Neuroscience Letters, 122 (1991) 75-78
75
ElsevierScientificPublishers Ireland Ltd. NSL 07467
Distribution of trigeminal sensory nucleus neurons projecting to the mesencephalic parabrachial area of the cat Haruhide Hayashi and Takayoshi Tabata Department of Physiology, School of Dentistry, Tohoku University, Sendai (Japan)
(Received 19 July 1990;Revisedversion received 1 October 1990;Accepted2 October 1990) Key words: Parabrachialarea; Spinal trigeminalnucleus; Mesencephalon;Cat; Horseradishperoxidase
Horseradish peroxidase(HRP) retrograde tracing experimentsin the cat demonstratedprojectionsfrom the trigeminalsensorynuclei to the mesencephalic parabrachial area (PBA),which is locatedventral to the inferiorcolliculusand dorsal to the brachiumconjunctivumand includesthe nucleus cuneiformisand the most lateral part of the periaqueductalgray. After HRP injectioninto the mesencephalicPBA, HRP-labeledneuronal cellbodies in the trigeminal sensorynuclei were mainly distributed in the interpolar and caudal spinal trigeminal nuclei (Vi and Vc) bilaterallywith a clear-cut contralateral dominance. In Vi, HRP-labeledneurons were mainly distributed in the lateral and medial border regions. In Vc, labeled neurons were located mainly in laminae I and V. The mesencephalic parabrachial area (PBA), which is located ventral to the inferior colliculus and dorsal to the brachium conjunctivum and includes the nucleus cuneiformis and the most lateral part of periaqueductal gray, has been reported to receive many projections from all spinal cord segments in the cat (see ref. 6). After horseradish peroxidase (HRP) injection into the pontine PBA of the cat, HRP-labeled neuronal cell bodies have been observed in the trigeminal sensory nuclei [7, 10, 11]. The distribution of trigeminal sensory nucleus neurons that send projection fibers to the mesencephalic PBA, however, has not yet been amply investigated. In the present study, the distribution of trigeminal sensory nucleus neurons projecting to the mesencephalic PBA was examined in the cat. Adult cats of either sex (2.0-2.8 kg) were sedated with ketamine hydrochloride (20-25 mg/kg, i.m.) and then anesthetized with sodium pentobarbital (35 mg/kg i.v.). Under sterile conditions, H R P (Sigma Type VI, 0 . 1 5 4 . 2 /A, 25% w/v in saline) was injected stereotaxically into the mesencephalic PBA with a Hamilton microliter syringe through a blunt-tip n~¢edle (tip diameter, 100 pm). After the surgery the cats were treated with penicillin. After 51-72 h of survival time, the cats were deeply anesthetized with sodium pentobarbital (50 mg/kg i.v.) and perfused through the aorta with 0.5% paraformaldehyde2.5% glutaraldehyde in 0.1 M phosphate buffer for 30 min, followed by 0.1 M phosphate buffer containing 10% Correspondence: H. Hayashi, Department of Physiology, School of Dentistry, Tohoku University,4-I Seiryo-machi,Sendai 980, Japan.
0304-3940/91/$ 03.50 © 1991 ElsevierScientificPublishers Ireland Ltd.
sucrose. Frozen brainstems were cut into transverse sections of 100/~m thickness. The sections from the midbrain were reacted with 3,3'-diaminobenzidine by the method of Adams [1] to demonstrate the injection sites. The sections from the pons and medulla were reacted with tetramethylbenzidine by the method of Mesulum [9]. The sections were counterstained with 1% Neutral red. Retrogradely labeled neurons were plotted using a camera lucida apparatus. H R P was injected successfully into the mesencephalic PBA in 11 cats; the injection sites are shown in Fig. 1. The dense, central core of the H R P injections were centered on the PBA and, in a few cats, extended to the ventral aspect of the inferior colliculus, the rostral part of the pontine parabrachial nucleus (Cat 11), or the intercollicular junctional area (Cat 5). Labeled neurons were found in the trigeminal sensory nuclei, the spinal trigeminal tract, and the lateral reticular formation. The patterns of distribution of these labeled neurons in 2 cats are shown in Fig. 2. At the levels rostral to the obex, labeled neurons in the trigeminal sensory nuclei were mainly distributed in the medial and lateral border regions of the nuclei (Fig. 2, Cat 3, A-D; Cat 11, A--C). Labeled neurons were densely distributed in the paratrigeminal nucleus (Fig. 2, Cat 3, D), which is an interstitial nucleus located within the spinal tract of the trigeminal nerve at the level of the caudal pole of the interpolar spinal trigeminal nucleus (Vi) [4]. The majority of the labeled neurons were small stellate cells (about 10/tm in diameter). A few medium-sized elliptical cells (25 x 10/~m) were also found.
