Abstract
Enkephalins are endogenous opioid pentapeptides that play a role in neurotransmission and pain modulation in vertebrates. However, the distribution pattern of enkephalinergic neurons in the brains of reptiles has been understudied. This study reports the organization of the methionine-enkephalin (M-ENK) and leucine-enkephalin (L-ENK) neuronal systems in the central nervous system of the gecko Hemidactylus frenatus using an immunofluorescence labeling method. Although M-ENK and L-ENK-immunoreactive (ir) fibers extended throughout the pallial and subpallial subdivisions, including the olfactory bulbs, M-ENK and L-ENK-ir cells were found only in the dorsal septal nucleus. Enkephalinergic perikarya and fibers were highly concentrated in the periventricular and lateral preoptic areas, as well as in the anterior and lateral subdivisions of the hypothalamus, while enkephalinergic innervation was observed in the hypothalamic periventricular nucleus, infundibular recess nucleus and median eminence. The dense accumulation of enkephalinergic content was noticed in the pars distalis of the hypophysis. In the thalamus, the nucleus rotundus and the dorsolateral, medial, and medial posterior thalamic nuclei contained M-ENK and L-ENK-ir fibers, whereas clusters of M-ENK and L-ENK-ir neurons were observed in the pretectum, mesencephalon, and rhombencephalon. The enkephalinergic fibers were also seen in the area X around the central canal, as well as the dorsal and ventral horns. The widespread distribution of enkephalin-containing neurons within the central nervous system implies that enkephalins regulate a variety of functions in the gecko, including sensory, behavioral, hypophysiotropic, and neuroendocrine functions.
Similar content being viewed by others
Data availability
Data will be made available upon reasonable request.
Abbreviations
- ACC:
-
Nucleus accumbens
- AM:
-
Amygdala
- AMC:
-
nucleus centralis amygdalae
- AME:
-
nucleus externus amygdalae
- AX:
-
Area X of central canal
- BSA:
-
Bovine serum albumin
- CA:
-
Anterior commissure
- CB:
-
Cerebellum
- CC:
-
Central canal
- CNS:
-
Central nervous system
- CP:
-
Posterior commissure
- CTX:
-
Cortex
- DCTX:
-
Dorsal cortex
- DF:
-
Dorsal funiculus
- DH:
-
Dorsal horn of the spinal cord
- DLH:
-
Dorsolateral hypothalamic nucleus
- DLT:
-
Dorsolateral thalamic nucleus
- DMT:
-
Dorsomedial thalamic nucleus
- DVR:
-
Dorsoventricular ridge
- EPL:
-
External plexiform layer
- FLM:
-
Fasciculus longitudinalis medialis
- GC:
-
Griseum centrale
- GCL:
-
Granular layer of the cerebellum
- GL:
-
Glomerular layer
- GP:
-
Globus pallidus
- IGL:
-
Inner granular layer
- IPN:
-
Interpeduncular nucleus
- IR:
-
Infundibular recess
- ir:
-
immunoreactive
- IRN:
-
Infundibular recess nucleus
- IS:
-
Isthmus
- L-ENK:
-
Leucine-enkephalin
- LA:
-
Lateral amygdala
- LCO:
-
Locus coeruleus
- LDT:
-
Laterodorsal tegmental nucleus
- LCTX:
-
Lateral cortex
- LF:
-
Lateral funiculus
- LFB:
-
Lateral forebrain bundle
- LHA:
-
Lateral hypothalamic area
- LM:
-
pretectal lentiform mesencephalic nucleus
- lPOA:
-
Lateral preoptic area
- M-ENK:
-
Methionine-enkephalin
- MCL:
-
Molecular layer of the cerebellum
- MCTX:
-
Medial cortex
- ME:
-
Median eminence
- ML:
-
Mitral cell layer
- MP:
-
Medial posterior thalamic nucleus
- MT:
-
Medial thalamic nucleus
- MV:
-
Motor nucleus of trigeminal nerve
- NCP:
-
Nucleus of the posterior commissure
- NdB:
-
Nucleus of the diagonal band of Broca
- OC:
-
Optic chiasma
- OLF:
-
Olfactory bulb
- ON:
-
