[The role of somatostatin in area CA1 of rat hippocampus in experimental epilepy]

In area CA1, intrahippocampal microinjection of somatostatin(SS, 0.03 to 0.3 nmol) caused single or a series of spike-sharp waves in the cortex electroencephalogram (EEG), the spectrum average total power of which is increased dose-dependently from 0.006 to 0.15 nmol. Microinjection of SS into the hippocampal CA1 subregion brought out epileptic-like behavioral responses and aggregated kainic acid (KA)-induced epileptiform activity of rats. With extracellular recording technique, the effects of SS on 114 units epileptiform discharge were investigated in penicillin (PEN)-treated 95 rat hippocampal slices. In response to the application of SS (10(-10), 10(-8), 10(-6) mol/L), the burst frequency of area CA1 62/105 (59.05%) recorded unit discharges was increased significantly, while that of 23/105 (21.9%) was decreased. These results suggest that SS in hippocampal CA1 subregion mainly precipitates epileptiform discharge. The addition of anti-somatostatin antibody (1 1000) to the perfusate partly blocked the epileptiform bursts triggered by PEN perfusion, while this antiepileptic effect of SSAB was reversed by application of SS (10(-8) mol/L). These indicate that endogenous SS may be involved in epileptiform discharge in area CA1 of hippocampus.

Effects of Veratrum nigrum alkaloids on central catecholaminergic neurons of renal hypertensive rats

AIM

To study the central hypotensive mechanism of Veratrum nigrum L var ussurience Nakai alkaloids (VnA) in renal hypertensive rats(RHR).

METHODS

The quantitative method of immunocytochemistry (ICC) was used to observe and detect the effect of VnA (30 micrograms.kg-1, i.v.) on activity of central catecholaminergic (CA) neurons of C1, C2, A1, and A5 areas in RHR.

RESULTS

VnA increased the immunoreactivity (IR) of tyrosine 3-monooxygenase (TM)-immunopositive (IP) neurons of C1, C2, and A5 areas in RHR experimental group compared with RHR control group [positive units: (1.9 +/- 0.4), (1.18 +/- 0.23), (1.2 +/- 0.4) vs (0.15 +/- 0.22), (0.31 +/- 0.16), (0.69 +/- 0.20), respectively]; IR of TM-IP neurons of C1 and C2 areas in RHR control group was decreased compared with sham-operated group [positive units: (0.15 +/- 0.22), (0.31 +/- 0.16) vs (1.45 +/- 0.29), (1.36 +/- 0.25), respectively].

CONCLUSION

VnA increased the activity of central CA neurons in RHR to exert its hypotensive effect.

[Effect of norepinephrine on the thermosensitive neurons in preoptic area of hypothalamus tissue slices in cold acclimatized rats]

In this work, single unit firing activities were recorded in the preoptic anterior hypothalamus (POAH) brain slices of cold acclimatized and room-temperature housed rats (CR and RR) and the effects of NE on the neuronal discharges were observed. The neurons of POAH in CR became much more sensitive to NE than that in RR (the threshold concentration of NE of CR became significantly lowered). In comparison with RR, the percentage of warm sensitive neurons that could be excited by NE was decreased and some of them even showed inhibitory responses. On the other hand, the percentage of cold sensitive neurons that could be inhibited by NE was decreased and some of them even showed excitatory responses. The percentage of thermo-insensitive neurons that could be either excited or inhibited by NE were increased.

[Adaptive changes of preoptic thermosensitive neurons in hypothalamic tissue slices of rats after long-term exposure to cold environmental temperature]

In the present work, thermosensitivity and spontaneous firing rate of 86 preoptic neurons in hypothalamic tissue slices from 20 cold acclimated rats (CR, at 5 +/- 1 degrees C for more than 3 weeks) and 127 neurons from 35 warm acclimated rats (WR, at 20 +/- 3 degrees C for the same period) were recorded and compared. The results showed that: (1) The percentage of cold-sensitive neurons in CR were higher than that in WR, the critical temperature and the lowest temperature of the spontaneous firing activity of cold-sensitive neurons in CR were also lower than that in WR. (2) Thermosensitivity and critical temperature of the warm-sensitive neurons in CR were remarkably decreased, and spontaneous firing rate under 37 degrees C was increased. (3) Spontaneous firing rate (37 degrees C) of temperature insensitive neurons in CR were conspicuously increased and the lowest temperature extended downward. These profound changes in response to long-term cold exposure suggested that plasticity of preoptic neurons was involved in the thermoregulation in cold adaptation.