996
Pages
327 - 334
Database
ISI
SICI code
0952-5238(1996)13:2<327:CDOSSA>2.0.ZU;2-U
Abstract
This study was performed in order to establish whether selective deple tion of somatostatin (SS) in the rat primary visual cortex obtained by cysteamine (CSH) administration results in changes of visual evoked p otentials (VEPs). VEPs in response to a contrast reversal (0.5 Hz) of an optimal sinusoidal grating (0.1 cycle/deg, contrast 90%, mean lumin ance 15 cd/m(2)) were recorded from different layers of the binocular portion of the primary visual cortex of anesthetized rats with saline injection as well as before and after CSH treatment (90 mg/kg, s.c.). VEPs of CSH treated rats, as compared to those obtained either in sali ne-injected animals or before drug administration, are reduced in ampl itude at intermediate cortical layers whereas they are increased at de eper layers. VEP changes depend on CSH treatment and not on the extend ed anesthesia since no alterations in the VEP profile can be observed in saline-injected animals maintained in the same experimental conditi on. Forty-eight hours following CSH treatment, the VEP profile is comp arable to that of saline-injected animals. Immunocytochemical analysis of the visual cortex of rats recorded 7 h after CSH treatment shows a 20-30% reduction in the number of SS-containing cortical cells. The h ighest reduction can be observed in cortical layer 5 although a signif icant decrease is also found in layers 2-3. In contrast, the pattern o f SS immunoreactivity of the visual cortex of rats recorded 48 h after CSH administration is similar to that obtained in control conditions. These results indicate that a selective toxin for somatostatinergic s ystems induces a transient decrease of SS-containing cell number in se lected cortical layers. Accordingly, CSH can serve as a useful pharmac ological tool for the study of somatostatinergic function in the rat v isual cortex since changes in VEPs can be related to a reduction of so matostatinergic neurons associated to CSH treatment. In particular, th e present results suggest that one of the possible actions of somatost atinergic neurons in the rat visual cortex is to modulate the excitato ry-inhibitory balance.