Optic nerve
- OT:
-
Optic tectum
- PB:
-
Parabrachial nucleus
- PD:
-
Pars distalis
- PDN:
-
Posterodorsal nucleus
- PH:
-
Periventricular nucleus of hypothalamus
- PIT:
-
Pituitary gland
- POA:
-
Preoptic area
- pPOA:
-
Periventricular preoptic area
- PRD:
-
Dorsal pretectal nucleus
- PVN:
-
Paraventricular nucleus
- RAS:
-
Superior raphe nucleus
- RF:
-
Reticular formation
- ROT:
-
Nucleus rotundus
- RS:
-
Superior reticular nucleus
- SP:
-
Septum
- SA:
-
Anterior septal nucleus
- SAC:
-
Stratum album centrale
- SC:
-
Spinal cord
- SCN:
-
Suprachiasmatic nucleus
- SCO:
-
Subcommissural organ
- SD:
-
Dorsal septal nucleus
- SGC:
-
Stratum griseum centrale
- SGFP:
-
Stratum griseum et fibrosum periventriculare
- SGFS:
-
Stratum griseum et fibrosum superficiale
- SL:
-
Lateral septal nucleus
- SM:
-
Medial septal nucleus
- SN:
-
Substantia nigra
- SO:
-
Stratum opticum
- SON:
-
Supraoptic nucleus
- ST:
-
Striatum
- TEGM:
-
Tegmentum
- TH:
-
Thalamus
- TS:
-
Torus semicircularis
- TSC:
-
Torus semicircularis pars centralis
- TSL:
-
Torus semicircularis pars lateralis
- V:
-
Ventricle
- VF:
-
Ventral funiculus
- VH:
-
Ventral horn of the spinal cord
- VTA:
-
Ventral tegmental area
References
Báez-Mendoza R, Schultz W (2013) The role of the striatum in social behavior. Front Neurosci 7:233. https://doi.org/10.3389/fnins.2013.00233
Batten TFC, Moons L, Cambre M, Vandesande F (1990) Anatomical distribution of galanin-like immunoreactivity in the brain and pituitary of teleost fishes. Neurosci Lett 111:12–17. https://doi.org/10.1016/0304-3940(90)90336-8
Benton MJ (2005) Vertebrate Palaeontology. 3rd Edition, Blackwell Publishing Company, Hoboken 229–231
Bodnar RJ (2018) Endogenous opiates and behavior. Peptides 101:167–212. https://doi.org/10.1016/j.peptides.2018.01.011
Bodnar RJ, Klein GE (2005) Endogenous opiates and behavior: 2004. Peptides 26(12):2629–2711. https://doi.org/10.1016/j.peptides.2005.06.010
Brauth SE (1984) Enkephalin-like immunoreactivity within the telencephalon of the reptile Caiman crocodilus. Neuroscience 11(2):345–358. https://doi.org/10.1016/0306-4522(84)90028-9
Code RA, Carr CE (1995) Enkephalin-like immunoreactivity in the chick brainstem: possible relation to the cochlear efferent system. Hear Res 87(1–2):69–83. https://doi.org/10.1016/0378-5955(95)00080-n
Cruce JA (1975) An autoradiographic study of the projections of the mammillothalamic tract in the rat. Brain Res 85(2):211–219. https://doi.org/10.1016/0006-8993
de Lanerolle NC, Elde RP, Sparber SB, Frick M (1981) Distribution of methionine-enkephalin immunoreactivity in the chick brain: an immunohistochemical study. J Comp Neurol 10(4):513–533. https://doi.org/10.1002/cne.901990406
Domínguez L, Morona R, Joven A, González A, López JM (2010) Immunohistochemical localization of orexins (hypocretins) in the brain of reptiles and its relation to monoaminergic systems. J Chem Neuroanat 39(1):20–34. https://doi.org/10.1016/j.jchemneu.2009.07.007
Dores RM, Finger TE, Gold MR (1984) Immunohistochemical localization of enkephalin and ACTH-related substances in the pituitary of the lamprey. Cell Tissue Res 235:107–115
Ebbesson SOE (1967) Ascending axon degeneration following hemisection of the spinal cord in the tegu lizard (Tupinambis nigropunctatus). Brain Res 5:178–206
Fernández-Espejo E (2000) Cómo Funciona El nucleus accumbens? [How does the nucleus accumbens function?]. Rev Neurol 30(9):845–849
