Smithkline Beecham Prize for Young Psychopharmacologists: A review of the relationship between calcium channels and psychiatric disorders

Chronic lithium does not alter human myo-inositol or phosphomonoester concentrations as measured by 1H and 31P MRS

Lithium may act by decreasing intracellular concentrations of myo-inositol. The present study measured the effects of chronic lithium on myo-inositol concentrations in volunteers. Eleven subjects received either lithium (n = 7) or placebo (n = 4) for 7 days in a double-blind study. Myo-inositol concentrations at baseline and day 8 were measured in vivo using 1H magnetic resonance spectroscopy (MRS). The results showed that lithium did not alter brain myo-inositol concentrations compared to placebo. In 5 other subjects we used 1H MRS and 31P MRS to measure changes in both myo-inositol and phosphomonoester concentrations. This second study showed that lithium did not alter myo-inositol or phosphomonoester concentrations. Thus, the present studies do not support the hypothesis that lithium significantly affects the brain concentrations of myo-inositol or phosphomonoesters; however, it is possible these findings represent an inability to detect the changes in myo-inositol and phosphomonoester concentrations that may have occurred following lithium administration.

Ultrastructural localization of calbindin-D28k and GABA in the matrix compartment of the rat caudate-putamen nuclei

The calcium binding protein, Calbindin-D28k, is known to be localized within spiny neurons of the matrix of the dorsal striatum, caudate-putamen nuclei. This compartment is also known to contain an abundance of GABAergic neurons and to receive extensive input from excitatory limbic and cortical afferents whose activation produces rapid influxes of calcium in neuronal targets. We used electron microscopic immunocytochemistry to examine a potential role for calbindin in GABAergic neurons in the caudate-putamen nuclei. Sections of striatal tissue from acrolein-fixed adult rat brains were dual-labeled using immunoperoxidase for the localization of rabbit anti-calbindin and immunogold-silver for the localization of rat anti-GABA antibodies. Calbindin-D28k and GABA were mainly co-localized in somata and large dendrites. The peroxidase reaction product for calbindin was diffusely distributed throughout the neuronal cytoplasm, but appeared more densely localized along asymmetric, excitatory-type, postsynaptic junctions of dendritic spines, as well as saccules of smooth endoplasmic reticulum near dendritic appositions. In contrast, the immunogold-silver labeling for GABA was largely restricted to perikarya and large dendrites. Axon terminals forming symmetric junctions were also sometimes dual-labeled for calbindin and GABA. However, the majority of the calbindin-immunoreactive terminals did not contain GABA and many formed asymmetric excitatory-type synapses with either unlabeled or calbindin-labeled dendritic spines. These results suggest that, in the striatal matrix, Calbindin-D28k contributes to the immobilization of calcium (i) in selectively activated postsynaptic spines of GABAergic and possibly non-GABAergic neurons and (ii) in terminals containing GABA as well as other excitatory and inhibitory transmitters. The extent to which calbindin is able to restrict the cytosolic increases in calcium to selective sites of utilization in these neurons may have important consequences for normal synaptic function and for neuroprotection against excitoxicity.

Severe hypotension associated with combined lithium and chlorpromazine therapy: a case report and a review

The case of a patient who developed a severe hypotensive reaction with a persistent hemianaesthesia following the addition of lithium carbonate to her treatment regimen is described. The patient had been receiving chlorpromazine therapy for the management of hypomania and the addition of lithium carbonate to the chlorpromazine produced a severe hypotensive episode which compromised her neurological functioning. Only three doses of lithium carbonate had actually been taken by the patient. This type of hypotensive response associated with the simultaneous use of chlorpromazine and lithium has not previously been noted in the literature.

Effects of nimodipine and/or haloperidol on the expression of conditioned locomotion and sensitization to cocaine in rats

The development of classical conditioning of cocaine's locomotor effects can be dissociated from the development of sensitization to cocaine by co-administration of haloperidol, a dopamine D2-like receptor antagonist, and nimodipine, an L-type calcium channel antagonist. The effects of these agents on the expression of conditioning and sensitization are described in the present report. Rats were given injections of vehicle or cocaine (10 mg/kg, IP) for 10 days before placement in a specific context in which locomotor activity was recorded. Neither haloperidol (0.05 mg/kg, IP) nor nimodipine (10 mg/kg, SC) influenced the expression of classical conditioning of cocaine's locomotor effects to the situational context on a subsequent cocaine-free test. Combined treatment of rats with both drugs did block classical conditioning with cocaine. Nimodipine, but not haloperidol, blocked the expression of behavioural sensitization to cocaine after a cocaine challenge. It is concluded that the expression of cocaine-induced classical conditioning can be pharmacologically dissociated from the expression of behavioural sensitization to cocaine. Furthermore, the effects of nimodipine and haloperidol on the expression of conditioning and sensitization are different from their effects on the development of these phenomena.

Effect of L-type calcium channel modulators on stimulant-induced hyperactivity

The present study investigated the effect of L-type calcium channel modulators on stimulant-induced locomotor activity. The L-channel activator, (+/-)BayK8644, produced a marked, long-lasting enhancement of cocaine-induced activity, while having no effect on amphetamine hyperactivity. Nicardipine reduced cocaine hyperactivity but had no effect on the amphetamine response.