Distribution of the mRNA for a pituitary adenylate cyclase-activating polypeptide receptor in the rat brain: an in situ hybridization study
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1Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, Japan.
Abstract:
The distribution of the mRNA for a pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (PACAP-R) was examined in the rat brain, and also in the hypophysis and pineal gland, by in situ hybridization with a specific 35S-labeled riboprobe which was generated from a rat PACAP-R cDNA clone. In the brain, expression of PACAP-R mRNA was most prominent in the periglomerular and granule cells of the olfactory bulb, granule cells of the dentate gyrus, supraoptic nucleus, and area postrema. The expression was also intense in the piriform, cingulate, and retrosplenial cortices, pyramidal cells in CA2, non-pyramidal cells in CA1-CA3, neuronal cells in the hilus of the dentate gyrus, lateral septal nucleus, intercalated amygdaloid nucleus, anterodorsal thalamic nucleus, most of the midline and intralaminar thalamic nuclei, many regions of the hypothalamus, dorsal motor nucleus of the vagus nerve, hypoglossal nucleus, and lateral reticular nucleus. No significant expression was detected in the mitral and tufted cells in the olfactory bulb, pyramidal cells in CA1 and CA3, posterior nuclear group of the thalamus, dorsal lateral geniculate nucleus, and Purkinje, Golgi, and granule cells in the cerebellar cortex. Moderate-to-weak expression was further observed in many other regions of the brain. In the cerebellar cortex, presumed Bergmann glia cells showed moderate expression. In the hypophysis, the expression was moderate in the anterior lobe, and weak to moderate in the posterior lobe; no significant expression was observed in the intermediate lobe. In the pineal gland, the expression was very weak, if any. Thus, the expression of PACAP-R was detected not only on neuronal cells but also on some particular glial cells. The present study has shown, for the first time, the exact site of PACAP-R expression in the brain and hypophysis. Although the functional significance of PACAP and PACAP-R in the brain still remains to be clarified, the present results are considered to provide some direction for future functional studies.
Insights
This study maps the pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (PACAP-R) mRNA distribution in rat brain and endocrine glands. Findings reveal PACAP-R expression in specific neurons and glial cells, guiding future research.
Area of Science:
- Neuroscience
- Endocrinology
- Molecular Biology
Background:
- Pituitary adenylate cyclase-activating polypeptide (PACAP) is a crucial neuropeptide with diverse physiological roles.
- The distribution and function of its receptor, PACAP-R, in the central nervous system and endocrine glands are not fully elucidated.
Purpose of the Study:
- To precisely map the expression sites of PACAP receptor (PACAP-R) mRNA in the rat brain, hypophysis, and pineal gland.
- To identify specific neuronal and glial cell populations expressing PACAP-R.
- To provide a foundation for understanding PACAP signaling in these tissues.
Main Methods:
- In situ hybridization using a 35S-labeled riboprobe derived from a rat PACAP-R cDNA clone.
- Detailed analysis of PACAP-R mRNA localization across various brain regions, including the olfactory bulb, hippocampus, cortex, thalamus, hypothalamus, and brainstem.
- Examination of PACAP-R expression in the anterior, intermediate, and posterior lobes of the hypophysis and the pineal gland.
Main Results:
- PACAP-R mRNA expression was prominent in olfactory bulb periglomerular and granule cells, dentate gyrus granule cells, supraoptic nucleus, and area postrema.
- Intense expression was observed in cortical regions, specific hippocampal cell types, thalamic nuclei, hypothalamus, and brainstem nuclei.
- Moderate expression was found in the anterior and posterior hypophysis, with some glial cell expression noted in the cerebellum; minimal expression in the pineal gland.
Conclusions:
- This study provides the first detailed map of PACAP-R expression in the rat brain and hypophysis.
- PACAP-R is expressed in a diverse range of neuronal populations and also in specific glial cells.
- These findings offer critical insights for future research into the functional roles of PACAP signaling in the neuroendocrine system.