Fernandez-Llebrez P, Perez J, Nadales AE, Cifuentes M, Grondona JM, Mancera JM, Rodríguez EM (1988) Immunocytochemical study of the hypothalamic magnocellular neurosecretory nuclei of the snake Natrix maura and the turtle Mauremys caspica. Cell Tissue Res 253:435–445. https://doi.org/10.1007/BF00222301
Fonken LK, Nelson RJ (2014) The effects of light at night on circadian clocks and metabolism. Endocr Rev 35(4):648–670. https://doi.org/10.1210/er.2013-1051
Furukawa Y, Kotegawa T, Tsutsui K (1995) Effects of opioid peptides on the electrical activity of preoptic and hypothalamic neurons in the quail brain. J Exp Zool 273(2):96–103. https://doi.org/10.1002/jez.1402730203. PMID: 7595282
Ganesh CB (2021) The stress—reproductive axis in fish: the involvement of functional neuroanatomical systems in the brain. J Chem Neuroanat 112:101904. https://doi.org/10.1016/j.jchemneu.2020.101904
Ganesh CB, Vijayalaxmi (2020) Methionine-enkephalin treatment suppresses the pituitary-ovary axis in the cichlid fish Oreochromis mossambicus. Aquac Rep 17:100311. https://doi.org/10.1016/j.aqrep.2020.100311
Ganesh CB, Vijayalaxmi (2021) Neuroanatomical organization of methionine-enkephalinergic system in the brain of the Mozambique tilapia Oreochromis mossambicus. J Chem Neuroanat 115:101963. https://doi.org/10.1016/j.jchemneu.2021.101963
Ganeyan A, Ganesh CB (2023a) The influence of the opioid pentapeptide methionine-enkephalin on seasonal and FSH-induced ovarian recrudescence in the gecko Hemidactylus frenatus. Gen Comp Endocrinol 1(342):114353. https://doi.org/10.1016/j.ygcen.2023
Ganeyan A, Ganesh CB (2023b) The opioid peptide leucine-enkephalin disrupts seasonal and gonadotropin-induced ovarian recrudescence in the gecko Hemidactylus frenatus. Comp Biochem Physiol Mol Integr Physiol 283:111454. https://doi.org/10.1016/j.cbpa.2023.111454
Ganeyan A, Ganesh CB (2023c) Organization of the galaninergic neuronal system in the brain of the gecko Hemidactylus frenatus. Neuropeptides 97:102310. https://doi.org/10.1016/j.npep.2022.102310
Goossens N, Dierickx K, Vandesande F (1979) Immunocytochemical localization of vasotocin and mesotocin in the hypothalamus of lacertilian reptiles. Cell Tissue Res 200(2):223–227. https://doi.org/10.1007/BF00236415
Gopal N, Sudha Devi AR (2019) Effect of leucine enkephalin administration on ovarian maturation in the freshwater crab Travancoriana schirnerae. Int J Aquat Biol 1:14–26. https://doi.org/10.22034/ijab.v7i1.526
Guirado S, Dávila J (2009) Evolution of the Optic Tectum in Amniotes. In: Binder MD, Hirokawa N, Windhorst U (eds) Encyclopedia of Neuroscience. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-29678-2_3162
Hammouche SB, Bennis M (2013) Galanin immunoreactivity in the brain of the desert lizard Uromastyx acanthinura during activity season. Folia Histochem et Cytob 51(1):45–54. https://doi.org/10.5603/fhc.2013.007
Hoogland PVIM (1977) Efferent connections of the striatum in Tupinambis nigropunctatus. J MorphoI 152:229–246
Hughes J, Smith TW, Kosterlitz HW, Fothergill LA, Morgan BA, Morris HR (1975) Identification of two related pentapeptides from the brain with potent opiate agonist activity. Nature 258:577–580
Kaminski T, Siawrys G, Bogacka I, Okrasa S, Przała J (2003) The regulation of steroidogenesis by opioid peptides in porcine theca cells. Anim Reprod Sci 78:71–84
Khachaturian H, Lewis ME, Watson SJ (1983) Enkephalin systems in diencephalon and brainstem of the rat. J Comp Neurol. 1;220(3):310 – 20. https://doi.org/10.1002/cne.902200305
Kishori B, Reddy PS (2003) Influence of leucine-enkephalin on moulting and vitellogenesis in the freshwater crab, Oziotelphusa senex senex (Fabricius, 1791) (Decapoda, Brachyura). Crustaceana 76:1281–1290
