Research Report PKC blockade differentially affects aversive but not appetitive gustatory memories Luis Núñez-Jaramillo, Ilse Delint-Ramirez, Federico Bermúdez-Rattoni ⁎ Departamento de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-253, 04510 México D.F., Mexico ARTICLE INFO ABSTRACT Article history: Accepted 14 February 2007 Available online 24 February 2007 After consumption of a new taste, there are mainly two possible outcomes for the establishment of a taste memory, either it will be aversive or safe depending on the consequences of taste consumption. It has been proposed that both types of learning share a common initial taste memory trace, which will lead to two different memory traces, safe or aversive. To study the role of PKC activity in aversive or safe taste memory formation, we administered chelerythrine, a PKC inhibitor, into the insular cortex or parietal cortex 20 min before conditioned taste aversion or attenuation of neophobia training. The results suggest that PKC activity is needed in the insular cortex for the establishment of aversive taste memory, but not for safe taste memory. © 2007 Elsevier B.V. All rights reserved. Keywords: Taste Recognition memory Insular cortex Learning Memory Conditioning 1. Introduction In order to survive, animals have developed mechanisms to recognize safe or toxic meals. When an animal finds a new taste it consumes only a small amount of food or drink, which is known as neophobic response. The consequences of food ingestion will determine the future reaction of the animal to that taste. If it has no toxic consequences, the taste cue will be recognized as safe and the animal will increase its consump- tion, presenting attenuation of neophobia. Conversely, if the taste is followed by signals of toxicity such as gastric malaise, it will be recognized as aversive and the animal will reduce its consumption. Since both types of learning can be derived from the same taste, this taste must be able to unleash mechanisms necessary to learn either of them. It has been proposed that both learnings (safe and aversive) share a common initial taste memory trace (TMT), which is the neural representation of the taste that will eventually form a gustatory memory, once the consequences of taste consumption have been established. This initial memory trace apparently will divide afterwards in at least two different TMT. These two processes might share similar mechanisms, such as the need of muscarinic acet- ylcholine receptors activation in the insular cortex (IC) during the consumption of the taste and the initial processing of the TMT (Gutierrez et al., 2003a,b), or proteins synthesis in the same cortex (Rodriguez-Ortiz et al., 2005; Rosenblum et al., 1993). However, these memory traces also differ in some other mechanisms, for example, it has been reported that the systemic injection of anaesthesia, or the blockade of muscari- nic receptors in the IC after the consumption of a new taste impair only safe taste recognition memory formation, but have no effect on aversive taste learning (Buresova and Bures, 1980; Gutierrez et al., 2003a,b). After a novel taste presentation, de- pending of its visceral consequences, one of these TMTs, will BRAIN RESEARCH 1148 (2007) 177 – 182 ⁎ Corresponding author. E-mail address: fbermude@ifc.unam.mx (F. Bermúdez-Rattoni). Abbreviations: TMT, taste memory trace; PKC, protein kinase C; CTA, conditioned taste aversion; AN, attenuation of neophobia 0006-8993/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2007.02.032 available at www.sciencedirect.com www.elsevier.com/locate/brainres