Impaired acquisition in a 14-unit T-maze following medial septal lesions in rats is correlated with lesion size and hippocampal acetylcholinesterase staining.
Septohippocampal cholinergic system involvement in acquisition of an aversively motivated 14-unit T-maze was evaluated in 4-month-old male Fischer-344 rats. Each rat was assigned to one of two groups that received either a bilateral electrolytic lesion to the medial septal area (MSA) or a sham operation. One week after surgery, each rat began pretraining in one-way active avoidance (footshock = 0.8 mA) consisting of 10 trials per day on each of 3 consecutive days. Criterion for successful completion of pretraining was 8/10 avoidances on the third day. On the day following completion of pretraining, each rat received 10 trials in a shock-motivated 14-unit T-maze. The performance requirement was to move through each of five maze segments within 10 s to avoid footshock (0.8 mA). A second 10-trial session was provided 24 h later. Performance measures included errors, alternation errors, runtime, shock frequency, and duration. Following maze training, each rat was sacrificed, and formalin-fixed brains were frozen for histology, which included procedures for thionin Nissl and acetylcholinesterase (AChE) staining. MSA-lesioned rats were observed to be significantly impaired on all measures of maze performance compared to sham-operated controls. Densitometric analysis of hippocampal AChE staining revealed a 30% reduction in relative AChE staining of MSA-lesioned rats compared to sham-operated controls. Lesion size was observed to be highly positively correlated with maze errors. A negative correlation of mean error score with density of AChE staining was observed for MSA-lesioned rats, but not for sham-operated rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Kametani
H
H
Molecular Physiology and Genetics Section, Nathan W. Shock Laboratories, Gerontology Research Center, Baltimore, MD.
Spangler
E L
EL
Bresnahan
E L
EL
Kobayashi
S
S
Long
J M
JM
Ingram
D K
DK
D000110:Acetylcholinesterase / Q000502:physiology*; D000375:Aging / Q000502:physiology*; D000818:Animals; D001143:Arousal / Q000502:physiology; D001362:Avoidance Learning / Q000502:physiology; D001931:Brain Mapping; D002799:Cholinergic Fibers / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D009410:Nerve Degeneration / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009949:Orientation / Q000502:physiology*; D011340:Problem Solving / Q000502:physiology; D051381:Rats; D011916:Rats, Inbred F344; D012153:Retention, Psychology / Q000502:physiology; D012686:Septal Nuclei / Q000502:physiology*
D000110:Acetylcholinesterase