PubMed Health⌕ Search

Biomedical subjects

Ilene L Bernstein

Publications and source records attributed to Ilene L Bernstein.

16 recordsLinked to original sources
PubMed2006

Molecular signaling during taste aversion learning.

Behavioral and neural assessment tools have been used to identify cellular and molecular events that occur during taste aversion acquisition. Studies described here include an assessment of taste information processing and taste-illness association using fos-like immunoreactivity (FLI) to mark populations of cells that react strongly to the taste conditioned stimulus (CS), the illness unconditioned stimulus (US), or the pairing of CS and US. Exposure to a novel, but not a familiar, CS taste (saccharin) was found to induce robust increases in FLI in some, but not all, brain regions previously implicated in taste processing or taste aversion learning. Striking effects of taste novelty on FLI were found in central amygdala (CNA) and insular cortex (IC) but not in basolateral amygdala (BLA), pontine parabrachial nucleus (PBN), or nucleus of the solitary tract (NTS). Of those regions responding to taste novelty, only CNA showed significant elevations in FLI in response to the US, LiCl. In additional studies, FLI was examined after an effective training experience, novel CS-US pairing, and compared with an ineffective one, familiar CS-US pairing. After CS-US pairing, taste novelty modulated FLI in virtually all the regions previously implicated in conditioned taste aversion (CTA) learning, including PBN, CNA, BLA, IC, as well as NTS. Thus, a distributed and interdependent neural CTA circuit is mapped using this method, and the use of localized lesion and inactivation studies promises to further define the functional role of structures within this circuit.

Animals↗
PubMed2006

Induction and expression of salt appetite: effects on Fos expression in nucleus accumbens.

Sodium depletion is a strong natural motivator that creates a pronounced sodium appetite and has been shown to activate neural regions associated with fluid and sodium balance. However, it is not known whether sodium appetite affects the mesolimbic circuitry associated with reward motivation. The present studies examined expression of the immediate early gene Fos in the nucleus accumbens (NAc) as a marker of neuronal activation following the induction and expression of furosemide-induced sodium appetite. During sodium appetite expression, sham-drinking and normal drinking were used to dissociate effects of NaCl taste stimulation from the repletion that follows absorption of sodium. These studies revealed that the combination of NaCl taste stimulation and persistent sodium depletion experienced by sham-drinking animals dramatically activates the NAc, while neither induction nor expression of sodium appetite alone is sufficient to increase Fos expression in this region. Results are discussed in terms of current theories of reward motivation.

Animals↗
PubMed2006

A role for D2 but not D1 dopamine receptors in the cross-sensitization between amphetamine and salt appetite.

A history of sodium depletions has been found to potentiate the psychomotor as well as the rewarding effects of amphetamine, an indirect dopamine agonist. The present experiments were conducted to further define the role of dopamine receptor subtypes in this cross-sensitization effect. Rats with a history of sodium depletions were found to display psychomotor sensitization to a D2 but not a D1 direct agonist. Cross-sensitization between salt appetite and amphetamine was found to be blocked by a D2 but not a D1 antagonist. Together, these results implicate D2 but not D1 receptor function in the cross-sensitization seen after sodium depletions.

Amphetamines↗
PubMed2006

Conditioning method determines patterns of c-fos expression following novel taste-illness pairing.

Conditioned taste aversions (CTAs) can be established by exposing rats to a novel taste CS through a bottle or through intra-oral (IO) infusion. Lesion studies suggest differences between the two methods in their engagement of brain circuits, as excitotoxic amygdala lesions have no effect on bottle-conditioned CTAs, but eliminate CTAs produced using IO infusion. Fos-like immunoreactivity (FLI) was used to compare patterns of brain activation after pairing CS taste and US drug using bottle and IO methods. Conditioning rats using the bottle method was associated with widespread elevations in FLI throughout the putative CTA circuit (basolateral and central nuclei of amygdala, insular cortex and nucleus of the solitary tract). In contrast, IO conditioning led to activation only in the central nucleus of amygdala. This supports the suggestion of differences in aversion processing as a function of conditioning method and may explain the greater reliance on amygdala of IO-conditioned CTAs due to engagement of a less distributed neural network.

Administration, Oral↗
PubMed2006

Sensitization of salt appetite is associated with increased "wanting" but not "liking" of a salt reward in the sodium-deplete rat.

To examine the role of incentive sensitization in the potentiation of salt appetite by prior depletions, the authors assessed the motivation to obtain salt ("wanting") and the palatability of salt ("liking") independently in salt-sensitized rats. Breakpoint on a progressive ratio reinforcement schedule was used to measure salt wanting and taste reactivity was used to measure salt liking in rats with and without a history of Na+ depletion. Salt-sensitized rats displayed higher breakpoints relative to controls. However, a history of Na+ depletion was not associated with a greater positive shift in taste reactivity measures. The data suggest that these components of reward are separable in this model and support the general proposition that sensitization may alter wanting but not liking.

