We investigated whether modifications in noradrenergic neurotransmission occurred during the development of hippocampal kindling in rats. We measured the release of [3H]norepinephrine (NE) induced by field-electrical stimulation, NE-stimulation of inositol phosphates ([3H]IP) accumulation in the presence of LiCl and isoproterenol-induced accumulation of cAMP in hippocampal slices taken from rats electrically kindled at stages 2 and 5 in the dorsal hippocampus. One week after the last of at least 3 consecutive stage 5 seizures or 48 h after the last stage 2 stimulation, 2 min electrical stimulation of stratum pyramidale CA1-CA3 or dentate gyrus (DG) slices from kindled and contralateral hippocampi induced frequency-dependent NE release (respectively 2, 4 and 8 times spontaneous release measured at 2, 5 and 10 Hz) which did not significantly differ from that observed in shams (implanted with electrodes but not stimulated). Basal release of NE from kindled and sham-treated rats did not differe either. Isoproterenol induced a dose-dependent increase above basal cAMP concentration ranging from 40% at 0.01 μM to 180% at 10 μM (P <0.01, Dunnett's test) which did not differ between stages 2 and 5 and sham-hippocampi. NE (1-1000 μM) induced a dose-dependent, prazosin-sensitive increase in [3H]IP accumulation in the hippocampal slices. A significantly higher increase was found at stages 2 (P <0.05, Tukey's test) and 5 (P <0.05 and P <0.01, Tukey's test) compared to shams at all doses studied. No differences were observed in the basal cAMP or [3H]IP concentrations in kindled versus sham animals. No differences were observed in [3H]IP accumulation induced by carbachol (10, 100, 1000 μM) in stage 5-kindled rats and shams. These changes have various possible implications for kindling-induced plasticity.
- Cyclic adenosine monophosphate
- Phosphatidyl inositol turnover
ASJC Scopus subject areas
- Developmental Biology
- Molecular Biology
- Clinical Neurology