title: Stress and re-stress increases conditioned taste aversion learning in rats: possible frontal cortical and hippocampal muscarinic receptor involvement.
abstract: Symptoms of posttraumatic stress disorder are often precipitated by sensory cues in the form of visual, auditory, olfactory and gustatory "flashbacks" resulting in enhanced fear-memory consolidation and the characteristic symptoms of re-experiencing, avoidance and hyper-arousal. Single prolonged stress with and without re-stress have been used to explore the neurobiology of this disorder, particularly with respect to contextual conditioning and spatial memory impairment. However, less work has been done regarding associative sensory-related memories linked to aversive events. Although growing evidence supports a role for cholinergic pathways in stress, this has not been studied in the above animal models. We studied the effects of single prolonged stress with and without re-stress on conditioned taste aversion learning in rats, together with differential analysis of frontal cortical and hippocampal [3H]-quinuclidinyl benzylate ([3H]-QNB) muscarinic receptor binding. Single prolonged stress with and without re-stress both enhanced associative sensory aversion learning 7 days after stressor-taste pairing, although re-stress did not strengthen this response. Increased cortical and hippocampal muscarinic receptor density (Bmax) was found 7 days after single prolonged stress with re-stress, although receptor affinity remained unaltered. Frontal cortical and hippocampal muscarinic receptor changes may thus underlie conditioned taste aversion learning in rats exposed to stress and re-stress. These data suggest that it may be useful to study the role of cholinergic pathways in mediating associative memory in psychiatric disorders such as posttraumatic stress disorder.
authors.affiliation: Unit for Drug Research and Development, School of Pharmacy (Pharmacology), North-West University (Potchefstroom Campus), Potchefstroom, 2520, South Africa.
authors.forename: Linda
authors.initials: L
authors.lastname: Brand
authors.forename: Ilse
authors.initials: I
authors.lastname: Groenewald
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Stein
authors.forename: Gregers
authors.initials: G
authors.lastname: Wegener
authors.forename: Brian H
authors.initials: BH
authors.lastname: Harvey
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D018021:Lithium Chloride / Q000494:pharmacology; D008297:Male; D011939:Mental Recall / Q000187:drug effects; D018727:Muscarinic Antagonists / Q000494:pharmacology; D017397:Prefrontal Cortex / Q000187:drug effects / Q000502:physiology*; D011813:Quinuclidinyl Benzilate / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D043643:Receptor, Muscarinic M1 / Q000187:drug effects / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D013313:Stress Disorders, Post-Traumatic / Q000523:psychology; D013315:Stress, Psychological / Q000523:psychology*; D013649:Taste / Q000187:drug effects / Q000502:physiology*
chemical_list: D018727:Muscarinic Antagonists; D043643:Receptor, Muscarinic M1; D011976:Receptors, Muscarinic; D011813:Quinuclidinyl Benzilate; D018021:Lithium Chloride