title: Combination of hypothyroidism and stress abolishes early LTP in the CA1 but not dentate gyrus of hippocampus of adult rats.
abstract: Clinical experience suggests that both hypothyroidism and stress interfere with mental concentration and memory. This electrophysiological study examined the effect of hypothyroidism and stress, separately or combined, on long-term potentiation (LTP), a widely accepted cellular model for learning and memory. Measurements of early LTP (E-LTP) were carried out in the hippocampus of urethane-anesthetized adult Wistar rats. Hypothyroidism was achieved by thyroidectomy, and the 'intruder' stress was used as a model of chronic psychosocial stress. Stimulating electrodes were placed in the left CA3 region and right angular bundle and a recording electrode was placed in the right CA1 or the dentate gyrus (DG). The results showed that in the CA1 region of the hippocampus, hypothyroid or stress partially blocked E-LTP. However, when hypothyroidism and stress were combined, they eliminated E-LTP. In contrast, no significant change in E-LTP was seen in the DG of the three groups of rats. These results suggest that impaired memory because of hypothyroidism or stress may be related to impairment of the E-LTP in the Schaffer collateral synapses but not of that of the perforant path synapses.
authors.affiliation: Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204-5515, USA.
authors.forename: N Z
authors.initials: NZ
authors.lastname: Gerges
authors.forename: J L
authors.initials: JL
authors.lastname: Stringer
authors.forename: K A
authors.initials: KA
authors.lastname: Alkadhi
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology; D003345:Corticosterone / Q000097:blood; D018891:Dentate Gyrus / Q000378:metabolism* / Q000503:physiopathology; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D007037:Hypothyroidism / Q000150:complications*; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D019580:Perforant Pathway / Q000378:metabolism* / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D013312:Stress, Physiological / Q000150:complications*; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology; D013965:Thyroidectomy; D013974:Thyroxine / Q000097:blood
chemical_list: D013974:Thyroxine; D003345:Corticosterone