Kotegawa T, Abe T, Tsutsui K (1997) Inhibitory role of opioid peptides in the regulation of aggressive and sexual behaviors in male Japanese quails. J Exp Zool 277(2):146–154. https://doi.org/10.1002/(sici)1097-010x(19970201)277:2<146::aid-jez6>3.0.co;2-p
Kozicz T, Lázár G (2001) Colocalization of GABA, enkephalin and neuropeptide Y in the tectum of the green frog Rana esculenta. Peptides 22(7):1071–1077. https://doi.org/10.1016/s0196-9781(01)00430-2
Kumar S, Nagaraju GP, Song H, von Kalm L, Borst DW (2012) Exposure to exogenous enkephalins disrupts reproductive development in the Eastern Lubber Grasshopper, Romalea microptera (Insecta: orthoptera). PLoS ONE 7:e51126. https://doi.org/10.1371/journal.pone.0051126
Kusuma A (1979) The organization of the spinal cord in reptiles with different locomotor patterns. Thesis, University of Nijmegen, Netherlands.
Lewis JW, Baldrighi G, Akil H (1987) A possible interface between autonomic function and pain control: opioid analgesia and the nucleus tractus solitarius. Brain Res 424(1):65–70. https://doi.org/10.1016/0006-8993(87)91193-0
Linster C, Wyble B, Hasselmo ME (1999) Electrical stimulation of the horizontal limb of the diagonal band of Broca modulates population EPSPs in piriform cortex. J Neurophysiol 81(6):2737–2742. https://doi.org/10.1152/jn.1999.81.6.2737
Merchenthaler I, Lázár G, Maderdrut JL (1989) Distribution of proenkephalin-derived peptides in the brain of Rana esculenta. J Comp Neurol 281(1):23–39. https://doi.org/10.1002/cne.902810104
Miselis RR (1981) The efferent projections of the subfornical organ of the rat: a circumventricular organ within a neural network subserving water balance. Brain Res 230:1–23. https://doi.org/10.1016/0006-8993(81)90388-7
Naik DR, Sar M, Stumpf WE (1981) Immunohistochemical localization of enkephalin in the central nervous system and pituitary of the lizard, Anolis carolinensis. J Comp Neurol 198. https://doi.org/10.1002/cne.901980404
Northcutt RG, Pritz MB (1978) A spinothalamic pathway to the dorsal ventricular ridge in the speckled caiman, Caiman crocodilus. Anat Rec 190:618
Pestarino M, Vallarino M, Polzonetti-Magni A, Carnevali O, Mosconi G, Facchinetti F (1992) Occurrence of immunoreactive met- and Leu-Enkephalin-like peptides in the ovary of the green frog, Rana esculenta. Gen Comp Endocrinol 85(1):118–123. https://doi.org/10.1016/0016-6480(92)90179-n
Peter R, Paulencu CR (1980) Involvement of the preoptic region in gonadotropin release-inhibition in goldfish, Carassius auratus. J Neuroendocrinol 31(2):133–141. https://doi.org/10.1159/000123064
Piñuela C, Northcutt RG (2007) Immunohistochemical organization of the forebrain in the white sturgeon, Acipenser transmontanus. Brain Behav Evol 69(4):229–253. https://doi.org/10.1159/000099612
Pritz M (1995) The thalamus of reptiles and mammals: similarities and differences. Brain Behav Evol 46:197–208. https://doi.org/10.1159/000113274
Reddy PS (2000) Involvement of opioid peptides in the regulation of reproduction in the prawn Penaeus indicus. Naturwissenschaften 87:535–538
Reiner A (1987) The distribution of proenkephalin-derived peptides in the central nervous system of turtles. J Comp Neurol 259(1):65–91. https://doi.org/10.1002/cne.902590106
Reiner A, Karten HJ, Brecha NC (1982) Enkephalin-mediated basal ganglia influences over the optic tectum: immunohistochemistry of the tectum and the lateral spiriform nucleus in pigeon. J Comp Neurol 208(1):37–53. https://doi.org/10.1002/cne.902080104
