Viral Vectors for Optogenetics of Hypothalamic Neuropeptides - Viral Vector Approaches in Neurobiology and Brain Diseases - page 300

Chapter 16

Viral Vectors for Optogenetics of Hypothalamic
Neuropeptides

H. Sophie Knobloch , Alexander Charlet , Ron Stoop , and Valery Grinevich

Abstract

During the last decade, viral technologies have progressively been used in the studies of different aspects
of brain functions. Relatively recently, viral techniques have been combined with optogenetics, which
allows the study of modifi cations of the activity of different brain regions and circuits in vitro in brain slices
and in behaving animals. In the vast majority of these cases, the viral/optogenetic approach has been used
to manipulate the release of the classical neurotransmitters, L -glutamate, and GABA. Recently, several
studies have focused on viral/optogenetic manipulation of “nonclassical” neurotransmitters—neuromod-
ulators, primarily the biogenic amine dopamine. However, another large group of neuromodulators—neu-
ropeptides-has as yet remained unexplored by viral/optogenetic approaches. In this chapter, we present
an overview of viral and transgenic techniques applied to targeting neuropeptidergic hypothalamic neu-
rons. We provide examples of using optogenetics for manipulating neuropeptide-expressing neurons,
including our own protocols on the expression of Channelrhodopsin 2 in oxytocinergic hypothalamic
neurons. Furthermore, in this chapter we provide some advice for the correct interpretation of results of
optogenetically altered release of oxytocin (and potentially other neuropeptides) and perspectives of com-
bining optogenetics with other techniques, such as functional magnetic resonance imaging (fMRI), micro-
dialysis, and electrophysiological fi eld recording for further exploration of neuropeptide functions in the
brain.

Key words Neuroendocrinology, Neuropeptides, Oxytocin, Virus, Optogenetics, Electrophysiology,
Behavior

1 Introduction

The term “optogenetics” describes a technology of genetic inter-
vention in biological cells to render them light sensitive and con-
trol their activity. Algae and microbes offer blueprints for the
required molecular modules, membrane-bound ion pumps and
channels, which became a rapidly advancing and indispensable,
successful tool in neuroscience [ 1 - 5 ]. Boyden et al. (2005) fi rst
demonstrated the initiation of light-dependent action potentials in
mammalian neuronal tissue via viral delivery of an opsin, channel-
rhodopsin 2 [ 6 ]. ChR2 is a 7-transmembrane protein derived from