Neuropsychopharmacological actions of taurine.

Taurine, an endogenous amino sulfonic acid, exhibits numerous neuropsychopharmacological activities. Previous studies in our laboratory have shown that it is an effective anti-cataleptic and neuro-protective agent. Current investigations show that acute or chronic administration of psychotropic drug cocaine may increase extracellular release of endogenous taurine which may protect against deleterious effects of the substances of abuse. Taurine administration was found to prevent cocaine-induced addiction by suppressing spontaneous locomotor activity and conditioned place preference. Taurine markedly delayed tail-flick response in rats which was significantly different from that in the group of animal receiving the same volume of saline, thereby indicating that taurine is a potentially valuable analgesic agent. Both taurine and endomorphin-1 were found to suppress the delayed broad negative evoked field potentials in anterior insular cortex (upper layer 5) by partially inhibiting NMDA receptor system. Thus, taurine is a unique psychopharmacological compound with potential for a variety of therapeutic uses including as a neuro-protective, anti-cataleptic, anti-addicting, and analgesic agent.

Sex differences in hyperalgesia during morphine infusion: effect of gonadectomy and estrogen treatment.

Morphine treatment can paradoxically increase nociception (i.e. hyperalgesia). Since there are putative sex differences in nociception and morphine sensitivity, we compared nociception in male and female mice using the tail-withdrawal test during continuous infusion of two morphine doses (1.6 and 40.0 mg/kg/24 h). Both doses caused hyperalgesia in both sexes, but onset in females always preceded that of males. Although the larger dose initially evoked analgesia, naltrexone (NTX) pellets implanted prior to morphine infusion abolished analgesia but not hyperalgesia. Distinct sex differences also characterized each morphine dose. Specifically, the lower morphine dose caused hyperalgesia that dissipated after 6 days in males but persisted in females for a minimum of 14 days. Despite this difference, N-methyl-d-aspartate (NMDA) receptor antagonists reversed hyperalgesia in both sexes. In contrast, the higher morphine dose evoked hyperalgesia that resolved concurrently in both sexes, but hyperalgesia was reversed by NMDA receptor antagonists in males only. Ovariectomy (OVX), but not OVX followed by estrogen treatment, abolished both sex differences, and resulted in females exhibiting the male-typical pattern. This study thus demonstrates NTX-insensitive morphine hyperalgesia in females as previously reported for males. However, females utilized hyperalgesic mechanisms which were distinct from those employed by males. Data from females subject to OVX/estrogen replacement further indicate that females possess functional male-typical hyperalgesic mechanisms, but are diverted from their use by ovarian sex steroids. Finally, the finding that each morphine infusion dose was characterized by a unique sex difference provides additional evidence for distinct multiple hyperalgesic systems.

Increased locomotor activity in mice lacking the low-density lipoprotein receptor.

While the low-density lipoprotein receptor (LDLR) is best known for its role in regulating serum cholesterol, LDLR is expressed in brain, suggesting that it may play a role in CNS function as well. Here, using mice with a null mutation in LDLR (LDLR-/-), we investigated whether the absence of LDLR affects a series of behavioral functions. We also utilized the fact that plasma cholesterol levels can be regulated in LDLR-/- mice by manipulating dietary cholesterol to investigate whether elevated plasma cholesterol might independently affect behavioral performance. LDLR-/- mice showed no major deficits in general sensory or motor function. However, LDLR-/- mice exhibited increased locomotor activity in an open field test without evidence of altered anxiety in either an open field or a light/dark emergence test. By contrast, modulating dietary cholesterol produced only isolated effects. While both C57BL/6J and LDLR-/- mice fed a high cholesterol diet showed increased anxiety in a light/dark task, and LDLR-/- mice fed a high cholesterol diet exhibited longer target latencies in the probe trial of the Morris water maze, no other findings supported a general effect of cholesterol on anxiety or spatial memory. Collectively these studies suggest that while LDLR-/- mice exhibit no major developmental defects, LDLR nevertheless plays a significant role in modulating locomotor behavior in the adult.

CK2-An Emerging Target for Neurological and Psychiatric Disorders.

Protein kinase CK2 has received a surge of attention in recent years due to the evidence of its overexpression in a variety of solid tumors and multiple myelomas as well as its participation in cell survival pathways. CK2 is also upregulated in the most prevalent and aggressive cancer of brain tissue, glioblastoma multiforme, and in preclinical models, pharmacological inhibition of the kinase has proven successful in reducing tumor size and animal mortality. CK2 is highly expressed in the mammalian brain and has many bona fide substrates that are crucial in neuronal or glial homeostasis and signaling processes across synapses. Full and conditional CK2 knockout mice have further elucidated the importance of CK2 in brain development, neuronal activity, and behavior. This review will discuss recent advances in the field that point to CK2 as a regulator of neuronal functions and as a potential novel target to treat neurological and psychiatric disorders.

Vasopressin stimulates ventromedial hypothalamic neurons via oxytocin receptors in oxytocin gene knockout male and female mice.

A wealth of neuropharmacological data demonstrates that oxytocin (OT) actions in the mammalian forebrain support a wide variety of affiliative behaviors and repress aggressive behaviors. Based on that literature, it was expected that reproductive and affiliative behaviors would be vastly decreased and aggression markedly increased in OT gene knockout (OTKO) mice. The initial publications reporting the behaviors of these mice did not include such phenotypes. Here, we compared single-unit activities recorded from the ventromedial hypothalamus in tissue slices of male and female OTKO mice and their wild-type littermate to test two hypotheses about OT functional genomics. First, we proposed that in OTKO mice, a very similar 9-amino-acid neuropeptide, arginine vasopressin (a likely gene duplication product), can 'cross over' and compensate for the lack of OT. This hypothesis was confirmed in both males and females. Further, we proposed that because of the lifelong absence of OT in OTKO, OT receptors would be more sensitive to OT in the knockout animals. We tested this idea in males and found that it was correct. Thus, an answer to the 'OTKO paradox' is put forth, with implications for OT-sensitive behaviors in a variety of species.