Reiner A, Brauth SE, Karten HJ (1984) Evolution of the amniote basal ganglia. Trends Neurosci 7:320–325
Rodríguez Díaz MA, Candal E, Santos-Duran GN, Adrio F, Rodríguez -Moldes I (2011) Comparative analysis of Met-enkephalin, galanin and GABA immunoreactivity in the developing trout preoptic–hypophyseal system. Gen Comp Endocrinol 173:148–158. https://doi.org/10.1016/j.ygcen.2011.05.012
Roy S, Wang JH, Balasubramanian S, Sumandeep, Charboneau R, Barke R, Loh HH (2001) Role of hypothalamic-pituitary axis in morphine-induced alteration in thymic cell distribution using mu-opioid receptor knockout mice. J Neuroimmunol 1;116(2):147 – 55. https://doi.org/10.1016/s0165-5728(01)00299-5
Russchen FT, Smeets WJAJ, Hoogland PV (1987) Histochemical identification of pallidal and striatal structures in the Lizard Gekko gecko: evidence for compartmentalization. J Comp Neurol 256(3):329–341. https://doi.org/10.1002/cne.902560303
Sanchez VA, Segura L, Pradhan AA (2016) The delta opioid receptor tool box. Neuroscience 338:145–159
Sar M, Stump WE, Miller RJ (1978) Immunohistochemical localization of enkephalin in rat brain and spinal cord. J Comp Neurol 182:46–482
Sarojini R, Nagabhushanam R, Fingerman M (1995) Evidence for opioid involvement in the regulation of ovarian maturation of the fiddler crab, Uca pugilator. Comp Biochem Physiol 111A:279–282
Schwarz I, Muller M, Pavlova I, Schweihoff J, Musacchio F, Mittag M, Fuhrmann M, Schwarz MK (2020) The diagonal band of broca regulates olfactory-mediated behaviors by modulating odor-evoked responses within the olfactory bulb. bioRxiv 372649. https://doi.org/10.1101/2020.11.07.372649.
Sha A, Sun H, Wang Y (2012) Leucine-enkephalin immunoreactivity is also present in the nervous and digestive systems of the octopus, Octopus ocellatus. Mar Freshw Behav Physiol 45:155–160
Silla A, Calatayud N, Trudeau V (2021) Amphibian reproductive technologies: approaches and welfare considerations. Conserv Physiol 9(1). https://doi.org/10.1093/conphys/coab011
Simantov R, Snyder SH (1976) Morphine-like peptides in mammalian brain: isolation, structure elucidation, and interaction with the opiate receptor. Proc Natl Acad Sci USA 73:2515–2519
Smeets WJ, Hoogland PV, Lohman AH (1986) A forebrain atlas of the Lizard Gekko gecko. J Comp Neurol 254(1):1–19. https://doi.org/10.1002/cne.902540102
Stuesse SL, Adli DSH, Cruce WLR (2001) Immunohistochemical distribution of enkephalin, substance P, and somatostatin in the brainstem of the leopard frog, Rana pipiens. Microsc Res Tech 54:229–245
Swanson LW, Petrovich GD (1998) What is the amygdala? Trends Neurosci 21(8):323–331. https://doi.org/10.1016/s0166-2236(98)01265-x
Takahashi A (2021) Enkephalin. Ando H, Ukena K, Nagata S (Eds.), Handbook of Hormones 91–94. https://doi.org/10.1016/b978-0-12-820649-2.00023-1
Tanaka J, Saito H, Seto K (1988) Involvement of the septum in the regulation of paraventricular vasopressin neurons by the subfornical organ in the rat. Neurosci Lett 92:187–191. https://doi.org/10.1016/0304-3940(88)90058-4
ten Donkelaar HJ, Bangma GC, Barbas-Henry HA, de Boer-van Huizen R, Wolters JG (1987) The brain stem in a lizard, Varanus exanthematicus. Adv Anat Embryol Cell Biol 107:1–168. https://doi.org/10.1007/978-3-642-72763-4
ten Donkelaar HJ, Kusuma A, de Boer-van Huizen R (1980) Cells of origin of pathways descending to the spinal cord in some quadrupedal reptiles. J Comp Neurol 192(4):827–851. https://doi.org/10.1002/cne.901920413.
