The Role of Claustrum in Pavlovian Heart Rate Conditioning in the Rabbit (Oryctolagus cuniculus) : Anatomical, Electrophysiological, and Lesion Studies.

The role of the claustrum in Pavlovian heart rate (HR) conditioning was studied in the rabbit (Oryctolagus cuniculus) by (a) mapping claustral projections to the prefrontal cortex (PFC), (b) recording claustral single-unit discharge to sensory stimulation and conditioning stimuli during HR conditioning, and (c) assessing the effects of claustral damage on HR conditioning. Contralateral and ipsilateral claustral projections to the PFC were found. Claustral cells responded to nonsignal stimulation with increased discharge and also showed conditioned stimulus-evoked increases in discharge during Pavlovian HR conditioning. Moreover, claustral lesions diminished the magnitude of the HR-conditioned response without affecting the cardiac-orienting response to the conditioned stimulus or the cardiac-unconditioning response to the unconditioned stimulus, suggesting a role for the claustrum in associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complex maze performance in rats: Effects of noradrenergic depletion and cholinergic blockade.

Noradrenergic (NA) involvement in acquisition (AQ) and retention (RET) of a shock-motivated 14-unit T-maze after intraperitoneal (ip) administration of DSP4, a neurotoxin that depletes forebrain NA, was evaluated in 2 experiments using 3-month-old male F-344 rats. In Experiment 1, DSP4 rats did not differ from saline-treated (SAL) rats on any measure of maze performance during AQ (DSP4 2 weeks prior to testing) nor during a RET test 2–3 weeks later (DSP4 immediately after the last AQ trial or 1 week after AQ). In Experiment 2, DSP4 and scopolamine (SCOP), a cholinergic (ACh) antagonist, were administered in combination to test for an NA-ACh interaction. DSP4 again had no effect on AQ performance nor did DSP4 interact with either dose of SCOP to further impair performance. SCOP impaired all measures of maze performance except shock duration. These experiments suggest that central NA systems may not be involved directly or interactively with ACh systems required for efficient performance in this maze. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amygdala-prefrontal interactions and conditioned bradycardia in the rabbit

Damage to the amygdala or medial prefrontal cortex (mPFC) produces deficits in learned autonomic adjustments. Whether connections between these 2 structures are necessary for acquiring classically conditioned heart rate (HR) decelerations was studied. Connections between them were interrupted by unilateral lesions of the mPFC and amygdala, but on opposite sides of the brain. One experiment focused on the mPFC and amygdala central nucleus and a second on the mPFC and amygdala basolateral complex. Bilateral lesions of either structure disrupted the HR conditioned response. The response of the 2 crossed lesioned groups also was smaller than that of the sham-operated and unilateral lesioned groups, but significant conditioned stimulus-evoked bradycardia occurred in both, suggesting that although interactions between the amygdala and mPFC may normally occur during associative emotional responding, these connections are not necessary for the acquisition of conditioned bradycardia.     

Subicular lesions disrupt but do not abolish classically conditioned bradycardia in rabbits.

Rabbits and rats received horseradish peroxidase injections in the medial prefrontal cortex. and retrograde labeling was examined in the hippocampus (HC) and subicular complex (SC). Labeled cells were observed in HC and SC in the rat, but only in the SC of the rabbit. In a second experiment, separate groups of rabbits with sham, SC, or cortical control lesions were subjected to differential classical heart rate conditioning, in which 4-s, 75-db tones served as conditioned stimuli and a 3-mA paraorbital shock was the unconditioned stimulus. Although conditioned bradycardia was obtained in animals with SC lesions, it was slower to develop and was much shorter in duration than in the cortical and sham control groups. In the animals with SC lesions, the bradycardiac response was quickly replaced with tachycardia, suggesting a sympathetic bias in these animals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amygdala–prefrontal interactions and conditioned bradycardia in the rabbit.

Damage to the amygdala or medial prefrontal cortex (mPFC) produces deficits in learned autonomic adjustments. Whether connections between these 2 structures are necessary for acquiring classically conditioned heart rate (HR) decelerations was studied. Connections between them were interrupted by unilateral lesions of the mPFC and amygdala, but on opposite sides of the brain. One experiment focused on the mPFC and amygdala central nucleus and a second on the mPFC and amygdala basolateral complex. Bilateral lesions of either structure disrupted the HR conditioned response. The response of the 2 crossed lesioned groups also was smaller than that of the sham-operated and unilateral lesioned groups, but significant conditioned stimulus-evoked bradycardia occurred in both, suggesting that although interactions between the amygdala- and mPFC may normally occur during associative emotional responding, these connections are not necessary for the acquisition of conditioned bradycardia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)