Journal of Neuroscience, Vol 7, 662-670, Copyright © 1987 by Society for Neuroscience
Interruption of the connections of the mammillary bodies protects against generalized pentylenetetrazol seizures in guinea pigs
MA Mirski and JA Ferrendelli
Electrolytic lesions in the anterior and mid-diencephalon and ventral
midbrain in guinea pigs were produced to examine the effects of
interruption of the fornix (FX), mammillothalamic tracts (MT), and
mammillary peduncles (MP), respectively, on the expression of
pentylenetetrazol (PTZ) seizures. As a group, all mid-diencephalic lesioned
animals had some degree of protection from the electroencephalographic and
behavioral convulsant and lethal effects of the drug. Through a composite
volume analysis of protected versus unprotected animals, as well as a
retrospective comparison between MT and non-MT lesioned animals, it was
demonstrated that small mid- diencephalic lesions incorporating only the
MTs and their immediate vicinity were capable of completely preventing the
convulsant and lethal effects of PTZ. Lesions of the FX and MP were also
protective against PTZ seizures but to a lesser degree than the MT lesions.
These results demonstrate that the major afferent and efferent connections
of the mammillary bodies are involved in expressing PTZ seizure activity
and suggest that the MT may be the major pathway mediating paroxysmal
activity from brain stem to the thalamus.