76
Cat 3
Cat 4
Cat 5
Cat 11
Fig. 1. Camera lucida drawings of sections through the midbrains of 4 cats, indicating the extent of reaction product after injection of HRP into the PBA. Dark zones indicate areas covered by a dense reaction product that obscured all cytological detail. There was a lighter halo of reaction product within the stippled zones. SC, superior colliculus; BC, brachium conjunctivum; IC, inferior colliculus; PAG, periaqueductal gray; CFN, cuneiform nucleus; PBN, pontine parabrachial nucleus.
In the caudal spinal trigeminal nucleus (Vc), labeled neurons were located superficially within lamina I, along the border between laminae IV and V, and in lamina V (Fig. 2, Cat 3, E, F; Cat 11, D, E). The majority of the labeled neurons in lamina I were small fusiform cells and a few were medium-sized multipolar cells. The labeled neurons in lamina V were small stellate cells. Histograms of the rostrocaudal distribution of trigeminal sensory nucleus neurons, which were labeled with HRP injected into the mesencephalic PBA in one cat (Cat 3), are shown in Fig. 3. Labeled neurons were seen bilaterally with a clear-cut contralateral dominance, and most frequently at the levels of the caudal three-fourths of Vi and the rostral three-fourths of Vc. A few cells were labeled in main sensory trigeminal nucleus (Vms) and oral spinal trigeminal nucleus. In the caudal part of Vc and the first cervical cord segment, labeled neurons were less numerous than in the rostral part of Vc. It is known that trigeminal sensory nucleus neurons project to the regions adjacent to the mesencephalic PBA, i.e., the pontine parabrachial nucleus [7, 10, 11] and intercollicular region [2, 14]. In the case in which
Cat 11
Cat 3
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Fig. 2. Distributions of retrogradely labeled neurons in the brain stems of two cats (Cats 3 and l 1). Each section is a diagrammatic representation of the HRP-labeled cells, shown by dots. Vmo, trigeminal motor nucleus; Vms, main sensory trigeminal nucleus; Vst, spinal tract of the trigeminal nerve; 7N, facial nerve; Vo, Vi and Vc, oral, interpolar and caudal spinal trigeminal nucleus, respectively; SO, superior olivary nucleus; C, cuneate nucleus; Cx, external cuneate nucleus; NTS, nucleus of the solitary tract; G, gracile nucleus. I and V, laminae I and V of Vc, respectively. Numbers in parentheses indicate distance in millimeters rostral (A) or caudal (P) to the obex.
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75
ElsevierScientificPublishers Ireland Ltd. NSL 07467
Distribution of trigeminal sensory nucleus neurons projecting to the mesencephalic parabrachial area of the cat Haruhide Hayashi and Takayoshi Tabata Department of Physiology, School of Dentistry, Tohoku University, Sendai (Japan)
(Received 19 July 1990;Revisedversion received 1 October 1990;Accepted2 October 1990) Key words: Parabrachialarea; Spinal trigeminalnucleus; Mesencephalon;Cat; Horseradishperoxidase
Horseradish peroxidase(HRP) retrograde tracing experimentsin the cat demonstratedprojectionsfrom the trigeminalsensorynuclei to the mesencephalic parabrachial area (PBA),which is locatedventral to the inferiorcolliculusand dorsal to the brachiumconjunctivumand includesthe nucleus cuneiformisand the most lateral part of the periaqueductalgray. After HRP injectioninto the mesencephalicPBA, HRP-labeledneuronal cellbodies in the trigeminal sensorynuclei were mainly distributed in the interpolar and caudal spinal trigeminal nuclei (Vi and Vc) bilaterallywith a clear-cut contralateral dominance. In Vi, HRP-labeledneurons were mainly distributed in the lateral and medial border regions. In Vc, labeled neurons were located mainly in laminae I and V. The mesencephalic parabrachial area (PBA), which is located ventral to the inferior colliculus and dorsal to the brachium conjunctivum and includes the nucleus cuneiformis and the most lateral part of periaqueductal gray, has been reported to receive many projections from all spinal cord segments in the cat (see ref. 6). After horseradish peroxidase (HRP) injection into the pontine PBA of the cat, HRP-labeled neuronal cell bodies have been observed in the trigeminal sensory nuclei [7, 10, 11]. The distribution of trigeminal sensory nucleus neurons that send projection fibers to the mesencephalic PBA, however, has not yet been amply investigated. In the present study, the distribution of trigeminal sensory nucleus neurons projecting to the mesencephalic PBA was examined in the cat. Adult cats of either sex (2.0-2.8 kg) were sedated with ketamine hydrochloride (20-25 mg/kg, i.m.) and then anesthetized with sodium pentobarbital (35 mg/kg i.v.). Under sterile conditions, H R P (Sigma Type VI, 0 . 1 5 4 . 2 /A, 25% w/v in saline) was injected stereotaxically into the mesencephalic PBA with a Hamilton microliter syringe through a blunt-tip n~¢edle (tip diameter, 100 pm). After the surgery the cats were treated with penicillin. After 51-72 h of survival time, the cats were deeply anesthetized with sodium pentobarbital (50 mg/kg i.v.) and perfused through the aorta with 0.5% paraformaldehyde2.5% glutaraldehyde in 0.1 M phosphate buffer for 30 min, followed by 0.1 M phosphate buffer containing 10% Correspondence: H. Hayashi, Department of Physiology, School of Dentistry, Tohoku University,4-I Seiryo-machi,Sendai 980, Japan.