Animals↗
PubMed2005

Mapping conditioned taste aversion associations using c-Fos reveals a dynamic role for insular cortex.

Novel tastes are more effective than familiar tastes as conditioned stimuli (CSs) in taste aversion learning. Parallel to this, a novel CS-unconditioned stimulus (US) pairing induced stronger Fos-like immunoreactivity (FLI) in insular cortex (IC), amygdala, and brainstem than familiar CS-US pairing, suggesting a large circuit is recruited for acquisition. To better define the role of IC, the authors combined immunostaining with lesion or reversible inactivation of IC. Lesions abolished FLI increases to novel taste pairing in amygdala, suggesting a role in novelty detection. Reversible inactivation during taste preexposure increased FLI to familiar taste pairing in amygdala and brainstem. The difference between temporary inactivation, which blocked establishment of "safe" taste memory, and lesions points to a dual role for IC in taste learning.

Amygdala↗
PubMed2005

Polycose taste pre-exposure fails to influence behavioral and neural indices of taste novelty.

Taste novelty can strongly modulate the speed and efficacy of taste aversion learning. Novel sweet tastes enhance c-Fos-like immunoreactivity (FLI) in the central amygdala and insular cortex. The present studies examined whether this neural correlate of novelty extends to different taste types by measuring FLI signals after exposure to novel and familiar polysaccharide (Polycose) and salt (NaCl) tastes. Novel Polycose not only failed to elevate FLI expression in central amygdala and insular cortex, but also failed to induce stronger taste aversion learning than familiar Polycose. Novel NaCl, on the other hand, showed patterns of FLI activation and aversion learning similar to that of novel sweet tastes. Possible reasons for the resistance of Polycose to typical pre-exposure effects are discussed.

Analysis of Variance↗
PubMed2004

Afferent and efferent connections of the parvicellular subdivision of iNTS: defining a circuit involved in taste aversion learning.

Conditioned taste aversion (CTA) expression is associated with strong increases in Fos-like immunoreactivity (FLI) in a region of the brainstem identified as the parvicellular subdivision of the intermediate nucleus of the solitary tract (iNTSpc). To identify the projections to and from cells in iNTSpc which display strong FLI in response to expression of a CTA, anterograde and retrograde tract tracing was used. When appropriate, tract tracing was combined with double labeling for FLI in animals which received CTA training as well as tracer injections and were re-exposed to the CS taste. With respect to afferent projections, iNTSpc receives a strong, direct, ipsilateral projection from amygdala and the distribution of the fiber terminals yields a striking match to that of cells expressing FLI after CTA expression. As for efferent projections, these cells in iNTSpc are characterized by a mixed, rather than homogeneous, projection pattern. Targets of these cells include pons and forebrain as well as local medullary sites, all of which are known to be involved in gastrointestinal function. Thus, activation of these cells may provide a circuit through which gastrointestinal/visceral responses are coordinated as a component of the conditioned aversion.

Afferent Pathways↗
PubMed2004

Reciprocal cross-sensitization between amphetamine and salt appetite.

Previous work in our laboratory has demonstrated a potentiation of the psychomotor effects of amphetamine in animals with a history of sodium depletion, a process referred to as cross-sensitization. The present studies were done to further develop this finding by assessing multiple effects of amphetamine in rats with and without a history of sodium depletion. For Experiments 1-3, rats were depleted of sodium twice then subjected to one of three experimental procedures [open-field activity, conditioned place preference (CPP) and conditioned taste aversion (CTA)]. A history of depletion produced an elevation in the psychomotor effects of amphetamine. CPP, used to assess the rewarding properties of amphetamine, developed in rats with a history of depletion but not in controls. The aversive component of amphetamine as measured by CTA was unaffected by previous experience with sodium depletion. Finally, acute salt appetite after depletion was assessed in rats exposed to a sensitizing regimen of amphetamine. Animals with a drug history demonstrated a significant elevation in NaCl solution intake after depletion in comparison to controls. Together, the data provide strong evidence for the reciprocal cross-sensitization of salt appetite and response to amphetamine.

Amphetamine↗
PubMed2003

Conditioned taste aversion memory and c-Fos induction are disrupted in RIIbeta-protein kinase A mutant mice.

