Expression of type I adenylyl cyclase in intrinsic pathways of the hippocampal formation of the macaque (Macaca nemestrina) Pananghat A. Kumar a,b,1 , Lauren P. Baker c,1 , Daniel R. Storm c , Douglas M. Bowden a,d, * a Regional Primate Research Center, University of Washington, Box 357330, Seattle, WA 98195±7330, USA b PSG Institute of Medical Sciences and Research, Peelamedu, Coimbatore, India c Department of Pharmacology, School of Medicine, University of Washington, Box357280, Seattle, WA 98195±7330, USA d Department of Psychiatry and Behavioral Sciences, School of Medicine, University of Washington, WA, USA Received 21 February 2000; received in revised form 29 November 2000; accepted 15 December 2000 Abstract The mossy ®ber pathway of the hippocampal formation and type 1 adenylyl cyclase (AC1) have been implicated in long-term potentiation and memory function. Using immunohistochemical labeling and light microscopy we demon- strated intense labeling of AC1 in the mossy ®bers and less intense labeling in the molecular layers of both the dentate gyrus and ®elds CA1, CA2 and CA3 of the hippocampus, i.e. in terminal ®elds of the perforant pathway. These ®ndings indicate that, in the non-human primate, AC1 is found in the mossy ®bers and in terminal ®elds of the perforant pathway where it may play a role in long term potentiation similar to that demonstrated in the rodent. q 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Adenylyl cyclase; Hippocampal formation; Perforant pathway; Dentate gyrus; Mossy ®bers; Endfolial pathway; Immunohis- tochemistry; Macaque; Neuroanatomy Adenylyl cyclases catalyze the formation of cyclic adeno- sine monophosphate (cAMP). Of the ten identi®ed isoforms of mammalian adenylyl cyclase [13] adenylyl cyclase type 1 (AC1) is of particular interest to neuroscientists because of its potential role in learning [16]. AC1 is a calcium- and calmodulin-dependent enzyme [7] hypothesized to play a role in long-term potentiation in the rodent hippocampus. Mice in which the gene for AC1 has been deleted show a reduced capacity for long-term potentiation in hippocampal preparations [14,15] and are behaviorally de®cient in spatial memory [15]. In situ hybridization of AC1 in the rat shows the strongest expression in the dentate gyrus (DG) of the hippocampal formation and in the cerebellum [16], two areas widely studied for their potential involvement in learning and memory. Although AC1 mRNA expression is most intense in granule cells of the DG, it is also found in pyramidal cells in the entorhinal area and in the hippocam- pus. The discovery of AC1 in the hippocampal formation led us to explore its localization in the non-human primate by assaying the neural circuit linking the entorhinal cortex, DG, and hippocampus. Brains from four adult pigtailed macaques (Macaca nemestrina) were studied. The animals were maintained and euthanized in accordance with Federal Guidelines [6]. Non-perfused brains were removed within 3±5 min after cardiorespiratory arrest, cut into 5-mm thick coronal blocks perpendicular to the bicommissural line, and immersed in ®xative (6% paraformaldehyde in 0.1 M phosphate buffer, pH 7.4) at room temperature for 24 h. The blocks were transferred to 30% sucrose in phosphate buffer (pH 7.0) until they sank (approximately 24 h). Forty-micron coronal sections were produced using a freezing-sliding microtome (Microma, Walldorf, Germany). Sections were collected in phosphate-buffered saline (PBS) containing 0.02% sodium azide. Immunohistochemistry was performed on representative sections from the rostral, middle, and caudal regions of the hippocampal formation, corresponding approximately to sections at 3, 8 and 13 mm posterior to the anterior commissure of the macaque atlas of Martin and Bowden [11]. The sections were washed twice in Neuroscience Letters 299 (2001) 181±184 0304-3940/01/$ - see front matter q 2001 Elsevier Science Ireland Ltd. All rights reserved. PII: S0304-3940(01)01493-8 www.elsevier.com/locate/neulet * Corresponding author. Tel.: 181-206-543-2456; fax: 11-206- 685-0305. E-mail address: dmbowden@u.washington.edu (D.M. Bowden). 1 Co-primary author.