0304-3940/91/$ 03.50 © 1991 ElsevierScientificPublishers Ireland Ltd.
sucrose. Frozen brainstems were cut into transverse sections of 100/~m thickness. The sections from the midbrain were reacted with 3,3'-diaminobenzidine by the method of Adams [1] to demonstrate the injection sites. The sections from the pons and medulla were reacted with tetramethylbenzidine by the method of Mesulum [9]. The sections were counterstained with 1% Neutral red. Retrogradely labeled neurons were plotted using a camera lucida apparatus. H R P was injected successfully into the mesencephalic PBA in 11 cats; the injection sites are shown in Fig. 1. The dense, central core of the H R P injections were centered on the PBA and, in a few cats, extended to the ventral aspect of the inferior colliculus, the rostral part of the pontine parabrachial nucleus (Cat 11), or the intercollicular junctional area (Cat 5). Labeled neurons were found in the trigeminal sensory nuclei, the spinal trigeminal tract, and the lateral reticular formation. The patterns of distribution of these labeled neurons in 2 cats are shown in Fig. 2. At the levels rostral to the obex, labeled neurons in the trigeminal sensory nuclei were mainly distributed in the medial and lateral border regions of the nuclei (Fig. 2, Cat 3, A-D; Cat 11, A--C). Labeled neurons were densely distributed in the paratrigeminal nucleus (Fig. 2, Cat 3, D), which is an interstitial nucleus located within the spinal tract of the trigeminal nerve at the level of the caudal pole of the interpolar spinal trigeminal nucleus (Vi) [4]. The majority of the labeled neurons were small stellate cells (about 10/tm in diameter). A few medium-sized elliptical cells (25 x 10/~m) were also found.
76
Cat 3
Cat 4
Cat 5
Cat 11
Fig. 1. Camera lucida drawings of sections through the midbrains of 4 cats, indicating the extent of reaction product after injection of HRP into the PBA. Dark zones indicate areas covered by a dense reaction product that obscured all cytological detail. There was a lighter halo of reaction product within the stippled zones. SC, superior colliculus; BC, brachium conjunctivum; IC, inferior colliculus; PAG, periaqueductal gray; CFN, cuneiform nucleus; PBN, pontine parabrachial nucleus.
In the caudal spinal trigeminal nucleus (Vc), labeled neurons were located superficially within lamina I, along the border between laminae IV and V, and in lamina V (Fig. 2, Cat 3, E, F; Cat 11, D, E). The majority of the labeled neurons in lamina I were small fusiform cells and a few were medium-sized multipolar cells. The labeled neurons in lamina V were small stellate cells. Histograms of the rostrocaudal distribution of trigeminal sensory nucleus neurons, which were labeled with HRP injected into the mesencephalic PBA in one cat (Cat 3), are shown in Fig. 3. Labeled neurons were seen bilaterally with a clear-cut contralateral dominance, and most frequently at the levels of the caudal three-fourths of Vi and the rostral three-fourths of Vc. A few cells were labeled in main sensory trigeminal nucleus (Vms) and oral spinal trigeminal nucleus. In the caudal part of Vc and the first cervical cord segment, labeled neurons were less numerous than in the rostral part of Vc. It is known that trigeminal sensory nucleus neurons project to the regions adjacent to the mesencephalic PBA, i.e., the pontine parabrachial nucleus [7, 10, 11] and intercollicular region [2, 14]. In the case in which
Cat 11
Cat 3
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Fig. 2. Distributions of retrogradely labeled neurons in the brain stems of two cats (Cats 3 and l 1). Each section is a diagrammatic representation of the HRP-labeled cells, shown by dots. Vmo, trigeminal motor nucleus; Vms, main sensory trigeminal nucleus; Vst, spinal tract of the trigeminal nerve; 7N, facial nerve; Vo, Vi and Vc, oral, interpolar and caudal spinal trigeminal nucleus, respectively; SO, superior olivary nucleus; C, cuneate nucleus; Cx, external cuneate nucleus; NTS, nucleus of the solitary tract; G, gracile nucleus. I and V, laminae I and V of Vc, respectively. Numbers in parentheses indicate distance in millimeters rostral (A) or caudal (P) to the obex.
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