Strychnine and taurine modulation of amygdala-associated anxiety-like behavior is ‘state’ dependent

Abstract

Strychnine-sensitive glycine receptors are expressed in many adult forebrain regions, yet the biological function of these receptors outside the spinal cord/brainstem is poorly understood. We have recently shown that rat lateral/basolateral amygdala neurons express strychnine-sensitive glycine-gated currents whose pharmacological and molecular characteristics are consistent with those established for classic ligand-gated chloride channels. The current studies were undertaken to establish the behavioral role, if any, of these strychnine-sensitive glycine receptors. Adult LongEvans male rats were implanted with guide cannulae targeted at the lateral amygdala and were microinjected with standard artificial cerebrospinal fluid with or without various doses of strychnine or taurine. Anxiety-like behaviors were assessed with the elevated plus-maze or the light/dark box. In the elevated plus maze, strychnine decreased closed-arm time and increased open-arm time, suggestive of an anxiolytic effect. Similarly, strychnine produced a modest anxiolytic effect in the light/dark box. Post-hoc analysis of 'open-arm' time and 'light-side' time indicated that aCSF-treated animals were distributed into two apparent groups that displayed either high or low amounts of anxiety-like behavior in a given apparatus. Surprisingly, the pharmacological effects of both strychnine and taurine in these assays were dependent upon a given animal's behavioral phenotype. Together, these findings are significant because they suggest that the basal 'emotional state' of the animal could influence the behavioral outcome associated with drug application directly into the lateral/basolateral amygdala. Furthermore, our findings also suggest that compounds acting at amygdala strychnine-sensitive glycine receptors may actively modulate this basal anxiety-like state.

Phosphatidylinositide Dependent Kinase Deficiency Increases Anxiety and Decreases GABA and Serotonin Abundance in the Amygdala

“…Recently, first evidence for a control of GABAergic function through PI3K-mediated pathways has been reported [61]. Moreover, the additional observation of decreased taurine in both brain areas as observed in PDK1 hm mice is in line with the role of taurine as an anxiolytic-like amino acid after single and repeated administration and its modulation of amygdala associated anxiety [62,63].…”

“…The observed decreases of taurine concentrations in amygdala and olfactory bulb of PDK1 amygdala have been shown to reduce anxiety behavior [63] and an anxiolytic effect of taurine (i.p.) was also observed in mice [62].…”

Taurine supplementation improves the utilization of sulfur-containing amino acids in rats continually administrated alcohol

“…Although it was first labeled a nonessential, biologically inert amino acid, taurine and its analogues are now believed to be correlated with many psychological disorders, such as major depression, epilepsy, anxiety and alcoholism [10][11][12].…”

Ethanol-induced anxiolysis and neuronal activation in the amygdala and bed nucleus of the stria terminalis

“…Two behavioral tests were used as prior studies have demonstrated that re-exposure to tests like the EPM cannot be used to test drug responses, since EPM exposure produces one-trial tolerance and reduces the observed anxiolytic-like effects of benzodiazepines and ethanol in subsequent trials (File, Mabbutt, & Hitchcott, 1990; Bertoglio & Carobrez, 2002). We chose to use the LD box to assess ethanol-induced changes in anxiety because percent open arm time (%OAT) on the EPM has been shown to correlate with anxiety-like behaviors in the LD box (McCool & Chappell, 2007). We also analyzed the peripheral stress responses following the initial exposure to the EPM to examine if stress-induced changes in CORT or NPY levels correlated with the individual differences in anxiety-like responses in the EPM and/or ethanol-induced responses.…”