ANATOMICAL AND IMMUNOHISTOCHEMICAL IDENTIFICATION OF CATECHOLAMINERGIC NEURONS IN BRAIN SLICE PREPARATIONS USED IN ELECTROPHYSIOLOGY

The physiological characteristics of central neural populations are be ing increasingly explored in slice preparations. A major challenge of this approach is to correlate the physiological properties of individu al neurones or groups of neurones with their anatomical and chemical p roperties in order to gain key insights into their functional identiti es. The present study describes a method for determining the precise t opographical position and the immunohistochemical characteristics of n eurones in brain slice preparations that are used frequently in electr ophysiological investigations. Thick horizontal slices of rat brainste m were re-cut using a method that provided thin sections that were alw ays in the same plane as the parent slice and that were of suitable th ickness for immunohistochemistry. Catecholaminergic neurones in these co-planar (horizontal) sections were stained using antisera to tyrosin e hydroxylase, the rate-limiting enzyme for catecholamine synthesis. T o identify individual catecholamine neurones in the co-planar sections , we constructed a reference atlas of the distribution of catecholamin e neurones in the horizontal plane of the rat brain. The combined use of the horizontal atlas and of immunohistochemical techniques in co-pl anar sections of horizontal slices enables the determination of severa l key properties: (1) whether a neurone is TH-positive, (2) its precis e topographical position and (3) its content of neuropeptides and othe r immunohistochemical markers, Thus our study offers a readily feasibl e method for correlative anatomy and immunohistochemistry of physiolog ically identified catecholaminergic neurones in brain slices.