L-type calcium channels selectively control the defensive behaviors induced by electrical stimulation of dorsal periaqueductal gray and overlying collicular layers
Lc. Schenberg et al., L-type calcium channels selectively control the defensive behaviors induced by electrical stimulation of dorsal periaqueductal gray and overlying collicular layers, BEH BRA RES, 111(1-2), 2000, pp. 175-185
The present study reports the involvement of L-type calcium channels in the
control of defensive behaviors produced by electrical stimulation of dorsa
l periaqueductal gray and overlying collicular layers. Rats that had chemit
rodes in the dorsal midbrain and which stimulation produced freezing or fli
ght behaviors with less than 55 mu A were selected for drug experiments. St
imulation was repeated the day after the screening session 20 min following
the microinjection into the dorsal periaqueductal gray of 15 nmol of eithe
r verapamil, a selective L-type calcium channel antagonist, or cobalt chlor
ide (CoCl2), a calcium-specific channel modulator. Post-drug sessions were
performed 48 h after. Threshold functions were obtained by logistic fitting
of accumulated response frequencies. Verapamil and CoCl2 significantly att
enuated the output of immobility, exophthalmus, running and jumping. Althou
gh to a lesser degree, verapamil also attenuated defecation. Because CoCl2
had no effect on defecation, the attenuation of this response by verapamil
suggests a non-specific action of this drug. Neither verapamil nor CoCl2 ch
anged the output of micturition. Finally, whereas there was a complete reco
very of defensive thresholds following the microinjection of verapamil, the
attenuating effects of CoCl2 were still present 48 h after. These results
support an important role of L-type calcium channels in the neurogenesis of
dorsal periaqueductal gray-evoked immobility, exophthalmus, running and ju
mping, but not defecation and micturition responses. (C) 2000 Elsevier Scie
nce B.V. All rights reserved.