Abstracts

Using AAV vectors it has previously been shown that in vivo expression and secretion of the neuroactive peptide galanin significantly attenuates electrically elicited, focal seizure activity and prevents hippocampal damage after kainic acid-induced seizures (Haberman et al., Nat. Med. :1076,2003). However, intractable temporal lobe seizures represent the most likely application of this gene therapy. Therefore, it is important to demonstrate that limbic seizure activity can be attenuated using this gene therapy approach. AAV vectors were constructed where the fibronectin secretory signal sequence preceded the coding sequence for galanin, and a hybrid chicken beta actin promoter drove gene expression (AAV-FIB-GAL). This construct provided a means to both express and constitutively secrete galanin. Rats were anesthetized and subsequently received bilateral stereotaxic infusions of the recombinant AAV-FIB-GAL vectors (8 X 10e12 viral particles/ml) into the piriform cortex (2 microliters/ side over 20 minutes; -0.26mm anterior to Bregma, 5.6 mm lateral, 7.8 mm vertical; N=6). One week after the AAV-FIB-GAL vector infusions, the rats received a 10 mg/kg, i.p. injection of kainic acid, and the appearance of limbic seizure behaviors was determined. In control untreated rats (N=5), the first class IV limbic seizure activity appeared 61 [plusmn] 5 minutes after the kainic acid injection, while the first class V limbic seizure activity appeared 86 [plusmn]10 minutes after the kainic acid injection. This seizure activity proved to be repetitive with bouts of class III seizure activity that evolved to class V seizures. For the AAV-FIB-GAL treated rats, wet dog shakes first appeared 51 [plusmn] 3 minutes after the kainic acid treatment, and continued sporadically throughout the observation period. These animals also exhibited hyperactive and stereotyped behaviors throughout the observation period. However, in marked contrast to the controls, none of the AAV-FIB-GAL treated animals exhibited any class IV or class V seizure activity over a period of 240 minutes post-kainic acid treatment. Furthermore, only one of the five animals exhibited a single, brief class III seizure 129 minutes after the kainic acid treatment. AAV vector transduction of the piriform cortex and subsequent expression and secretion of the neuroactive peptide, galanin prevented limbic seizure activity evoked by peripheral administration of kainic acid. Thus, this gene therapy approach can effectively attenuate limbic seizure activity. (Supported by NINDS grant 35633 to TJM.)