Uliuski PS (1978) Organization of anterior dorsal ventricular ridge in snakes. J Comp Neurol 178:411–450
Vallarino M, Bucharles C, Facchinetti F, Vaudry H (1994) Immunocytochemical evidence for the presence of Met-enkephalin and leu-enkephalin distinct neurons in the brain of the elasmobranch fish Scyliorhinus canicula. J Comp Neurol 347:585–597. https://doi.org/10.1002/cne.903470409
Vallarino M, Thoumas JL, Masini MA, Trabucchi M, Chartrel N, Vaudry H (1998) Immunocytochemical localization of enkephalins in the brain of the African lungfish, Protopterus annectens, provides evidence for differential distribution of Met-Enkephalin and Leu-enkephalin. J Comp Neurol 396:275–287
Vecino E, Ekström P (1990) Distribution of Met-enkephalin, Leu-enkephalin, substance P, neuropeptide Y, FMRFamide, and serotonin immunoreactivities in the optic tectum of the Atlantic salmon (Salmo salar L). J Comp Neurol 299(2):229–241. https://doi.org/10.1002/cne.902990207
Vecino E, Perez MTR, Ekstrom P (1995) Localization of enkephalinergic neurons in the central nervous system of the salmon (Salmo salar L.) by in situ hybridization and immunocytochemistry. J Chem Neuroanat 9(2):81–97. https://doi.org/10.1016/0891-0618(95)00068-I
Vijayalaxmi, Ganesh CB (2017) Influence of leucine-enkephalin on pituitary-ovary axis of the cichlid fish Oreochromis mossambicus. Fish Physiol Biochem 43:1253–1264. https://doi.org/10.1007/s10695-017-0369-9
Vijayalaxmi, Sakharkar AJ, Ganesh CB (2020) Leucine-enkephalin-immunoreactive neurons in the brain of the cichlid fish Oreochromis mossambicus. Neuropeptides 81:101999. https://doi.org/10.1016/j.npep.2019.101999
Voneida TJ, Sligar CM (1979) Efferent projections of the dorsal ventricular ridge and the striatum in the Tegu lizard. Tupinambis nigropunctatus. J Comp Neurol 186(1):43–64. https://doi.org/10.1002/cne.901860104
Wang X, Wang W, Tang Y, Dai Z (2021) Subdivisions of the mesencephalon and isthmus in the Lizard Gekko gecko as revealed by ChAT immunohistochemistry. Anat Rec 304(9):2014–2031. https://doi.org/10.1002/ar.24595
Wolters JG, Ten Donkelaar HJ, Verhofstand AAJ (1986) Distribution of some peptides (substance P, [Leu] enkephalin, [met] enkephalin) in the brain stem and spinal cord of a lizard, Varanus exanthematicus. Neuroscience 18:917–946
Xu XJ, Hokfelt T, Bartfai T, Wiesenfeld-Hallin Z (2000) Galanin and spinal nociceptive mechanisms: recent advances and therapeutic implications. Neuropeptides 34(3–4):137–147. https://doi.org/10.1054/npep.2000.0820
Yin W, Gore AC (2010) The hypothalamic median eminence and its role in reproductive aging. Ann N Y Acad Sci 1204:113–122. https://doi.org/10.1111/j.1749-6632.2010.05518.x
Funding
This research was supported by a grant (No. CRG/2020/4764) from Science and Engineering Research Board–Department of Science and Technology (SERB-DST), New Delhi, Government of India.
Author information
Authors and Affiliations
Contributions
Methodology, formal analysis and investigation, original draft preparation (AG); Conceptualization, funding acquisition, Project supervision, review and editing (CBG).
Corresponding author
Ethics declarations
Ethics approval
The experimental procedures were approved by an IAEC (No. 639/GO/Re/S/02/CPCSEA).
Informed consent
Not applicable.
Conflict of interest
The authors have no conflicts of interest to declare.
Additional information
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Ganeyan, A., Ganesh, C.B. Organization of enkephalinergic neuronal system in the central nervous system of the gecko Hemidactylus frenatus. Brain Struct Funct 229, 1365–1395 (2024). https://doi.org/10.1007/s00429-024-02805-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00429-024-02805-4