Local infusion of calcium-free solutions in vivo activates locus coeruleus neurons.
Microinfusion of calcium (Ca++)-free artificial cerebrospinal fluid onto locus coeruleus (LC) neurons in vivo potently increased their discharge rate, while response of these cells to a sensory stimulus was significantly reduced. These effects resulted in part from interference with the calcium-dependent potassium conductance in these neurons, as microinfusions of solutions having barium substituted for calcium partially mimicked the effects of Ca(++)-free infusions. In addition, microinfusion of control medium containing the Ca++ channel blocker, cadmium (2-20 mM), also mimicked the effect of the Ca(++)-free solution. This study presents an effective means by which extracellular concentrations of neuromodulatory ions can be manipulated in vivo. In addition, these results indicate that extracellular Ca++ potently modulates the spontaneous as well as evoked activity of central noradrenergic neurons in vivo.
Shiekhattar
R
R
Department of Mental Health Sciences, Hahnemann University, Philadelphia, PA 19102-1192.
Aston-Jones
G
G
Chiang
C
C
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013238:Stereotaxic Techniques
D001464:Barium; D002118:Calcium