Eptor subunits together [47,48]. One possibility is that the increase in hippocampal NMDA Gracillin site receptor expression observed by Besnard et al. [8] was a response to the sequence of UVD behavioural syndromes. However, this seems too simplistic an explanation, since we did also observe a decrease in NR1 expression in the ipsilateral CA2/3 region, using western blotting, at 2 weeks following UVD [17]. It is possible that the upregulation occurs in response to the change in vestibular input to the hippocampus as the second UVD occurs. Whatever the explanation, since both sequential and simultaneous vestibular lesions occur clinically in humans, both paradigms are of interest in terms of their effects on spatial memory and the hippocampus. It was very surprising to find no significant change in the expression of the different NMDA and AMPA receptor subunits, and CaMKIIa, in the hippocampal subregions following BVD. Given the evidence that hippocampal place cell firing and theta rhythm are dysfunctional following BVD [9,11?4] and hippocampal field potentials are reduced in hippocampal slices from rats that had received a UVD several months previously [49], we predicted changes in glutamate receptor subunit expression. One possibility is that the receptor changes that underlie the physiological abnormalities in the hippocampus that are caused by BVD, are too subtle to be detected using western blotting, that they are membrane-specific, and can only be detected using receptor autoradiography with beta-imaging [8]. However, it is conceivable that many of the neurophysiological changes that takeplace in the hippocampus following BVD do not require changes in the expression of glutamate receptors, but occur as a result of changes in receptor affinity or efficacy, or perhaps do not require receptor plasticity at all. Interestingly, when we analysed field potentials in anaesthetised or alert behaving animals following BVD, we found no significant differences in baseline field potentials or in the induction or maintenance of long-term potentiation [16]. It could be argued that the lack of a significant difference between sham and 1655472 BVD animals was merely due to experimental error. However, we did find significant effects of T maze training in all hippocampal subregions at 6 months Avasimibe post-op., and these effects were usually an increase in the expression of glutamate receptor subunits, as well as CaMKIIa and pCaMKIIa. In CA1, CaMKIIa, NR1 and NR2B expression were significantly increased, and the expression of GluR1 was significantly decreased. In CA2/3, CaMKIIa and pCaMKIIa expression were significantly increased, as was the expression of GluR1-3. In the DG, CaMKIIa and pCaMKIIa expression were also significantly increased, as was the expression of GluR1 and GluR3. These results are consistent with previous studies in showing that experience can alter the expression of glutamate receptor subunits in the hippocampus (e.g., [50,51]). For example, Ghafari et al. [50] found that C57BL/6J mice that were trained in a multiple T maze, exhibited a significant increase in the expression of GluR1 and a significant decrease in the expression of GluR2, in the hippocampus. It was particularly interesting that, using cluster analysis in the current study, the expression of the neurochemical variables in CA2/3 could reliably distinguish between the animals that received T maze training and those that did not. These results also demonstrate that significant changes in protein e.Eptor subunits together [47,48]. One possibility is that the increase in hippocampal NMDA receptor expression observed by Besnard et al. [8] was a response to the sequence of UVD behavioural syndromes. However, this seems too simplistic an explanation, since we did also observe a decrease in NR1 expression in the ipsilateral CA2/3 region, using western blotting, at 2 weeks following UVD [17]. It is possible that the upregulation occurs in response to the change in vestibular input to the hippocampus as the second UVD occurs. Whatever the explanation, since both sequential and simultaneous vestibular lesions occur clinically in humans, both paradigms are of interest in terms of their effects on spatial memory and the hippocampus. It was very surprising to find no significant change in the expression of the different NMDA and AMPA receptor subunits, and CaMKIIa, in the hippocampal subregions following BVD. Given the evidence that hippocampal place cell firing and theta rhythm are dysfunctional following BVD [9,11?4] and hippocampal field potentials are reduced in hippocampal slices from rats that had received a UVD several months previously [49], we predicted changes in glutamate receptor subunit expression. One possibility is that the receptor changes that underlie the physiological abnormalities in the hippocampus that are caused by BVD, are too subtle to be detected using western blotting, that they are membrane-specific, and can only be detected using receptor autoradiography with beta-imaging [8]. However, it is conceivable that many of the neurophysiological changes that takeplace in the hippocampus following BVD do not require changes in the expression of glutamate receptors, but occur as a result of changes in receptor affinity or efficacy, or perhaps do not require receptor plasticity at all. Interestingly, when we analysed field potentials in anaesthetised or alert behaving animals following BVD, we found no significant differences in baseline field potentials or in the induction or maintenance of long-term potentiation [16]. It could be argued that the lack of a significant difference between sham and 1655472 BVD animals was merely due to experimental error. However, we did find significant effects of T maze training in all hippocampal subregions at 6 months post-op., and these effects were usually an increase in the expression of glutamate receptor subunits, as well as CaMKIIa and pCaMKIIa. In CA1, CaMKIIa, NR1 and NR2B expression were significantly increased, and the expression of GluR1 was significantly decreased. In CA2/3, CaMKIIa and pCaMKIIa expression were significantly increased, as was the expression of GluR1-3. In the DG, CaMKIIa and pCaMKIIa expression were also significantly increased, as was the expression of GluR1 and GluR3. These results are consistent with previous studies in showing that experience can alter the expression of glutamate receptor subunits in the hippocampus (e.g., [50,51]). For example, Ghafari et al. [50] found that C57BL/6J mice that were trained in a multiple T maze, exhibited a significant increase in the expression of GluR1 and a significant decrease in the expression of GluR2, in the hippocampus. It was particularly interesting that, using cluster analysis in the current study, the expression of the neurochemical variables in CA2/3 could reliably distinguish between the animals that received T maze training and those that did not. These results also demonstrate that significant changes in protein e.
