Gabaergic and cholinergic basal forebrain and preoptic-anterior hypothalamic projections to the mediodorsal nucleus of the thalamus in the cat

• Published in: Neuroscience 1998-07, Vol.85 (1), p.149-178
• Main Authors: Gritti, I., Mariotti, M., Mancia, M.
• Format: Article
• Language: English
• Subjects: Animals; Anterior Hypothalamic Nucleus - cytology; Anterior Hypothalamic Nucleus - physiology; basal forebrain; Biological and medical sciences; Brain Mapping; Cats; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; choline acetyltransferase; Choline O-Acetyltransferase - metabolism; Cholinergic Fibers - physiology; Female; Fundamental and applied biological sciences. Psychology; gamma-Aminobutyric Acid - physiology; Glutamate Decarboxylase - metabolism; glutamic acid decarboxylase; Male; Molecular Probes; Neurons - physiology; Preoptic Area - cytology; Preoptic Area - physiology; preoptic-anterior hypothalamus; Prosencephalon - cytology; Prosencephalon - physiology; retrograde transport; Synaptic Transmission - physiology; Thalamic Nuclei - physiology; thalamus; Vertebrates: nervous system and sense organs; Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(97)00573-3

The present study examined projections of GABAergic and cholinergic neurons from the basal forebrain and preoptic-anterior hypothalamus to the “intermediate” part of the mediodorsal nucleus of the thalamus. Retrograde transport from this region of the mediodorsal nucleus was investigated using horseradish peroxidase-conjugated wheatgerm agglutinin in combination with peroxidase-antiperoxidase immunohistochemical staining for glutamic acid decarboxylase and choline acetyltransferase. A relatively large number of retrogradely-labelled glutamic acid decarboxylase-positive neurons are located in the basal forebrain, amounting to more than 7% of the total population of glutamic acid decarboxylase-positive cells in this region. Moreover, retrogradely-labelled choline acetyltransferase-positive cells are interspersed among glutamic acid decarboxylase-positive neurons, accounting for about 6% of the total choline acetyltransferase-positive cell population in the basal forebrain. The glutamic acid decarboxylase-positive and choline acetyltransferase-positive retrogradely-labelled neurons are distributed throughout several regions of the basal forebrain, including the medial septum, the diagonal band of Broca, the magnocellular preoptic nucleus, the substantia innominata pars anterior, the substantia innominata pars posterior, and the globus pallidus where only a few retrogradely-labelled neurons were seen. The choline acetyltransferase-positive mediodorsal-projecting neurons are morphologically different from the choline acetyltransferase-positive neurons in the basal forebrain, suggesting that those projecting to the mediodorsal nucleus are a small proportion of the cholinergic neuronal population in the basal forebrain. In the preoptic-anterior hypothalamus, many retrogradely-labelled glutamic acid decarboxylase-positive cells were found, amounting to more than 7% of the total population of glutamic acid decarboxylase-positive cells in this region. These retrogradely-labelled glutamic acid decarboxylase-positive neurons are distributed throughout the preoptic-anterior hypothalamus in a continuous line with those in the basal forebrain, including the lateral preoptic area, the medial preoptic area, the bed nucleus of the stria terminalis, and the anterior and dorsal hypothalamic areas. The highest percentage of mediodorsal-projecting GABAergic neurons is in the anterior lateral hypothalamus where more than 25% of the total population of glutamic acid decarboxylase