The cAMP-dependent protein kinase (PKA) signaling pathway has been implicated in many forms of learning. The present studies examined conditioned taste aversion (CTA) learning, an amygdala-dependent task, in mice with a targeted disruption of a gene for a specific regulatory subunit of PKA (RIIbeta), which is selectively expressed in amygdala. Null mutant (RIIbeta(-/-)) mice and littermate controls (RIIbeta(+/+)) were tested for protein synthesis-independent short-term memory (STM) and protein synthesis-dependent long-term memory (LTM) for CTAs. The ability of the unconditioned stimulus (US) drug, LiCl, to induce c-Fos in regions thought to be important in this learning was also determined. RIIbeta(-/-) mice showed significant impairment in CTA memory when tested 24h after training (LTM). In contrast, STM was normal. With regard to the c-Fos response to LiCl, the US drug, significant elevations were evident in brainstem (nucleus of the solitary tract) and pontine (parabrachial nucleus) regions, in mutants as well as wild-type controls. However, in amygdala, elevations were seen in controls but were absent in the mutants. These findings suggest that disruption of PKA signaling interferes with LTM consolidation of CTA and that a possible mediator of this effect is interference with c-Fos expression in amygdala which may be necessary for CTA memory.

Amygdala↗
PubMed2003

Inhibition of protein kinase A activity during conditioned taste aversion retrieval: interference with extinction or reconsolidation of a memory?

The involvement of the cAMP-dependent protein kinase A (PKA) signaling pathway in protein synthesis-dependent memory consolidation has been supported by studies of fear conditioning and conditioned taste aversion (CTA). The present experiment examined whether inhibition of PKA activity at the time of memory retrieval impedes or promotes subsequent extinction. When Rp-cAMPS was infused into the amygdala at the time of CTA testing (retrieval), extinction was accelerated. Results confirm recent findings that stored memories become more labile when they are retrieved and extend these findings to CTA memories.

Amygdala↗
PubMed2003

Novel tastes elevate c-fos expression in the central amygdala and insular cortex: implication for taste aversion learning.

Taste novelty strongly modulates the speed and strength of taste aversion conditioning. To identify molecular signals responsive to novel tastes, immunostaining for c-fos protein (Fos-like immunoreactivity [FLI]) was used to mark neurons that responded differentially to taste novelty. Novel saccharin induced larger increases in FLI than familiar saccharin. This pattern was seen in central amygdala and insular cortex, but not in basolateral amygdala, parabrachial nucleus, or nucleus of the solitary tract. Other parameters known to influence aversion learning were tested for effects on FLI. Manipulations known to reduce the strength of learning blunted the FLI response, supporting the idea that FLI marks neural pathways critical to taste processing during acquisition, and that c-fos expression is a key transcriptional event underlying this plasticity.

Amygdala↗
PubMed2002

Induction of a salt appetite alters dendritic morphology in nucleus accumbens and sensitizes rats to amphetamine.

Sensitization to drugs, such as amphetamine, is associated with alterations in the morphology of neurons in the nucleus accumbens, a brain region critical to motivation and reward. The studies reported here indicate that a strong natural motivator, sodium depletion and associated salt appetite, also leads to alterations in neurons in nucleus accumbens. Medium spiny neurons in the shell of the nucleus accumbens of rats that had experienced sodium depletions had significantly more dendritic branches and spines than controls. In addition, a history of sodium depletions was found to have cross-sensitization effects, leading to enhanced psychostimulant responses to amphetamine. Thus, neuronal alterations common to salt and drug sensitization may provide a general mechanism for enhanced behavioral responses to subsequent exposures to these challenges.

Amphetamine↗
PubMed2002

Induction of a brainstem correlate of conditioned taste aversion expression: role of the pontine parabrachial nucleus.

Increases in Fos-like immunoreactivity (FLI) in the intermediate division of the nucleus of the solitary tract (iNTS) are seen following the expression of a conditioned taste aversion (CTA). In studies limited to behavioral assessment, the pontine parabrachial nucleus (PBN) has been demonstrated to play a critical role in the acquisition, but not the expression, of CTAs. To better define the role of the PBN in taste aversion learning, the present study examined the effects of PBN lesions on FLI in iNTS in animals with lesions placed either before or after CTA training. As is the case with behavioral expression of a CTA, timing of PBN lesions was found to be critical. Lesions placed prior to conditioning blocked evidence of conditioning, including both taste rejection and FLI in iNTS. Lesions placed after conditioning, but before testing, did not interfere with either taste rejection or FLI. These results support and extend prior claims that PBN is critical for CTA acquisition but not expression. They also demonstrate that input from PBN to iNTS is not necessary for the FLI seen there during CTA expression.

Animals↗
PubMed2002

Inhibition of protein kinase A activity interferes with long-term, but not short-term, memory of conditioned taste aversions.

The present experiments examined whether inhibition of cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) activity interferes with conditioned taste aversion (CTA) memories. Rats were centrally infused with the selective PKA inhibitor Rp-adenosine 3',5'-cyclic monophosphothioate triethylamine (Rp-cAMPS) before conditioning. Direct infusions of Rp-cAMPS into the amygdala showed no interference with short-term memory but did show significant attenuation of long-term memory and more rapid extinction. Results suggest that PKA activity is involved in the consolidation of long-term memory of CTAs, and that the amygdala may be 1 site that is important for this activity.

Amygdala↗